10TH AAPA INTERNATIONAL FLEXIBLE PAVEMENTS CONFERENCE

SESSION 2 - INNOVATION 3

Emulsion Treated Bases: a South African Perspective

BMJA Verhaeghe, Project Manager, CSIR Division of Roads and Transport Technology, South Africa

H Theyse, Senior Researcher, CSIR Division of Roads and Transport Technology, South Africa

RM Vos, Technical Director, SABITA, South Africa

EMULSION-TREATED BASES: A SOUTH AFRICAN PERSPECTIVE

BMJA Verhaeghe Pr.Eng, BSc(Eng), MSc(Eng) Project Manager, CSIR Division of Roads and Transport Technology, South Africa

H Theyse Pr.Eng, BSc(Eng) Senior Researcher, Division of Roads and Transport Technology, South Africa

RM Vos Pr.Eng, BSc(Eng) Technical Director, Sabita, South Africa

1. INTRODUCTION Emulsion treated bases (ETBs) have been used successfu l ly as part of pavement structures on South African roads carrying low to high volumes of traffic. I n fact, the results of a performance audit conducted on 53 sections, including sections which carried in excess of 30 m i l l ion ESALs over a period of 15 years , showed no evidence of fai lu res attributab le to the ETB layer.

ETBs are defined as new or reclaimed gravels (often of a qual ity not su itable for use as a base cou rse) treated with a small percentage of bitumen emulsion (usual ly less than 2 , 5 per cent, depending on the qual ity of the parent materia l) so as to produce a base course qual ity type of materia l . The addition of emu lsion reduces the internal friction of the grave l , thus improving its compacted density and its workabil ity. It also reduces water susceptib i l ity, al lows the layer to be trafficked sooner and, by enrichment of the upper ETB layer during construction, usually el iminates the need for prim ing . The above benefits , together with the abi l ity to use local or in ­s i tu materia ls , thus obviating the need to hau l i n su itable base course material over long d istances, make the addition of small percentages of emulsion attracti ve from the point of view of costs .

In the paper, the following topics wi l l be addressed : a historical overview on the use of ETBs in South Africa, structural design, economic considerations, ETB mix design and the construction of ETBs.

2. HISTORICAL OVERVIEW Over the past 30 years , great success has been achieved by South African road engineers with the technique of adding smal l quantities of b i tumen emulsion to gravels of fai r to good qual ity. Some examples of the successful application of ETBs on National Roads are g iven in Table 1.

Table 1: Performance data of selected-ETBs on National Roads

Road Length Age Traffic Visual PSI Rut depth number (km) (1997 base) class condition i ndex (mm)

N 1/13 55 17 ES9 88 3 ,6 5 N 1/14 20 18 ES9 88 3 ,9 5 N 1/14 70 18 ES9 79 3 , 8 5 N2/16 15 15 ES9 78 3 ,1 6 N12/19 26 23 ES10 90 3 ,6 2

Traffic class : ES9: 10 - 30 x 106 ESALs (80kN) ES10: 30 - 100 x 106 ESALs (80 kN)

During 1981, a cracked cement-treated base (CTB) pavement on Main Road 37 near Cape Town was rehabi l i tated by us ing a mi ll ing and recycl ing procedure. As part of this p roject, two experimental sections were bui lt using a technique of mi l l ing and recycl ing half the depth of the cracked CTB. On one of these sections (Section 1), the material was treated with a low

percentage of emulsion (1,4 per cent), whi le the other section (Section 2 ) was recompacted without any emu lsion being added. Heavy Vehicle Simulator (HVS) tests were conducted on both sections and the fol lowing conclusions were d rawn from the observations (Horak et ai, 1984):

Benkelman beam deflections and radi i of curvature on Section 1 were respectively lower and h igher than those on Section 2 ;

• less permanent deformation was measured in the HVS test on Section 1 (th is was also reflected in DCP resu lts , where greater bearing capacity and greater resistance to shear forces were measured ), and

• the emulsion treatment of Section 1 resulted in a considerable reduction in the moisture sensitivity of the treated layer as a resu lt of lower permeabi l ities and the binding of the f ines.

On account of the above, the predicted l ives for Section 1 and Section 2 were estimated to be between 3 and 12 and between 0,8 and 3 mi ll ion equ ivalent 80 kN axle loads, respectively.

The above confirmed earl ier f indings from Spottiswoode (1979) who also stated that a 30 per cent reduction in deflections cou ld be expected on the completed road . Spottiswoode stated that, in addition to other advantages: • emulsion treatment would improve the res istance to reflective cracking; • construction time and costs would be reduced by reducing the compactive effort and by

e l im inating the s lushing process (for G 1 materials) and the need for p riming; • prior to being sealed, the ETB layer can withstand heavy traffic for extended periods, and

that • emu lsion treatment is a cost-effective rehabi l itation option.

Between 1988 and 1992, the Southern African Bitumen Association (Sabita) sponsored a research programme the objective of which was the development of national ly acceptable mixing, testing and evaluation methodologies for G ranular Emu lsion M ixes (GEMs). Whereas the emphasis of this project was on the upgrading of substandard materials to base standards by the addition of relatively h igh percentages of emulsion (residual bitumen contents in excess of two per cent), the project nevertheless attempted to formal ize the design procedures of ETBs. In October 1993, Sabita (Sabita, 1993) launched a design manual for GEMs with recommended design procedures for stabi l ised GEMs (h igh emuls ion contents) as well as for modified GEMs (low emulsion contents; s imi lar i n concept to ETBs).

The publ ication of the G EMs design manual , however, d id not address al l the needs identified by the road bui ld ing industry. Although the ETB technology had proved itself in the f ield, there was st i l l a· number of unknown factors which made it d ifficult for road agencies or their representatives to specify ETBs as part of their works. Some of the main problems were : • the sh ift between properties at the design stage and those in the f ield ; • the lack of rel iable performance indicators; • that constructibi l ity issues and acceptance criteria were not well developed/documented,

and • that the potential advantages of the use of emulsions were not adequately addressed.

As a result of the above, Sabita launched a project i n 1 996 with the objective of broadening the range of appl ication of ETBs as a competitive basecourse material in both rural and urban appl ications by extending the design scope of the cu rrent technology and entrenching it in p ractice. The aim of the above p roject was to provide • gu idel ines on structu ral design ; • economic gu ide l ines; • gu idel ines on material design, and • guide l ines on constructib il ity based on best practice and complemented by additional activities in order to refine the technology. The above wi l l be addressed in this paper.

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3. STRUCTURAL DESIGN Two d ifferent pavement design approaches were investigated in the process of developing the gu idelines set in this paper for the des ign of pavements incorporating emulsion-treated material. Regardless of the approach fol lowed, the aim of structural pavement design remains the optimal util ization of the individual and combined strengths of all the materials to provide a pavement that wi l l endure the traffic load imposed on it. Different pavement structures designed for the same traffic load , may then be compared economical ly to determine the most appropriate design . It is , however, important to real ise that the anticipated traffic load for which a pavement is designed, is expressed in terms of a number of standard axles and referred to as the bearing capacity of the pavement. I n general a pavement may therefore be designed for a specific bearing capacity, regardless of the composition of the actual traffic spectrum it wi l l be subjected to.

Mechanistic-Empirical Design Approach

A mechanistic-empirical design method al lows the designer some latitude, in that designs slightly outside the domain in which the method was developed may be investigated. Loading conditions may, for instance, be varied somewhat to investigate the effect on expected performance and new materials may be incorporated in the design method with less data than would normally be required by a purely empirical method. The d iagram in Figu re 1 il lustrates a basic mechanistic­empirical design process.

Material Input Parameters: • Resilient properties • Strength properties Load Characterization

Structural Analysis Model: Pavement Response

0&&

Pavement Performance Model Transfer Function

Figure 1: Mechanistic design flow diagram

There is, however, a number of prerequisites for incorporating a new or fairly u nknown material in such a design p rocess :

• The basic behaviour of the particular material i n question should be wel l understood . This does not imply that the ful l behavioural pattern or the timescale of the total l ife cycle should be known , but requ ires at least some general description of how the material is expected to behave in terms of some resi l ient, strength and performance characteristics. If th is description fits in with some of the behavioural models for wel l known materials already i ncluded in the design method, the process for developing a model for the new material could be s imp l ified and accelerated .

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• Once the appropriate input parameters have been decided upon by considering the expected behaviour pattern and fai lure mechanisms for the new material , representative values of these parameters should be obtained for the particular material type. These input parameters wou ld typically include the resi l ient properties of the material and some strength parameters related to the mode of fai l u re of the material .

• A well establ ished performance model (transfer function) relating the calcu lated stress condition in the different pavement layers to the expected performance of the d i fferent material types should be avai lable . I n this case the performance i s defined as the number of stress/strain repetitions that can be sustained by the material at that particu lar stress/strain leve l unti l a certain terminal condition is reached.

To be able to incorporate an emulsion treated material i n a mechanistic-empirical method , the above three conditions would have to be satisf ied.

Draft TRH4 (CSRA, 1996) describes the bas ic behaviour of th ree generic material types commonly used for pavement structu ral layers in South Africa. The South African Mechanistic Design Method (SAMDM) (Theyse et ai, 1996) contains design models for these materials . These are granular materials, l ightly cemented materials and hot-mix asphalt. Of these three material types, the l ightly cemented material seems most l ikely to be equivalent to an emulsion­treated material in terms of general behaviour, although the timescale for the ful l l ife cycle may differ. The general behaviour and the res i l ient and strength parameters for these two material types are therefore d iscussed in more deta i l .

Granu lar pavement layers may fail because of a rapid shear deformation of the layer under extreme load and/or moistu re conditions within a few load repetitions or may gradual ly deform at a steady rate under repeated loading. Both these modes of fai lu re are , however, bel ieved to be related to the ratio between the appl ied shear stresses and the shear strength of the material under the prevai l ing conditions of moisture and density. This ratio is also known as the Safety Factor for granular materials. The shear strength of granular road bu i ld ing materials is quantified by the cohesion (c) and internal angle of friction (cI». Once these values are known for a particular material , the safety factor may be calcu lated under the design load conditions . The SAMDM provides a performance prediction model relating the safety factor to the number of load appl ications that can be sustained at that level of the safety factor. In addition to the shear strength parameters , the resi l ient properties of the material must also be known . The effective elastic modu l i of granu lar materials are general ly lower than those of l ightly cemented and asphaltic materials and are model led as constant values for the duration of the pavement l ife. Typical values range from below 100 MPa for a relatively poor material to an average of about 450 MPa for a well supported G1 materia l .

The behaviour of a l ightly cemented material is more complex than that o f a granular materia l . The l ightly cemented material starts off with a relatively high effective modulus immediately after construction , typ ically in the range of 3000 to 4000 MPa, with the cemented layer acting as a slab. These values are soon reduced to a range of 1 500 to 2000 MPa at the onset of the effective fatigue l ife phase with the layer being broken down to blocks with d imensions 1 to 5 times the layer th ickness. During the effective fat igue l ife phase, the effective e lastic modu lus of the l ightly cemented layer is further reduced to values in the order of 200 to 500 MPa, with the material being broken down to particle s izes less than the thickness of the layer. This last phase is refe rred to as the equivalent granular phase. These values may decrease even further to between 50 and 200 M Pa when moisture enters the layer. Once water enters the pavement during the equivalent g ranu lar phase, there is a rapid deterioration of the pavement, with pumping and deformation taking place. The SAMDM provides a performance prediction model to predict the duration of the effective fatigue l ife phase from the ratio of the appl ied horizontal tensile strain at the bottom of the cemented layer to the strain at break, 8b of the cemented material .

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A l ightly cemented material may also exh ibi t crushi ng fai l u re when the applied vertical stress at the top of a l ightly cemented base layer is very h igh . The SAMOM provides performance prediction criteria for this mode of fai lure of l ightly cemented material , based on the ratio of the appl ied vertical stress to the Unconfined Compressive Strength (UCS) of the materia l . The strength parameters requ i red for l ightly cemented material are therefore the strain at break, 8b and the UCS values.

Dynamic Cone Penetrometer Design Approach

The Dynamic Cone Pel)etrometer (OCP) (Kleyn, 1 984) desig n method is basically an empirical design method in essence simi lar to a CSR cover design approach . The OCP is mainly used for the evaluation of existing pavements and the processing and interpretation of OCP-data is wel l advanced in South Africa. The OCP design method evolved from the concepts defined during the process of developing the data interpretation procedures and was veri fied with a number of HVS tests.

The former Transvaal Roads Department's pavement des ign catalogue was based on a OCP design approach. All the pavement structu res i ncluded in the d raft TRH4 design catalogue (CSRA, 1996) were designed with the SAMOM and verified with the OCP design approach. The resu lts obtained from these two design approaches agreed wel l (Theyse, 1 995).

The main concepts involved in the OCP design approach and the input parameters requ ired by this design approach are : • The OCP penetration rate, ON (mm/blow). Typical ON-values for d i fferent road bui ld ing

materials are listed in Table 2 , and Figure 2 i l lustrates the relationship between ON , CSR and UCS which was developed by Kleyn. A typical OCP penetration rate is therefore required for any new material to be introduced in the design method . The number of blows requ i red to cause the OCP cone to penetrate to a certain depth of material is referred to as the OSNd-value, the subscript "d" indicating the depth of material penetrated . An empirical correlatio n has been developed between OSN aoo and the bearing capacity of a pavement.

a e yplca T bl 2 T .

I OC P t r pene ra Ion ra es

Description of material Material specifications (CSRLAB & UCSLAB)

G 1 : C rushed stone 86 - 88 % SO

G2: Crusher run 100 - 102 % Mod AASHTO

G3: Crusher ru n 98 % Mod AASHTO

G4: Natu ral gravel CSR > 80

G5: Natu ral gravel CSR > 45

G6 : Natu ral gravel CSR > 25

G7: Natu ral gravel CSR> 15

G8 : Natu ral gravel CSR> 10

G 9: Natu ral gravel CSR > 7

G 10 : Natu ral gravel CSR > 3

C3: Cemented gravel UCS: 1.5 - 3 .0 MPa

C4: Cemented gravel UCS: 0 .75 - 1 .5 MPa

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or roa d t ' I ma ena s

OCP : ONDep (mm/blow)

1.4 - 1. 1

1 . 8 - 1 .4

< 2.0

< 3 .7

< 5.7

< 9. 1

<14

<19

< 25

< 48

1. 8 - 0 .6

3 .4 - 1. 8

OCP derived E-values (MPa)

780 - 1 000

600 - 780

> 535

> 278

> 176

> 107

> 68

> 50

> 37

> 18

600 - 2 000

300 - 600

• The relative contribution of the di fferent pavement layers to the strength of the total pavement system, also referred to as the pavement strength balance. The pavement Balance Number, "B" is related to Standard Balance Curves (SBCs) and expresses the pavement strength contained in the upper 12 ,5 per cent depth of the pavement (DSN12•5%) as a percentag e of the strength of the total depth of pavement (DSN100%). A high B-value would therefore imply that most of the pavement strength is situated i n the top 12 ,5 per cent of the depth of the pavement. The pavement strength balance for a particular pavement is obtained by comparing the actual balance p rofi l e with the SBCs and selecting the best f it SBC based on the min imum area, "A" between the SBC and the actual balance. Experience has shown that pavements with a B-value betweet:l 35 and 45 perform best and de Beer (1991 ) showed that the modular ratios between successive layers are virtually constant for these B-values . The d eviation "A" of the actual balance profi le from the best fit SBC should preferably not exceed a valu e of 3000. A typ ical p lot of the strength balance for a pavement is shown in Figure 3 .

• During the DCP design process, typical DN-values are therefore assigned to the different material types used in the layers of a potential design . The number of blows requ i red to penetrate each of the individual layers are then calculated from the p roduct o f the DN­value and thickness o f the layers . The total number o f blows requ i red to penetrate the fu ll pavement depth (800 mm) may therefore be calculated and the bearing capacity of the design may be predicted from the relationship between DSNaoo and bearing capacity. Layer thicknesses and material qual ity are then adjusted in an iterative process unt i l the requ ired bearing capacity is achieved whi le ensuring that the pavement balance remains within the prescribed l imits.

� ::s � :J I-caR I "0 c <1l -ucs ' � ___ =i a: �

0.1 10 100 DCP Penetration. ON (rrm'blow)

Figure 2 : DCP DN , CBR and UCS correlation

Curing Behaviour of Emulsion Treated Material

Data on the curing behaviour of emulsion and cement treated material were obtained from DCP tests done on a construction project on road R2388. The curing behaviou r of the l ightly cemented material wi l l be d iscussed in paral lel to the discussion on the curing behaviour of the emulsion treated material in order to highl ight som e simi larities in the curing behaviour of these two materials .

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Pavement Balance Cun�s \,ith optimum balance em�lope

Percentage of DSN800 20 40 60 80

• Structure Balance Curve • Best Fit Standard Balance Curve

100

Figure 3 : OCP standard balance curves

Table 3 provides a summary of the ON , CBR and UCS values at 7 and 2 8 days for the cemented and the emulsion treated materials. If the data in Table 3 are considered in terms of OCP strength parameters, the curing of the material to which 0 ,6 per cent residual bitumen and 1 per cent cement were added is similar to the curing behaviour for a 3 per cent cement-treated material in terms of the values of the strength parameters achieved after 7 and 28 days. OCP tests done 60 days after the construction of the ETB showed l ittle additional strength gain compared to the 28 day resu lts. TRH 14 (CSRA, 1989) specifies the range of UCS values for a C4 material after 7 days' cu ring at 97 per cent of mod. AASHTO density as 500 to 1000 kPa and at 1000 to 2000 kPa for a C3 material . The OCP-derived UCS values for the ETB agree well with these values.

Table 3: Summary data for the fie ld curing behaviour of cemented materials and ETBs (road R2388)

Age Parent Material and Residual Binder ON CBR (%) UCS (kPa) (days) (mm/blow)

7 Sandstone gravel with 3 % cement 2,9 1 05 903

Sandstone gravel with 0,6 % residual bitumen 3,2 95 827 and 1 % cement

28 Sandstone gravel with 3 % cement 2,3 1 39 1 1 49

Sandstone gravel with 0,6 % residual bitumen 2, 1 1 56 1 267 and 1 % cement

The OCP penetration values l isted in Table 2 for a C4 material agree well with the ON-value l isted in Table 3 for the ETB at both 7 and 28 days' cu ring . The ETB therefore seems to be very simi lar to a C4 l ightly cemented material in terms of strength parameters and curing behaviour.

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DCP tests conducted on long-term pa vement performance (L TPP) sections

Several types of f ield tests were conducted on a number of L TTP sections during 1 989/90 as part of an in itial series of tests initiating the process of monitoring the long term performance of pavements with emu lsion-treated base layers. Table 4 provides a summary of the average penetration rates for the emulsion-treated base layers per L TTP section .

In general, the OCP penetration rates are in the order of 0 ,5 to 0 ,7 mm/blow, with the exception of the resu lts on P66-1. These values are substantial ly lower than those l isted in Table 3. The values l isted in Table 3 were, however, measured 28 days after construction whi le the OCP tests on the L TTP sections were conducted several months after construction . A fu rther strength increase may have occurred over that period of t ime. The amount of cement or l ime added to the base layers of the L TPP sections is not known and cou ld have had an inf luence on the strengths of these layers. These two factors may explain the lower OCP penetration rates and higher material strengths for the L TPP sections compared to those on road R2388 .

Table 4 : Summary of OCP penetration data for the ETB layers of L TTP sections

Section description Residual binder content Average OCP penetration rate

N 7-7, Springfontein 1,0% 0,52

N3-4, Nottingham Road 1,0% 0,46

N 1-1, Kraaifontein 1,0% 0,53

M R2 7, Stel lenbosch 0 ,8% 0,56

N2-16, Ea�London 1,0% 0,66

P66-1, W epener 0 ,9% 1,60

Pavement design catalogue

Based on previous f indings, OCP penetration, CBR and UCS valu es were suggested for design purposes for three d i fferent emu lsion-treated material categories . These are g iven in Table 5 . Although very l ittle data o n the effective resi l ient modulus of ETBs are available, values between 1000 and 3000 MPa seem to be appropriate at the early stages of trafficking .

Table 5 : Suggested OCP strength parameters for emulsion-treated material

Material Age (days) OCP ON OCP CBR (%) OCP UCS Code (mm/blow) (kPa)

ETB3 7 3 ,2 > 100 > 800

28 2 , 1 > 150 > 1200

ETB2 7 2 , 1 > 150 > 1200

28 1,2 > 300* > 2100

ETB1 7 1,2 > 300* > 2100

28 0 ,7 > 400* > 3000

* At these values the DCP DN, CBR and UCS relationship levels off (Figure 2) and the CBR value may not be an appropriate parameter at such high strengths.

In terms of in itial strength, stiffness and behaviour under accelerated repeated load test ing , the behaviour of emulsion-treated materials closely resembles that of cement-treated materials. This, however, does not imply that the performance of these two material types would be simi lar.

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Both materials would start off at more or less the same level of strength with a s imi lar d eterioration pattern , but the t ime scale during which this deterioration takes place may d iffer. Fu rthermore, although the general trend in deteriorat ion, as far as stiffness and physical condition is concerned, is simi lar for both materials , the resu lts may not be the same. It has been stated by practit ioners that an emulsion-treated material wi l l not pump f ines to the road surface under traffic when wet. This would certain ly happen once a cement treated base has broken down to an equivalent granular state. In order to model the deterioration of ETBs, input data from pavement management systems was used .

I n Figure 4, a pavement design catalogue for ETB pavements i s shown . This catalogue i s based on the DCP design approach. The d ifferent road categories in the catalogue relate to d i fferent approximate design rel iabi l ity values' for d ifferent levels of service provided . The concept of approximate d esign rel iabi l ity is , however, l inked to the SAMDM and not to the DCP design method. Some eng ineering judgement was therefore necessary to obtain the same transition in pavement d esigns between road categories as was obtained for the draft TRH4 pavement d esign catalogue (CSRA, 1996). Appendix A contains some extracts of the TRH4 pavement d esign catalogu e for comparison .

4. ECONOMIC CONSIDERATIONS The addition of low percentages of emulsion to granu lar materials can be economically very effective for the fol lowing reasons:

• If used in rehabil itation, the addition of emulsion enables the in-situ materials to be used to their fu l l benefit and thus el iminates the need for the removal of the present material and its replacement by new materia l . Savings would be g enerated in terms of material costs , hand l i ng costs , haulage costs and t ime.

• The addition of emulsion would enable the layer to be opened soon after completion of construction . Savings would be generated in terms of reduced road user delay costs and of the costs for the construction of deviations .

• By enriching the upper part of an ETB layer (ct. Section 6), the need for priming would be el im inated .

• By addition of emulsion, better compaction is achieved ( i .e. greater densities), the layer wou ld be rendered less moisture sens itive and, therefore, improved performance ( i .e. longer structu ral l i fe) would be expected .

To i l lustrate the above, the total cost of the rehabi l itation of national road N12, Section 18 with ETB was approximately one-thi rd of the cost of the three non-ETB alternatives which were considered . This section of the N 12 has carried in excess of 30 mi l l ion ESALs since it was rehabi l itated 23 years ago (cf. Table 1). I n Appendix B , the present worth of costs (PWOC) of typical pavement structu res (ct. F igure 4 and Appendix A) are compared . The PWOC excludes potential savings in the re-use of materials, hau lage costs, user delay costs and the cost for the construction of deviations. It can be seen from the appendix that, in almost al l cases, the PWOC of ETB pavements are on par or less than that of the granu lar or cemented alternatives, which demonstrates that ETB pavements can be very cost-effective.

5. ETB MIX DESIGN The mix design process for materials treated with small percentages of emulsion (less than three per cent) is based on the fol lowing (Verhaeghe et ai, 1997a): i . Characterization o f materials to be used in ETBs i i . Determ ination o f the optimum moisture content (OMC) i i i . Preparation o f samples , where the amount o f residual bitumen varies from 0 to 2 per

cent in increments of 0 ,5 per cent, but where the optimum moistu re content (hydroscopic water, emu lsion water and compaction water) remains u nchanged

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EMULSION TREATED BASES

PAVEMENT CLASS AND DESIGN BEARING CAPACITY (80 kN AXLES/LANE)

ROAD CATEGORY ES1 ES2 ES3 ES4 ES5 ES6

O,1-0,3x104 O,3-1,Ox104 1,O-3,OX104 3,O-10x10 4 O,1-0,3x10 6 O,3-1,Ox10 6

A: Major interurban freeways and roads. (95 % approximate design reliability)

B: Interurban IS '�'100 ETB2

collectors and major � 150C4 rural roads. (90 % approximate

m' design reliability) �:� 125 ETB2 020 150G5 . �.

C: Llightly trafficed S ms I

S rn 100ETB3 '�. 100 ETB2 ' ? ' 100 ETB2 rural roads and :�� 150G6

'0' 125 C4 strategic roads.

�o2 150G6

(80 % approximate design reliability)

D: Light pavement S1 S1

structures, rural [Hj

100 ETB3

rn

100 ETB3

access roads. ' ? ' 100 G6 ��� 125G6

(50 % approximate design reliability)

-

Symbol A denotes AG, AC , OR AS. A O, AP may be recommended as a surfacing measure for improved skid resistance when wet or to reduce water spray

S denotes Double Surface Treatment (seal or combinations of seal and slurry) S1 denotes Single Surface Treatment * If seal is used, increase C4 and G5 subbase thickness to 200mm.

ES7 ES8 ES9 1,O-3,Ox10 6 3,O-10x106 10-30x106

�

i

�� 125 ETB1 � ... j 250 C4

lin'" S*/30A � 40A � 125 ETB2 � �� 125 ETB1

� 150 C4 � 200C4 Lm �

m "130' m 40A

• 0' • �� 150 ETB2 � 150 ETB1

020 150G5 � 150 C4 • o· lJ:Zl

c=J Most likely combinations of road category and design bearing capacity.

Figure 4 : Pavement d esign catalogu e for pavements with emulsion-treated base layers

r--------�

r 1997 I

ES10 30-100x10 6 Foundation

rrn W 150 G7

• 0'

W 150G9 • o· o· a G10 � o·

�� 0'0 150 G9 � 0'0

WG10

iv. Compaction in accordance with the standard mod ified AASHTO method at room temperature

v. Curing of samples (24 hours at ambient temperatures fol lowed by 48 hours' oven curing at 40°C)

vi . Determination of CBR and UCS after 4 and 6 hours ' soaking , respective ly vi i . Determination of opti mum residual bitumen and optimum f lu id contents vi i i . Use of the rapid compaction control device (RCCD) as an addit ional too l for qual ity

control and to establ ish when the ETB can be opened to traffic .

STEP 1: Characterization of the parent material to be used in ETBs

A sieve analys is should be carried out and the AUerberg l imits determined on the parent material . If cement-treated (CTB) or l ime-treated (L TB) materials are considered for the manufacturing of ETBs, such materials should be crushed to produce a grad ing s imi lar to that obtained from field processes prior to the determination of grading and Atterberg l imits .

The parent material should be classified in accordance with the classification g iven in TRH14 (CSRA, 1989). Preference should be g iven to G 1 to G3 or CTB type materials as these would seldom require more than one per cent residual bitumen. This, however, should not be seen as excluding materials of a lower class. G4 or G5 type materials may be used successfu lly in ETBs, p rovided that the requ i red amount of residual bitumen does not exceed two per cent. ( I f it is greater than two per cent, the stabil ization approach (Sabita, 1993) should be considered for the design of the ETB . ) Also, the grading properties of subgrade-qual ity materials could be improved by mixing in coarse gravels. This would al low the use of lower emulsion contents. The fol lowing natu ral gravels may be considered for construction of ETBs: • decomposed gran ites; • decomposed dole rites; • decomposed basalts ; • decomposed quartzitic gravels, and • laterite/ferricrete g ravels • chert g ravels • sandstone g ravels

Both the grading of the parent material and the material properties obtained after addition of the e muls ion wi l l determine whether the ETB wi ll be su itable for the intended pavement structure and design traffic. A high traffic category wou ld requ i re a good continuous grading (such as that obtained from crushed stone) to allow for aggregate interlock. Natural gravels may be used for pavements carrying low volumes of traff ic.

Both the P I and the shrinkage product (product of the l inear shrinkage and the percentage of material passing the 0,425 mm sieve) may be used to verify whether natu ral g ravels wou ld be su itable for use in ETBs. Material with a P I greater than 6 or a shr inkage product greater than 50 shou ld not be considered for use in its natu ral state . Lime should be added and/or the grading modified (for instance, by mixing in coarse aggregate) to reduce the PI to below 6 and the sh rinkage product to below 50.

It is recommended that one per cent of cement be added to the parent material to assist the breaking p rocess of the emu lsion and to increase the early strength which is requ i red to a l low the layer to be trafficked soon after completion of construction . This is i l l ustrated in Figure 5, in which it can be seen that the addition of cement accelerates the curing t ime considerably and that the amount of cement (0,5%C; 1 ,O%C and 1,5%C) has an impact on both the curing rate and the CBR values obtained after 28 days' ambient curing (Verhaeghe et ai, 1997b). Whereas the addition of 0,5 per cent cement (W+O,5%C+E) or 1, 0 per cent cement (W+ 1 , O%C+E) to the ETB resu lted in CBRs of s imilar magnitude after 3 to 28 days' curing but were lower than those of ETBs to which either no cement (W+E) or 1, 5 per cent cement (W+ 1 ,5%C+E) was added, the addition of 1 , 5 per cent cement produced ETBs whose CBR values after 28 days' curing were

1 1 \

comparable with those of ETBs to wh ich no cement was added. For this particular ETB, the addition of 1, 5 per cent cement wou ld be recommended if the road had to be opened soon after completion of construction.

300 ,--------------------------------------------,

-eft. 200 --a:: III () 't:J � � 100

en

. --, -: .. -:: ... �

. .,,: .. -:: .

. ":':

...

.. , .

. . . . _........... . . -- f

f·, ...... : ................. � ..... ��;?: ::::::::::: :::::::: ::::::::: :::::: :::::::::::: : :x , + ....... �::::: •••••••• + .

.

f • ,

: :l( •••••••••• ::. • • • . / . . • : , ..... '/ .

.

; : .....

, i .. . .i

..

- /' .', / t.� ,./

\«1 U\J ... < U U U ...

o ��L-� __ � __ � __ � __ -L __ � __ � __ � __ � __ �� o 5 10 15 20

Curing period (days) 25

W W+E W+0,5%C+E w+ 1 ,O%C+E w+ 1 ,5%C+E U - .. - ..... )1+..... • .... ,...... • .... � .....

Figure 5: Effect of cement content on CBR (G4 material )

STEP 2: Determination of optimum fluid content

30

The maximu m dry density and optimu m f lu id content are determined by establishing the flu id ­density relationship o f the material when prepared and compacted at the Modified AASHTO compaction effort at different f lu id contents .

The optimu m f lu id content is approximate ly equal to the optimu m moisture content of the untreated material p lus the residual b itu men with in the quantity of emu lsion to be added (expressed as a percentage of the mass of the dry materia l ). Although this is not necessary, i t is advisable to determine the optimu m moisture content before the optimum f lu id content is determined, especial ly if several d ifferent emu lsion contents are to be investigated .

The fol lowing definitions are g iven for f luid content, maximum density and optimum fluid content: • Fluid content is the total quantity of f lu id in the mix, inc luding hygroscopic moisture, the

bitu men and water within the e mulsion and moisture added for compaction; • The maximum density of a material at a specific compactive effort is the h ighest density

obtainable when compaction is carried out on the material at various f lu id contents, and • The optimum fluid content for a specific compactive effort is the fluid content at which the

maximum dens ity is obtained .

STEP 3: Manufacturing and curing of specimens

It is recommended that samples be p repared over a range of f lu id contents, where the amount of residual b itu men varies from a to 2 per cent in increments of 0 ,5 per cent, but where the optimum moisture content (hydroscopic water, emu lsion water and compaction water) remains unchanged . Samples prepared at various residual b inder contents should be compacted at room temperature accord ing to the standard mod ified AASHTO method .

If natural coarse g ravels contain ing over-s ize material are encountered , the over-s i ze material should not be crushed to less than 19mm after the addition of e mu lsion as the crushed faces

1 2

would be uncoated, which would detract from the strength of the ETB. Instead , -19mm + 13mm fractions from untreated material should be screened out and used to replace the over-s i ze material in the sample to be treated and compacted , before addition of the emulsion .

After compaction, the specimens are cured in their moulds for 24 hours at ambient temperatu res , fo l lowed by 48 hours ' curing in an oven set to a temperature of 40°C (when cement has been added). Alternatively, specimens can be cured for 7 and 28 days at ambient temperatu re.

The relationship between oven and ambient curing is i l lustrated in F igure 6 for one particular type of material (Verhaeghe et ai, 1 997b). It shows that, in the case of ETBs to which one per cent cement is added , the soaked CBRs of samples left to cure at ambient temperatures for one day, fol lowed by two days' oven curing at 40°C are representative of 7-day curing at ambient temperatures or, in the case of ETBs contain ing no cement, 28-day curing at ambient temperatures.

...... -c C1l

.c E

350

!!. 300 en c

VI � 250 "C co N ... o

':: 200 C1l --(1)

a: 150 ID o

. . ...... .

.. -

....... ,

.' .

'

W+C+E (unsoaked} •• •

• ,

7 days ' .,.'

W+E (un soaked) ,

••

' • 7 days'

W.O •• ".,k.d) ••

••

••

•• /

••

•

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7 days •

••

••

•

.......... .' ....

' ..

� .

-.',

W+E (soa'ked) • ••

••

28 days' ••

••

,

.. -

....... ;�.-.

.'

.'

.'

.'

.'

••

' i i ; ; 100 � __ � ____ -L __ __ � __ __ � ____ L-__ � ____ -L ____ � ____ L-__ �

100 150 200 250 300 CBR (%) after 24 hrs ambient + 48 hrs at 40°C curing

F i g u re 6: Re la t io n s h i p b e t w e e n a m b i e n t a n d ove n c u rin g

350

Before CBR and UCS testing , the cured specimens should be submerged in water at ambient temperature for fou r hours and six hours respectively.

STEP 4: Testing of specimens

The CBR values obtained are used for the determination of: • the optimu m res idual bitumen content;

whether the material is su itable for the traff ic class envisaged ; • whether the material is su itab le for use in the base layer, and • determination of cover requ i rements.

After curing and 4 hours ' soaking, the CBR values of the various specimens, each prepared at a g iven residual bitu men content, are determined to a penetration depth of 2 ,54 mm. The optimum residual bitu men content is defined as the res idual bitu men content at which the C B R requ i rements defined in Table 6 are met.

1 3

a e IX eSlg T bl 6 M' d . n cn ena or Sin erms 0 't .

f ETB . t f CBR

Material Code Min imum CBR

ETB-D1 150% @ 100% Mod . AASHTO compaction ETB-D2 100% @ 100% Mod . AASHTO compaction

ETB-D 1 type materials would typically consist of parent materials of G1 to G3 or CTB qual i ty with a residual b i tumen content of less than 1,0 per cent (CTB, G1 or G2) or less than 1,5 per cent (G3). ETB-D1 type materials would be su i ted for use on med ium to high volume roads (>0, 15 mi l l ion ESALs).

ETB-D2 type materials would typically consist of parent materials of G4 to G5 qual i ty with a res idual b i tumen content of less than 1, 8 per cent. ETBl type materials would be su i ted for use on low volume roads «0 , 15 mi l l ion ESALs).

I t should be noted that the designations ETB-D1 and ETB-D2 d iffer from the material classifications used for structural design purposes ( i .e. ETB1, ETB2 and ETB3). The reason for this is that the mix design classification is based on soaked CBR and UCS values whereas those used for s tructural design are derived from DCP testing at in-s i tu moisture contents ( i .e . at moisture contents between those of soaked and unsoaked cond i ti ons).

After curing and 6 hours ' soaking, the UCS values of the various specimens, each prepared at a g iven res idual b i tumen content, are determined in order to establ ish whether or not the material compl ies with base standards. The optimum residual b i tumen content is defined as the residual b i tumen content at which the min imum UCS requ i rements defined in Table 7 are met.

Table 7 : M ix desig n cri teria for ETBs i n terms of UCS

Material Code Min imum UCS

ETB-D1 1200 kPa ETB-D2 700 kPa

Rapid Compaction Control Device (RCCD)

This test method (de Beer et ai, 1993) is proposed as a tool which could be used to cal ibrate the resu l ts obtained in the laboratory with those obtained in the f ield in order for the RCCD to be used for the fol lowing purposes during and after constructi on : • to m oni tor the degree of compacti on of the ETB dur ing construction ; • to m oni tor the gain in strength during cur ing, and • as a decision tool , to establ ish when the layer can be opened to traffic.

The fol lowing procedure is proposed for the cal ibration of the RCCD: i . Determ ine the OFC based on CBR and UCS resu l ts i i . C om pact fou r samples at OFC us ing a vibratory table Ii i . Determine the th ree-blow RCCD penetration (mm) on two unsoaked samples

immediately after compaction in the i r mou lds (three b lows on four points per sample) iv. Cure the remaining two samples for one day at ambient temperatures, fol lowed by two

days ' curing at 40°C v . De te rmine the three-b low RCCD penetration (mm) on the two remaining unsoaked

samples after curing in the i r m oulds (th ree b lows on fou r points per sample) vi. Calcu late the average th ree-blows RCCD penetrations (mm) immediately after

com paction and after three days' cu ring

14

The average RCCD penetration measured immediately after compaction can be used to evaluate the degree of compaction on the road . The average RCCD penetration measured after curing can be used to determine when the road can be opened to traffic . General ly, the road cou ld be opened to traffic when the RCCD penetration (mm per 3 blows) is less than 18 mm. A l ternatively, DCP measu rements can be used to ensure that the 7 and 2 8 days' penetration rates (and derived CSR and UCS values) comply wi th those of the structu ral design material classif ications.

6. CONSTRUCTION OF ETBS The construction process for materials treated with smal l percentages of emuls ion (less than three per cent) consists of the fol lowing s teps (Lea, 1996):

i . Material p reparation ; i i . Appl ication of b i tumen emulsion ; i i i . Mixing and shap ing , and iv. Compaction .

STEP 1 : Material Preparation

If a new material is to be modified by the add i tion of b i tumen emuls ion , i t should be placed and spread in accordance with conventional practice. If a chemical stabi l i zing agent has been prescribed it shou ld be evenly spread over the layer and un iformly mixed in before the add i tion of the emuls ion , again i n accordance with current practice.

I f a material is being recycled, i t should be r ipped and broken down using a grid rol ler . Any mechanical or chemical stabi l izing agents should then be mixed in . If an in place mi l l ing machine is being used then the stabi li zing agents can be mixed in using the machine . H owever, in both cases, care should be taken to ensure that the f inal material , especially the grading, is un iform and complies with the specification for the material .

These processes can be performed the day before application of the emuls ion , but the material shou ld be l ightly wetted before the emuls ion is appl ied . The moisture con tent of the material shou ld then be determined, for use later in the determination of the requ i red quanti ty of compaction water. If the material is porous then no dry material present a t the time of mixing in the emuls ion , s ince the water absorption of the aggregate may lead to the emuls ion breaking .

I f batch m ix ing is used then a s imi lar process should be adopted, where the addi tive is mixed i n to the s tockpi led un treated material before the emuls ion is added . There should be no dry material in the mix. The moisture content of the mixed material should be determined from a trial mix and be moni tored during the construction process, since the moisture content of the material f rom the s tockpi le may vary.

STEP 2: Application of the bitumen emulsion

The emulsion shou ld be d i lu ted with the com paction water and applied in several appl ications, with mixing of the material between each application . This al lows for more uniform mixing of the e mu ls ion and s impl ifies the construction p rocess. The material shou ld be compacted at the optimum f lu id con tent. The compaction m oisture con ten t does not appear to be critical in the construction of ETSs, but the drier the material is at the time of compaction the faster i t wi l l break and be able to be trafficked . The degree of d i lu tion of the emuls ion is not cri tical and, should weather conditi ons be particu larly hot or d ry, proportionately more water may have to be added to compensate for evaporation . The f lu id con tent shou ld not be so h igh as to resu lt in deformation of the surface under final compaction . The laboratory optimum fluid content may be amended by the engineer, based on on-site observations, to account for the type of compaction equipment being used .

15

Ten per cent of the emuls ion should be held back for enrichment of the upper 25 to 30 mm of the layer. Under no c ircumstances may water alone be applied once bitumen emu lsion has been added to the layer. Care should be taken to ensu re that the d i luted emuls ion is applied in such a way that no rivu lets are formed and that the emuls ion does not run off the layer before it has been mixed in .

STEP 3: Mixing and shaping

I n i tial mixing in of the bitumen emuls ion , combined with pre l iminary compaction and shaping, should be carried out with a view to achieving the fol lowing combined objectives: • ensure the thorough, un iform and proper mixing of the gravel or the aggregate and the

emuls ion throughout the material to be treated, unti l the result ing mixture is homogeneous and has the same appearance th roughout wi thout any individual spots of the stabi l izing agent being vis ib le;

• obtaining (by grid rol l ing or other su i table means) substantial pre l iminary compaction in the lower two-th i rds of the layer;

• bring ing the layer to f inal level and cross-section ; and • achieving a reasonably un iform surface texture, free from segregation of coarse or f ine

material in the relatively less compacted upper third of the layer.

The upper th i rd of the layer shou ld then be enriched by the even applicat ion of the d i luted emulsion held back for this pu rpose.

M ixing may be done by road grader, disc harrow, rotary mixer or s imi lar plant, or by means of an in place mi l l ing machine .

STEP 4: Compaction

The layer should be f inal ly rol led whi le at the same time: • slushing, using an additional quantity of d i lute emuls ion , so as to bring just sufficient fine

material to the surface for improving rough spots , but not in excess ; • brooming , b lad ing or otherwise redistribut ing f ine material which is brought to the

surface, and • provid ing a f inished surface which is acceptably smooth , un iformly textured, adequately

enriched with bitumen and free of any loose material .

Final rol l ing is best performed by means of the heaviest avai lable pneumatic-tyred rol ler (normal ly 28 tonnes) fol lowed by a 10 to 12 tonne steel wheel rol ler, to finish the surface. Should the material be wetter than optimum, care should be taken to prevent excessive deformation of the surface by too much rol l ing . The final surface should be smooth, tightly knit and free of undulations, corrugations, holes, bumps or loose material .

Construction limitations

Within the industry i t is generally accepted that the construction process from the mixing in of the emulsion unti l the f inal rol l ing should be performed within a normal 8 hour working peri od .

. The slushing process is normally performed after the layer has d ried out to some extent and is performed up to 4 days after the compaction process. The respective maximum al lowable times

· for completion are suggested:

M ixing and addit ion of the d i luted emuls ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 h ours Compaction with grid or pad rol ler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 h ours Cutting and f in ishing off to f inal leve l , and f inal rol l ing . . . . . . . . . . . . . . . . . . . 2 hours Maximum allowable total uninterrupted period . . . . . . . . . . . . . . . . . . . . . . . . . 8 hours

Mixing of additives (e .g . l ime) can be performed up to 24 hours earl ier and slushing up to 4 days after compaction .

1 6

7. CONCLUSIONS I n th is paper, a "best practice" approach for the structural des ign , material design and construction of ETBs has been proposed. This approach is based on approximate ly 30 years' experience with this type of materia l . H istorical records show that:

• the use of ETBs in pavement structures, particularly in rehabi l itation, can be very cost­effective as they require a min imum of maintenance during the l ifespan of the pavement structure ;

• by the addition of emuls ion, better compaction is ach ieved and the moistu re sensitivity of the layer is reduced. Consequently, improved performance is achieved in both dry and wet cl imatic regions, and

• the early strength generated by the addition of emulsion enables the road to be opened to traffic earlier.

8. ACKNOWLEDGEMENTS The Director of the Division of Roads and Transport Technology of the CSI R in South Africa is thanked for permission to publ ish this paper. The establishment of the "Best Practice" gu idel ines has been sponsored by the Southern African Bitumen Association (Sabita).

9. REFERENCES D E BEER , M . 1991. Use of the Dynamic Cone Penetrometer (DCP) in the design of road

structures. Pretoria: Division of Roads and Transport Technology, CSI R . (Research Report DPVT-187).

DE B E E R , M . , Kalombo, D .K. & Horak, E. 1993. Rapid compaction control for trench re-instatements and pavement layers. In: Proceedings of the 13th Annual Transportation Convention. Pretoria: Un iversity of Pretoria, Vol . 2B , paper 7 , pp 1-19.

DRAFT TRH4 1 996: Structural design of flexible pavements for interurban and rural roads. P retoria: Committee of State Road Authorities, Department of Transport. (Technical Recommendations for Highways; Draft TRH4).

KLEYN, E .G. 1984. Aspekte van plaveiselevaluering en -ontwerp soos bepaal met behulp van die dinamiese kegelpenetrometer. Pretoria: Department of Civi l Engineering , Un iversity of Pretoria. (PhD Thesis).

H O RAK, E . , Myburgh , P.A. and Rose , D .A . 1 984. Rehabi l itation of a cement treated base pavement. I n : Proceedings of the 4th Conference on Asphalt Pavements for Southern Africa, Cape Town, South Africa, Volume 1, pp 316-326.

LEA, J .D . 1996. Conventional construction of ETBs: Best practice. Pretoria: Division of Roads and Transport Technology, CS IR . (Contract report; CR-96/081).

SOUTHERN AFRICAN BITUMEN ASSOCIATION. 1 993. GEMS - The design and use of granular emulsion mixes. Cape Town: Sabita. (Sabita Manual 1 4).

SPOTTISWOODE, B .H . 1979. Emulsion treatment of crushed stone bases. I n : Proceedings of the 3rd Conference on Asphalt Pavements for Southern A frica, Durban, South Africa, Volume 1 , pp 191- 1 97 .

TH EYSE, H . L. 1995. TRH4 revision ( 1 995), Phase II: Mechanistic design analysis o f the pavement structures contained in the TRH4 pavement design catalogue. Pretoria: Committee of State Road Authorities, Department of Transport. (National Service Contract NSC 24/2).

1 7

THEYSE, H .L . , de Beer, M . And Rust, F .C . 1 996. Overview of the South African Mechanistic Pavement Design Method . I n : Flexible Pavement Design and Rehabilitation Issues. Washington D .C . : Transportation Research Board , national Academy of Sciences. (Transportation Research Record : 1539), pp 6- 1 7 .

TRH 1 4 1 989: Guidelines for road construction material. Pretoria : Committee of State Road Authorities, Department of Transport . (Techn ical Recommendations for Highways; TRH14).

VERHAEG H E , B .M .J .A . , Napier, R .C . & Kong Kam Wa, N . J . 1997a. A revised mix design approach for emulsion treated base materials. Pretoria: Division of Roads and Transport Technology, CSI R . (Contract report; CR-97/056).

VERHAEG H E , B .M .J .A . , Napier, R .C . & Kong Kam Wa, N.J . 1997b. A revised mix design approach for emulsion treated base materials - laboratory investigations. Pretoria: Division of Roads and Transport Technology, CSI R . (Contract report; CR-97/057).

18

APPENDIX A: PAVEMENT DESIGN CATALOGUE (NON-ETB AND NON-ASPHALT BASE STRUCTURES)

<0

G R A N U LAR B A S E S (DRY R E G IO NS) , DATE 1 99 6 , PAV EM ENT C LASS AN D D E S I G N B EA R I N G CAPAC ITY (80 kN A X L E S/LAN EJ

R O A D ESl ES2 1 ES3 ! ES4 1 ES5 I ES6 I ES7 Ese ES9 ES 1 0 CAT, O,l -0,3x l 0 4 O,3-1 ,OX1 0 4 l ,O-3,OX1 0 4 1 3 ,O-1 0Xl 0 4 O,l-0,3xl 0 6 O,3-1 ,Oxl 0 6 l ,O-3,OX 1 0 6 3,O-1 0xl0 6 1 0-30xl 06 30_1 00x l 0 6 l Foundat ion

�40A '�" 'V 40A '�1 50A �, 50A : v�x�,1 P4JV" f\'VV I \�;.�'':! �{�1 25 G 2 v;;::j 1 50 G2 \0�(j 1 50 G l J1j 1 5 0 G l 1 "":' 1 50 C3 I , I I '� i 'r@,�:j

40A II : 1 250 C3 I ; I 250 C3 I : i 300 C3 , rd I I A 1 ' \:·""1 ' 50 G2

I " � C 1� ;� 1 50 G5 I O ... till

[TIl' , ,' S I�S./30A �1 40A ? " �I

rr�11 25 G 4 ;ij;;: 1 5 0 G3 r,il� 1 50 G2

� �tI1 50 G7

" ,. ; 1 5 0 C4 [ :--; 1 50 C4 P ? � �1 1 50 G9 B n> ;.;' }&J 200 C4 � : ?j " " , ; ': ;', G l 0 k,, :)

�r:�: �OO G5 ml.:� �25 G5 ��_� �25 G 4 ��50 G3 (('J 1 25 C4 �j 1 25 C4 ';., 1 25 C4 r:;).' C I "", ', �-

1 '",:1 1 50 C4

rn; �� ;25 G4 10 � � ;25 G4 rni�'� �25 G4 i,! (J<: rlfo� ro n

. I'l..QS 1 25 G6 � (, � 1 5 0 G6 . (, � 1 50 G5

a.�.D. 0. " 01

---1--

ffi'-:-�I ;�o G5 I &TI;�0 G5 I rn;':� ;�O G 4 rn�i� ;�O G 4 Frnj;1 ;25 G 4 r�� 'll ;25 G4 o f" ; . 0 � �I ' . � . � o · I '" fro\) 1�. ' I "1 D I . o 1 00 G7 G

_� 1 25 G7 �jJ 125 G7 ) c�1 1 25 G6 �li

, 1 25 G6 g �J 1 5 0 G6 �n;1 5 0 G9

!!"I'1T:1 Sl �� . . S �-:" S � ; i:! G l 0

S y m b o l A denotes AG, AC, OR AS,

r:2Sj: 1 00 G5 �,:� 1 00 G5 . ;� 1 25 G5 v " , .> 1 00 C4 < . . j I

" '· ,'" ", 1 25 C4 ", " 1 5 0 C4 .;;:.�

AD, AP m a y be rec o m m ended as a s u rfacing m e a s u re for i m p roved skid resistance when wet or to reduce water spray

S den oles D o u ble S u rface Treal m e n l (seal o r com b i n al i o n s of seal a n d s l u rry)

S I denOles S in g le Su rface Trea l m e n l

• I f seal is u s e d . i n c r e a s e C4 a n d GS s u b b ase th ickness to 2 0 0 m m .

N o

G R AN U LA R B A S E S (W ET REG IONS) PAV E M E N T C LASS A N D D E S I G N B EA R I N G C APAC ITY (80 kN AXL ES/LAN E)

R O A D

CAT.

A

B

C

D

ESl 0, 1 -0,3xl 0 4

!

Sl • 1 00 G5 ' ? ' 1 00 G7

ES2 0,3-1 ,Oxl 0 4

I

Sl , 1 00 G5 : ?� 1 25 G7

Sym b o l A denotes A G , A C , O R A S .

ES3 1 ,0-3,Oxl 0 4

I

Sl • 1 00 G4 ' � � 1 25 G7

ES4 3,0-1 Oxl 0 4

m �OO G5 � 1 25 C4

m

s ' 0 ' - :� 1 25 G4 ' �,; 1 25 G6

m

Sl , 1 00 G4 ��� 1 25 G6

Sl 1 00 G5 1 00 C4

ES5 0,1 -0,3x l 0 6

II! �25 G5 Eil 125 C4

I

s 150 G4

, �,; 1 5 0 G6 , 0 '

I

s 1 25 G4

: �� 1 25 G6

m �OO G5 � 1 25 C4

ES6 0,3-1 ,Oxl 0 6

1 5 0 C4

200 G5

1�25 G2 1150 C4

150 G5

I

s 150 G4

' 0 '

. ,;� 1 5 0 G6

I S 1 25 G5 1 50 C4

ES7 1 ,0-3 ,Oxl 0 6

IIVV 30A

9vVJvV 150 G 1 ··

. 200 C3 '-'-

S

1 50 G4

A O , A P m ay b e rec o m m en d e d as a s u rfacing m ea s u re f o r i m p roved skid resistance w h e n wet o r t o reduce water s p ray .

S denotes D ou b le S u rface Treatm ent (seal or c o m b inations of seal a n d s l u rry)

Sl d e n otes S in g le S u rface Treatm ent

• If water is prevented from entering the base, the subbase thickness m ay be red uced to the values i n d icated in bra ckets .

.. B ase thickness m ay be red u c e d by 25 m m if cemented s u bbase thickness is increased by 50 m m .

Esa 3,0-1 Ox l 0 6

vvv 40A w. 1 50 Gl

[J: 300 C3 � '(250 C3)

40A 1 50 Gl

300 C4 (250 C4)

ES9 1 0-30xl 06

L 400 C3 [(300 C3)

[DATE 1 996 [ ES1 0

30-1 OOxl 0 6 F o u n dation

� 1 50 G7 • 0 '

� � � 1 50 G9

: �� G l 0

mO' � � ? 150 G9

: �� G 1 0

I\) ....

CEMEN TED BASES

PAVEMEN T CLASS AND DESIG N BEARIN G CAPACITY (80 kN AXLES/LAN E) R OAD ES1 ES2 ES3 ES4 ES5 ES6 ES7

CAT. 0, 1 -0,3x1 0 4 0,3-1 ,Ox1 0 4 1 ,0-3,Ox 1 0 4 3,0-1 0x10 4 0,1-0,3x1 0 6

0,3-1 ,Ox1 0 6

1 ,0-3,Ox1 06

A '1 ::: :: �'OA

� S �s � 1 25 C3 � 1 25 C3

B 1 5 0 C4 200 C4

[l2

S

00 C3

� S �s � 1 25 C3 1 ::: �: C 1 2 5 C4

I S . I S 1 00 C4 1 25 C4 1 00 G6 • o · ' 0 1 25 G6

I S1 m S1 I S1 � S � S �" D 1 0 0 C4 • 1 00 C4 1 25 C4 150 C4 1 25 C4 1 25 C4 ' 0 ' : �� 1 25 G7 : �� 1 25 G6 1 00 G 8 � . � 1 25 G 8 : �� 1 5 0 G7

• o · � - � 1 5 0 G6

Symbol A den otes AG, AC, OR AS,

AO, AP may be recommended as a surfacing measure for im proved skid resistance when wet or to reduce water spray,

S denotes Double Surface Treatment (seal or combinations of seal and slu rry)

S1 denotes Single Surface Treatment * Crushing of cemented base may occur

ES8 ES9

3,0-1 Ox1 0 6

1 0-30X1 06

1 ::: ::* ��OA

I DATE 1 996 I

E S 1 0

30-1 00x1 0 6 Foundation

�'" G'

• o · . �� 1 5 0 G 9

: �O G 1 0

m . o � 1 5 0 G9 o • • 0 '

. �� G 1 0

APPENDIX B Table B1 : Comparison of the l i fe-cycle costs of various types

of pavement structu res (dry regions)

Pavement structure Percentage difference in PWOC compared to lowest cost option

Material code Thickness (mm) Discount rate 6% 8% 1 0%

Road Category D, 30 000 ESALs design bearing capacity, 1 0 year structural design period

Seal- ETB3-G6 Seal: 1 00-1 00 0% 0% 0%

Seal-C4-G7 Seal- 1 25-1 25 42% 40% 38%

Road Category D, 1 00 000 ESALs design bearing capacity, 1 0 year structural design period

Seal- ETB3-G6 Seal- 1 00-1 25 0% 0% 0%

Seal-C4-G7 Seal- 1 50- 1 50 49% 47% 45% Seal-G5-C4 Seal-1 00-1 00 1 % 1 % 1 %

Road Category C, 1 00 000 ESALs design bearing capacity, 1 5 year structural design period

Seal- ETB3-G6 Seal- 1 00- 1 50 0% 0% 0%

Seal-C4-G7 Seal - 1 00-1 00 1 5% 1 3% 1 2% Seal-G5-C4 Seal- 1 00- 1 25 6% 6% 6%

Road Category C, 300 000 ESALs design bearing capacity, 1 5 year structural design period

Seal-ETB2-G6 Seal - 1 00-1 50 5% 6% 6% ,

Seal-C4-G6 I Seal - 1 25- 1 25 1 6% 1 5% 1 4% Seal-G5-C4 Seal- 1 25 - 1 2 5 0% 0% 0%

Road Category C, 1 mil l ion ESALs design bearing capacity, 1 5 year structural design period

Seal- ETB2-C4 Seal- 1 00- 1 25 1 4% 1 4% I 1 4%

Seal-C3-C4 Seal- 1 25- 1 25 42% 4 1 % 40% . Seal-G4-C4 Seal- 1 25- 1 25 0% 0% 0%

Road Category B, 1 mil l ion ESALs design bearing capacity, 1 5 year structural design period

Seal-ETB2-C4 Seal- 1 00-1 50 1 3% 1 3% 1 3% Seal-ETB2-G5 Seal- 1 25- 1 50 6% 6% 6%

I Seal-C3-C4 Seal- 1 25- 1 50 39% 38% 38% Seal-G4-C4 Seal-1 25- 1 50 0% 0% 0%

Road Category B, 3 mil l ion ESALs design bearing capacity, 20 year structural design period

Seal- ETB2-C4 Seal-1 25-200 24% 25% 25% Seal- ETB 1 -G5 Seal- 1 00-1 50 0% 0% 0%

Seal-C3-C4 Seal-1 25-200 48% 45% 43% Seal-G3-C4 Seal- 1 50- 1 50 30% 28% 27%

Road Category B, 1 0 mil l ion ESALs design bearing capacity, 20 year structural design period

AC-ETB 1 -C4 40-1 25-200 0% 1 % 2% AC- ETB1 -C4 40- 1 50- 1 50 1 % 1 % 2%

AC-C3-C4 30-1 50-300 1 2% 1 1 % 1 1 % AC-G3-C4 40-1 50-200 0% 0% 0%

Road Category A, 1 0 mi l l ion ESALs design bearing capacity, 20 year structural design period

AC- ETB 1 -C4 40- 1 25-250 0% 0% 0%

AC-G3-C3 40-1 50-250 1 1 % 1 1 % 1 0%

22

Table B2: Comparison of the l ife-cycle costs of various types of pavement structures (wet regions)

Pavement structure Percentage difference in PWOC compared to lowest cost option

Material code Thickness (mm) Discount rate 6% 8% 1 0%

Road Category C, 1 00 000 ESALs design bearing capacity, 1 5 year structural design period

Seal- ETB2-C4 Seal-1 00- 1 25 1 % 1 % 1 %

Seal-G3-G5 Seal- 1 25-1 50 0% 0% 0%

Road Category B, 1 mi l l ion ESALs design bearing capacity, 1 5 year structural design period

Seal- ETB2-C4 Seal- 1 00-1 50 7% 7% 7% Seal- ETB2-G5 Seal- 1 25-1 50 0% 0% 0%

Seal-G3-G5 Seal-1 50-200 1 4% 1 5% 1 5% Seal-G3-C4 Seal- 1 50- 1 50 25% 26% 26%

Road Category B, 3 m il l ion ESALs design bearing capacity, 20 year structural design period

AC-ETB2-C4 30-1 25-200 1 9% 20% 20% AC-ETB1 -G5 30- 1 00-1 50 0% 0% 0%

AC-G1 -C4 30-1 50-200 54% 53% 53%

Road Category B, 1 0 mi l l ion ESALs design bearing capacity, 20 year structural design period

AC- ETB1 -C4 40- 1 25-200 0% 0% 0% AC- ETB1 -C4 40- 1 50-1 50 1 % 1 % 1 %

AC- G 1 -C4 40- 1 50-250 22% 2 1 % 20%

Road Category A, 1 0 mi ll ion ESALs design bearing capacity, 20 year structural design period

AC-ETB 1 -C4 40- 1 25-250 0% 0% 0%

AC- G 1 -C3 40- 1 50-250 33% 33% 32%

23