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BrickIndustry

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Flexible VehicularBrick Paving

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ContentsDesign Guide for Vehicular Brick Pavements . . . . . . . . . . . .2

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Part I: Structural Design and Detailing . . . . . . . . . . . . . . . .8Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Subgrade Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Traffic Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12AASHTO Design Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13AASHTO Design Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14CALTRANS Design Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Design of Bituminous Setting Bed Systems . . . . . . . . . . . . . . . . . . . . . . . .17Mortared Brick Paving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17Detailing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17Design Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Part II: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Base and Subbase Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Soil and Base Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23Setting Beds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23Jointing Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Brick Pavers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26Other Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Part III: Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Subgrade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Subbase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31Base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31Sand Setting Bed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32Bituminous Setting Bed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33Paver Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34Tolerances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37In Service Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

Closing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40Appendix A: Definitions of Terms . . . . . . . . . . . . . . . . . . . . . .40Appendix B: Referenced Standards . . . . . . . . . . . . . . . . . . . . . .41Appendix C: Guide Specification . . . . . . . . . . . . . . . . . . . . . . .42

ForewordThis Guide was prepared by the staff of the Brick IndustryAssociation (BIA) with theassistance of several membersand a consultant. Instrumentalin the development of the content were:

Brian Trimble, formerly BIA staff, now International Masonry Institute,Pittsburgh, PA

Ted Corvey, Pine Hall Brick Company,Winston-Salem, NC

Steve Jones, Pave Tech, Prior Lake, MN

Mark Smallridge, Mark Smallridge andAssociates, The Colony, TX

Mr. Smallridge is a paving consultant with considerable expertise and experience in segmental paving designand construction. His assistance wasespecially helpful. The members of the BIA Paving Committee also assisted in the review of this Guide.

Published January 2003Catalog Number: 530

Brick Industry Association11490 Commerce Park DriveReston, VA 20191

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IntroductionThe concept of segmental pavements (including clay bricks,concrete pavers, stone cobbles, stone and timber sets) isnot new. Surviving segmental pavements can be tracedback to the Romans and their network of roads, and toeven earlier times. The oldest references to brick surfacedstreets are believed to date back to Mesopotamian times,5,000 years ago. Brick roads and streets provide a stableriding surface that is very durable. Brick has been used asa road paving material in this country since the late 1800’sand was used through the early 1900’s when the firstnational network of roads was constructed. Although theuse of brick as a road surfacing material decreased withincreasing vehicle speeds, and the improvement of concreteand asphaltic paving materials and construction methodsin the 1930’s and 1940’s, it is still in use today. Therebirth of central business districts and new festival marketplaces demands that street and pedestrian areasbe made of materials with a more human scale. Theappearance, strength, warmth, and flexibility of brick meet this challenge.

Present day practices enable bricks to be set using threebasic methods when they are constructed as a pavementsurfacing material. These are the sand set, bituminous set and mortar set methods. The former two methods areflexible in nature and are covered in this publication.They are able to accommodate surface applied loads andenvironmentally induced stresses without the need for discontinuities such as movement joints. Mortar set bricksurfaces are considered to be rigid, and require regularplacement of movement joints. They are covered in otherpublications, including BIA Technical Notes on BrickConstruction 14 Series.

Pavement design methodsconsider two differenttypes of pavement. Theseare “flexible” pavementsand “rigid” pavements.Flexible pavements spreadthe surface applied loads tothe underlying layers byload distribution. Thematerials generally requirelower strength propertieswith increasing depth,because the stresses reduceas the load is spread over a wider area. Rigid pave-ments spread the surfaceapplied loads by flexure.Rigid pavements include aportland cement concreteslab and brick pavers set inmortar. A rigid pavement’sthickness is frequently lessthan that of an equivalentflexible pavement.

Prior to the publication of the first edition of thisGuide in 1993, the struc-tural design of brick pave-ments had generally beenbased upon empirical methods. Their use hadbeen primarily for pedestri-an areas and streets sub-ject to only light traffic.The Brick Industry

Association recognized the need for a rationalapproach to provide designers with the meansof proportioning thickness-es of brick pavements forheavy vehicular applica-tions such as major roadsand streets. The AmericanAssociation of StateHighway andTransportation Officials(AASHTO) publication Guidefor Design of PavementStructures was revised in 1993 and provided anationally accepted methodthat could be adapted toconsider the flexible bricksurface. Research on flexi-ble pavements had demon-strated the equivalency ofthe brick and sand bedconstruction with otherpavement materials consid-ered in the AASHTO DesignGuide. Therefore, it wasonly necessary to develop asuitable layer coefficientfor the brick and sand bedin order to apply theAASHTO flexible pavementdesign methodology to thebrick surfaced pavement.

Design Guide for Vehic

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Information in this Guide isbased on research anddevelopment carried outaround the world.

The previous version of thisGuide provided instructionthat was very comprehen-sive; however, many usersexpressed a need for a sim-plified method of designingflexible brick pavements.This version of the Guideprovides such a methodbased upon specific appli-cations and site conditions.The design solutions wereprepared in accordancewith the AASHTO method,and the input values aredeclared in the relevantsections of this Guide.There was also an identifi-

able need to include con-sideration of rigid pave-ment where portlandcement concrete was man-dated below the brick sur-facing, as this was not cov-ered in the previous ver-sion. In addition to theserevisions related to theAASHTO design method,this edition also discussesan alternative designmethod for use in thosestates that have adoptedthe Caltrans design methodor derivations thereof.

This Guide is intended toaid in the proper design,specification, and installa-tion of brick paving sys-tems. The designs present-

ed in this Guide are notintended as a replacementto the advice of an experi-enced pavement designer.Although the proposedpavement sections may beappropriate in developingpreliminary sections andbudget costs, it is recom-mended that an engineerwith appropriate pavementexperience certify the finaldesign.

ular Brick Pavements

General Flexible brick pavements, as defined in this Guide,consist of sand set or bituminous set brick paversover layers of conventionalpavement materials. Theflexible brick pavementshown in Figure 1 consistsof a compacted subgradebeneath a subbase layer,base layer, and setting bedsurfaced with brick paversand jointing sand. A subbase may not always be necessary between thesubgrade and the base. Anedge restraint is providedaround the flexible brickpavement as part of thesystem. Sand set brickpavers, and to a lesserextent bituminous set brickpavers, with sand filledjoints, develop interlockbetween adjacent pavers,which distributes theapplied loads into theunderlying layers. Thisdoes not occur with mortarset pavers. Mortared brickpaving is only used over aconcrete slab and is notcovered in this Guide.Although this pavementtype has been used success-fully, the emphasis in thisGuide is on flexible wearingsurfaces. Information on other types of brickpavements can be found inBIA Technical Notes on BrickConstruction 14 Series.

Interlock is a phenomenonthat occurs in segmentalpavements as a result of the interaction of thepavers and the jointingsand between the pavers.The tight, sand-filled jointstransfer loads between

adjacent brick paversthrough friction. Interlockincreases over time as thejoint sand becomes thor-oughly compacted anddebris builds up in thejoints. When interlock ispresent, the wearing surfacecontributes to the strengthof the system. Specially-shaped pavers provide littleadditional contribution tovertical interlock. However,some bond patterns, such as herringbone, help to distribute horizontal loads.In areas subjected to heavyvehicular traffic, the brickpavers may be required tohave a minimum thicknessto achieve sufficient interlock.

Adequate design and con-struction results in threetypes of interlock: verticalinterlock, rotational inter-lock, and horizontal inter-lock. See Figure 2. If a ver-tical load were applied to asingle brick in a pavementwithout vertical interlock,that brick would be forceddown between adjacentbricks, transmitting concen-

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Figure 1: Flexible Brick Pavement

Figure 2: Vertical Interlock

Edge RestraintBrick Pavers

No Vertical Interlock

Vertical Interlock

Shear

Displaced SandDisplaced Sand

Jointing SandSetting Bed

Wearing Surface

Base

Subbase

Subgrade

Figure 4: Horizontal Interlock

No Rotational Interlock

Rotational Interlock

HorizontalDisplacement

No Horizontal Interlock

Horizontal Interlock

HorizontalDisplacement

trated stresses onto the set-ting bed. Brick pavers thatare compacted into the set-ting bed and have well con-solidated sand in the jointsbetween them provide shearresistance in the wearing surface. Thus, the load isspread over a wide area ofsetting bed. See Figure 2.Sand set pavers developgreater vertical interlockthan bituminous set paversas they are vibrated to com-pact the sand bed and den-sify the joint sand to ahigher degree.

If a load is applied asym-metrically to an individualbrick, the brick may rotate,displacing the setting bedand adjacent bricks.Rotational interlock holdsthe brick in place whilerigid edge restraints preventthe bricks from moving lat-erally, thereby eliminatingrotation. See Figure 3.

Horizontal interlock is notachieved if horizontal move-ment is allowed. In vehicu-lar traffic areas, horizontalbraking, cornering andaccelerating forces try tomove pavers along the road;this is known as creep.Sand filled joints and aninterlocking bond patterntransfer these forces withina paving area to rigid edg-ing. See Figure 4. Loadscreated by turning vehiculartraffic are distributed moreevenly in all directions by aherringbone pattern thanby running bond pattern,which has acceptable hori-zontal interlock in only onedirection. See Figure 5.Basket weave patterns mayhave continuous joints intwo directions, resulting inunacceptable horizontalinterlock. Sand set brickpavers initially developgreater horizontal interlockthan bituminous set brickpavers as the joint sand isbetter compacted.

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Figure 3: Rotational Interlock

Figure 5: Horizontal Load Interlock

TABLE 1: Brick Paving System Selection GuideSystem Advantages DisadvantagesFlexible brick paving • Most durable over time • May require a thicker baseover flexible base (Fig. 6a) • Easy to repair utilities • Permits some water percolation through system

• Usually most economical• Allows use of semi-skilled labor

Flexible brick paving over • Good as an overlay to existing pavement • Slightly more expensivesemi-rigid base (Fig. 6b) • Good over poor soils or small, confined areas

• Better aesthetic repairs than asphalt

Flexible paving over • Good as an overlay to existing pavement • Requires good drainagerigid base (Fig. 6c) • Good over poor soils or small confined areas • More expensive

• Better aesthetic repairs than continuous concrete • Vulnerable to frost heave

Sand setting system • Good load transfer • Susceptible to deficiencies in the bedding sand• Simple and expedient installation • Susceptible to sand loss and creep issues• Pavers easily reused for repairs

Bituminous setting system • Enhanced water resistance • More expensive and slower to install• Good containment of setting bed material • Pavers difficult to salvage during repair work• Less onerous edge restraint requirements • Poor tolerance to paver thickness variations or poor

base elevations

Mortared paving over • Matches adjacent walls with mortar joints • Must have a concrete baserigid base (Fig. 6d) • Good over poor soils • Most costly of all brick paving

• Can be used on steeper grades • Requires maintenance of mortar joints• Requires movement joints

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Although a flexible brickpavement provides adurable surface for lightor heavy vehicular appli-cations, the surface of asegmental pavement maynot provide a smooth rideat high speeds. Brickroads tend to slow trafficas subtle variations in thesurface cause decreasingride comfort as speedincreases. These varia-tions help reduce speedsin areas where fastervehicular traffic may be aconcern. This is one ofmany traffic calmingmeasures that cities use

to slow traffic in residen-tial neighborhoods.However, segmental pave-ments are not recom-mended where vehiclespeeds exceed 40 mph (64kph).

Deciding on the appropri-ate brick paving system touse is important to ensureproper performance.Since brick can be used ina variety of ways, asshown in Figure 6, Table 1is provided to assist inselecting the most appro-priate system.

Figure 6b: Mortarless Brick PavingAsphalt Base

Figure 6: Brick Paving Systems

Figure 6d: Mortared Brick PavingConcrete Base

Mortarless Brick Paving

Modified Asphalt Adhesive

3/4 IN. (19MM) Bituminous Setting Bed

Mortared Brick Paving

3/8 IN. to 1/2 IN. (10MM to 13MM) Mortar Setting Bed

MIN. 4 IN. (100MM) Concrete Base

Tack Coat

MIN. 4 IN. (100MM) Asphalt Base

Compacted Subgrade Compacted Subbase Compacted Subgrade Compacted Subbase

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Figure 6a: Mortarless Brick PavingAggregate Base

Figure 6c: Mortarless Brick PavingConcrete Base


1 IN. (25MM) Sand Setting Bed

MIN. 4IN. (100MM) Compacted Aggregate Base


1 IN. (25MM) Sand Setting Bed

MIN. 4IN. (100MM) Concrete Base

Compacted Subgrade

Compacted Subgrade Compacted Subbase

The existing soil conditionsfor a project should bedetermined prior to commencing the design of the pavement sections.A geotechnical engineerwho specializes in siteinvestigation work willgenerally test and classifythe soil conditions for the project area. Testingwill be carried out at theproject site and sampleswill be recovered for additional testing in the laboratory.

The site investigationshould include test pits and borings along thealignment of the road or street, or over the areaof the pavement. Samplesshould be collected for the following laboratorytests considered essentialto determine the

engineering properties of the soils over which the pavement will be constructed:

• Grain-size distribution:sieve analysis test andhydrometer test to deter-mine the percentage ofthe individual grain sizesin the sample;

• Atterberg Limits: consis-tency tests to determinethe moisture content atwhich the sample changesfrom a semi-solid state toa plastic state (PlasticLimit) and from a plasticstate to a liquid state(Liquid Limit);

• Natural moisture content:test to determine the in-place moisture content ofthe soil;

• Natural Density: test todetermine the in-placedensity of the soil;

SubgradeClassificationThe subgrade is classified by the existing soilconditions, the environment and drainage.The more accurate the subgrade classification,the better the performance of the pavement.

Introduction

Part I: Structural Design

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The AASHTO methodology was described in detail in thefirst edition of this Guide. Direction was given on deter-mining the amount of traffic that would use the pavement,dependent on the many factors identified in the 1993AASHTO Design Guide. Tables were provided for calculating the estimated traffic in the design lane based upon axle loads, equivalency factors, structural numbers, growthfactors and lane distribution factors. The equations used tocalculate the required structural number for the pavement,and to proportion the individual pavement layers were setout, along with figures and tables to assess the layer anddrainage coefficients necessary to design the pavement. Inaddition, nomographs and design examples were provided toclarify the procedure.

This version of the Guide provides a method based uponspecific applications and site conditions rather than themore complex procedure of the first edition. The designsolutions were prepared in accordance with the AASHTOmethodology, and the input values are declared in the rele-vant sections. Although the proposed pavement sectionsmay be appropriate in developing preliminary sections andbudget costs, it is recommended that the final design becertified by an engineer with pavement design experience.

In addition to these revisions related to the AASHTO designmethod, this edition also discusses an alternative designmethod for use in those states that have adopted theCaltrans design method or derivations thereof. Design solu-tions are not provided using this method, but gravel equiva-lent factors are suggested for use with the Caltrans manual,so that it can be adapted to consider brick pavers.

Because of the range of climates and the variability of soils,base and subbase materials, designers must use good engi-neering judgment in detailing a flexible brick paving system. The designer should be acquainted with site condi-tions and use all available resources to create a cost-effec-tive solution. Consult references listed at the end of thisGuide for more information.

Soil Conditions

• Dry density/optimummoisture content relation-ship (standard or modi-fied): compaction test todetermine the ideal mois-ture content to achievethe specified state ofcompaction;

• Strength tests [CaliforniaBearing Ratio (CBR) orResistance Value (R-value)]: mechanical teststo determine the bearingcapacity of the soil foruse in the design.

The CBR test method is setout in ASTM D 1883 TestMethod for CBR ofLaboratory Compacted Soils(AASHTO T193). It can beconducted on treated anduntreated base, subbaseand subgrade materials.This test is a comparativemeasure of the load-bear-ing capacity of a soil. Itmeasures the load requiredto drive a standard plungera set depth into a sampleof soil at a standard rate ofpenetration. The CBRvalue is the ratio of theload measured in the testand the load used toachieve the same penetra-tion in a standard sampleof crushed stone. The testis generally undertaken inthe laboratory, but in-placetests can also be carried

out. The values are greatlyaffected by the degree ofcompaction and the mois-ture content of the speci-men. The test should beconducted on a specimencompacted to a density rep-resentative of the materialto be used in the pave-ment, or alternatively at arange of densities likely tobe encountered. To repre-sent the material’s poten-tial moisture condition inthe pavement, the testshould be conducted onspecimens that have beensoaked after compaction for a period of four days.

The R-value test method isset out in ASTM D 2844Test Method for ResistanceR-Value and ExpansionPressure of Compacted Soils(AASHTO T190). It can beconducted on treated anduntreated base, subbaseand subgrade materials, butthe test can only be under-taken in the laboratory.For base, subbase and non-expansive granular soils,the R-value is determinedat a density equivalent tothe density used duringconstruction. For cohesivesoils and expansive granu-lar materials, the R-valuetest involves two separate

procedures. One procedurecalculates the estimatedthickness of the overlyingpavement layers required tomaintain the state of com-paction of the material.The other procedure esti-mates the thickness of theoverlying pavement layersrequired to prevent plastic

deformation in the materi-al. The R-value is deter-mined at the moisture con-tent and density at whichthe thickness of overlyingmaterials is similar in thetwo procedures.

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n and Detailing

The AASHTO design method uses the resilient modulus (MR)

as the design input for the subgrade properties. The mean

value of all test results for each pavement section or soil

type should be used for design. The test to directly deter-

mine MR is not widely used, so AASHTO has proposed the

following relationships between the CBR and R-value test

results. These relationships are as follows:

MR (MPa) = 10.3 X CBR (Eq. 1)

Where: MR is the resilient modulus

and CBR is the California Bearing Ratio

MR (MPa) = 6.9 + 3.8 X R-value (Eq. 2)

The Caltrans design method uses the R-value as the designinput for the subgrade properties. The lowest R-valueshould be used for design over a section of pavement.However, if there are one or two significantly lower R-val-ues in a localized section, consideration should be given toreplacing these areas with better material and using thenext lowest value.

This Guide provides design solutions based on five subgradecategories as set out in Table 2. The table provides CBRand R-values for each subgrade category, based upon rela-tionships to the resilient modulus value MR as set out inEquations (1) and (2). Soils with a CBR value of less than3.0 or R-value of less than 6 require some form of improve-

States, but the two mostcommon are the UnifiedSoil Classification System(USCS), used for generalengineering purposes, andthe AASHTO System, usedfor highway engineeringpurposes. The USCS is setout in ASTM D 2487 andthe AASHTO system is setout in AASHTO Standard

M145, Classification of Soilsand Soil-Aggregate Mixturesfor Highway Construction.

In the USCS, the soils areclassified in twenty-fivegroups by two letter desig-nations dependent on thesoil type and physical prop-erties. The first letter rep-

are classified in seven maingroups (and in twelve sub-groups) based upon theirgrain-size distribution andAtterberg Limits. The twosystems are given in Tables3 and 4, in a manner thatcorrelates each group withthe suggested subgrade cat-egories (U -unsatisfactory,P - poor, F - fair, G - good,E - excellent).

A geotechnical engineer’sreport will include adescription of the soilsencountered at the projectsite and will set out thetest results. In addition, itwill generally provide rec-ommendations on thestrength properties of thesoils to be used for designand may contain somedesign options for thepavement section. If a rec-ommended value is given inthe report, this should beused to select the subgradecategory (see Table 2). Ifthere is no recommendedvalue, but CBR or R-valuetest results are given, theaverage of these valuesshould be used for theAASHTO design methodolo-gy. When the design is tobe undertaken using theCaltrans adaptation, theminimum R-value should beused for selecting the sub-grade category. If only thesubgrade’s USCS or AASHTOclassification is known,Table 3 or 4 can be used toestimate the subgrade cate-gory from the column titled“Average”. The remainingcolumns are addressed inthe following section.

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TABLE 2: Subgrade CategoriesSubgrade Category CBR Range R-value RangeUnsuitable < 2.9 < 6Poor 3.0 - 5.9 6 - 13Fair 6.0 - 9.9 14 - 24Good 10.0 - 14.9 25 - 38Excellent > 15.0 >38

ment that is beyond thescope of this Guide. Theyare considered unsuitable asa subgrade.

Soils or subgrades are typi-cally classified into differ-ent groups to representtheir engineering proper-ties. There are several sys-tems used in the United

TABLE 3: Subgrade Categories from USCSUSCS Environmental/Drainage Conditions

Designation Wet Average Dry Frost

GW E E E EGP E E E E

GW-GM E E E GGW-GC E E E GGP-GM E E E GGP-GC E E E G

GM E E E PGC` E E E P

GM-GC E E E PSW E E E ESP G E E E

SW-SM G E E FSW-SC G E E FSP-SM G E E FSP-SC F G E F

SM G E E USC F G E P

SC-SM G E E UCL P F G P

CL-ML P F G UML P F G UOL U U U UCH P P F PMH P F F UOH U U U U

resents the main soil type(gravel, sand, silt, clay ororganic), and the secondmodifies the first letterbased upon the grain-sizedistribution for granularsoils or the AtterbergLimits for cohesive soils.Eleven groups have paireddesignations. In theAASHTO system, the soils

Environment and DrainageEnvironmental conditions and the quality ofsubgrade drainage can have a major effect onthe support offered by the subgrade. In wetclimates, poorly drained areas, or those thatexperience freezing conditions, the subgradesupport is likely to be reduced during certainperiods of the pavement’s life. Conversely, inarid climates or well-drained areas, it is likelythat a higher degree of subgrade support willbe experienced during part of the pavement’slife. These factors can have a significanteffect on the performance of the pavement.

Saturation of the subgrade,and the materials in thepavement section, can leadto premature distress asthis condition reduces thestrength of these materials.Water can enter the pave-ment through the jointsbetween bricks, throughcracks and joints in thebound base materials, orfrom a high ground watercondition. The amount ofwater penetrating from thesurface depends on theregional climate.Fluctuations in moisturecontent can also be prob-lematic, leading to changesin volume and load sup-port. Rapid removal ofwater from the pavement istherefore an importantdesign objective, and apositive drainage systemshould be considered.Design of such a system isbeyond the scope of thisGuide.

Figure 7 presents the sixclimatic regions experi-enced in the United States.It depicts two regions ofhard freezes where springthaw conditions are likely

to affect the subgrade, tworegions where there is apotential effect from frost,but only if the pavement isthin, and two regions notsusceptible to frost.Average depths of frostpenetration are indicatedfor the eastern and centralstates, although frostdepths can vary locallybased on many factors.Local data should be usedin its place if this is avail-able for a specific projectsite. This is particularlytrue in the western states,and no frost depth data istherefore included in Figure7 for this part of the coun-try. If the depth of frostpenetration is greater thanthe pavement thicknessdetermined in this Guidebased on one of the firstthree columns of Tables 3and 4, it will be necessaryto revise the pavement con-struction. Either non-frostsusceptible material shouldbe added to the thicknessof the pavement section sothat it is thicker than thedepth of penetration, or arevised depth should be

determined based upon theanticipated loss of strengthin the subgrade. In thiscase, if the project is locatedin Regions III or VI onFigure 7, it will be necessaryto use the subgrade categoryfrom the column for FrostEnvironmental/ DrainageConditions. If the project is located in Regions II or V, and the project site drains poorly, it will also benecessary to use the FrostEnvironmental/ DrainageConditions column to deter-mine the subgrade category,since, once again, pavementthickness is a factor.

The AASHTO design methodutilizes an effective resilientmodulus that is derived fromthe seasonal resilient mod-uli. These vary dependingon the moisture conditionsof the subgrade during eachseason. Such an analysis isbeyond the scope of thisGuide. It is recommendedthat the design be undertak-en using a subgrade categoryas described earlier or fromthe geotechnical report, asthe geotechnical consultants

will consider these factorswhen providing their recom-mendations. If these valuesare not available, but theUSCS or AASHTO designationis known, Tables 3 and 4should be used to develop the appropriate subgrade category. Most pavementsshould be designed using thesubgrade category from the column for AverageEnvironmental/DrainageConditions. However, if theproject is located in RegionsI, II or III of Figure 7, andthe project site drains poorly,such that the subgrade is frequently saturated, itwill be necessary to use the subgrade category from the column for WetEnvironmental/DrainageConditions. If the project is located in Regions IV, V or VI and the project site drains well, such that the subgrade is rarely saturated, it may be appropriate to use the col-umn for Dry Environmental/Drainage Conditions.

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TABLE 4: Subgrade Categories from AASHTOAASHTO Environmental/Drainage ConditionsDesignation Wet Average Dry FrostA-1-a E E E EA-1-b E E E GA-2-4 E E E UA-2-5 E E E UA-2-6 F G E PA-2-7 G E E PA-3 G E E FA-4 P G E UA-5 P P F UA-6 P F G PA-7-5 P P F PA-7-6 P F G P

Traffic AnalysisThe traffic analysis for the project should be undertaken before com-mencing design of the pavement sections. A traffic engineer is typi-cally contracted for this work. When undertaking a design it is nec-essary to determine the existing (or initial) traffic volume using theroad, and to estimate the future traffic volumes over the analysisperiod. Based upon these data and local experience, it is necessary toestablish the traffic flow in each direction and in the design lane.Most of the damage to a pavement is caused by truck traffic; passen-ger cars, pick-ups and light two axle trucks generally have a negligi-ble effect. Using local data on the anticipated types of vehicles thatwill use the road, the number of load applications of each axle groupcan be calculated. Next, all of the repetitions of each axle group areconverted into the equivalent number of repetitions of one axle loadcondition.

In the AASHTO designmethodology, the traffic isrepresented as the equiva-lent number of load appli-cations of an 18-kip axleload that represents themixed traffic using thepavement. This is knownas an equivalent single axle

load (ESAL). Tables in theAASHTO Design Guide pro-vide values for convertingdifferent axle loads intoESALs.

In the Caltrans method,this number of ESALs isfurther converted into a

traffic index (TI). Thisvaries in accordance withEquation 3 below, exceptthat the TI is rounded tothe nearest 0.5:

TI = 9.0 X (ESAL/106)0.119

(Eq. 3)

In this Guide, a simplifiedapproach is adopted usingpavement classes. Ninepavement classes are iden-tified in Table 5, togetherwith a description of theiranticipated use and anindication of the totalnumber of ESALs and TI for each class.

The life of the pavementcan be expressed in a num-ber of ways depending onlocal policy. Two terms areused in the AASHTO DesignGuide covering differentlong-term strategies. Theseare the performance periodand the analysis period.The performance period isthe length of time that apavement will remain serv-iceable before it requiresrehabilitation such as anoverlay. The analysis peri-od is the amount of timeover which the pavementlife is to be considered,including any rehabilitationwork. For high volumeroads (collectors andabove), an analysis periodof at least thirty years isfrequently considered. Forlow volume roads (localsand below) and all otherpavements, a twenty-yearlife is generally acceptable.As rehabilitation of flexiblebrick pavements cannot beachieved by strengtheningmeasures without liftingthe bricks, this Guide con-siders the analysis periodas the design life of thepavement.

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III

II

VI

V

IV

I

II30”

35” 40”

30”35”

40”40”35”

25”20”

15”10”

6”

3”

35”40”

I

25”

20”

15”

10”

6”

3”

Average depth of annual frostpenetration in inches

Region CharacteristicsI Wet, no freezeII Wet, freeze/thaw cyclingIII Wet, hard freeze, spring thawIV Dry, no freezeV Dry, freeze/thaw cyclingVI Dry, hard freeze, spring thaw

Figure 7: Climatic Regions in the United States and Average Depth of Annual Frost Penetration

TABLE 5: Pavement Class Description and TrafficPavement Class Description Design ESALs TI

PC-1 Through traffic with access to high-density, regional, commercial and office 9,000,000 11.5Arterial or Major Street developments, or downtown streets. General traffic mix.

PC-2 Through traffic with access to low-density, local, commercial and office 3,000,000 10.0Major Collector development or high density, residential sub-divisions. General traffic mix.

PC-3 Through traffic with access to low-density, neighborhood, commercial 1,000,000 9.0Minor Collector development or low-density, residential sub-divisions. General traffic mix.

PC-4 Public Transport Centralized facility for buses to pick up passengers from other modes of 500,000 8.5Interchange or Bus Parking transport, or for parking of city or school buses.

PC-5 Commercial and Limited through traffic with access to commercial premises and multi-family 330,000 8.0Residential Local and single-family residential roads. Used by private automobiles, service

vehicles and heavy delivery trucks.

PC-6 No through traffic with access to multi-family and single-family residential 110,000 7.0Residential Access properties. Used by private automobiles, service vehicles and light delivery

trucks, including limited construction traffic.

PC-7 Open parking areas for private automobiles at large facilities with access 90,000 7.0Facility Parking for emergency vehicles and occasional use by service vehicles or heavy

delivery trucks.

PC-8 Restricted parking and drop-off areas associated with business premises, 30,000 6.0Business Parking mostly used by private automobiles and occasional light delivery trucks.

No construction traffic over finished surface.

PC-9 Predominantly pedestrian traffic, but with access for occasional heavy 10,000 5.0Commercial Plaza maintenance and emergency vehicles. No construction traffic over

finished surface.

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The reliability of thedesigned pavement sectionis an important feature inthe AASHTO design process.The reliability of the pave-ment is the probability thatit will perform satisfactorilyover its design life for thetraffic and environmentalconditions experienced. Thereliability level adopted inthis Guide is taken as an 85percent likelihood that thepavement will reach itsdesign life (analysis period)for pavements with hightraffic volumes (collectorsand above); and a 75 per-cent likelihood that thepavement will reach itsintended design life forpavements with low trafficvolumes (locals and below).

Non-highway pavements arealso considered to have areliability of 75 percent.This means that 85 percentor 75 percent of the pave-ments for each respectiveuse would achieve or exceedthe design life.

The AASHTO design methoduses a subjective measure ofthe loss of serviceability andfailure of the pavement. Itwas developed as an inter-pretation of the quality ofthe ride experienced by theaverage road user. A scalefrom 0 to 5 represents thequality of the ride and isknown as the PresentServiceability Index (PSI). A PSI of 0 represents animpassable road while a PSI

AASHTO DesignConceptsThe AASHTO Design Guide is based uponempirical test results from full-scale road testsconducted in the 1960’s. As a result of themeasured behavior of the test sections, theresearchers developed a performance equationupon which design of new pavement sectionscan be achieved. The equation relates thedesign life, in terms of 18 kip ESALs, to anumber of different input parameters. Theseinclude the reliability of the pavement, theacceptable level of loss in serviceability, thevariability of the traffic predictions and per-formance, the structural number and the aver-age subgrade resilient modulus.

of 5 represents a perfect road. The change between the ini-tial and final (terminal) PSI, known as the ServiceabilityLoss, used in this Guide is taken as 1.7 for high traffic vol-umes and 2.2 for low traffic volumes. This is based upon aninitial value of 4.2 and terminal values of 2.5 and 2.0respectively. This compares favorably with those used fortypical flexible pavements. An exception is in pedestrianareas where the potential for trip hazards is an importantconsideration. Therefore, a serviceability loss of 1.7 is rec-ommended in these locations. Other AASHTO reliabilityparameters are presented in Table 6.

The variability of the traffic prediction and pavement per-formance is taken as 0.35. This is comparable with the fig-ures used for flexible pavements using asphaltic concrete asa surface course.

The structural number is the only parameter directly relatedto the pavement section. It is derived from the layer coef-ficient of each layer, the thickness of each layer, and thedrainage coefficient for each layer. This Guide is producedunder the assumption that adequate drainage will be pro-vided to the pavement materials such that the latter coeffi-cient can be taken as 1.0. Typical layer coefficients arepresented in Table 7, with the default values used in subse-quent design tables in this Guide.

The values presented in Table 7 can be used to adjust thelayer thicknesses derived from the design tables. The ratioof the layer coefficients can be used to determine theequivalent thickness of an alternative material. For exam-ple, to include a 6-in. (150 mm) thick lime stabilized sub-base it is possible to reduce the aggregate base by0.11/0.14 times the 6-in. (150 mm) thickness, i.e. by 4.5in. (114 mm). Similarly, to replace 8.5 in. (216 mm) ofgraded crushed aggregate (CBR 100) with graded aggregate(CBR 60) multiply 8.5 by 0.14/0.12, i.e. replace with 10 in.(254 mm) of graded aggregate. However, it is recommendedthat the top of the aggregate base directly under the paversetting bed always be constructed with graded, crushedmaterial that is 4 in. (100 mm) thick when the ESALs arebelow 500,000 or 6 in. (150 mm) thick when the ESALs are at 500,000 and above respectively.

Table 8 presents the thick-ness of graded aggregatesubbase course required foreach application. Theresultant pavement sectionwill be comprised of 2-5/8

in. (67 mm) thick flexiblebrick surface on 1 in. (25mm) of bedding sand, over4 in. (100 mm) of crushed,graded aggregate base ontop of the thickness ofgraded aggregate subbasedetermined from the table.Note that the thickness ofcrushed, graded aggregatebase is increased from 4 in.to 6 in. (100 to 150 mm)for traffic levels over500,000 ESALs. Anunbound base course is notconsidered appropriate fortraffic levels above2,000,000 ESALs.

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AASHTO DesignSolutionsTables 8 through 11 of this Guide have beenprepared to provide design solutions to eachpavement class and subgrade category. Thewearing surface is always a 2-5/8 in. (67 mm)paver on a 1 in. (25 mm) setting bed. Thebituminous setting bed is usually specified at3/4 in. in thickness, and an adjustment to thedeveloped thicknesses is required as discussedin the bituminous setting bed section. Thebase is as indicated in the tables.

Similarly, Table 9 providesthe required thickness ofgraded aggregate subbasewhen a cement treatedbase is used under the bed-ding sand. Note that inthis case the thickness ofcement treated base isincreased from 4 in. to 6in. (100 to 150 mm) fortraffic levels over 2,000,000ESALs. Table 10 can beused when an asphalttreated base is provided.

Table 11 provides typicalportland cement concreteslab thicknesses, with a 4 in. (100 mm) aggregatesubbase below and a wear-ing surface of flexible brickpaving. This table is forguidance if the bricks areto be used over such a substrate. Little structuralbenefit is provided by thebricks in this pavementsection, and care needs tobe exercised in ensuringthat detailing allows forthermal and moistureinduced movement in theconcrete, and for egress ofmoisture penetrating thebrick surface.

TABLE 6: AASHTO Reliability ParametersPavement Class Reliability Serviceability LossPC-1 0.85 1.7PC-2 0.8 1.7PC-3 0.85 1.7PC-4 0.75 1.7PC-5 0.85 2.2PC-6 0.75 2.2PC-7 0.75 2.2PC-8 0.75 2.2PC-9 0.75 1.7

TABLE 8: Graded Aggregate Subbase Thickness Under 4 in.Graded, Crushed Aggregate Base

Subgrade CategoryPavement Class ESALs TI Poor Fair Good Excellent

PC-1 Arterial or Major Street 9,000,000 11.5 N.A. N.A. N.A. N.A.

PC-2 Major Collector 3,000,000 10.0 N.A. N.A. N.A. N.A.

PC-3 Minor Collector 1,000,000 9.0 15.0* 7.0* 4.0* 0.0*

PC-4 Public Transport Interchange or Bus Parking 500,000 8.5 9.5* 4.0* 4.0* 0.0*

PC-5 Commercial or Residential Local 330,000 8.0 10.5 4.5 4.0 0.0

PC-6 Residential Access 110,000 7.0 5.5 4.0 0.0 0.0

PC-7 Facility Parking 90,000 7.0 4.5 0.0 0.0 0.0

PC-8 Business Parking 30,000 6.0 4.0 0.0 0.0 0.0

PC-9 Commercial Plaza 10,000 5.0 4.0 0.0 0.0 0.0

* with 6 in. graded, crushed aggregate base

TABLE 9: Graded Aggregate Subbase Thickness Under 4 in.Cement-Treated Base


PC-1 Arterial or Major Street 9,000,000 11.5 24.5* 15.0* 9.0* 6.0*

PC-2 Major Collector 3,000,000 10.0 18.0* 9.0* 6.0* 6.0*

PC-3 Minor Collector 1,000,000 9.0 15.0 7.5 4.0 4.0

PC-4 Public Transport Interchange or Bus Parking 500,000 8.5 10.0 4.0 0.0 0.0






* with 6 in. cement treated base

TABLE 7: Layer CoefficientsPavement Layer Pavement Material or Property Layer Coefficient

Pavers on sand setting bed (increases with traffic volume) 0.31 to 0.40

Pavers on bituminous setting bed (increases with traffic volume) 0.30 to 0.37

Cement-treated base 7 day compressive strength 800 psi 0.227 day compressive strength 650 psi 0.20 (default)7 day compressive strength 500 psi 0.17

Asphalt-treated base Marshall stability 1,800 lbs 0.32Marshall stability 1200 lbs 0.26 (default)Marshall stability 750 lbs 0.20

Aggregate base graded crushed aggregate (CBR 100) 0.14 (default)graded aggregate (CBR 60) 0.12

Subbase graded aggregate (CBR 30) 0.11cement-stabilized subgrade (250 psi) 0.13lime-stabilized subgrade (150 psi) 0.11

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The Caltrans designmethod considers the vari-ous pavement materials interms of a gravel factor(Gf). Tables are includedin the Caltrans designmanual setting out thegravel factors for variousmaterials dependent on thematerials properties andthe TI. The gravel factor isa representation of the rel-ative ability of the materi-als to resist the effects oftraffic loading, when com-pared to an equivalentthickness of gravel.

The design of the pavementsection is based upon arelationship between the R-Value (R), and the TrafficIndex (TI) to develop theGravel Equivalent (GE) forthe pavement. The rela-tionship is represented byEquation 4:

GE (mm) = 0.975 X (TI) X (100-R) (Eq. 4)

The procedure is carried outfrom the top of the pave-ment to the bottom.Treated base layers general-ly have an R-value greaterthat 100 and so the equa-tion is typically applied to

TABLE 10: Graded Aggregate Subbase Thickness Under 3 in.Asphalt-Treated Base


PC-1 Arterial or Major Street 9,000,000 11.5 26.0* 16.5* 10.0* 6.0*

PC-2 Major Collector 3,000,000 10.0 19.0* 10.5* 6.0* 6.0*








* with 4 in. (150mml) asphalt treated base

TABLE 11: Concrete Slab Thickness with 4 in. Aggregate SubbaseSubgrade Category

Pavement Class ESALs TI Poor Fair Good Excellent

PC-1 Arterial or Major Street 9,000,000 11.5 10.5 10.0 9.5 9.5

PC-2 Major Collector 3,000,000 10.0 9.0 8.5 8.0 7.5








16

CALTRANS DesignConceptsThe Caltrans design method is also based upona wide range of information including: theory,test track studies, experimental pavement sections, observations of pavementperformance, and research on materials.Pavements are generally designed for a twenty year life, but it is accepted thatasphalt concrete surfaced pavements willrequire maintenance at ten to fifteen years if they are to achieve this life. This is generally a surface material issue, and this Guide assumes that the brick pavers will provide a twenty year life.

Design of Bituminous SettingBed SystemsBituminous setting bed systems as shown in Figure 6b can be used inmost of the same applications as sand setting bed systems. Higher speedapplications are less desirable as the interlock between pavers is reduced.Although it has reduced structural benefits, the system can provide bettermoisture protection to the underlying layers. In addition, the bondingaction of the system enables the use of pavers with a lower standard ofdimensional tolerances where wider joints would lead to reduced “lock-up”in a sand set system. Joint widths of up to 1/4 inch (6 mm) can be toler-ated, especially in low traffic applications. As there is no vibration usedto compact the pavers, chipping is less of a problem, particularly withpavers that do not have chamfers or lugs. This system may also haveadvantages where edge restraints are less reliable, or where movement maybe encountered. This typically occurs where pavers are placed againststeel rails for light rail applications.

the highest layer in thepavement section with anR-value less than 100. Thethickness of the overlyinglayers is determined. Theprocess is then used for theunderlying layer, and so ondown to the subgrade. Thethickness of each layer iscalculated by dividing theGE by the appropriate Gf.The thickness of each layeris generally rounded to thenext 0.05 ft (15 mm) incre-ment.

To allow for deviations fromthe specified thickness as aresult of construction pro-cedures the Caltransmethod uses a safety factorprocedure. This involvesadding 0.2 ft (60 mm) tothe GE of the asphalt con-crete surface material andsubtracting 0.2 ft (60 mm)from the GE of the subbase,or if no subbase is used,from the thickness of thebase. The thickness of thebrick pavers cannot bechanged, and so this prac-tice needs to be undertak-en between the base andthe subbase, if used.

Design solutions using theCaltrans procedure are notpresented in this Guide,however, a Gf of 2.0 is pro-posed for the brick paverand sand setting bed, and1.8 is proposed for thebrick pavers on a bitumi-nous setting bed, basedupon the above noted typi-cal relationship with equiv-alency to asphalt concrete.This value can be usedwhen the Caltrans manualis appropriate for thedesign, rather than theAASHTO methodology.

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The bituminous setting bedsystem can be used as analternative to a sand set-ting bed system. The 1 in.(25 mm) thick sand settingbed is replaced by a 3/4 in.(19 mm) thick asphaltcoated sand mixture that is“bonded” to the underlyingpavement layer using atack coat. The brick paversare bonded onto this layerwith a rubberized asphaltadhesive. The joints arefilled with stabilized sand,but no vibration is used.Consequently, “lock-up” isnot as well established andthe load spreading isreduced. The base thick-nesses presented in thisGuide can be used for thissystem; however, the thick-ness of the underlying lay-ers needs to be increased.This can be achieved byadding an additional 1 in.(25 mm) to the thicknessof the cement treated baselayer, 3/4 in. (19 mm) tothe thickness of the

asphalt treated base layer,or 1-1/2 in. (38 mm) to thethickness of the graded,crushed aggregate base. Norevision is necessary forthe portland cement con-crete sub-slab option.

MortaredBrickPavingThe structural design ofmortared brick paving fol-lows the design of rigidpavements. The brickpavers and the mortar set-ting bed are not taken intoaccount in the thicknessdesign. The design ofmortared brick paving isnot the aim of this Guide.Refer to the AASHTODesign Guide or BIATechnical Notes 14 Series.

DetailingSurfaceProfileSatisfactory slopes for flexi-ble paving must be provid-ed to avoid ponding water.A minimum slope of 2 per-cent, (1/4 in. per foot or 1mm per 50 mm), is sug-gested for all exterior brickpaving. Crowns on roadsusually provide adequateslope. A maximum slope of10 percent is recommendedfor flexible brick streetsand roads, since largerslopes will cause washoutof the jointing sand andbraking vehicles willincrease the creep of thepavement. Surface gradesof up to 15 percent, oreven 20 percent, can beused on pavement areassubject to slow movingtraffic or pedestrians.However, joint sand stabi-lization, as well as a high

portland cement concreteslab or a cement or asphalttreated base. Weep holesplaced vertically throughthe portland cement con-crete slab may be neces-sary depending on theenvironmental conditions.Drainage is less of a con-cern with bituminous set-ting beds as some waterwill percolate throughthem. It may be necessaryto provide a sub-surfacedrainage system. Sub-sur-face drainage weeps shouldbe provided at low pointsand at the edge restraintsto drain water to the pave-ment edge or storm drains.A perforated pipe wrappedwith an appropriate geot-extile material may beused. The geotextile isnecessary to keep smallparticles from washing out

of the setting bed intosub-surface drains. Adrainage layer of opengraded aggregate may alsobe used, but requires prop-er planning, designing andspecifications. Design anddetailing of such systemsare not included in thisGuide, and the reader isdirected to the referencesfor several manuals on this subject.

Bond PatternsMany different bond pat-terns exist, providing dif-ferent aesthetic effects, afew of which are shown inFigure 8. Herringbone pro-vides the best resistance tothe horizontal forces fromaccelerating, braking andturning of wheels, andshould be used in areas

subjected to heavy vehicu-lar traffic. This is requiredfor sand setting beds andrecommended for bitumi-nous setting beds. Thepattern can be oriented at45 degrees or 90 degrees tothe direction of traffic. Itis not necessary to turnthe pattern at corners andbends, as the horizontalinterlock is good in alldirections.

Many of the pavements laidin the 19th and 20thCentury were laid in run-ning bond, either directlyacross the streets, or occa-sionally at up to 45degrees across them.Running bond patternshave continuous joints inone direction. They do nottransfer loads well alongthe continuous joints, and

Figure 8: Bond Patterns18

level of installation quality,is desirable to reduce creepthat occurs.

DrainageDrainage is one of the mostimportant design require-ments, since improperdrainage may cause failureof the pavement, erosion ofthe base or subbase, possi-ble deterioration of thepavers, or slippery pave-ments. Drainage needs tobe considered at three lev-els in the pavement. Theseare at the surface, to thesetting materials and tothe pavement structure andsubgrade. Surface drainageis undertaken in accor-dance with standard designconcepts for pavementareas. The pavement sur-face should be finished 1/8

to 1/4 in. (3 to 6 mm)above drainage gratings toallow for potential second-ary compaction of the set-ting bed under trafficking.Surface profiles are coveredin the previous paragraph.The bond pattern mayaffect the flow rate ofwater over the surface ofthe paving, as water tendsto flow along the jointlines. Surface runoff willincrease with time as thejoints become filled withdebris, however, somewater will penetrate thebrick surface layer.

Water that penetrates thewearing surface should bedrained away from the set-ting bed and base when theunderlying layers are notfree-draining. This is par-ticularly the case when thesetting bed is placed over a

Running Bond

Herringbone Stack Bond

Basketweave

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so careful consideration isnecessary with their use.They require smaller jointsbetween pavers in order tominimize creep. Runningbond pattern is not recom-mended for high volumeroads and streets. For lowtraffic volume paved areasthe traffic should run per-pendicular to the directionof the continuous joints.

Other bond patterns, suchas basketweave and stackbond, can be used inpedestrian areas. This alsoapplies to derivations ofthese patterns, such asSpanish bond. In all ofthese arrangements, thepatterns include continuousjoints in two perpendiculardirections. For most basketweave patterns laid in aflexible pavement thebonding ratio of the paveris 2:1 or 3:1 (length:width) for proper align-ment of the pattern.Herringbone bond, runningbond and stack bond donot have to follow thisrule, although joints willnot align with a herring-bone bond using an irregu-lar module, which mayaffect installation quality.Basketweave and stackbond patterns tend to showirregularities of the paversand misalignment of thebond pattern more thanother bond patterns. Greatcare needs to be exercisedwith such patterns if thereis any likelihood of in-placewheel turning.

Some pedestrian plazas andother facilities have beeninstalled using the brickpavers in modules that

coincide with the buildinggrids, tree pits, or otherfeatures. Other designshave been created in her-ringbone bond or bandsusing different colorpavers. When setting out apattern using fixed dimen-sion modules or differentcolors, it is important toremember that the individ-ual bricks are not exactsizes. In a modular patterna consistent 1/16 in. (2 mm)under or over sizing of thebricks, allowable in stan-dard manufacturing toler-ances, will soon lead to ashortfall or overrun of sev-eral inches in a grid mod-ule. This should only beovercome by cutting thebricks to fit, as spacing thepavers with wider jointscan affect the structuralintegrity of the pavement.When mixing different col-ors of pavers in a patternarea, it is necessary tohave an understanding ofthe potential for differentsizes so that the desiredappearance is achieved.

EdgeRestraintsEdge restraints are neces-sary along the perimeter ofthe pavement to preventlateral movement of thepavers and loss of the set-ting bed. The edgerestraints should be able toresist anticipated loadswith minimal movement inorder to maintain interlock.Edge restraints can beplaced before laying thesetting bed, and thoseincorporating concreteshould be cured before

required, by a single saw-cut joint line, or by a care-fully introduced series ofstaggered sawcut joints tomaintain continuity.

Inlays are also frequentlyused where a panel of brickpavers is incorporated asan entrance feature. Suchinlays are usually surround-ed by concrete dividers, orportland cement concretepavement. When detailingsuch an inlay it is impor-tant that the sides of thedividers are vertical so thatinterlock can be generatedbetween the bricks and theconcrete. The brick paversshould be finished approxi-mately 1/8 in. (3 mm) highagainst the concrete sothat there is accommoda-tion for secondary settle-ment of the setting bedunder traffic. It is alsoadvisable to keep the cutpieces of brick against theedge divider as large aspossible, with no piecesless than a quarter of apaver. Thin slivers are par-ticularly vulnerable to dam-age at these positions.Some benefit can be gainedby incorporating a header,sailor, or string courseadjacent to the concreteedge.

TrafficButtons,Reflectors andPaintMarkingsTraffic buttons are fre-quently used as lane mark-ings in streets and roadswhere snow clearance is

compaction of the brickpavement begins. All edgerestraints should be placedto a depth of at least thebottom of the setting bed.Edge restraints are requiredfor both sand set and bitu-minous setting methods,although the formerrequires more robust con-struction. It is importantthat the inside face of theedge restraint is vertical sothat the pavers can be laidagainst it without atapered joint that willreduce the integrity.

ConcreteDividers andInlaysIn many pavement areas,the brick pavers are laidbetween concrete elementsthat divide the pavementinto sections. These aretypically 8 to 16 in. (200to 400 mm) wide. The per-ception is frequently thatthis will provide the oppor-tunity to change the pat-tern orientation or that byincorporating such fixedfeatures it will be possibleto prevent creep of thebrick pavers. In actuality,it introduces a discontinu-ity into the pavement thatcreates a weakness withinthe traffic area. Placementof small cut pieces, open-ing of the joints, and set-tlement of the pavers oftenoccurs at these locations.Therefore concrete dividersare not recommended.Changes in the pattern ori-entation can be formed byincorporating a header orsailor course of bricks if aband type feature is

large horizontal pressureinto the brick paver layer,possibly causing pavermovement that may resultin chipping and spalling ofthe pavers, and in extremeconditions heaving of thesurface. It is therefore nec-essary to continue expan-sion joints through thebrick and setting bed layerby incorporating edgerestraints on either side ofthe joint. This should beapplied to both sand setand bituminous set pavers.

Portland cement concreteslabs are also provided withcontraction joints to controlcracking during curing.Movement at these loca-tions is less than at expan-sion joints, and it is notnormally necessary toreflect the joints into thesurfacing if the underlyingcontraction joints are atless than 10 ft (3 m) cen-ters. In order to distributethe movement over a widerarea it is beneficial to coverthe control joints with astrip of geotextiles underthe sand bedding course.This is not done under bitu-minous setting materials.

20

fic markings is not a legis-lated requirement, inlayingcontrasting colored paverscan provide the mostdurable option.

MovementJointsPavement materials expandand contract as a result oftemperature and moisturechanges. Flexible pave-ment materials, such asaggregate, asphalt concreteand cement treated basematerials, distribute thismovement over the entirepavement areas such thatlocalized strains are verysmall. As a result thepavers are unaffected bythe underlying movement.Brick pavers behave simi-larly, with any movementtaken up in the jointsbetween pavers withoutputting stress on the brickor edging. Expansionjoints are therefore nottypically required in suchflexible brick pavements.However, when a portlandcement concrete slab, usedunder the flexible brickpaving wearing surface,expands and contracts, themovement is concentratedat the joints between theslabs. This movement willbe reflected into the over-lying pavers, which can bedetrimental to the pave-ment. When the concretecontracts, it causes theoverlying joints to open.This results in a loss ofinterlock, settling of thepavers and a loss of integri-ty. When the concreteexpands it causes the jointsto close. This can impose

not an issue. These buttonsand reflectors are generallysecured on the pavementsurface with an epoxy adhe-sive. Setting onto individ-ual brick pavers can bedetrimental to the pave-ment. The impact fromvehicle tires can loosen andeven dislodge the bricks. Itis recommended that alter-native means of lane mark-ings are adopted for brickpavers, or that larger, low-profile buttons are usedthat fix to more than onepaver. One effective solu-tion has been to inlay con-crete pavers that have aspecialized top surface fin-ish. As concrete pavers aretypically 3-1/8 (80 mm)thick, they protrude abovethe pavement surface suffi-ciently to create tire feed-back to indicate their pres-ence.

There are several differenttypes of traffic markingmethods for the pavementsurface. These includeadhesive strips, paints, andthermo-plastics. When inservice, the individual brickpavers continue to moveindependently of each otherto a slight degree. As such,the joints open and close asmall amount when a wheelpasses over them. Thismovement is often suffi-cient to cause cracking ofthe adhesive strip and ther-mo-plastic markings.Although thinner paintmarkings frequently have ashorter service life on otherpavement materials, theymay be more cost effectiveon brick paved surfaces.Where the visibility of traf-

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Design ExamplesExample 1Project Location: Phoenix, AZ

Project type: A residential sub-division local collectorstreet. Used by private automobiles, service vehicles andheavy delivery trucks.

Soil conditions: Low plasticity clay CL

Pavement options: Consider 2-5/8 in. (67 mm) brickpavers on a 1 in. (25 mm) and setting bed, with an aggregate base course on aggregate subbase and an asphalt treated base on aggregate subbase.

From Figure 7 the project is located in Region V (dry withfreeze/thaw cycling). Local data indicates that frostdepth is insignificant.

From Table 5 the Pavement Class is PC-5 (Commercial andResidential Local) with traffic expectations of 330,000ESALs over 20 years.

From Table 3 the soil conditions are fair for average conditions and good for dry conditions.

From Table 8 and the design requirements, the pavementthickness will be 2-5/8 in. brick pavers on 1 in. sand set-ting bed, laid on 4 in. graded crushed aggregate base over4-1/2 in. graded aggregate subbase. The total pavementthickness would be 12-1/8 in. (Considering the subgrade similarly drained would only save 1/2 in. of graded aggre-gate subbase, and so is ignored for the clay subgrade)

From Table 10, the pavement thickness would be 2-5/8 in.brick pavers on 1 in. sand setting bed, laid on 3 in.asphalt treated base over 4 in. graded aggregate subbase.The total pavement thickness would be 10-5/8 in.(Considering the subgrade similarly drained would save the full depth of graded aggregate subbase, but is ignored owing to the clay subgrade)

Example 2Project Location: Boston MA

Project type: A downtown thoroughfare where traffic studies indicate that the traffic over the design life willbe 8x106 ESALs

Soil conditions: Clayey sand with an average CBR value of 11.

Pavement options: Consider bituminous set bricks on acement treated base course (7-day compressive strength 800 psi) on an aggregate subbase and a portland cementconcrete slab on an aggregate subbase.

From Figure 7, the project is located in Region II (wetwith freeze/thaw cycling). Frost depth is around 22 in.

From Table 5, the Pavement Class is PC-1 (Arterial orMajor Street), with traffic expectations of 9,000,000 ESALs over 20 years.

From Tables 2 and 3, the soil conditions are good for average conditions and poor for frost conditions.

From Table 7, the layer coefficient for the CTB is 0.22

From Table 9, the pavement thickness will be 2-5/8 in.brick pavers on 1 in. sand setting bed, laid on 6 in. 650psi CTB over 9 in. graded aggregate subbase. To consider3/4 in. bituminous setting bed, add 1 in. to the 6 in. ofCTB. To consider 800 psi CTB, multiply 7 in. by 0.2/0.22= 6-3/8 in. The total pavement thickness would be 18-3/4

in. Add 4 in. to aggregate to exceed frost penetrationdepth. (Considering poor subgrade conditions to accommodate loss of support requires additional 15.5 in from Table 9)

From Table 11, the pavement thickness would be 2-5/8 in.brick pavers on 1 in. sand setting bed, laid on 9-1/2 in. portland cement concrete slabs over 4 in. graded aggregate subbase. No increase in pavement thickness is required to use a 3/4 in. asphaltic setting bed. The total pavement thickness would be 16-7/8 in. Add 6 in. aggregate subbase owing to frost penetration.(With poor subgrade, the loss of strength would increaseconcrete thickness by 1 in., rather than adding 6 in. ofaggregate subbase)

Part II: Materials

Base andSubbaseMaterialsSome pavement systemscontain only a base, whileothers contain a base and asubbase. See Figure 1 forlocation of layers. Thequality or type of base andsubbase materials is usuallydictated by the designrequirements. The designtables are based on variousCBR values for the aggre-gate layers, and compres-sive strength or Marshallstability for the cement andasphalt treated layers.

Base materials may consistof unbound granular mate-rials, such as crushed aggre-gate; cement-treated or

asphalt-treated aggregates;or concrete and asphaltbases. Subbases are usuallycomposed of aggregatematerials. Aggregate baseand subbase materials,including cement- and lime-stabilized materials, arecommonly specified in localstate and municipal stan-dards for highway construc-tion. All materials shouldconform to state or localDOT specifications.Materials conforming toASTM or other industrystandards can be used asalternates. The choice andquality of base and subbasematerials influences theperformance of the pave-ment. Typically, each layermaterial can resist progres-sively higher stresses fromthe subgrade upward to thewearing course.

AggregatesThe National StoneAssociation has providedgradation limits for baseand subbase aggregatematerials, see Table 12.This table is similar torequirements found inASTM D 2940 Specificationfor Graded AggregateMaterial for Bases orSubbases for Highways orAirports.

Crushed, quarry processedaggregate is preferredbecause of its ease of con-struction. The maximumsize of aggregate to beused in construction maydepend on the size of theproject and the size ofequipment being used.Proper gradation of materi-als is required to achieveadequate compaction.Layers consisting of single-size aggregate will not con-solidate during compactionand should not be used.

For flexible brick pave-ments subjected to pedes-trian and light vehiculartraffic, aggregate graded to“3/4 minus”, similar to thegradations in Table 12, isusually sufficient as a basematerial because it is easyto work with and is readilyavailable. Smaller gradedaggregates or rounded

aggregates may not be suf-ficient to achieve interlockwithin the aggregate layerand will not transfer loadsproperly. Open graded (gapgraded) aggregates can beused to promote waterdrainage in areas subjectedto frost heave to minimizedamage. Geotextiles maybe needed to prevent intru-sion of smaller materialinto the open graded aggre-gates.

Asphalt BasesNew or existing asphaltbases can be used for flexi-ble brick pavements.Specification of asphaltconcrete should followindustry standards or localDOT requirements. Theadequacy of existingasphalt and the materialsbeneath should be verified.

Concrete BasesNew and existing concretebases can be used for flexi-ble brick pavements. Newconcrete slabs should bespecified, with reinforce-ment as needed, and con-structed according toindustry practice. Concretebases should be properlycured before installing theflexible brick paving. Highearly strength cement maybe used to reduce the time

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IntroductionThe performance of any pavement is only asgood as the base, subbase and soil on whichit is laid. Quality materials for every layer inthe pavement system are vitally important togood performance. Materials should conformto state or local department of transportation(DOT) specifications, ASTM standards, or otherapplicable industry standards. Project specifi-cations typically require submission of qualifying tests set by the standards.

before the wearing surfaceis placed. Existing concreteslabs should be checked forappropriate strength andrepaired or reinforced asnecessary. A geotextile canbe used where there is apossibility of loss of sandthrough cracks or holes inthe existing slab. The ade-quacy of the materialsbeneath the existing con-crete slab should be veri-fied.

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TABLE 12: Gradation for Base and Subbase(National Stone Association)

Grading Requirements for Dense Graded MaterialSieve Size Design Rangea Job Mix Tolerances

Percent Passing, by Weight Percent Passing by WeightBases Sub-bases Bases Subbases

2 in. (50 mm) 100 100 -2 - 3

1-1/2 (37.5) 95 to 100 90 to 100 ± 5 ± 5

3/4 in (19 mm) 70 to 89 — ± 8 —

3/8 in. (10 mm) 50 to 70 — ± 8 —

No. 4 (4.75) 35 to 55 30 to 60 ± 8 ± 1-

No. 30 (600 µm) 12 to 25 — ± 5 —

No. 200 (75 µm) 0 to 8b 0 to 12b ± 3 ± 5

a Job mix formula should be selected with due regard to availability of materials in the area of the project. Job mix tolerancesmay permit acceptance of test results outside the design range.b Determine by wet sieving. Where climatic conditions (temperature and availability of free moisture) indicate that in order toprevent damage by frost action a lower percentage passing the No. 200 sieve than permitted above, appropriate lower percent-ages shall be specified.

Soil and BaseStabilizationSubgrade soils or granularmaterial unsuitable for usealone may be treated to pro-duce a stronger layer. Thesubgrade soil may be stabi-lized by adding portlandcement or lime, dependingon the quality of the soil.Subbase and base materialsmay be improved by addingportland cement, lime,asphalt or pozzolanic materi-als. Modifying unsuitablematerials is considered wheneconomically feasible orwhere suitable untreatedmaterials are in short supply,although caution should beused in specifying treatedsoils. Their use should bebased on local availabilityand experience.

Aggregate subbase materials,as well as cement- and lime-stabilized materials, are com-monly specified in local stateand municipal standards forhighway construction.

SettingBedsSand SettingBedSand used as the settingbed should be a washed,well-graded, sand with amaximum size of about 3/4

in. (4.8 mm). Sand con-forming to ASTM C 33Specification for ConcreteAggregates is acceptable.Table 13 shows the grada-tion limitations taken fromASTM C 33. In addition, theamount of material passingthe 75 µm (No. 200) sieveshould be limited to nomore than 3 percent. Thesand particles should besub-angular. For pavementssubjected to heavy channel-ized traffic, experience hasshown that only naturally

occurring, washed silica sandwith no silt content shouldbe used. The gradation forthe silica sand in channel-ized traffic should be asshown in Table 14 and nomore than 0.3% passing the75 µm (No. 200) sieve.

An excess of fine particlescan increase the moisturesensitivity of the beddingsand. Bedding sands withhigh fines content can leadto rutting and movementforms of distress. It is notonly important to ensurethat the fine content is sat-isfactory on the selectedbedding sand, but also thatit will not break down underheavy traffic. A degradationtest can be undertaken onthe bedding sand to comparedifferent bedding sandoptions. The test involvesrotating sand samples with a

charge of ball bearings, on abottle roller for six hours.The sand particles wear orbreak down in the process,generating finer particles.The increase in fine particlespassing the No. 50, No.100and No. 200 sieve sizes can becompared with each other toselect the best performingsand.

Mason’s sand, limestonescreenings, or stone dustshould not be used as they donot compact uniformly, arenormally too soft, and somemay cause efflorescence. Soft materials, such as stonescreenings, tend to breakdown over time into smallerparticles. Cement should notbe added to the sand becauseit makes removal and reuse ofthe pavers difficult, adds tothe expense of the system,and may cause durabilityproblems.

Bituminous Setting BedThe bituminous setting bed system can be used as an alterna-tive to a sand setting bed system. The sand bed is replaced byan asphalt coated sand mixture that is bonded to the underly-ing pavement layer with a tack coat. The brick pavers are inturn bonded on to this bituminous setting bed with a rubber-ized asphalt adhesive.

The most common material for the tack coat is an SS-1 or SS-1h asphalt emulsion complying with ASTM D 977 Specificationfor Emulsified Asphalt. Typical application rates are 0.05 to0.15 gallons per square yard (0.23 to 0.68 liters per squaremeter) dependent on the surface texture and porosity. Gradedcrushed aggregate base layers may require up to twice thisrate.

The asphalt cement for the bituminous setting bed should bethe same grade as that specified for the surface course con-struction in the appropriate state department of transporta-tion or city highway specification. This may be a viscositygrade conforming to ASTM D 3381 Specification for Viscosity-Graded Asphalt Cement for Use in Pavement Construction (AC-10 or AC-20, and AR-2000 or AR-4000 are the most common)or a performance grade conforming to AASHTO MP 1Specification for Performance Graded Asphalt Binder (designat-ed as PG grades that are dependent on high and low tempera-tures in the area). The type of asphalt cement will govern themixing and rolling temperatures. The fine aggregate for thebituminous setting bed should be a natural or manufacturedsand that complies with ASTM D 1073 Specification for fineAggregate for Asphaltic Paving Mixtures, grading No. 2, orsimilar material used as fine aggregate at the asphalt plant.All particles should pass the No. 4 sieve. A typical gradation isshown in Table 15.

A local asphalt plant supplies the bituminous setting bedmaterial. Generally only small loads, up to 5 tons (4.5 metrictons), are required at one time so that the work can be com-pleted before the material cools and becomes unworkable. Itis manufactured by combining the dried fine aggregate withhot asphalt in the asphalt plant. The approximate proportionsare 6-8% of asphalt cement with 94-92% of fine aggregate orapproximately 1 gallon of asphalt cement to 110 lbs of fineaggregate (1 liter to 13 kg). The exact proportions should beverified before supplying material for the project. The materi-als are mixed at a temperature of 300-325° F (149-163° C).

The adhesive is generally a neoprene modified asphalt productspecifically developed for setting pavers. It consists of a rub-berized asphalt (typically 2% neoprene) with inorganic fibers(typically 10% non-asbestos fibers). However, other productsincluding cold pour rubberized asphalt crack filling compoundshave also proven to be successful.

TABLE 13: Gradation forBedding Sand (ASTM C 33)Sieve Size Percent Passing,

by Weight

9.5 mm (3/8-in.) 100

4.75 mm (No. 4) 95 to 100

2.36 mm (No. 8) 80 to 100

1.18 mm (No. 16) 50 to 85

600 µm (No. 30) 25 to 60

300 µm (No. 50) 5 to 30

150 µm (No. 100) 0 to 10

75 µm (No. 200) Less than 3

TABLE 14: Gradation forBedding Sand in ChannelizedTrafficSieve Size Percent Passing,

by Weight

3/8 in. (9.5 mm) 100

No. 4 (4.75 mm) 95 to 100

No. 8 (2.36 mm) 75 to 100

No.16 (1.18 mm) 55 to 90

No. 30 (600 µm) 35 to 70

No. 50 (300 µm) 0 to 35

No. 100 (150 µm) 0 to 5

No. 200 (75 µm) 0 to 0.3

TABLE 15: Gradation forBituminous Setting BedAggregateSieve Size Percent Passing,

by Weight

No. 4 (4.5 mm) 100

No. 8 (2.36 mm) 75 to 100

No. 16 (1.18 mm) 50 to 74

No. 30 (600 µm) 28 to 52

No. 50 (300 µm) 8 to 30

No. 100 (150 µm) 0 to 12

No. 200 (7 µm) 0 to 5

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For bituminous setting bedsystems it is necessary toprovide stabilized jointsand as the joint sand isnot as well packed into thejoints. Without a stabilizer,creep can be excessive andjoint sand erosion is likely.Mixtures of portlandcement and sand have beenused with varying success,but are not recommended.If such a mixture is used itshould consist of 1 part ofportland cement and 6parts of sand. The materi-als are mixed dry beforefilling the joints, and arebrushed over the surface.The surface is fogged sothat water penetrates thejoints and hydrates thecement. Staining or aresulting rigid system isundesirable results of thispractice.

Liquid polymer sealants areproving to be more success-ful than the sand cementmix. They can also be usedfor areas subjected toheavy flows of water.

Jointing SandJointing sand used between the brick pavers should generally have smaller particles than the setting bed material so that it completely fills the joints. The sand particles should be sub-angular.Pavers without lugs and with tighter dimen-sional tolerances may require finer jointingsand. Appropriate materials must be used toavoid sand wash-out or sand being suckedout by tires. Bedding sand (ASTM C 33) isrecommended for joint filling in heavy vehicular pavements. However, the largerparticles often will not enter the joints and should be swept off the surface. Theremaining sand particles require significantencouragement to fully penetrate the joints.Success has been obtained by passing thebedding sand through a No. 8 sieve. Thiscan be done at the jobsite or by the sandsupplier before the material is delivered.Mason’s sand may be used for lighter trafficconditions, and should be graded to the limits in ASTM C 144 Aggregates for MasonryMortar shown in Table 16. The often roundedshape of the finer grade mason’s sand makes it susceptible to removal from thejoints. Thus, the use of stabilizers should be seriously considered. Other successfulsands have been specially graded, dried andbagged for joint filling. They are frequentlyavailable from some paver manufacturers.Limestone screenings or stone dust shouldnot be used for the reasons listed underSetting Beds.

These products are a waterrepellent, applied to bindjointing sand particlestogether. It is typicallysprayed and squeegeed overthe surface so that it soaksinto the joint sand and onlya thin film remains.

Dry mix stabilizers aremixed with dry jointingsand and swept into thejoints. The binding mecha-nism is activated by appliedwater. In order to achievesatisfactory penetration andbinding of the sand, it isinappropriate to use theASTM C 144 manufacturedsand when liquid polymersealants are applied. Thissand has a high percentageof very fine particles whichprevent the penetration ofthe stabilizer to a satisfac-tory extent. The stabilizersshould bind the sand in thetop 1/2 in. (12 mm) of thejoint.

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TABLE 16: Gradation forJointing Sand (ASTM C 144)

Percent Passing, by WeightSieve Size Natural Sand Manufactured Sand

4.75 mm (No. 4) 100 100

2.36 mm (No. 8) 95 to 100 95 to 100

1.18 mm (No.16) 70 to 100 70 to 100

600 µm (No. 30) 40 to 75 40 to 75

300 µm (No. 50) 10 to 35 20 to 40

150 µm (No. 100) 2 to 15 10 to 25

75 µm (No. 200) 0 to 5 0 to 10

TABLE 17: Brick Paver Types and ApplicationsASTM Specification and Type Traffic Type Typical Applications

ASTM C 1272, Type F and R Heavy vehicular traffic Roadways, city streets,parking lots, ports

ASTM C 902, Type I High frequency pedestrian, Driveways, entranceways,light vehicles parking lots

ASTM C 902, Type II Intermediate frequency pedestrian Exterior walkways,pedestrian plazas

MinimumThicknessBrick pavers set in a sandsetting bed with sandbetween the pavers used ina heavy vehicular pavementrequire a minimum thick-ness of 2-5/8 in. (67 mm) toachieve interlock. Thisthickness is exclusive of anychamfers. Thinner paverswill not provide interlockand may move in place,allowing cracking of thepavers. The same thick-nesses apply to pavers onbituminous setting beds.

DurabilityThe durability of brickpavers is predicted by prop-erties such as compressivestrength, absorption andsaturation coefficient. Thesaturation coefficient, alsoreferred to as the C/B ratio,is the ratio of 24 hour coldwater absorption to the 5hour boiling water absorp-

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Pavers covered by ASTM C902 are intended to supportpedestrian and light vehicu-lar traffic with low volumesof traffic. The pavers canbe used in applications suchas residential patios anddriveways, sidewalks,plazas, and commercialdriveways. Pavers coveredby ASTM C 1272 are intend-ed to support high volumesof heavy vehicles. Theheavy duty pavers can beused in applications such asroads, streets, and cross-walks. Heavy vehiculartraffic is defined as highvolumes of heavy vehiclesrepresenting trucks or com-bination vehicles that have3 or more loaded axles. Apossible measure of highvolume is over 25 ESALs perday or 200,000 ESALs overthe pavement life. Table 17shows the traffic type andapplications for brickpavers.

tion. ASTM C 1272 requiresthe brick to meet a mini-mum compressive strengthand a maximum cold waterabsorption. ASTM C 902pavers must meet a mini-mum compressive strength,a maximum cold waterabsorption, and a maximumsaturation coefficient.Table 18 shows the physicalproperty requirements forthe different classes ofpaving brick. Paving bricksubjected to freezing tem-peratures should equal orexceed the physical proper-ty requirements for ASTM C1272, Type R or F, or ASTMC 902, Class SX.

Because raw materials andproduction methods forbrick vary throughout thecountry, it is difficult touse only the physical prop-erty requirements to classi-fy all brick. Therefore,there are alternates whichpermit the use of thosebrick which perform satis-factorily in service but donot meet the physicalrequirements listed in Table18. Using the alternates inASTM specifications permitsthe use of brick that areknown to perform well intheir intended application.It does not signify that thebrick are of a lower quality.

Brick PaversBrick pavers should conform to ASTM C 902Specification for Pedestrian and Light TrafficPaving Brick or ASTM C 1272 Specification forHeavy Vehicular Paving Brick. The pavingpavers are classified by the type of traffic thepavers are subjected to during use.

FlexuralStrengthIt is unlikely that a brickpaver will ever fail in com-pression (crushing) while inservice. Instead, the criti-cal property is the flexuralstrength. A point load,such as a tire, transmits aforce to the paver that issupported beneath by auniform resisting load. Theability of a brick paver toresist a point load is meas-ured by either the modulusof rupture or the breakingload. Each is evaluatedaccording to ASTM C 67Test Methods of Samplingand Testing Brick andStructural Clay Tile AASHTOT32. In these tests anindividual paver is support-ed near its ends and adownward force appliedmidway between the twosupports. ASTM C 1272establishes a minimumbreaking load value shownin Table 18. ASTM C 902does not have requirementsfor flexural strength.

AbrasionResistancePaving brick are exposed tothe abrasive effect ofpedestrian and vehiculartraffic. Of these two typesof traffic, pedestrian trafficcan cause the most wear ofthe pavement surface.Areas attracting concentra-tions of pedestrian traffic,such as doorways, gates,and even automatic tellermachines, deserve specialattention. The high vol-ume and impact force ofhigh-heeled shoes cause

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the highest degree of abra-sion. Tires on roadways donot have such a drasticeffect, unless studded tiresare permitted. Brick roadswill polish with repeatedtire traffic which results ina slightly lower skid resist-ance value.

The abrasion resistance ofbrick pavers is determinedin one of two ways: 1) anabrasion index is calculatedby dividing the cold waterabsorption by the compres-sive strength and then mul-tiplying by 100, or 2) bydetermining the volumeabrasion loss in accordancewith ASTM C 418 TestMethod for AbrasionResistance of Concrete bySandblasting. The abrasionrequirements for pavingbrick are listed in Table 19.

The abrasion index is anexpedient measure sincecompressive strength andabsorption tests must becalculated for durabilitypurposes. The abrasionindex has correlated wellwith in-field performance.

The volume abrasion loss isdetermined by submitting apaver to the sandblastingtest for a duration of twominutes. The flow rate andgrading limits of the sanddiffer slightly from ASTM C418. The volume loss isdetermined by filling theabraded depression withmodeling clay, then calcu-lating the volume lost dur-ing sandblasting.

Slip and SkidResistanceThe slip resistance of apaving surface is related topedestrian traffic, whileskid resistance is related tovehicular traffic. The slipand skid resistance aremeasures of the slipperi-ness of a surface. A sur-face with a high slip orskid resistance is relativelysafe, while a low value mayindicate a hazardous sur-face.

Slip resistance is adverselyaffected by water on thesurface of the pavement.It is the surprise of walkingfrom a slip resistant surfaceonto a wet or nonslip

resistant surface that caus-es many falls. Since theslip resistance relies on themicrotexture of the pavingbrick, a brick with arougher wire cut surfacewill have a higher slipresistance value.

Skid resistance measuresthe potential of vehiclesskidding on the roadwaysurface. For the relativelyslow speeds expected onflexible brick pavements,the skid resistance dependsupon the microtexture ofthe paver surface. Jointsbetween the pavers andchamfered edges also havea positive effect on theoverall skid resistance. Apendulum friction tester isused to measure skid resist-ance. The pendulum tester,ASTM E 303 Method forMeasuring SurfaceFrictional Properties Usingthe British PendulumTester, measures the wetskid resistance value ofunused individual pavers.Typical values for new brickpavers from the BritishPendulum Test range from50 for smooth pavers toover 80 for wirecut sur-

TABLE 18: Physical Requirements for Brick PaversASTM Specification Minimum Compressive Minimum Breaking Load Maximum Cold Water Maximum Saturation

and Type Strength, psi (MPa) lb./in. (kN/mm) Absorption, % CoefficientAverage of 5 Individual Avg. of 5 Individual Avg. of 5 Individual Avg. of 5 Individual

C 1272, Type R 8,000 (55.2) 7,000 (48.3) None None 6 7 None None

C 1272, Type F 10,000 (69.0) 8800 (60.7) 475 (83) 333 (58) 6 7 None None

C 902, Class SW 8,000 (55.2) 7,000 (88.3) None None 8 8 0.78 0.80

4,000 (27.6)a 3,500 (24.1)a 16a 18a

C 902, Class MW 3,000 (20.7) 2,500 (17.2) None None 14 17 None Nonea Molded Brick

faces. Other tests, such asthe fixed trailer, allow thetesting of larger sections ofpavements that take intoaccount the positive aspectof joints.

Over time, the skid resist-ance of all paving surfacesdecreases because of thepolishing effect of the traf-fic. The skid resistancevalue for most brick is ini-tially very high anddecreases while in use,approaching an equilibriumcondition several monthsafter placement. The skidresistance values are alsoaffected by seasonal fac-tors. The British PendulumTester can also measure thePolished Paver Value (PPV)after the paver has been inservice.

DimensionsThe size and the associateddimensional tolerances ofpaving brick are moreimportant in flexible brickpavements than in otherbrick paving applications.Consistent dimensional tol-erances allow consistentjoint sizes. This in turnensures interlock and may

TABLE 19: AbrasionRequirements for PaversPaver Specification Abrasion Index Volume Abrasion Lossand Type (Max) (Max) (cm3/cm2)

ASTM C 1272, Type R and F 0.11 1.7

ASTM C 902, Type I 0.11 1.7

ASTM C 902, Type II 0.25 2.7

TABLE 20: Common Sizes of BrickPaversa

Width, in. (mm) Height, in. (mm) Length, in. (mm)

4 (102) 2 1/4 (58) 8 (203)

4 (102) 2 3/4 (70) 8 (203)

4 (102) 3 (76) 8 (203)

3 5/8 (92) 2 1/4 (57) 7 5/8 (194)

a Check with manufacturer for availability of chamfers and lugs.

TABLE 21: DimensionalTolerances for Pavers

Maximum Permissible Variation, in. (mm) ±Paver Specification < 3 in. Over 3 to 5 in. Over 5 to 8 in. Over 8 in.and Application (76 mm) (76 to 127 mm) (127 to 203 mm) (203 mm+)

ASTM C 1272, 1/8 (3.2) 3/16 (4.8) 1/4 (6.4) 5/16 (7.9)Application PS

ASTM C 1272, 1/16 (1.6) 3/32 (2.4) 1/8 (3.2) 7/32 (5.6)Application PX

ASTM C 902, 1/16 (1.6) 3/32 (2.4) 1/8 (3.2) 7/32 (5.6)Application PX

between the centers of thejoints. When lugs areincluded on both sides andboth ends of the paver, thelugs share the spacebetween the pavers. Thus,only one lug is includedwhen measuring the lengthor width of the paver.

The dimensional tolerancesfor pavers are shown inTable 21. For flexible pave-ments subjected to vehicu-lar traffic, ASTM C 1272,Type F or ASTM C 902Application PX is recom-mended. Brick with largerdimensional tolerances willbe difficult to install, espe-cially with herringbone andbasketweave patterns, andmay not provide interlock.

OtherMaterialsSurfaceCoatingsColorless coatings (i.e.water repellents) are gener-ally not recommended onexterior brick pavements.The wrong type of coatingmay not permit vaportransmission (evaporation)and may trap water withina paver. This may lead todamage due to freeze/thawor spalling of the face dueto build up of crystallinedeposits of soluble salts orice beneath the coating.Non-penetrating type coat-ings will wear off quickly inhigh traffic areas.

However, coatings that pre-vent erosion of the jointingsand may be beneficial. In

reduce chippage.Commonly available sizesof pavers for flexible pave-ments are listed in Table20. Rectangular paversmay have a small chamferor rounded edges. Whenthese are present it is rec-ommended that they notexceed 3/16 in (4.8 mm) indepth or width. The mini-mum height of the pavernecessary for interlockdoes not include theheight of any chamfer.Specially-shaped pavers areavailable from some manu-facturers lending a decora-tive effect to the pave-ment. The shape, otherthan the ratio of maximumlength to thickness, has nomeasurable effect on theinterlock between thepavers or on the strengthof the pavement. Paversshould be dimensioned sothat the ratio of maximumlength to thickness is lessthan 3 to 1.

Some pavers also are madewith lugs or spacers.These lugs, usually 1/8 in.(3 mm), space the paversapart and provide a uni-form gap for jointing sand.The lugs also keep thepaver edges from touchingduring compaction and inservice. This may reducethe amount of chippage onthe paver. Lugs are usual-ly necessary when thepavers are subjected toheavy vehicular traffic.When lugs are on only oneside or one end of thepaver, they are includedwhen measuring the lengthor width. This approxi-mates the dimensions

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CHAMFER

WIDTH

LENGTH

HEIGHT

LUGS

that case, the coatingshould be of a type thathas a high vapor transmis-sion rate, and will notaffect the slip/skid resistance of the paver.The stabilizer should bewater based.

GeotextilesGeotextile fabric materialscan be used to separatelayers of materials in thepaving system. Geotextilescan also be used as a filtermaterial in many drainageapplications. Subgrade soilcan be prevented frommigrating into the base orsubbase by use of a geotex-tile. Other uses of geotex-tiles range from providingerosion control to beingused to reinforce subgradebeneath the pavement byadding strength to the sys-tem. Geotextile manufac-turers should be consultedto determine applicabilityof geotextiles in flexiblebrick paving applications.The recommended minimumapparent opening size ofthe geotextile should beNo. 70 (0.2 mm). The geotextile fabric may beeither woven or nonwoven,and should be placed sothat the material extendsup the side of the excavat-ed area a sufficient dis-tance to cover the basematerial. They shouldoverlap approximately 24to 36 in. (610 to 914 mm)to maintain strength. Onlywoven geotextiles shouldbe used directly under thebedding sand, as this loca-tion is highly abrasive, andcan separate the fibers onnon-woven materials.

EdgeRestraintsEdge restraints are manda-tory in flexible brick pavements. Edge restraintshold the pavers togetherand provide for interlock ofthe wearing surface. Manydifferent types of edgerestraint materials exist,including brick, rigid plas-tic, wood, steel, aluminum,or concrete. The type ofapplication determineswhich material to use. Anyof the materials listed canbe used in pedestrian appli-cations. Only concrete,brick placed in concrete,some varieties of rigid plas-tic, or steel edgings shouldbe used in areas subjectedto vehicular traffic. Inheavy vehicular applica-tions, only cast-in-placeconcrete should be used.Flexible pavement materi-als, such as brick set insand, loose aggregates, orasphalt, are not suitable asedge restraints.

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Part III: Construction

Subgrade The subgrade is excavated,if necessary, to achieve therequired finished level. Any unsuitable material,such as organic material,large rocks, etc., should beremoved from the subgradeand replaced with suitablebackfill. The subgradeshould be drained and protected against floodingand ground water by sub-soil drainage. Theinstallation of pipes andsub-soil drainage should be completed before initiat-ing the base or subbaseconstruction. The width of the subgrade should besufficient to extend to theback edge of the proposededge restraint or abut existing structures.

To achieve the best performance from the subgrade it is necessary to scarify the top surface,condition it to the propermoisture content, and thento recompact it to estab-lished relative densities.The moisture content of the soil must be withinallowable limits of the optimum moisture contentand be carefully monitoredto achieve maximum compaction. The subgradesoil should be compacted to at least 95% maximumdensity if they are granularand to at lease 90% maximum density if they are cohesive. Themethod of compaction and compaction equipmentmay vary due to soil typeand size of area being compacted. Figure 9 is a general guide to the

appropriate choice of compaction equipment.Subgrade preparation iscommonly specified in local state and municipalstandards for highway construction. It is alsolikely that the geotechnicalreport will provide recom-mendations on minimumcompaction standards.

Various tests are used to determine the propercompaction and density of the soil. Laboratorycompaction tests to determine proper placementrequirements include:

• Standard Proctor Test,ASTM D 698 Methods forLaboratory CompactionCharacteristics of SoilUsing Standard Effort(12,400 ft-lb/ft3 (600 kN-m/m3)) or AASHTO T9 Test Methods forMoisture-Density Relations of Soils andSoil-Aggregate MixturesUsing 5.5 lb. (2.5 kg)Rammer and 12 in. (305 mm) Drop; and

• Modified Proctor Test,ASTM D 1557 Test Methodfor Laboratory CompactionCharacteristics of SoilUsing Modified Effort(56,00 ft-lb/ft3(2,700 kN-m/m3)) or AASHTOT180 Test Methods forMoisture-Density Relations

of Soils and Soil-Aggregate Mixtures Using 10 lb. (4.5 kg)Rammer and 18 in. (457 mm) Drop.

The latter of these tests is normally used to testmaterials that supportheavier loads for highershear strength.

Field tests which determine soil density provide a method to checkfor conformance to jobspecifications. Three fieldtests are often used:

• Sand Cone Test, ASTM D1556 (AASHTO T191) TestMethod for Density andUnit Weight of Soil inPlace by the Sand ConeMethod.

• Water Balloon Test, ASTMD 2167 (AASHTO T205)Test Method for Densityand Unit Weight of Soil inPlace by the RubberBalloon Method; and

• ASTM D 2922 (AASHTOT238) Test Methods forDensity of Soil and Soil-Aggregate in Place byNuclear Methods (ShallowDepth).

It is important to remember that the maximum density variesbetween samples, and soproper soil identification

30

IntroductionThe in-service performance of the pavementdepends on the preparation and installation ofthe underlying materials. If the materials arenot placed and compacted properly, then theentire brick pavement system may not performas intended. Properly sized joints betweenpavers, completely filled with jointing sand, are essential to complete interlock and for long term performance.

is required to establish the appropriate target density foreach location.

Because brick paving is frequently used as hard landscapingadjacent to major building projects, it is often the case that designers are not familiar with highway testing andconstruction procedures. Therefore, great care must be taken in evaluating and testing the subgrade. For bestresults then, follow the procedures outlined in this Guidealong with the advice of a pavement design professional.

Subbase This Guide considers various types of subbase material asset out in Table 7 and the associated text. These includegraded aggregate, cement- and lime- stabilized soils. Basicassumptions on the types of materials are in the table.Subbase courses should be designed following Part I of thisGuide, or guidelines and specifications of local authorities.

Geotextile fabric may be used to separate the subgrade soilfrom an aggregate subbase, especially in soils subject tomoisture levels near or at saturation. The geotextile willprevent intrusion of the subgrade soil into the bottom ofthe aggregate subbase or vice versa. They must be placedwithout wrinkles and lapped at their edges.

The aggregate subbase course materials should be spreadand compacted in layers. In-place mixing and compactionof the stabilized materials can be carried out, or mixing can be undertaken remotely and the mixture spread andcompacted in layers. The thickness of these layers must be consistent with the capabilities of the compaction equipment. All subbase materials should be compacted to a minimum of at least 95 percent of maximum density.The subbase should also extend at least one layer thicknesspast the edge of the overlying layer to enable adequatecompaction at the edges of the pavement. Typically, thethickness of each layer is approximately 3 to 4 in. (76 to102 mm), but can increase to double these thicknesses ifappropriately heavy compaction equipment is used.

Compaction should be completed as soon as possible after thematerial has been mixed and spread. The profiles should besuch that water is channeled towards drainage facilities.

Base The design tables in this Guide provide options for varioustypes of base course material. These include graded aggre-gate bases, cement-treated bases, and asphalt-treated bases.Thickness of portland cement concrete slabs on an aggregatesubbase is also considered. Details can be found in Table 7and the associated text. Base courses should be designedfollowing Part I of this Guide, or guidelines and specificationsof local authorities.

Geotextile fabric may be used to separate the subgrade soil from the compacted base, especially in soils subject to moisture levels near or at saturation. The geotextile willprevent intrusion of the subgrade soil into the bottom of theaggregate base or vice versa. They must be placed withoutwrinkles and lapped at their edges.

The base course materials should be spread and compacted in layers. The thickness of these layers must be consistentwith the capabilities of the compaction equipment. SeeFigures 10 and 11. All base materials should be compactedto a minimum of 95 percent maximum density. The baseshould also extend at least 6 in. (150 mm) past the edgerestraint if spikes are used to hold the restraint in place.

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Figure 9: Soil Compaction Guide

SOIL

NON-COHESIVESAND

100% 100%75 7550

PERCENT MIXSAND & CLAY

COHESIVE CLAY

RAMMERS

RAMMER PLATES

RAMMER WITH EXTENSION PLATES

VIBRATORY PLATES

VIBRATORY ROLLERS

STATIC ROLLERS

VIBRATION REQUIRED

NORMAL RANGE

TESTING RECOMMENDED

RAMMING REQUIRED

Figure 11: Proper Base Compaction

Typically, the thickness ofeach layer is approximately3 to 4 in. (76 to 102 mm).The surface of the baseshould be close-knit to pre-vent setting bed materialfrom filtering downwardsthrough the base. It mustbe of good quality to avoidfailure due to high stressconcentrations immediatelyunder the wearing surface.

Compaction should be com-pleted as soon as possibleafter the material has beenspread. It is essential thatthe intended surface profileof the base be formed sothat the pavers can beplaced on a uniform thick-ness of bedding sand.

SandSettingBedThe sand setting bed material is spread over thebase in a uniform thickness.The setting bed is notmeant to, and should not,be used to fill in low spotsor bring the pavement tothe correct grade. Thethickness of the setting bed should be 1 in. (25 mm) thick with a tolerance of plus or minus3/16 in. (5 mm) Setting bed thicknesses that areexcessive could lead toshifting of the setting bedmaterial, causing loss ofstrength.

The sand is typically spreadover the base between 1 in.(25 mm) diameter screedrails. These are set to a pro-

32

Figure 10: Leveling Base

moist without being satu-rated. Water should not beadded to screeded sandexcept as a very light mist-ing. Stockpiled materialshould be kept covered.

The screeded bedding sandis vulnerable to environ-mental disturbance fromwind or rain. Care needs to be taken so that watercannot drain back into thebedding sand when it isuncovered or covered withpavers but not vibrated.

BituminousSetting BedThe first step in constructing this system is to apply a tack coat over the base layer toachieve a level of bonding

file to provide sufficientdepth in the uncompactedbedding layer, to account for the reduction from compaction. Screed rails are typically placed 8 to 12 ft. (2.4 to 3.7 m) apart,and at closer centers when a changing grade isrequired. There are severalspecialized screeding systems that enable morerapid installation and resultin less foot traffic on thesand. On some large projects, asphalt pavingmachines have been used to spread the sand.

The setting bed sand shouldnot be spread too far infront of the laying face ofthe pavers to prevent dis-turbance. The sand shouldbe screeded without com-paction to a level slightlyhigher than the final thick-ness of the layer. See Figure12. The sand should be dis-turbed as little as possiblesince the final pavementsurface will reflect any vari-ation. The voids left by thescreed rails should be filledfrom the paver laying faceas work progresses. Thecommon practice of fillingfrom the screeding side canleave localized areas of overcompacted sand, whichresults in subsequent highspots. If the sand is dis-turbed, the area should berescreeded. Prepared areasshould not be leftovernight, unless they areproperly protected from disturbance and moisture.The moisture content of thesetting bed sand should beas uniform as possible, and the material should be

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and moisture protection.The tack coat will generallybe supplied to the site in drums or pails due to the limited area at anyapplication time. The airand substrate temperatureshould be above 50°F(10°C). The materialshould be at a temperatureof about 80°F (27°C) orabove when applied. Acontinuous, uniform coatshould be applied by spraying, squeegeeing orbrushing the material.Typical application rates are 0.05 to 0.15 gallons per square yard (0.19 to0.57 liters per squaremeter), depending on surface texture and porosity. Work should not be carried out in rainyconditions. The tack coatmust cure for 1/2 to 1 hour(until it turns black and is

Figure 12: Compacting Near Edge

dry to the touch) beforeapplying the bituminoussetting bed.

A local asphalt plant supplies the bituminoussetting bed material.Generally only small loads,up to 5 tons (4.5 Mg), are required at one time so that the work can becompleted before the material cools and becomesunworkable. The materialsare mixed at a temperatureof 300 to 325°F (149 to163°C). The mixed materi-al should be delivered tothe site in an appropriatecovered truck. The truckbed should be steel that isclean and a lubricantshould be used to help withdischarge.

Steel screed rails, typically12 ft. (3.7 m) long, are set

String lines or chalk linesmay be used to keep thepattern straight. Straightand true bond lines arenecessary in areas subject-ed to heavy vehicular traf-fic to provide a uniformdistribution of horizontalloads. The spacing of thestring lines should bebased on the contractor’sexperience, size of theproject and speed of lay-ing. It is inadvisable toopen joints above 1/8 in. (3mm) to avoid cutting at anedge. The wider joints arelikely to lead to greatercreep and a reduction instructural integrity.

Whole pavers should belaid first, followed by cutpavers. After the area islaid with whole pavers, itis easy to fill in the spaceswith pavers cut to size. Allpavers should be cut with amasonry saw to produce anaccurate, clean cut. The

up on timber packs to achieve a uniform profile. These aretypically at 10 to 12 ft (3 to 3.7 m) centers, oriented along the profile of the street. When establishing the profile, itis important to allow for the likely compaction of the set-ting bed. The hot material is spread over the surface ofthe tack coat and screeded off to a nominal thickness of3/4 in. (19 mm). Care should be taken to ensure thatrelease agents applied to the screed rails and tools do notcause damage to the bituminous setting bed. The screededpanels are advanced down the street as each screed raillength is completed. To minimize foot traffic on thescreeded material, alternate panels are constructed so thatthe screed rails and timber packs can be removed and theinfill panel screeded using the edges of the two outsidepanels. The infilling of narrow slots where screed railshave been removed should be minimized, as this can resultin a variable density and differential compaction. Screedingshould be undertaken while the material is still hot.Particles of colder material will drag under the screed ruleand result in a rough surface. As the layer is thin it willcool quickly. Once the asphalt sand mixture has cooled toa suitable temperature it is rolled to provide a smooth, uni-form surface. A walk-behind or small ride-on steel drumroller, with a weight of 200 to 300 lbs per ft (300 to 450kg per m) width of drum, should be used. On small proj-ects and in confined locations, a vibratory plate compactormay be used.

There are two different degrees of compacting the bitumi-nous setting bed. In one, the bituminous setting bed islaid and lightly compacted with the roller. This results ina setting bed with an open texture and high void content.In the second system, the bituminous setting bed is morethoroughly compacted during the rolling process. Thisresults in a more closed surface with less texture.

Paver Installation GeneralWork may start from an exact edge or fromthe centerline of the pavement. The paversshould not be forced together, as this canresult in excessively tight joints, which maycause the pavers to chip during installation or compaction. The pavers should be laid inthe desired bond pattern, with a joint widthbetween 1/16 in. (1.6 mm) and 1/8 in. (3 mm)on all sides. Pavers that butt directly againstthe adjacent paver result in chipping as thesystem flexes. Pavers with lugs provide thecorrect gap when they are placed in contactwith each other.

34

blade should have a softbond matrix and a highdiamond concentration inorder to cut clay paverseffectively. A trial areamay be laid out in advanceof work to determine paverpositions to minimize theamount of cutting andmaintain cut pieces of suf-ficient size. A rule ofthumb is to have the mini-mum face dimension of thecut piece not less than thepaver thickness. It is com-mon practice to run one ortwo rows of pavers laid instack bond (sailor course)along edge restraints. Thisfacilitates subsequent cut-ting of pavers and ensuresthat the cut is betweensimilar materials.

A herringbone pattern laidat 45° or 90° to the edgeof the pavement should beused for vehicular applica-tions. A 45° herringbonemay be started along an

Figure 13: 45° Herringbone Installation Pattern

Figure 14: 90° Herringbone Installation Pattern

CHALK LINE

NOSE OF PAVERS

12

34

56

1 2 3 4 5 6 7 8 9 10 11 12 13

14151617

78

910

1112

13

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edge and continue parallelto that edge. See Figure13. A 90° herringboneshould be started, if possi-ble, at an exact corner orthe centerline of the areato be paved. Otherwise, a“pyramid” of pavers shouldbe advanced over the areaalong a line, as in Figure14. If a running bond pattern is used, the paversshould be laid so that their long dimension isperpendicular to the flowof traffic. In all cases, thebond pattern should bechecked periodically to

ensure proper alignment.Slight adjustments can bemade in the thickness ofthe joint, since it is far easier to replace a row ortwo of pavers than toreconstruct an entire area.

Pavers onSand SettingBedThe installer works off ofthe pavers already in place.Felt or other geotextilesshould not be placed direct-ly beneath the brick pavers.Felt does not allow inter-

lock, since the setting bedis not allowed to integratewith the jointing sandbetween the pavers duringcompaction. After thepavers have been placed onthe sand setting bed, thebrick pavement is vibratedby a mechanical platevibrator/compactor. Thefirst pass is done withoutjointing sand spread on thesurface, as shown in Figure15. Prior to subsequentpasses of the compactor,jointing sand is spreadacross the surface beforecompaction, as shown in

Figure 16. The jointingsand should be dry andspread on the pavementuntil the joints appear full.If movement of the paversoccurs as a result of widejoints adopted when thebricks do not have spacers,a light distribution of bed-ding sand over the surfacebefore vibration can bebeneficial. If chipping ofthe pavers occurs, layinggeotextiles material on thesurface before vibrationcan be beneficial.Obviously the initial vibra-tion and placement of the

and full coverage of thebottom of the paver. It isgood practice to roll thesurface of the completedpaving with a heavy rubbertire roller. This willenhance the compaction of the bituminous settingbed if the pavement is tobe used by heavy vehicles,reducing the likelihoodthat rutting will develop in the wheel paths.

When the setting bed ishighly compacted, theadhesive does not pene-trate into the setting bedand the quantity of adhe-sive can be better con-trolled. Troweling is typi-cally used to spread it.The pavers are then setclose to their final posi-

jointing sand should beaccomplished as soon afterplacing the pavers as possi-ble and before any traffic ispermitted on the paving.

A plate compactor with ahigh frequency/low ampli-tude plate, equipped with arubber mat or a rubber-roller mechanical vibrator,is used. Use of a steeldrum roller is likely tocause some cracking of thebricks. If it is used invibration mode, significantdamage can occur. Theplate area should not beless than 2 ft2 (0.19 m2)and produce 3,000 to 5,000lbs. (13.3 to 22.3 kN) ofcentrifugal force.Compaction should notoccur within 6 ft (2 m) ofany unrestrained edge.

Pavers onBituminousSetting BedThe pavers are set on anadhesive spread on thebituminous setting bed.When the setting bed islightly compacted, theadhesive drains down intothe surface texture of thesetting bed. With the lightcompaction the pavers aretypically loose at first sothey can be aligned. Whenthe pavement surface car-ries traffic, the pavers com-press the lightly compactedsetting bed and squeezethe adhesive back to theinterface between the set-ting bed and the pavers.This achieves a good bond

tion, as they become diffi-cult to move when theadhesive hardens.

The adhesive can be coldapplied, but should beabove 70°F (21°C) for bestresults. It is applied at acoverage rate of 30 to 50sq ft per gal (0.84 to 1.2sq m per liter), by brush,squeegee or trowel,depending on its viscosity.The adhesive should bespread at least two hoursbefore setting the pavers.

The brick pavers are placedby hand onto the adhesive.The installer works off ofthe pavers alreadyinstalled. They are placedwith joint widths of 0 to1/16 in. (1.6 mm) to thecorrect laying pattern, andaligned as soon as possibleto form straight lines.Wider joints should be dis-couraged and the paversshould be placed as closetogether as possible whilemaintaining the alignment.When the pavers have lugs,they may be placed in contact with each other for best results and to minimize creep.

Traffic should not be per-mitted on the paving untilthe joints are filled withjointing sand that is stabi-lized. The preferredmethod is to use dry sandand a stabilizer. Dry jointsand is brushed into thejoints in the same manneras for sand set systems.No vibration is used.When the joints are full,the sand is swept off sothat it is level with the

36

Figure 15: Compaction of Brick Pavers, with Protection

bottom of the chamfers orthe top of the pavers. If adry stabilizer is used, it ismixed with the dry sandprior to application. Thedry stabilizer is activatedwith applied water to bindthe sand particles. A liq-uid joint sand stabilizerthat binds the sand parti-cles together, if used, isapplied after the dry sandis brushed into the jointsand the excess swept off. It is sprayed andsqueegeed over the surfaceso that it soaks into the

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Figure 16: Sweeping Joint Sand

joint sand and only a thinfilm remains on the sur-face of the pavers. It isimportant that the stabi-lizer is water based as sol-vents can harm the adhe-sive and setting bed mate-rials. It is possible to wetthe surface of the paversor allow time for the sandto settle to encouragecomplete filling of thejoints. However, the mois-ture should be allowed todissipate prior to applyingliquid stabilizer.

An alternative, and notrecommended process, ismixing cement with dryjoint sand and brushing itinto the joints. No vibra-tion is used. When thejoints are completely filled,the surface of the pavers islightly misted so that thewater penetrates the jointsand hydrates the cement.It is possible that some set-tlement of the joint fillingmaterial will occur so thata second treatment may berequired. Care must betaken to ensure that no

cement is left on the pave-ment surface as stains mayresult. This is particularlydifficult if the pavers havea rough surface texture orare engraved.

TolerancesThe final surface elevationshould be left slightlyabove adjacent pavement toallow for secondary com-paction of the beddinglayer under traffic. It istypical for an additional 1/8

in. (3 mm) of compactionto occur, but local experi-ence should govern. Themaximum variation in levelshould be within ±3/16 in.in 10 ft (± 5 mm in 3 m).Pavers adjacent to drainageinlets and channels shouldbe left slightly higher, butnot more than 3/MR in. (5mm) above it. The edgesof any two adjacent paversshould not differ more than1/8 in. (3 mm) if the pavershave chamfers, or 1/16 in.(1.6 mm) if they havesquare edges. Paver topaver tolerances are meas-ured either chamfer tochamfer or top edge to topedge. The bond line towhich the paver pattern islaid also has dimensionaltolerances. These shouldbe within ± 1/2 in. in 50 ft(± 10 mm in 15 m).

accommodate any consoli-dation. Providing a slightarch to the profile will helpin maintaining a good fit.

MaintenanceAlthough brick paving surfaces are very durable,some routine maintenancemay be necessary.

EfflorescenceEfflorescence, a white powdery substance produced by soluble salts,may be unavoidable on apaving surface. Deicersused on adjacent areas may be deposited onto thebrick pavement, solublesalts may be present withinpaving system components,or salts may migrate fromadjacent soils. Therefore,proper drainage and maintenance are especiallycritical to reduce theamount of efflorescence. If efflorescence does appear on the paving surface, natural weatheringor traffic will usually eliminate it. Efflorescenceshould not be removedfrom the surface with acids. There are proprietary efflorescenceremovers available.

Snow RemovalSnow removal from brickpavements should not present any particularproblem. It can be removedby plowing, blowing orbrushing away the snow.When using plows or shovels there are precautionary measures

that can be taken to preserve the surface character of the brick.Metal blades should be rubber or urethane tippedor mounted on smallrollers. The blade edgeshould be adjusted to aclearance height suitablefor the pavement surface.When hand shoveling,shovel at an angle to the paver edge to avoidcatching it. Avoid the use of any chemicals containing rock salt (calcium chloride) to aid in melting ice. Use of these materials may cause efflorescence.Calcium magnesiumacetate is recommendedfor snow and ice removal.Urea is used to melt ice atmany airports withoutcausing efflorescence, butit is not effective below20 °F (-7 °C). Otherwise, remove snow before it canbe compacted or turn toice. To render icy surfacespassable, use clean sandor ashes on the icy areas.

In ServiceConsiderationsSurface CoatingsColorless coatings, i.e. water repellents, are generally not recommended on exterior brick pavements. See thediscussion in Part II: Materials. If surface coatings are to be applied, the manufacturer’s instructions for applica-tion should be followed.

RepairsAt some time during the life of a flexible brick pavement,repairs or utility work beneath the pavement may requirethe removal and replacement of pavers from the workingarea. When starting repairs, a single brick should beremoved, preferably with a purpose-made tool. It may be necessary to break a few pavers to start the removal.Adjacent pavers are then be removed and stacked nearby to be used again if not damaged. The pavers should becleaned of adhering sand by brushing. Cleaning ofasphaltic material is usually difficult, and it may be necessary to remove pavers set on bituminous setting beds from the site for cleaning with a solvent. Temporary edge restraints should be placed at the perimeter of the removal area.

Excavation of trenches should follow established procedures. Proper compaction of the returned fill material is very important. If the area is too small forproper compaction, stabilized materials, such as concrete,should be used. The compacted fill should be brought upto the proper level. One or two feet (0.3 to 0.7 m) ofpavers around the perimeter of the excavated area shouldbe removed so that accurate levels can be establishedfrom undisturbed work. At all times, vehicular trafficshould be kept at least 6 ft (2 m) away from the workedges.

Setting bed material should be screeded to the propergrade. The setting bed should be compacted and a thinlayer of sand screeded on top. Temporary edge restraintsare removed and the pavers are then laid in the correctbond pattern. Some creep of the pavement may haveoccurred during repairs; therefore, some pavers may haveto be saw cut to fit. Jointing sand should be spread overthe top of the pavers and the system vibrated to the fin-ished level with a plate compactor. Two or three passesmay be necessary to fill the joints. Dependent upon thetype of backfill used in the excavation, it may be appro-priate to set the pavers high of the final surface so as to

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Closing Brick has been used as a paving material for centuries,however, the design and construction of an interlockingflexible brick pavement for heavy vehicular applications isa fairly new concept. This Guide provides designers withinformation on how to design, construct and specify aproperly performing flexible brick pavement. The materialsand construction procedures recommended in this Guideare similar to those used for other pavements.

The information and recommendations in this Guide mustbe used in conjunction with good engineering judgmentand a basic understanding of the properties of brick andrelated construction materials. Information on local materials and local experience should be applied when available.

Appendix ADefinitions of TermsAASHTO (American Association of State Highway andTransportation Officials): National association of highwayofficials.

Base: The layer or layers of specified materials of designed thick-ness placed on a subbase or a subgrade to support the wearingsurface.

CBR (California Bearing Ratio): A measure of the shearstrength or stability of a soil or granular material, expressed as apercentage of the strength of a standard material and measuredby a constant rate of strain penetration machine either in-situ orin a laboratory.

Cement Lime-Stabilization: A technique that improves thestrength or stability of clay soils (subgrades) by the incorporationof portland cement or lime.

Compaction: The process that consolidates the subgrade, subbaseor base; the process by which the brick pavers are settled into thesetting bed during construction and jointing sand is vibrated intothe joints between the pavers to create interlock.

Creep: Horizontal movement of the brick pavers generally causedby the braking actions of vehicular traffic.

Edge Restraint: Resistance to horizontal movement at the edgeof the pavement provided by sufficiently rigid supports.

ESAL (Equivalent Single Axle Load): The representation of thepassage of an axle of any mass (load) by a number of 18-kip (80kN) equivalent single axle loads.

Frost Heave: Localized volume changes that occur in theroadbed soil as moisture collects and freezes into ice lenses.

Geotextile Fabric: Any permeable textile material used to sepa-rate pavement layers.

Heavy Vehicular Traffic: Traffic consisting of high volumes ofheavy vehicles. Heavy vehicles are considered trucks.

Herringbone: A bonding pattern with alternate pavers at rightangles to each other forming a zigzag effect. Generally recom-mended in vehicular traffic applications.

Interlock (Lock-up): The effect of frictional forces, induced bysand beneath and between the brick pavers that inhibits move-ment of the paver and transfers loads between adjacent pavers.

Layer Coefficient: The empirical relationship between structuralnumber (SN) and layer thickness that expresses the relative abili-ty of a material to function as a structural component of thepavement structure.

References1. American Association of State Highway and

Transportation Officials, Guide for Design of PavementStructures, Washington, D.C., 1993.

2. Brick Development Association, BDA Design Note 9,Flexible Paving With Clay Pavers, United Kingdom, Oct.1988.

3. Brick Industry Association, Flexible Brick Pavements:Heavy Vehicular Pavements, Design and Installation Guide,Reston, Virginia, 1991.

4. Clay Brick and Paver Institute, Paver Note One, Specifyingand Laying Clay Pavers, Australia, Aug. 1989.

5. Clifford, J.M., Segmental Block Paving in Southern Africa -A Review and Structural Design Guide, National Institutefor Transport and Road Research, Republic of SouthAfrica, Sept. 1986.

6. Knapton, J. and Barber, S.D., UK Research into ConcreteBlock Pavement Design, 1st Concrete Block PavingConference, Newcastle-upon-Tyne, United Kingdom, 1982.

7. Knapton, J. and Mavin, K.C., Design Manual 1, ClaySegmental Pavements, Clay Brick and Paver Institute,Australia, Jan. 1989.

8. National Stone Association, Flexible Pavement DesignGuide for Roads and Streets, Jan. 1985.

9. Pavement Consultancy Services, Structural Design ofRoads and Streets using Concrete Block Pavements,National Concrete Masonry Association, Herndon, VA,Jan. 1989.

10. The Total Concept, Blockleys, plc, United Kingdom, 1988.

11. Understanding Soil Compaction, J.I. Case Co., Racine, WI,1988.

12. Walsh, I.P., A Comparative Field Study of the Performanceof Brick Pavers, Chemistry and Industry, Nov. 1985.

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Appendix BReferenced StandardsAASHTO MPI Specification for Performance Graded Asphalt

Binder

ASTM C 33 Specification for Concrete Aggregates

ASTM C 67 Test Methods of Sampling and Testing Brick (AASHTO T32) and Structural Clay Tile

ASTM C 144 Specification for Aggregates for Masonry Mortar

ASTM C 418 Test Method for Abrasion Resistance of Concrete by Sandblasting

ASTM C 902 Specification for Pedestrian and Light Traffic Paving Brick

ASTM C 1272 Specification for Heavy Vehicular Paving Brick

ASTM D 698 Test Methods for Laboratory Compaction (AASHTO T99) Characteristics of Soil Using Standard Effort

(12,400 ft-lb/ft3 (600 kN-m/m3))

ASTM D 977 Specification for Emulsified Asphalt

ASTM D 1073 Specification for Fine Aggregate for Asphaltic Paving Mixtures

ASTM D 1556 Test Method for Density and Unit Weight of Soil (AASHTO T191) in Place by the Sand Cone Method

ASTM D 1557 Test Method for Laboratory Compaction (AASHTO T180) Characteristics of Soil Using Modified Effort

(56,000 ft-lb/ft3 (2,700 kN-m/m3))

ASTM D 1883 Test Method for CBR of Laboratory Compacted (AASHTO T193) Soils

ASTM D 2167 Test Method for Density and Unit Weight of Soil (AASHTO T205) in Place by the Rubber Balloon Method

ASTM D 2844 Test Method for Resistance R-Value and (AASHTO T190) Expansion Pressure of Compacted Soils

ASTM D 2487 Standard Classification of Soils for Engineering (AASHTO M145) Purposes (Unified Soil Classification System)

ASTM D 2922 Test Method for Density of Soil and (AASHTO T238) Soil-Aggregate in Place by Nuclear Methods

(Shallow Depths)

ASTM D 2940 Specification for Graded Aggregate Material for Bases or Subases for Highways or Airports

ASTM D 3381 Specification for Viscosity-Graded Asphalt Cement for Use in Pavement Construction

ASTM E 303 Method for Measuring Surface Frictional Properties Using the British Pendulum Tester

Light Vehicular Traffic: Traffic consisting of automobiles orlighter vehicles.

Lug (Spacer or Nib): A small projection on paver edges, formedduring manufacturing, designed to provide a positive gap forjointing sand and to minimize chippage of the pavers duringinstallation and in service.

R-value: A measure of strength of a soil material.

Resilient Modulus (MR): The modulus of elasticity of roadbedsoil or other pavement material.

Saturation Coefficient: The ratio of the weight of waterabsorbed by a masonry unit during immersion in cold water tothe weight absorbed during immersion in boiling water. An indi-cator of the probable resistance of brick to freezing and thawing.

Serviceability: The ability of a pavement to serve traffic thatuses the facility at the time of observation.

Setting Bed (Bedding Course): The layer of specified materialsin which the brick pavers are bedded, taken together with thepavers to form the wearing surface.

Skid Resistance: A measure of friction between the pavementand a tire assessing the risk of vehicles skidding on the pavementsurface.

Structural Number (SN): An index number derived from theanalysis of traffic, roadbed soil conditions, and environmentwhich may be converted to thickness of flexible pavement layersthrough the use of suitable layer coefficients related to the typeof material being used in each layer of the pavement system.

Subbase: The layer or layers of specified materials of designedthickness placed on a subgrade to support a base.

Subgrade: The top surface of existing soil or prepared soil uponwhich the pavement system is constructed.

Wearing Surface: The layer of brick pavers and setting bed,which serves as the paving surface, and modeled as a single layer.

Appendix CGuide SpecificationSection 02780Flexible Brick PaversPART 1 - GENERAL1.01 SECTION INCLUDES

A. Brick PaversB. Sand Setting Bed

orB. Bituminous Setting Bed

1.02 RELATED SECTIONSA. Section 02710 - Bound Base Courses B. Section 02340 - Soil StabilizationC. Section 02720 - Base CoursesD. Section 02750 - Portland Cement Concrete PavingE. Section 02770 - Curbs

1.03 QUALITY ASSURANCEA. Brick Pavers: Test in accordance with ASTM C 67.B. Mock-up

1. Mock-up shall be 10 ft. by 10 ft.2. When required, provide a separate mock-up for each

type of brick and bonding pattern.3. Do not start work until Architect/Engineer/Landscape

Architect has approved mock-up.4. Use mock-up as standard of comparison for all work.

C. Installer: Company with at least three years experience in installing brick pavers.

1.04 SUBMITTALSA. Submit samples of brick pavers to be used in

construction, showing range of colors, textures, finishes and dimensions.

B. Submit sieve analysis for grading of bedding and jointing sand.

C. Test reports for masonry units from a qualified testing laboratory.

1.05 DELIVERY, STORAGE AND HANDLINGA. Store brick pavers off the ground to prevent

contamination, staining or other defects.B. Cover sand with waterproof covering to prevent exposure

to weather. Weigh down covering to prevent removal by wind.

C. Store different types of aggregates separately.

1.06 ALLOWANCESA. Refer to Section 01210 - Cash Allowances for the Cash

Allowance Sum applicable to this section.B. This allowance includes purchase and delivery of brick

pavers. Specially-shaped brick pavers shall have a separate allowance.

1.07 PROJECT CONDITIONSA. Do not install sand or pavers during rain or snowfall.B. Do not install frozen materials.

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1.08 REFERENCESA. ASTM C 33 - Concrete AggregatesB. ASTM C 67 - Method of Sampling and Testing Brick and

Structural Clay TileC. ASTM C 144 - Aggregate for Masonry MortarD. ASTM C 1272 - Heavy Vehicular Paving Brick

PART 2 - PRODUCTS2.01 BRICK UNITS

A. Paving Brick: ASTM C 1272, Type F, Application PX [PS] [PA], _________ as manufactured by _________.Size ________x_________x________.

2.02 SANDA. Bedding Sand: ASTM C 33

*** BEDDING SAND CAN BEUSED AS JOINTING SAND. ***

B. Jointing Sand: ASTM C 144

PART 3 - EXECUTION3.01 EXAMINATION

A. Examine base for correct grade and elevations.B. Examine edge restraints for proper location.

3.02 INSTALLATION OF FLEXIBLE PAVINGA. Spread bedding sand evenly over base and screed to

1 in. thickness ± 3/16 in. The screeded sand should not be disturbed.

B. Lay pavers in the pattern(s) as indicated in the drawings. Maintain straight lines.

C. Joints between the pavers shall be approximately 1/16 to 1/8 in. wide.

D. Fill out area with cut pavers along edges or interruptions.

E Vibrate the brick pavers into the sand using a plate vibrator capable of 3000 to 5000 lbs. centrifugal force. The plate vibrator shall have a rubber mat or roller feet to avoid chipping the pavers.

*** LUGS, CHAMFERS OR ROUNDED EDGED PAVERS REDUCE CHIPPING ALONG THE TOP EDGES OF THE PAVER. ***

F. After the first pass of the plate vibrator, sweep jointing sand into the joints and vibrate again. Repeat the process until the joints are full.

G. Do not permit traffic on the pavers until the joints are filled.

H. Do not vibrate within six feet of unrestrained edges.I. Sweep excess sand off of pavement.

3.03 TOLERANCESA. The final surface elevation shall be flush with adjacent

construction.B. Maximum variation in level shall be within ± 3/16 in.

in 10 ft.

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NOTES

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NOTES

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11490 Commerce Park DriveReston, VA 20191

(703) 620-0010(703) 620-3928 fax

e-mail: [email protected]: www.brickinfo.org

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