technical notes - volume 1 - road development …(modified). for road pavements the thickness of...

Ministry of Higher Education & Highways

Road Development Authority

Integrated Road Investment Program

Technical Notes - Volume 1 April 2018

Lime stabilisation practice

Cement stabilisation practice

Mechanical stabilisation – Blending method

Material specifications for low volume roads

Use of bottom ash for road construction

Technical Notes, Integrated Road Investment Program, April 2018

Contents

1. Lime stabilisation…………………………………………….………………............……..1

1.1 Introduction ………………………………………………………………………..1

1.2 The procedure of treatment …………………………………………..……………2

1.3 Soil suitability ………………............……………………………………………..…2

1.4 Lime reactivity …………………………………………………………….….3

1.5 Properties of lime stabilized soil ………………………………………………..3

1.5.1 Soil drying ………………………………………………………………………..3

1.5.2 Lime stabilisation ………………………………………………………………..3

1.6 Four major steps for mixture design and testing for lime stabilisation ………..3

1.7 Lime demand (LD) of soil and testing procedure ………………………………..4

1.7.1 Testing procedure ………………………………………………………………..4

1.7.2 Moisture content and percentage swell…………………………………………..6

1.7.3 CBR and percentage swell ………………………………………………..6

1.8 Construction ………………………………………………………………………..6

1.8.1 Spreading of lime ………………………………………………………..6

1.8.2 Mixing ………………………………………………………………………..7

1.8.3 Mellowing period ………………………………………………………..7

1.8.4 Time limitations ………………………………………………………..7

1.8.5 Compaction ………………………………………………………………..7

1.9 Field control testing ………………………………………………………………..8

1.10 Opening to traffic ……………………………………………………………..…8

1.11 References ………………………………………………………………………..9

2. Cement stabilisation practice ………………………………………………………10

2.1 Introduction ………………………………………………………………………10

2.2 Background ………………………………………………………………………10

2.3 Pozzolans ………………………………………………………………………11

2.4 Sampling ………………………………………………………………………11

2.5 Laboratory Testing ………………………………………………………………11

2.6 Classification ………………………………………………………………………11

2.7 UCS test analysis ……………………………………………………………....12


2.8 Property limit for cement stabilization ……………………………………....13

2.9 Plant for spreading ………………………………………………………………14

2.10 Stabilisation (Mixing) …………………………………………………………..…..14

2.11 Addition of water ……………………………………………………..………..14

2.12 Time limitations ………………………………………………………………14

2.13 Compaction ……………………………………………………………..………..14

2.14 Curing condition ………………………………………………………………15

2.15 Application ………………………………………………………………………15

2.15.1 Sub grade …………………………………………………..……....…..15

2.15.2 Selected Subgrade/ Capping layer ………..……………………………..15

2.15.3 Base course ………………………………………………………………15

2.16 Protection and maintenance before sealing ………………………………………16

2.17 Quality control measures ………………………………………………..……..16

2.18 References ………………………………………………………………………16

3. Mechanical Stabilisation – Blending Method ………………………………..……..17

3.1 Back ground …………….…………………………………………………...……17

3.2 Mission ………………………………………………………………...…….17

3.3 Approach …………………………………………………………...………….18

3.4 Determination of mixing proportions for samples A,B …………………..…..18

3.5 The procedure for determination of mix proportion for three samples …...….20

3.6 Field mixing ………………………………………………………………………21

3.7 Concluding remarks ……………………………………………...……………….22

4. Material specifications for low volume roads …………………………………..…..24

4.1 Introduction …………………………………………………………………...….24

4.2 Purpose …………………………………………………………………..…..24

4.3 Typical cross section ………………………………………………………………24

4.4 Sub grade ……………………………………………………...……………….24

4.4.1 Capping layer or selected subgrade ………………………………..……..25

4.4.2 Poor subgrade ………………………………………………………...…….25

4.4.3 Stabilised subgrade ………………………………………………………25


4.5 Subbase ………………………………………………………………………26

4.5.1 Use of sand ………………………………………………..……………..27

4.5.2 Subgrade ……………………………………………..………………..27

4.5.3 Subbase ……………………………………………...……………….27

4.6 Embankment material …………………………………………………………...….28

4.6.1 Zoned embankment …………………………………………………..…..28

4.6.2 Homogeneous embankment ………………………………..……………..29

4.6.3 Sub grade in cuttings ………………………………………………………29

4.7 Shoulder material ………………………………………………………………29

4.7.1. Emmerson class ………………………………………………………30

4.7.2 Shoulder protection …………………………………………..…………..30

4.8 Quality control/ quality assurance testing ………………………………………30

4.8.1 Dynamic Cone Penetrometer (DCP) Test ……………………………....30

4.8.2 Light weight falling deflectometer (LWFD) test …………………..…..31

4.8.3 Field density test – Sand cone method (ASTM D-1556) ……………....31

4.8.4 Non – nuclear density test …………………………………...………….31

4.9 References …………………………………………………………....…………31

4.10 Annexures ………………………………………………………………...…….31

5. Use of bottom ash for road construction ……………………………………...……….32

5.1 Introduction ………………………………………………………………………32

5.2 Properties of bottom ash ………………………………………………………32

5.2.1 Specific gravity ………………………………………………...…….32

5.2.2 Piratical size distribution …............…………………………...……….33

5.2.3 Chemical composition …………………………………………...….34

5.2.4 Environmental considerations ………………………………………………35

5.2.5 California bearing ratio ……………………………...……………….35

5.2.6 Compaction characteristics …………………………………………...….35

5.3 Use Bottom ash in the construction road embankment ……………...……….36

5.3.1 Zoned embankment configuration using bottom ash ………………………37

5.3.2 Embankment construction …………………………………………..…..38

5.3.3 Material property …………………………………………………...….38


5.3.4 Synthetic geomembrane ………………………………………………39

5.3.5 Placement of bottom ash ……………………………………...……….39

5.3.6 Compaction ………………………………………………………………39

5.3.7 Light weight falling deflectometer (LWFD) tests ………………...…….39

5.3.8 Dynamic cone penetrometer tests ………………………………………39

5.3.9 Stability assessment ………………………………………………………39

5.3.9.1 Method of Analysis ……………………………...……………….39

5.3.9.2 Parameters …………………………………………………...….40

5.3.9.3 Results of the stability analysis ………………………………40

5.3.10 Bottom ash stabilised marginal material for embankment construction 41

5.3.11 Embankment in low lying areas ………………………………..……..42

6. Use of bottom ash soil mixture for selected sub grade (capping layers) ..……………..42

6.1 Properties of stabilised bottom ash ………………………………………………42

6.1.1 Strength gain ………………………………………………………..……..42

6.1.2 Plasticity ………………………………………………...…………….44

7. Quality control ………………………………………………………………………45

8. References ………………………………………………………………...…………….45

1 Lime Stabilisation Practice – TN 01, Integrated Road Investment Program, April 2018

Technical Note

April 2018

Lime stabilization practice

1. Lime stabilisation

1.1 Introduction

Lime stabilization of clay subgrade to form a capping layer (prepared sub base / base) was first

introduced into a General Specification of Road Development Authority (RDA) in 1989. It has

been used as trials on many road projects since this date and is particularly beneficial in road

construction on weak ground. It enables full use all materials from within the site and minimises

tipping and material source from far distance.

The stabilisation of clay subgrades using lime has a long and successful history in many urban

and rural regions of other countries, and is cost effective and a necessary requirement for local

councils State Road Authorities seeking long-life roads to minimise future maintenance costs.

In situ stabilisation is normally adopted to improve the strength and durability of pavements

and reduce the moisture sensitivity of poor quality materials.

Cohesive soils are generally treated successfully with quick/hydrated lime to produce capping

layer that complies with the Standard Specification for roads with clay sub graded. This results

in:

• improve stiffness of sub grade or the rehabilitation of existing roads,

• reduce the PI of in subgrade material,

• improve stability for the upper ,

• modify subbase layers to improve stiffness of the pavement, and

• form a temporary construction platform for earth works

Capping/sub base or improved sub grade is a high strength and stiffness material used on weak

fills and poor subgrades. It acts as a working platform during the construction of the pavement

and as a structural layer in the long term.

The minimum strength requirement for capping (lower sub base/improved sub grade) is a

laboratory soaked California Bearing Ratio (CBR) of 15% after 4 days soaking at 95% MDD

(modified). For road pavements the thickness of capping is detailed in ICTAD Publication No:

SCA/5 and is directly related to the subgrade CBR. This specification allows for separate

capping and subbase layers composed entirely of subbase material.

The material type and condition of the existing material for treatment will govern the

application rate and construction practices. In order to understand the properties of lime and

its reaction with materials, this technical note aims to highlight:

• reaction of lime,

• types of lime,

TN01


• Lime demand (saturation pint)

• determination of rate of application,

• mixing operations

1.2 The procedure of treatment

The addition of quicklime (Calcium Oxide) to any soil causes a reduction in moisture content

as water is used in the hydration of the lime. This will be enough to produce an improvement

in the engineering properties of the soil.

Hydrated lime in the presence of water sets up an alkaline environment (pH>7) in which the

lime will react with any Pozzolans, materials containing reactive silica and alumina.

The reactions occur immediately the quicklime is dispersed into the soil. Stiff clays will lose

plasticity and become more friable due to the change in soil properties. The treated soil may

need mixing more than once to achieve the better results. This reaction alters the material

enhancing geotechnical properties. Compaction characteristics, moisture condition value,

plastic limit and bearing capacity are all changed significantly in this reaction.

The calcium oxide component of quicklime reacts with water to produce hydrated lime

(calcium hydroxide) as well as liberating heat.

The equation below shows the hydration process of lime and it requires 320 liters of water to

hydrate one tonne of CaO.

CaO + H20 Ca(OH)2 + heat

Hydrated lime and quicklime are used directly in soil stabilisation works. Quicklime is used

extensively for subgrade stabilisation in heavy clays.

Quicklime is chemically change to hydrated lime by the addition of water at site. In this process

the quicklime causes an exothermic reaction generating heat and steam.

1.3 Soil suitability

The properties of the soil will govern the properties of the lime stabilised layer. As quicklime

combines with the clay minerals in the clay it is essential to ensure that sufficient of these are

present to develop the required strength. Generally, the greater the plasticity of the clay, the

more clay minerals are present and a minimum Plasticity Index of 10 is specified for

stabilization requirement. If insufficient clay (PI <10) is present to develop the required

strength then cement may be added.

Organic materials have an unfavorable effect on the stabilisation process and require higher

additions of lime for satisfactory results. An upper limit of 2% is a general acceptable guide

but the type is more important than the amount present.

Generally material that are not suitable for lime stabilisation are likely to be non-reactive such

as:


• material with high silt content (ML, MH, OH)

• material with plasticity Index (PI) < 10

1.4 Lime reactivity

Factors which can affect the hydration of quicklime are there particle density, particle size

distribution and amount of impurities.

Concentrations of sulphate ions and organic impurities may prevent the reaction of lime with

the clay minerals. The current limit for the application of lime stabilisation of soils with

sulphate ions is < 0.3%.

1.5 Properties of lime stabilized soil

The following are three major effects when lime added into soil for stabilisation.

1.5.1 Soil drying

Soil drying is a rapid decrease in soil moisture content due to the chemical reaction between

water and quicklime and the addition of dry material into a moist soil.

1.5.2 Lime stabilisation

Lime stabilization occurs in soils containing a suitable amount of clay and the proper

mineralogy to produce long-term strength, reduction in soil plasticity significantly, increase in

optimum moisture content, decrease in maximum dry density, improved compactability and

reduction of the soil’s capacity to swell and shrink after compaction. Significant increase of

Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) with the

addition of lime. Potential increases of CBR from 3 to 20 with lime and further increase to

CBR 50 with a following treatment of cement.

Lime stabilised layer forms an impermeable barrier by hindering penetration of moisture from

above and below. The layer becomes a working platform allowing construction to proceed

unaffected by weather. An additional treatment with cement for long-term waterproofing

barrier unless the stabilised layer is protected by another pavement layer as quickly as possible.

These effects generally take place within a short time period after the lime is introduced –

typically 1 to 72 hours – and are more pronounced in soils with sizable clay content.

In general, lime stabilization occurs over a longer time period of “curing”. The effects of lime

stabilization are typically measured after 28 days.

1.6 Four major steps for mixture design and testing for lime stabilisation

• General understanding of its suitability for lime stabilization.

• Determine minimum amount of lime required for stabilization (Lime demand).

• Evaluate lime-stabilised soil strength for long term durability within its

exposure environment, with special attention to periods of extended soaking.

• If soils to be stabilized are expansive, evaluate using capillary soaking and

expansion measurements.

• Farm Tractors attached with harrow or similar machine.


1.7 Lime demand (LD) of soil and testing procedure

The following procedure describes the minimum lime requirements for soil stabilisation. The

soil react with lime (Calcium Hydroxide) through cationic exchange and pozzolanic reaction

with reactive clay minerals.

The aim of the lime demand test is to identify the quantity of lime to satisfy cation exchange

by reaching a specific pH level (ie alkaline level of 12.4) to produce long-term reaction.

When lime mix with soil the reaction is two-fold. Initially, soil pulverization takes place

braking fine clay particle into coarse, friable particles. Secondly, the lime increase the pH of

soil mix above 12, where pozzolanic reaction initiate with clay minerals forming calcium

silicates and aluminates.

1.7.1 Testing procedure

Step 1 - Initial evaluation

1. Asses soil characteristics to determine the suitability of lime stabilization.

2. Determine the amount of soil passing the 75 micron (75-μm) screen and wet method to

determine the soil plasticity index (PI) - ASTM C 316.

Generally, soil with at least 25% passing a .075 mm sieve and having a PI > 10 or equal are

suitable for lime stabilization.

Generally, lime is not an effective stabiliser for all soils. Some soil components such as sulfates,

phosphates, organics, and so forth can adversely affect soil-lime reactions and may produce

erroneous results using this test method.

Allowable limits of mineral content of soil are given below.

• Sulfate content (water soluble) < 0.3%

• Organic content < 1%  

• Ferric oxide < 2%.

Step 2 - Lime demand – minimum lime content

1. Determine the optimum soil-lime proportion for soil stabilization (ASTM D 627).

2. Soil lime mix that produces a laboratory pH of 12.4 (flat section of the pH vs. lime

percentage curve) is the minimum lime percentage required to satisfy cation exchange

to produce long-term reaction.

3. Plot the average pH against its hydrated lime content and join each point. Next, draw a

line parallel to the X axis corresponding to the pH for hydrated lime. Record the lowest

hydrated lime content (HLC) where the pH just reaches a stable peak value, that is, a

plateau where the pH values do not vary by more than 0.05 pH units over three

successive soil-lime mixtures (Figure 1).


Figure 1: Lime demand curve.

Step 3 - Determine optimum moisture content (OMC) and maximum dry

density (MDD) of the lime-treated soil

1. Make a mixture of soil, lime, and water at the minimum percentage of lime as

determined from Step 2, using a water content of OMC + 2-3%. Seal the mixture in an

airtight, moisture proof bag stored at room temperature for 18-24 hours to mellow. This

is necessary because adding lime will change the soil’s OMC and MDD.

2. Determine the optimum moisture content (OMC) and Maximum dry density (MDD)

(ICTAD Publication SCA/5) - heavy compaction effort).

Step 4 – Preparation of california bearing ratio (CBR) specimens

1. Prepare specimens for CBR testing (Step 6).

2. Prepare a minimum of two test specimens of lime, soil and water using the amount

(percentage) of lime determined from Step 2 at the OMC (± 1%) as determined from

Step 3.

3. Suggested lime content for CBR testing shall be commenced from the following mix

design range based on Lime Demand (LD) test.

• Sample 1 : with 0% lime

• Sample 2 : LD - 2%

• Sample 3 : LD

• Sample 4 : LD + 2%

• Sample 5 : LD +4%

4. The soil lime-water mixture should be stored in an airtight, waterproof bag for 18-24

hours prior to making the test specimens.

7

8

9

10

11

12

13

0 2 4 6 8 10

pH

Lime percentage

LD


Step 5 - Cure and condition the california bearing ratio (CBR)

specimens

1. Moist cure the specimens for 24 days in mould and 4 days immersed water curing in

mould. Take the initial reading for swell marking the reference point on top of the

sample.

2. Take the final reading for swell from the gauge after completion of 4 days soaked.

3. Remove the mould from the water bath and tilt to remove excess water, then keep it

vertical position for at least for 15minutes for further draining.

Step 6 - Determine the california bearing ratio (CBR)

Purpose: To determine the CBR for lime-stabilized soil to ensure adequate field performance

an extended soaking environment.

Procedure: Use BS 1337 Part 4 -1990 or ASTM –D 1883 to determine the CBR of the cured

and moisture conditioned specimens.

Criteria: The minimum desired CBR depends on the intended use of the soil, the amount of

cover material over the stabilised soil, exposure to soaking conditions.

1.7.2 Moisture content and percentage swell

After completion of CBR testing, extrude the sample from the mould and determine the

moisture content of each sample.

1.7.3 CBR and percentage swell

CBR and percent swell for each sample for 4 days soaked in water after completion of 24 days

air curing shall be required. Swell of each sample to the nearest 0.1% shall be recorded.

1.8 Construction

The subgrade shall be scarified to the specified depth and width and then partially pulverized.

Remove all non-soil materials larger than 3 inches, such as stumps, roots, turf, and aggregates.

A scarified or pulverized subgrade provides more soil surface contact area for the lime at the

time of lime application.

1.8.1 Spreading of lime

Hydrated lime shall be spread uniformly over the prepared surface to enable proper mixing

and distribution within depth of layer to be treated. Uniform spreading can be done manually

by placing lime bags at predetermined spacing and raking them over the entire area of

treatment.

At the time of spreading, hydrated lime shall comply with the grading requirements specified

below.


Sieve Size (mm) Test Value (% passing)

4.75 100

0.600 95 -100

0.075 85 -100

The Contractor shall visually observe uniformity of spreading of lime over area to be treated.

1.8.2 Mixing

Adequate pulverisation and mixing are required to achieve satisfactory results. Generally it

requires only one-pass mixing but high plastic soils require mixing with multiple pass. All lime

spread shall be mixed into the soil to a depth equal to the specified thickness of the stabilised

layer within 6 hours of spreading. The amount of lime content in the soil can be measured

either using Neutralisation of waste acid (ASTM C400-98) or Ethylenediaminetetra acid

(EDTA) titration method.

The moisture content shall be adjusted as necessary during the mixing process to maintain the

moisture ratio (before and after compaction) greater than 85% as determined by test using

modified compaction effort. The moisture content of the material can be varied significantly

during sampling and testing.

1.8.3 Mellowing period

The lime-soil mixture should mellow sufficiently to allow the chemical reaction to change

(break down clay particles) the material. Mellowing period is typically 72 hours to allow

sufficient time for clay lumps to react with lime. After mellowing, the soil should be remixed

before compaction.

1.8.4 Time limitations

Compaction shall commence within 2 hours and shall complete within 8 hours after completion

of mixing.

1.8.5 Compaction

Final mixing and pulverization shall be carried out until large particles breaks until at least 60

percent of non-stone material passes the 4.76mm sieve. Compaction should begin immediately

after final mixing.

The lime-soil mixture should be compacted to the density required by specification, typically

at least 95 percent of the maximum density (modified Proctor – BS 1377 Part 4 1990 or

AASHTO T 99-01). The density value should be based on the Proctor curve from a

representative field sample of the lime-soil mixture. Density testing shall be carried out within

12 hours after completion compaction.

Additional water may be required during final mixing (prior to compaction) to increase the

moisture content up to 3 percent above optimum moisture content (OMC) of the treated

material.

Before placing the next layer of subbase (or capping), the compacted subgrade (or subbase)

should be allowed to harden until loaded dump trucks can operate without rutting the surface.

During this time, the surface of the lime treated soil should be kept moist to gain strength.


Compaction requirements of different layer of lime-soil mixture are listed below.

• Lower layers of embankment - 93 % percent, modified proctor compaction

• Upper layers of embankment - 95 % percent, modified proctor compaction

• Sub base layer – 98 % percent, modified proctor compaction

• Shoulder – 95 % percent, modified proctor compaction

• Capping layer (selected sub grade) - 95 % percent, modified proctor compaction

1.8.6 Curing

Compacted surface should be allowed for hardening until loaded dump trucks can operate

without rutting the surface. During this time, the surface of the lime treated soil should be kept

moist for strength gain. Generally, 14 days curing period in the field is sufficient to achieve

required strength gain based on past research studies.

Curing can be done in two ways:

(a) moist curing - maintaining the surface in a moist condition by light sprinkling and light

rolling when necessary, and

(b) membrane curing - compacted layer with a bituminous prime coat emulsion, either in one

or multiple applications .

1.9 Field control testing

Field control testing shall be carried out for quality control measures to ensure that particular

design parameters such as lime content, CBR and degree of compaction are achieved.

Test Method

EDTA titration method

Sand replacement method

ASTM D 5102 Table 1: Test methods used for quality control measures

1.10 Opening to traffic:

There is not much research work has been carried out to determine the precise effects of opening a road

to traffic before completion of curing period. Early trafficking can cause pre cracking of the stabilised

layer. Layers which are pre cracked or trafficked early shall be allowed to gain an adequate strength at

the edges of each crack before open for construction traffic.


1.11 References

1. BS1924: Part 2: 1990. Stabilised materials for civil engineering purposes. Part 2.

Methods of test for cement-stabilised and lime-stabilised materials. BSI Chiswick,

London.

2. British Lime Association. Earthworks Improvement using Lime. BLA Technical Data

Sheet No 1. Quarry Products Association, London

3. Australian Standard (AS 4489.6.1, 1997) - Test methods for limes and limestones

4. Shahriar Shahrokh Abadi, Armin Yekkalam, Mohammad Bagher,i Kaffash Rafsanjani

- Determining Compaction and Water Content Ratio of Compacted Soil Using Hilf

Rapid Method, The 4th International Conference on Geotechnical Engineering and Soil

Mechanics, November 2-3, 2010, Tehran, Iran.

5. National Lime Association – Lime – Treated Soil Construction Manua, Lime

Stabilization & Lime Modificatio, January 2004.

6. DTMR - Testing of Materials for Lime Stabilisation, January 2017.

7. AustStab - Lime stabilisation practice, January 2008.

8. VicRoads –Section 290 – Lime Stabilisation of Earthworks Materials, December 2008.

16 Cement Stabilisation Practice – TN 02, Integrated Road Investment Program, April 2018

Technical Note

April 2018

Cement stabilisation practice

2. Cement stabilisation practice

2.1 Introduction

Cement stabilization has been used in Sri Lanka for many years. This practice was introduced

into Road Development Authority Standard specification in 1989. It has been used on many

road projects since then on trial basis.

Cement stabilization is primarily used to increase the bearing capacity of soil while the

moisture content will reduce due to hydration of the cement.

The stabilisation of weak granular subgrades and sub base material using cement has a long

and successful history in some areas of Sri Lanka, and is cost effective and a necessary

requirement for i Road program seeking long-life roads to minimize future maintenance costs.

Granular soils can be treated successfully with cement to produce sub base or capping layer

that complies with the Standard Specification for roads improving following properties.

• Strengthening of existing pavements.

• Improving low quality pavement material to make suitable for subbase or base.

• Reduce thickness of base to achieve required design strength.

• Drying out wet pavements.

This technical note is prepared to address a mix design procedure for the design of optimum

cement blend content for soil stabilisation. This note also provide guidelines, design criteria

and test procedures for characterizing the host soil and measuring the properties of the cement

treated material.

2.2 Background

Generally, cement is added road pavement materials or mix with weak sub grade to change its

properties. Generally the aim is to provide a modified material with a target unconfined

compressive strength (UCS) or California Bearing Ratio CBR) depending on payment layer

and to avoid making the material too stiff and susceptible to fatigue cracking.

The required strength of a layer stabilised in the pavement depends on the traffic volume. The

stabilised layer should be adequately strong enough to withstand the stresses induce from the

traffic load to avoid cracking. The strength required for each stabilised layer as per AustStab

technical note 5 is shown in Table 1.

TN02


* 7 day strength Table 1: Properties of cement stabilised layer (Road note 31)

• Modified materials: Flexible layer. Small amounts of cement are used. Materials may

be classified as an unbound granular material for pavement design.

• Lightly bound materials: Improved stiffness and tensile strength. Negligible cracking.

• Heavily bound materials: Enhanced stiffness and tensile strength. Fatigue and

shrinkage cracking.

2.3 Pozzolans

Portland cement is manufactured as a homogeneous product by grinding together Portland

cement clinker and calcium sulphate, and which, at the choice of the manufacturer, may contain

up to 7.5% of mineral additions.

The cement hydrates in the presence of water to form hydrated silicates and aluminates and

calcium hydroxide. A pozzolan is a siliceous or alumino siliceous material in finely divided

form. Chemical reaction will take place in ordinary room temperature with calcium hydroxide

released by the hydration of cement to form cementitious product.

2.4 Sampling

In order to identify material types and changes within any material, bulk samples of 10 – 50 kg

will be required, depending on the maximum particle size of the material.

Unified Soils Classification System (USCS) system shall be used to identify the soil types.

2.5 Laboratory testing

Laboratory testing carried out on materials to be stabilised should include:

• Particle Size Distribution (PSD) and Plasticity Index (PI) of the material to be

stabilised; and

• Unconfined Compressive Strength (UCS) Testing.

As an alternative, the strength of stabilized material shall be measured by CBR test after 7 days

of moisture curing and 7 days of soaking. Material with poor PSD or is susceptible to break

down during mixing and compaction, require prior stabilisation mixing with suitable material

to improve the PSD and achieve the required strength. Improving the PSD usually results in a

reduced amount of cementitious additive to achieve the required strength hence there is less

potential for subsequent shrinkage cracking.

2.6 Classification

Initially, classification tests including particle size distribution and Atterberg limits should be

carried out for material to be stabilised.

Material Type Layer Thickness (mm) Design UCS (MPa) Modulus (MPa)

Heavily bound > 250 > 2 2000-20000

Lightly Bound < 250 1 – 2 * 1500-2000

Modified - < 1 < 1500


Generally, materials that are not suitable for stabilisation are:

• poorly graded materials.

• materials with a plasticity index (PI) > 10.0 where more than 25% passing the 0.075

mm sieve.

• materials where less than 25% passing the 0.075 mm sieve may be suitable with a

plasticity index higher (PI) than 10.0.

The following limits may be applied for material to be stabilised:

Chemical Limit

Sulfate Content (water soluble) < 0.3%

Organic Content* < 1.0%

Ferrous Oxide (FeO)* < 2.0% Note*: The limit shown is a guide

Table 2: Deleterious materials limits.

2.7 UCS test analysis

The UCS test is required to determine the optimum cement content for stabilisation.

Three specimen are to be undertaken at a range of cement contents usually commencing with

1% cement. Suggested cement contents (%) for a target strength of 1.5 MPa are: 0.5, 1.0, 1.5

and 2.0. The strength of all compacted soil is greatly influenced by compacted density.

The cement/soil mixture is allowed to condition in an air-tight container for 45 minutes before

further mixing and compaction. A standard curing regime comprising moist curing for 7 days

and soaked for 7 days in accordance with BS 1924. All specimens are to be tested using the

standard UCS test, long term immersion testing is not usually undertaken for cement stabilised

specimens.

Plot the UCS data versus cement content and determine the cement content corresponding to a

target strength (MPa). As an example, in Figure 1 the cement content corresponding with the

target strength of 1.5 MPa would be the optimum cement content of 1.65%.

Figure 1: Cement content vs UCS

0

0.25

0.5

0.75

1

1.25

1.5

1.75

2

0 0.5 1 1.5 2 2.5

UC

S (M

Pa)

Cement content %

Cement percentage Vs UCS


2.8 Property limit for cement stabilization

Materials, which have a low volume of voids when compacted, will usually require the addition

of relatively small amounts of cement compared to poorly-graded high void content material.

The selection of the stabilizer, either lime or cement is based on the plasticity and particle size

distribution of the material to be treated. The appropriate stabiliser can be selected according

to the criteria shown in Table 3 adapted from NAASRA (1986).

Type of

stabiliser

More than 25% passing 0.075 sieve Less than 25% passing 0.075 sieve PI < 10 10< PI <20 PI > 20 PI < 6 PI < 10 PI > 10

Cement Yes Yes - Yes Yes Yes

Lime Yes Yes No Yes Table 3: Guide to cement stabilisation

Material to be stabilised should be within the gradation envelope given in Figure 2. Stabilised

layers constructed using material within this range are more likely to perform satisfactory

results. Materials which do not comply with Figure 2 can sometimes be stabilised but more

additive will be required and the cost and the risk from cracking and carbonation will increase.

Figure 2: Gradation envelope for material to be stabilized

Sugars and reactive organic compounds can retard the hydration process and prevent the

hardening of the binder. In some circumstances, soluble sulphates can also destruct the

stabilisation process.

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10 100

Per

cen

tage

pas

sin

g (%

)

Sieve Size (mm)

Desireble boundary of material before stabilisation


Material Property Limit

Liquid Limit (%)

Plasticity Index (%) < 40 < 20

Table 4: Material property limit for cement stabilization.

2.9 Plant for spreading

The equipment shall be capable of spreading cement efficiently for different road widths.

Where the cement is applied directly to the surface of the road before stabilising, the spreader

unit shall be a purpose-built calibrated belt or pneumatic rotor spreader incorporating

adjustable spreader curtains.

2.10 Stabilisation (Mixing)

It is important to distribute cement throughout the full design depth of the material. It is usual

to increase the laboratory determined cement content (usually by 0.5%) to allow for waste or

mixing inefficiently.

For field mixing, two passes of the cement stabiliser are required to produce optimum mixing

results. Additional passes of the stabiliser may produce excess fines and be deleterious to the

stabilisation process.

Pre-conditioning with small amounts of hydrated lime or quicklime often benefits the break-

down of plastic clay soils.

2.11 Addition of water

Sufficient water shall be added during the stabilising process. Special care shall be taken to

prevent any portion of the work from excessive wetting.

The water content during compaction shall be in the range of 90% to 100% of the material’s

optimum water content.

2.12 Time limitations

Allowable time period (maximum), from mixing of the materials with cement to primary

compaction of the stabilised layer shall be less than 2 hours.

2.13 Compaction

Adequate compaction is required to obtain the targeted strength. Target optimum moisture

content (OMC) and maximum dry density (MDD) shall be determined for each layer to be

stabilised.

The cement-soil mixture should be compacted to density requirement listed below.

• Lower layers of embankment - 93 % percent, modified proctor compaction.

• Upper layers of embankment - 95 % percent, modified proctor compaction.

• Sub base layer – 98 % percent, modified proctor compaction.

• Shoulder – 95 % percent, modified proctor compaction.

• Capping layer (selected sub grade) - 95 % percent, modified proctor compaction.


Delays in compaction, after the addition of cement and water will result in reduced densities

and subsequent reduced strengths.

2.14 Curing condition

It is recommend to cover the areas treated to prevent the stabilised materials from drying out

before completion of the hydration reactions.

If this is not practical, then the surface must be kept damp for up to seven days by frequent

surface wetting. It is important not to over water the stabilised layers to avoid leaching.

There are two principal forms of cracking in cement stabilised materials:

• shrinkage cracking from hydration and drying, and

• fatigue cracking.

Cracking of stabilised surface can be controlled by:

• the use of slow setting binders

• reducing the amount of cementitious material

• proper compaction, and

• a proper curing regime.

2.15 Application

2.15.1 Sub grade

Subgrade stabilisation is usually carried out to:

• Improve subgrade strength - possible reduction of the overlying pavement thickness.

• Provide a working platform for construction equipment.

• Provide a water-resistant subbase for permeable or jointed pavements.

For more plastic clay subgrades, hydrated lime or quicklime will be more suitable than cement

stabilisation.

2.15.2 Selected sub grade / capping layer

Subbase and Capping are a high strength and stiffness material used on weak fills or poor

subgrades. It acts as a working platform during the construction of the pavement and as a

structural layer in the long term. It can be created by treating low cost imported material, if the

pavement levels are low, and from in situ soils if the levels are high.

The minimum strength requirement for capping is a laboratory soaked California Bearing Ratio

(CBR) of 15% after 7 days curing. For road pavements the thickness of capping is detailed in

ICTAD Publication No: SCA/5 and is directly related to the subgrade CBR. This specification

allows for separate capping and selected subgrade layers composed entirely of subbase

material.

2.15.3 Base course

Cement stabilised base course can be recognized as a potentially cost effective solution for

rural road construction.


Cement treatment base course can be used to:

• upgrade a marginal base course material to comply with the specification

• improve low cohesion base materials that deform., and

• reduce moisture sensitivity lowering Plasticity Index (PI) and Linear Shrinkage (LS).

• Flood ways and other moisture sensitive structures

2.16 Protection and maintenance before sealing

The Contractor shall protect and maintain the completed stabilised layer until the next layer or

surfacing is applied. In addition to the curing of the stabilised layer by frequent light watering,

maintenance shall include the immediate repair of any damage to or defects in the layer, and

shall be repeated as often as it is necessary.

2.17 Quality control measures

Full time quality control measures are required during the stabilisation process. This include

the verification of cement content, adequate moisture and density testing and minimal sand

cones, proper compaction and mixing techniques, and timely mixing and placement of soils.

After a period of 7 days, coring of the stabilised soil layer shall be tried for laboratory testing.

If quality specimens is difficult, acceptance should be based on density results and other

observed stability of the roadway.

2.18 References:

1. Y.S. Yeo and H. Nikraz – Cement Stabilisation of Road Base Course: A Chronological

Development in Western Australia.

2. Issmge – TC 211, Soil Cement Stabilization - Mix Design, Control and Results during

Construction - International Symposium on Ground Improvement IS-GI Brussels 31

May & 1 June 2012.

3. DTMR - Testing of Materials for Cement or Cementitious Blend Stabilisation, January

2017.

4. Auststab - Cement Stabilisation Practice, March 2012.

Mechanical Stabilisation – Belding Method – TN 03, Integrated Road Investment Program, April 2018 23

Mechanical stabilisation – blending method

Technical Note January 2018

3. Mechanical stabilisation – blending method

3.1 Back ground

The I Road Project, commenced in 2015 envisage improvement, rehabilitation and

maintenance of approx. 8000 km Island wide, mainly Rural Roads. Work on 3000 Km of Rural

Roads has already commenced covering Southern, Sabaragamuwa,Central,North Central,

North Western Provinces and Kalutara district in Western Province.

This is only one major project among other ongoing projects of the RDA such as Southern

Highway extension from Matara to Hambantota(96km) and Central Expressway project

(approx 100Km), other donor funded Projects amounting to many hundred Billion Rupees. One

of the major obstacles in implementation is the difficulty in sourcing earth material satisfying

specification requirement. Sometimes it is required to haul these materials over very long

distances making it very uneconomical while causing other adverse environmental and social

effects.

Since 2005 many major road improvement programmes have been implemented, covering the

whole Island, mainly A and B class Roads but an equal length of minor roads too have been

improved simultaneously. This programme required mining of millions of cubic meters of

naturally occurring soil material satisfying specification requirements. During the course of

time prevalent laws and procedures have been tightened aiming protection of environment.

Present Road work projects and some other Engineering Projects such as water and sewer

laying projects find it is almost impossible to source naturally occurring earth materials which

satisfy specification requirement for Roads, subbases and embankment construction.

This has caused inevitable delay in completion of Projects and also cost overrun. The Road

Development Authority and the funding agencies are equally concerned about this situation

and to find suitable solutions.

This Technical Note is to provide a solution to the problem which considered most appropriate

as the next step towards effective, environmentally friendly within shortest possible time for

implementation which is blending two or three easily available soils in predetermined

proportions to satisfy specification requirement like gradation, PI,LL,CBR.

3.2 Mission :

To make use of all excavated materials of embankment cutting, drains, culverts and bridge

foundation excavations as construction materials, which are usually disposed of without any

investigation, blending those materials with soils closely available for mining is necessary. This

will help to improve exiting subbase quality and meet specification requirement which

TN

03


• Economizes the use of soil material

• Minimizes harm to the environment

• Minimizes transport cost

3.3 Approach

a) We have been fortunate to mine naturally occurring soils satisfying Engineering

specifications but it is no more practicable. Hence investigation of available soil

characteristics and blending them in a predetermined proportion to achieve

resultant mix satisfying the specifications is a way forward.

b) It has been found when soil gradation is complying with specification requirement

generally PL,PI and CBR requirement follow the specifications. Hence it is

recommended to conduct sieve analysis of available material, giving priority to

cut/excavated material from the site or vicinity of the site. This will enable

Materials Engineer to decide which particle size range is deficient for satisfying

the specification requirement. This is best achieved by plotting the specification

grading band and particular soil sample (A) side by side.

c) The next exercise is to find a suitable soil source from fresh material surveys or

available material data bases (Including sand or crushed rock material) which

dominate the missing particle size range (B). This is not trial and error altogether.

The Materials Engineer knowing the deficient particle size range in the main soil

source, aim in finding a soil source rich in the missing particle size range (Sandy,

Silty, clayey Etc.) After finding such soil source its soil gradation is also plotted in

the same sheet as desirable gradation, and the sample A.

d) Next task is to find the mix proportion to achieve the desired gradation satisfying

the specification requirement, followed by other tests like LL, PI, CBR as

appropriate for the resultant soil mix. We would be lucky if we can get the right

blend with two soil samples suitably selected. If not a third soil source

supplementing the sample A and B to satisfy specification requirement is to be

found (C).

e) The procedure for determining the mix proportions for two sources (A, B) and three

sources(A,B,C) are described separately. Both graphical and numerical methods

are explained

3.4 Determination of mixing proportions for samples A, B;

The method of determining mix proportion is directly abstracted from the following reference

and appended below.

Military Soil Engineering Field Manual

Department of Army

Washington DC-1997


Chapter -9 Soil Stabilization for Roads and Air fields


3.5 The procedure for determination of mix proportion for three samples.

Graphical Method

The method is directly abstracted from the book –Soil Mechanics for Road Engineers, Road

Research Laboratory, DSIR London- 1952 reprinted 1961 Chapter 11 , Page 220-231. And

appended below.

Figure II

(l) The required size distribution is represented by the diagonal 00' of a rectangle (Fig.

II). The vertical ordinates of the rectangle are graduated for percentages from O to

100 on a linear scale. The horizontal scale for sieve aperture size is graduated by

drawing for each sieve size a vertical line that cuts the diagonal at a point where

the ordinate equals the percentage passing that sieve, i.e. 100 per cent for I in., 92

per cent for in., 82 per cent for in. and so on.

(2) The size distribution of the aggregates to be mixed (Table Il , columns 4, 5 and 6

are plotted on this scale of sieve size (Fig. Il ), giving the lines BAO' (crusher-run),

BFE (sand) and OG (silty clay).

(3) The nearest straight lines to these size distributions are drawn with the aid of a

transparent straight-edge, by the " minimum balanced areas " method described


above. They are the dotted lines CO', BD and OG (the last being coincident with

the actual size distribution).

(4) The opposite ends of these lines are joined, giving the chain lines CD and BG (in

this case, the latter coincides with the No. 200 B.S. sieve ordinate). The points

where these lines cross the required size-distribution line are marked by the circles

L and M. The proportions in which the three aggregates should be mixed are

obtained from the differences between the ordinates of these

The particle-size distribution that will result from mixing the aggregates in these proportions

is given in column 7 of Table Il . Although not identical with the required size distribution

(column 3), it is within the specified limits (column 2).

EXAMPLE OF ROTHFUCHS' METHOD FOR PROPORTIONING MIXTURES OF AGGREGATE

MIXTURE FOR SURFACINGS

Table II

Note: This reference should be considered as guidance only, in practice the correct sieve

sizes as per specification should be used.

3.6 Field mixing

In the field proportioning of different materials could be done using a plant or on a suitably flat

area with the use of an excavator or wheel loader.

In the field, if mix in - situ is adopted, the materials used in a mechanically stabilized soil

mixture probably will be proportioned by loose volume. Assume that a mixture incorporates

75 percent of the existing subgrade soil, while 25 percent will be brought in from a nearby

burrow source. The goal is to construct a layer that has a compacted thickness of 150mm. It is

1 2 3 4 5 6 7

B.S.

sieve

size

Percentage passing Mixture

37%A

45% B

18 % C

Required size

distribution Aggregates available

Limits Average

(A) Crusher-

(B) Sand

(C)

Silty

clay

1 in.

3/4 in.

3/8in.

3/16in.

No. 7 No. 36 No.

200

100 85 — 100 65 — 100 55 — 85 40 — 70 25 — 45 10 — 25

100 92 82 70 55 35 18

95 70 21 11

Trace 100 85 55 Nil

100

98 89

67 58 43 18


estimated that a loose thickness of 200mm will be required to form the 150mm compacted

layer. A more exact relationship can be established in the field as construction proceeds, of the

200mm loose thickness, 75 percent (or 0.75(200) = 10mm) will be the existing soil, The

remainder of the mix will be mixed thoroughly to a depth of 8 inches using an agricultural

machines.

3.7 Concluding remarks.

Both the graphical and arithmetical methods have advantages and disadvantages. The

graphical method eliminates the need for precise blending under field conditions and the

methodology requires less effort to use, Its drawback becomes very complex when blending

more than two soils. The arithmetical method allows for more precise blending, such as mixing

at a batch plant, and it can be readily expanded to accommodate the blending of three or more

soils. It has the drawback that the precise blending is often unattainable under field conditions.

This reduces the quality assurance of the performance of the blended soil material.

1. It is required to carry out other complying tests to decide the conformity with the

specifications. However, an approximate value could be worked out as follows

taking the values in the sample A, and B used in the blending of two soil samples,

2. It is required to ensure thorough mixing before loading to trucks for

transportation.

3. Also it is required to ensure those soils are free of roots and foreign matter.

4. This re transportation could be beneficial in taking soil material in small tippers

or tractors on rural roads leading to the roads under improvement without

violating load restrictions.


Date of Issue : 1/11/2017

Authority to amend : Chairman/DG- RDA

Circulation : Internal

Initiated by : PD iRoad Project RDA

Version : V. 0.0

Material specification for low volume Roads – TN 04, Integrated Road Investment Program, April 2018 31

Technical Note

April 2018

Material specifications for low volume roads

4. Material specifications for low volume roads

4.1 Introduction

Rural farm-to-market access roads, roads connecting communities, and roads for are significant

parts of any transportation system in Sri Lanka. They are necessary to serve the public in rural

areas, to improve the flow of goods and services, to help promote development, public health

and education. Scarcity of material not meeting current speciation and refusal of material due

to slight deviation from the specs are severer issues in road construction industry.

The basic objective of this note is to revise the existing material specification maximising the

use of locally available material for road construction.

A low volume road is commonly defined as a road that has an average daily traffic <1000

4.2 Purpose

The aim of this technical note is to provide a basic set of quality requirements for the use of

locally available material sources for the road industry.

4.3 Typical cross section

Typical cross sections of current i Road program are given in Annexure 1. These sections are

taken from the standard drawing of i Road program.

4.4 Sub grade

It is usually necessary to add subgrade structural support or to improve the road bed native soil

surface with materials such as gravel, coarse rocky soil, crushed aggregate.

The subgrade for the full width of the roadbed shall be scarified to a depth of at least 150 mm,

and the scarified material brought to uniform moisture content either by drying or by adding

water.

The upper 150 mm of soil may be removed and replaced with suitable material, or removed

and manipulated with suitable equipment before replacing. The material shall be compacted to

produce a subgrade having a density not less than the density required and within the moisture

content specified.

A range of options can be considered to improve the structural capacity of the subgrade in areas

of soft soils or poor subgrades (CBR < 2).

These commonly include:

• Remove and replace with quality granular material or rock

• Stabilising with cementitious material such as lime, cement or bottom ash.

TN04


• Bridging with layer/s with geotextile.

• Placing and compaction of layers of gravel or crushed aggregates.

4.4.1 Capping layer or selected subgrade

When the California Bearing Ratio (CBR) of subgrade is found below a 2 %, a capping layer

is normally provided to reduce the effect of weak subgrade on the structural performance of

the road.

It also provides a working platform for sub-base to be constructed on top in wet weather

condition because the compaction of wet subgrade is difficult on site.

Material specification for selected subgrade or capping layer shall be comply with the

following Table. Material selected for selected subgrade shall be naturally occurring material

or blended gravel and sand with no high plastic clays.

Property Value required

Liquid limit (LL) % < 40

Plasticity Index(PI) % < 15

Soaked CBR (4 days) % > 15 CBR at 95% MDD (Modified Compaction Table 1: Plasticity and CBR requirement for capping layer or selected subgrade.

Plasticity Product (PP) is defined as the product of plasticity index (PI) and percentage of fines

less than BS No 200 sieves (i.e., % < 0.075mm).

PP = PI× (% < 0.075mm)

If Capping layer or selected sub grade material exhibits the plasticity product (PP) less than

300, soils up to PI, 20% can be used.

4.4.2 Poor subgrade

Sub grade with CBR less than 2 % require treatment with granular fill typically comprises a

well-graded coarse gravel, crushed rock or material comply with capping layer as specified

above. Materials with CBR less than 2% are unlikely to behave elastically under vehicle

loading.

The minimum thickness of treatment layer typically 400mm for sub grade CBR less than 1.5

and 300mm for CBR between 1.5 and 2 or to suit site condition.

In areas where rock fill is used for soft subgrade, a minimum 150mm cementitious stabilised

granular material shall be used to provide a stable platform for construction of the pavement.

Clay subgrade with water sensitivity and volume changes during wet and dry condition shall

be cement or lime treated to a maximum depth of 300mm or as required where the material to

be stabilised are suitable (iRoad /TN01 &02).

4.4.3 Stabilised subgrade

Subgrade material can stabilised when required. In situ or plant mix stabilisation should be

carried out using either lime or cement in accordance with the i Road Technical Note 1 and 2.

Lime and cement stabilsed subgrade shall achieve unconfined compressive strength (UCS) not


less than 1MPa and not greater than 2MPa at 28 days soaked. Parent material requirement for

stabilisation is given in Table 3.

Property Lime Cement

Plasticity Index (PI) >10 < 10

Percentage passing 0.075mm - < 25

Maximum aggregate size 75mm 75mm

Ferric oxide < 2% --

Soluble sulfate < 0.3% -- Table 2: Material requirement for stabilisation

4.5 Subbase

Sub base is a secondary load spreading layer in the pavement structure and also acts as a

working platform. This layer required an adequate bearing capacity to avoid excessive

movements and cracks on the road surface.

The material selected for subbase shall be naturally occurring material or stabilised soil with

cementitious binder such as lime, cement or bottom/fly ash. Method of stabilisation of marginal

subbase material with these ingredients are given in RDA Technical Notes 1, 2 and 3.

Required grading, plasticity characteristic, CBR strength and plasticity product (PP) of material

for subbase is given in Table 3 & 4.

Sieve Size

(mm)

Percentage Passing

(%) 50 100

37.5 80-100 20 60-100 5 30-100

1.18 17-75 0.3 9-50

0.075 5-25 Table 3: Grading requirement

Property Value

required

Liquid limit (LL) % < 40

Plasticity Index(PI) % < 15

Soaked CBR* (4 days) % > 30

Plasticity Product (PP) < 300

Table 4: Material Characteristics for Sub base * CBR at 98% MDD (modified compaction)

Plasticity Product (PP) is defined as the product of plasticity index (PI) and percentage of fines

less than BS No 200 sieve (i.e., % < 0.075mm).

PP = PI× (% < 0.075mm)

If sub base material exhibits the plasticity product (PP) less than 300, soils up to PI, 20% can

be used.


Figure 1: Gradation envelop of sub base material

4.5.1 Use of sand

In general, sandy soils do not comply with the specification for road material mainly due to the

inadequacy of the gradation especially for structural pavement layers.

The plasticity and strength characteristics are fulfil the specified requirements and with

appropriate design, and construction procedures, sand can be used as subbase, subgrade and as

an embankment material.

4.5.2 Subgrade

Due to poor compaction and excessive volumetric movements, sand subgrade layer usually fail

due to poor support to withstand the traffic loads. Sand subgrade with adequate compaction

has relatively low chances of failure. A control compaction trial are necessary before

construction to achieve required CBR value.

4.5.3 Subbase

There are types of sand provide required CBR value when compacted to an appropriate density.

This particular sand can be used as a sub base layer and only apply to low traffic volume single

lane. Grading requirement for sand subbase layer is presented in Table 5

Sieve Size Passing %

2.36 100

1.18 70-90

0.425 35-65

0.150 18-38

0.075 8-25

Plasticity Index (PI) < 6

Plasticity Product (PP) < 150

CBR % (soaked) >30 Table 5: Subbase material property

0.01 0.1 1 10 100

0

20

40

60

80

100

Grain Size(mm)

Per

cen

tGE

Pas

sin

g (%

)Partical Size Distribution Curve


4.6 Embankment material

The embankment consists of a series of compacted layers or lifts of suitable material placed on

top of each other until the level of the subgrade surface is reached. The subgrade surface is the

top of the embankment (above upper zone) and the surface upon which the subbase is placed.

Material for embankment shall comply with the propertied given in Table 6 & 7. The

requirement of percentage passing 0.075mm shall apply for the material in compacted state.

Weighted plasticity index (WPI = PI x percentage passing 0.425mm) shall also apply to the

compacted material.

Material

Type

WPI % Passing

0.075mm

Liquid

Limits (LL)

Plasticity

Index (PI)

Emersion

Class

CBR

% Type 1 < 1200 < 35 < 50 > 6 > 3 > 7

Type 2 1200 -2200 - < 55 > 6 >3 > 5

Table 6: Embankment fill material property

4.6.1 Zoned embankment

Figure 2: Embankment zone

Note: it is prefer to construct outer zone and core layers simultaneously.

Material type for zoned embankment in different rainfall zones are

Embankment

Type

Embankment

height (m)

Structural

fill

Lower

zone

Upper

zone

Rain fall

Homogeneous < 10 Type 1 -- -- Low/High

Zoned

< 3

-- Type

2

Type 1

(1m) Low

-- Type

2

Type 1

(0.8) High

Zoned 3-10

-- Type

2

Type 1

(1.2m) Low

-- Type

2

Type 1

(1m) High

Table 7: Embankment fill properties

Embankment fill

Lower Zone (Type 2)

Upper Zone (Type 1)

Subgrade level


4.6.2 Homogeneous embankment

Figure 3: Homogeneous embankment

Type 1 material shall be used for homogenous embankment construction in and around the

structures such as bridge abutment, culverts and pipes.

4.6.3 Sub grade in cuttings

Figure 4: Road section in cuttings

The subgrade shall be built and tested as per requirements of this Technical Note before

pavement structure is constructed. If subgrade material is not comply with the specification,

shall be replace with fill material or in situ stabilised as per section 4.

4.7 Shoulder material

Shoulders are an important part of the road system, providing space for emergency stops,

structural support for the pavement, and increased roadway width to accommodate passing

vehicle for single lane road. Natural soils or blended soils for shoulder construction shall

conform to the following grading requirement and other material properties as shown in Table

8 and 9.

Sieve Size

(mm)

% Passing

37.5 100

20 77-100

5 41-100

2.36 30-80

600 18-50

0.075 5-25 Table 8: Gradation for shoulder material

Homogeneous Embankment (Type 1)

Subgrade level

Road Pavement (surfacing, sub base, improved layer)

Subgrade (stabilised if required) ))

Shoulder


Property Wet Zone Dry Zone

CBR > 15 >15

Liquid Limit (LL) < 50 < 55

Plasticity Index (PI) 4 - 25 6 -25

Emersion Class > 3 > 3

WPI <1200 <1200 Table 9: Material property for shoulder construction

4.7.1 Emerson class

Soil dispersion potential is the likelihood that soils will release a cloud of fine clay particles

when brought into contact with water. Soil dispersion potential is measured as the Emerson

Class number (AS 1289.3.8.1-2006 - a simple semi-quantitative dispersion test), or by

Emersion Crumb test (ASTM D6572-06) which considers soil consistency and depth. Soils

which are less than emersion class 3 are highly likely for erosion.

Method of testing for determination of emersion class is described in Annexure 2.

4.7.2 Shoulder protection

Earthen shoulders usually have a problem with finer material washing away and leaving stones

in the surface which gives a rough and rutting undesirable shoulder surface. Grassing can be

used to maintain road shoulders from erosion. There is a danger in this as the vegetation may

keep water from draining off the pavement. Therefore, proper maintenance of shoulders are

required.

Turf can be grown on stabilized soil-aggregate materials where moisture is adequate. Under

occasional traffic the turf will serve as an economical wearing surface having shear resistance

against wing and rain erosion.

Topsoil is not essential for turf. The slope of the shoulder should be adequate to permit surface

water to drain properly and to assist in delaying as long as possible the necessity of blading.

Appropriate maintenance procedures are essential to maintain a vegetative cover under the

imposed conditions of growth.

4.8 Quality control/ quality assurance testing

In-situ Measurement of Stability of Aggregate Subbase:

4.8.1 Dynamic cone penetrometer (DCP) test:

DCP is an instrument designed for rapid in-situ measurement of sub surface material

strength. The cone penetration is inversely related to the strength of the material. DCP

test is conducted according to ASTM D 6951 (Standard Test Method for Use of

Dynamic Cone Penetrometer in Shallow Pavement Applications). This test involves

measurement of penetration rate per each blow of a standard 17.6pound hammer,

through undisturbed and/or compacted materials. Penetration to be commenced from

the top of subbase layer to a required depth. Primary advantages of this test are its

availability at lower costs and ease to collect and analyze the data rapidly.

http://www.freestd.us/soft2/609064.htm


4.8.2 Light weight falling deflectometer (LWFD) test:

The LWFD test is a simple and rapid non-destructive test that does not entail removal

of pavement materials, and hence is often preferred over other destructive methods. In

addition, the testing apparatus is easily transported. Layer moduli can be back-

calculated from the observed dynamic response of the subbase surface to an impulse

load.

4.8.3 Field density test - sand cone method (ASTM D-1556)

4.8.4 Non – nuclear density test

Non-Nuclear Soil Density Gauge is used for detecting density of Soil specimens with non-

nuclear type. It displays a GPS position and completely nondestructive test with fast, reliable

and accurate readings.

4.9 References

1. NCHRP – Recommended Practice for Stabilization of Subgrade Soils and Base

Materials, National Academy of Sciences and Medicine.

2. Gordon Keller, PE, James Sherar, PE – Low Volume Road Engineering – Best Management Practices Field Guide , July 2003.

3. NZ Transport Agency B/6:2012 – Specification for In-situ Stabilisation of bound sub – Layers, 2012.

4. Mircea Radulescu - Technical Specifications for Low Cost Rural Roads, PMU, Rural

Development Project, Ministry of Administration and the Interior, March 2005.

ICTAD.

Annexure 1: Typical Section of iRoad Program

Annexure 2: Emersion class test procedure

OCEDUR E FOR EMERSION CLASS TEST

45 Use of bottom ash for road construction – TN 05, Integrated Road Investment Program, April 2018

TN05

kykyhkhjhh

Technical Note

April 2018

Use of bottom ash for road construction

5. Use of bottom ash for road construction

5.1 Introduction

Bottom Power Station at Norochcholai, is producing about 290,000 Mt of fly ash and bottom

ash (Bottom ash) annually. Only small percentage of the total production of fly ash was

recycled. Due to increasing disposal costs, reduction of landfill space and need for conservation

of natural resources, it is essential to find beneficial ways of reusing fly and bottom ash in

secondary applications.

Laboratory trail on engineering properties of bottom ash exhibit relatively high bearing

capacity, friction angle (φp ranges from 25 deg to 30 deg) and relatively low dry unit weight

(12 kN/m3). In addition, the hydraulic conductivity of bottom-ash mixtures is similar to that of

a fine sandy silt or silt.

These engineering properties make the use of bottom-ash mixtures suitable as, subbase,

capping layers, fill materials for embankments and retaining structures. Bottom ash has been

utilized successfully as a fill material in several projects in many other countries. However,

there is limited information in the literature on the performance of highway embankments

constructed with Bottom ash mixtures. This Technical Note presents the use of Bottom ash in

road industry.

This specification does not address the environmental issues that may be associated with the

permitting and regulation of the use bottom ash by the Environment Authority.

5.2 Properties of bottom ash

5.2.1 Specific gravity

The specific gravity of bottom ash varies with the chemical composition of the Bottom used in

power plants. Higher iron contents in the ash may result in higher specific gravity values (Kim

2003). Typical values of Gs range from 2.1 to 2.9.

The specific gravity of bottom ash mixture used for the construction of the demonstration

embankment, as determined by method A (ASTM D 854-00), is equal to 2.5.


5.2.2 Piratical size distribution

Analyses were performed during the course of the bottom ash evaluation to gauge whether the

material is consistent throughout different samples. The method used is detailed in (ASTM D

422).

Calculations show the Coefficient of Uniformity (Cu) and the Coefficient of Gradation, Cc,

and the criteria needed to classify as “well-graded.” The bottom ash material meets the criteria

for well-graded, which is an indicator of a good representation of all particle sizes, and can aid

in compaction potential.

Cu = D60 /D10

Cu = 22

Cc = (D30)2 / (D60) (D10)

Cc = 1

The Unified Soil Classification System (USCS) is a standardized system used to group and

identify similar soil types, and identify them with a unique standardized identification system,

published as ASTM D 2487. According to the USCS, the bottom ash falls into the classification

of a SW-SM, sand with silt.

0

20

40

60

80

100

120

0.01 0.1 1 10 100

% P

assi

ng

Seive Size (mm)

Figure 1: Particle Size distribution curve – Bottom ash


5.2.3 Chemical composition

The chemical composition of ash depends on the characteristics and composition of the Bottom

burned in power plants. Figure 2 shows heavy metal composition of the bottom ash from

Norochcholai power plant. The presence of silica and alumina indicate good ingredients for

pozzolanic reaction when mix with hydrated lime. This improves mechanical properties of soil

mix with bottom ash

However, it is strongly recommended to get a consent from Central Environmental Authority

(CEA) to use bottom ash for any road construction activity in advance. Road construction using

bottom in residential areas, a test report including detail chemical analysis should be submitted

for CEA approval.

Chemical Fly Ash Bottom Ash

Silica (SiO2) 48.09% 47.98%

Phosphorus (P2O5) 2.29% 2.03%

Sulphur (SO3) 0.31% 0.08%

Iron Oxide (Fe3+) 3.61% 4.86%

Aluminium (AL) 16.48% 15.59%

Titanium (Ti) 0.98% 0.98%

Calcium (Ca) 6.68% 7.22%

Potassium (K) 0.45% 0.40%

Magnesium (Mg) 0.94% 1.01%

Manganese ( Mn) 0.04% 0.04%

Sodium (Na) 0.02% 0.20%

Nickel (Ni) <0.010% <0.010%

Arsenic (As) 77.67 ppm 70.90 ppm

Cadmium ( Cd) ND ND

Lead (Pb) 5.31 ppm ND

Antimony (Sb) ND ND

Figure 2: Chemical composition of Bottom ask


5.2.4 Environmental considerations

Leaching of trace metals from bottom/fly ash is the main environmental concern in

embankment construction using these materials. Migration of metals from ash into ground

water shall be studied collecting ground water sample at regular intervals.

5.2.5 California bearing ratio

California Bearing Ratio (CBR) is defined as the ratio of the force required to cause a circular

plunger of 1932 mm2 area to penetrate the material for a specified distance expressed as a

percentage of a standard load. This particular test is being carried to assess the strength of

pavement layers. The test procedure is published in ASTMD 1883.

Table 1 presents the results of 4 days soaked CBR tests of bottom ash. The data in Table 1

indicates that in a confined condition the bottom ash performance is close to that of sand with

high CBR value.

Description OMC

(%)

MDD

(kN/m3)

Plasticity *CBR %

Bottom Ash 30 12 NP 52 Table 1: CBR value of Bottom ash

* 4 days soaked (moist), compacted at 98% MDD

5.2.6 Compaction characteristics

Modified compaction tests of bottom (ASTM D698) below Figure 3 indicates the maximum

dry of 12 kN/m3, and the optimum moisture content 30 %.

Figure 3: Modified proctor compaction results

1.08

1.12

1.16

1.20

10.0 15.0 20.0 25.0 30.0 35.0

Dry

Density

(g/c

m3)

Moisture Content %


5.3 Use bottom ash in the construction road embankment

The use of bottom ash for highway embankment construction in other countries are extremely

promising and large quantities of ash have been used successfully and economically. The

proposed embankment configuration in this section of the report is not recommended for flood

prone areas and bridge approaches.

However, an appropriate embankment slope protection against erosion is essential for

embankment in in law lying areas where embankment toe is submerded. A typical section of

embankment with batter protection is shown in figure 9.

Mechanical characteristic Bottom ash mix are important when using this material for

embankment construction.

Material use for embankment construction for satisfactory performance, the following two

major criteria should be satisfied.

a) It must have adequate strength to support safely its self-weight and that of the traffic

loads, and

b) It must be sufficiently stiff to prevent excessive settlement during the service life of the

pavement. Slope stability and settlement analyses were carried to determine the best

way to meet these requirements at the embankment design stage.

Dry Bottom ash can sustain particle degradation during compaction (Kim et al 2005). Crushing

of the bottom ash particles during compaction contributes to an increase in the maximum dry

unit weight. Compaction characteristics of mixtures of fly ash and bottom ash have well graded

size distributions, which allows the Bottom ash particles to pack more closely, resulting in an

increase in the maximum dry unit weight of the mixture (Kim et al. 2005). Some engineering

properties of bottom ash is shown in Table 2.

Bottom ash is non plastic material with particles size ranging from fine gravel to fine sand.

With very low percentages of silt-clay sized particles. Bottom ash is predominantly sand-sized,

usually with 90 to 100 percent passing the No. 4 sieve (4.75 mm) and 0 to 5 percent passing

the No. 200 sieve (0.075 mm). Top particle size for bottom ash is typically less than 10m.

Granular materials with angular particles are typically more compressible than those with well-

rounded particles because the sharp edges of the angular particles tend to be break during

compression as well as shear. Compressibility of bottom ash is very similar to sand placed at

the same relative density (Seals et al. 1972) and consolidates rapidly and therefore

compressibility is not a design concern.

Property Value range

Maximum dry density (kN/m3) 11-12

Optimum Moisture Content, % 30

Internal Friction Angle (drained) 25-35

Hydraulic Conductivity cm/sec 1E-3 Table 2: Engineering properties of Bottom ash


5.3.1 Zoned embankment configuration using bottom ash

Low embankment less than 4m

Typical cross sections of low embankment using Bottom ash is shown in Figure 3. Outer layer

(cladding) for both embankments are necessary to control erosion. Material for outer layer can

be either Type I or II embankment material of thickness not less than 1m. Core material, bottom

Bottom ash fill is a compacted zone of layers not exceeding a height of 3m. Geosynthetic

membrane or compacted layer of clayey soil (k < 1E-08 m/s) is required to prevent any potential

for heavy metal leaching. Properties of geo synthetic membrane is given in section 5.3.3

High embankment over 4m

For embankment over 4m shall be constructed using multiple layers of bottom ash and general

fill layers (Type I or II) in between (not less than 500 mm) as shown in Figure 4. The thickness

of outer zone shall be not less than 1 m. The thickness of compacted bottom ash layer shall not

exceeds more than 2m.

Figure 4: Typical embankment section H > 4

Figure 3: Typical embankment < 4m high


5.3.2 Embankment construction

Water shall be added or other suitable means shall be taken to prevent dust results from the

transporting and placing of dry material.

Before the fill material is placed the subgrade should be levelled to produce a plane surface

having a 1:30 cross fall. Some filling maybe necessary to achieve the required levels. Bottom

ash fill for the embankment deliver from Norochcholai power plant shall be spread over

prepared subgrade of proposed embankment in layers of each maximum 300 mm loose

thickness. A synthetic geomembrane shall be place over the prepared subgrade before

commandment of embankment filling. Each layer of fill shall be wetted up to the optimum

moisture content. The average moisture content of each layer to be determined from samples

taken immediately prior to the placing of the next layer of fill.

Compaction of loose layer shall be carried out immediately after placing the loose layer to a

degree of compaction not less than 95% of modified proctor to achieve the required density.

The material selected for outer zone shall be constructed along with the progress of core

material (Bottom ash) as shown in Figure 4.

Quality control programs for bottom ash embankments is similar to such programs for

conventional earthwork projects as per ICTAD – SCA/5. These programs typically include

visual observations of lift thickness, number of compactor passes per lift, and behavior of the

ash under the weight of the compaction equipment , supplemented by laboratory and field

testing to confirm that the compacted material has been constructed in accordance with design

specifications.

5.3.3 Material property

Outer zone:

The material for outer zone shall conform to the following gradation limits or as directed:

Property Standard Value

% passing

100 mm BS 1377-2

100

% passing

0.075 mm BS 1377-2

10 - 35

Earth Fill

Material

WPI PI (%) Liquid

Limits (%)

% Passing 0.075

mm AS sieve

Emerson Class

Number

Outer Zone

(Type1) < 1200 > 6 < 50 < 35 > 3

Table 3: Required material properties of outer zone


5.3.4 Synthetic geomembrane

Synthetic geotextile use as a membrane within embankments shall be non-woven type shall

meet the following specifications (Table 4).

Test Properties Unit Value

Thickness mm 1.5

Density g/cc 0.94

Yield strength kN/m >22

Break strength kN/m >16

Tear resistance N >187

Puncture resistance N > 400

Yield elongation % 12

Break elongation % 100

Table 4: specification for HDPE geomembrane

5.3.5 Placement of bottom ash

Initially the stockpiled materials were moved into position on the test area by front end-loader,

and then spread with a dozer to the designated 225 mm thickness (ICTAD Publication - SCA/5

section 304.3). As the stockpiles were depleted, more material was hauled in, stockpiled, or

dumped directly on the area designated. As the dozer spread the bottom ash material across the

test area, a survey level or other measurement method is required to check each lift thickness.

5.3.6 Compaction

10T vibratory roller is required to compact the bottom ash lifts. A series of tests shall be

performed between passes of the roller followed by additional tests after completion of each

lift.

5.3.7 Light Weight Falling Deflectometer (LWFD) tests

The Light Weight Falling Deflectometer (LWFD) equipment can be used to measures

composite in-situ modulus value of near-surface materials.

5.3.8 Dynamic cone penetrometer tests

The DCP testing is required to carry out along the crest of finished embankment at 20 m interval

in a zig zag pattern. The results should be compared with the LWFD results.

5.3.9 Stability assessment

5.3.9.1 Method of analysis

Stability analyses were undertaken for the bottom ash embankment design using a computer

based modelling program. The computer models analysed the stability of potential circular


slip planes within the mass of the embankment by Morgenstern method. The computer

program, SLOPE/W, was used in the analyses. A probability assessment of seismic loading

has not been considered for these analyses

Two cases were examined in the stability analyses for the design embankment less than 4m

and above.

Case 1: Embankment to final height with traffic load of 20 kPa – low water level

Case 2: Embankment to final height with traffic load of 20 kPa – water level 1m above

ground level

5.3.9.2 Parameters

Parameters adopted for the embankment and foundation materials in the analyses were

assumed and are believed to be conservative.

Parameters adopted for the bottom ash embankment, outer zone and foundation materials are

shown in Table 5.

Material Density

(kN/m3)

Cohesion

(kN/m2)

Angle of friction

(Deg)

Bottom Ash 12 0 29*

Outer Zone 18 20 34

Foundation 20 18 35 * as per direct shear test

Table 5: Material Property

5.3.9.3 Results of the stability analyses

The results of the stability analyses for the two cases examined for embankment sections are

summarised in Tables 6 and 7, with the Slope W computer printouts presented on Figures 5, 6,

7 and 8.

Figure 5 & 6: 4m and 6m embankments with low ground water level (Case 1)


Figure 7 & 8: High ground water level (Case 2)

Low embankment

Case Factor of

Safety

Recommended

Minimum Factors of Safety*

1 1.81 1.5

2 1.68 1.5

Table 6: Results of stability analysis, Embankment height < 4m

High embankment

Case Factor of

Safety

Recommended

Minimum Factors of Safety*

1 1.56 1.5

2 1.52 1.5 Table 7: Results of stability analysis, Embankment height > 4m

The stability analyses indicate that for the cases examined the embankment has an adequate

factor of safety against failure for all the cases.

5.3.10 Bottom ash stablised marginal material for embankment construction

Marginal soil can be modified to fulfill the requirements for embankments construction by

adding 30% - 40% of bottom ash to obtain required CBR other propertied. Below Table 8

shows the improved propertied of marginal material to qualify for embankment construction.

Soil/ Mix % Passing

0.075mm

Liquid Limits

(LL)

Plasticity

Index(PI) *CBR %

Marginal Material (1) 26 59 24 29

Soil 70% + Bottom ash 30% 26 36 8 42

Marginal Material (2) 40 40 20 26

Soil 70% + Bottom ash 30% 21 36 9 39 *: 4 days soaked, modified compaction 98 % MDD

Table 8: Stabilized marginal material for embankment


5.3.11 Embankment in low lying areas

Bottom ash embankment construction in flood prone areas is not recommended. However,

embankment batter protection is essential in marshy, low lying areas to prevent erosion. A

typical section of embankment with batter protection is shown in Figure 9.

Placing geosynthetic filter membrane for erosion control for embankment in flood prone areas

is not a long term solution due to clogging of pores in the membrane.

Figure 9: Typical embankment protection in flood prone area (H < 4m)

6 Use of bottom ash soil mixture for selected subgrade (capping layers)

Laboratory trial carried out for four different marginal soils mix with different percentage of

bottom ash varies from 20% to 40% of the soil weight as shown in Table 9. Additional tests

were carried out for bottom as soil mix with 1% cement and 1% lime as shown in Table 9.

The properties of original soil before mixing is shown in Table 9.

Soil

Type

LL (%)

PI

(%)

Type OMC

(%)

MDD

(kN/m3)

CBR (%)

A 52 24 SC 15.2 1.78 17

B 22 8 SC 12.3 1.92 11

C 59 24 SM 15.3 1.87 29

D 40 20 SC 16.8 1.81 26

6.1 Properties of stabilised bottom ash

6.1.1 Strength gain

Addition of bottom ash to the sub grade soil resulted in the mixture having significant

improvement to CBR values. Variation of CBR with different proportion of bottom ash is

illustrated in Figure 10 where 30% bottom ash mix by weight generally represent as a proper


mix design for soil stabilisation. Soil mixture become non plastic with the addition of 40%

bottom ash to soil type C. This indicates bottom ash and soil particles get more closed packed

together comparatively with this mix ratio causing increase in the mechanical strength. During

compaction the bottom ash particle subject to crushing in to fine particle thus further filling up

remaining voids increasing shear strength. Further increase in bottom ash content will decrease

the CBR values due to predomination of bottom ash particle

.Stabilised mix Percentage

Bottom ash

Percentage Soil Percentage

Cement

Percentage

Lime

Bottom ash +

soil mix 20% 30% 40% 80% 70% 60% Nil Nil

Bottom ash +

soil + Cement

mix

30% 70% 1% Nil

Bottom ash +

soil + Lime mix 30% 70% Nil 1%

Table 9: Results of Soil Bottom Ash Mixture

Figure 10: Variation CBR with Bottom ash mix

A significant increase of CBR value can be noticed an addition of 1% cement to 30% bottom

ash mix as shown in Figure 11. The cement particles further improve binding properties of

bottom ash mix and may control the leachate.

Figure 11: Variation of CBR value with 1% cement

1711

2926

46

3842

39

0

10

20

30

40

50

Soil A Soil B Soil C Soil D

CB

R %

Natural Soil + 20% Ash Soil + 30% Ash Soil + 40% Ash

11

26

38

72

N A T U R A L S O I L

S O I L + 1 % C E M E N T

S O I L + 3 0 % A S H

S O I L + 1 % C E M E N T + 3 0 % A S H

CB

R %


A significant increase in CBR value of 30% bottom ash mix can be obtained by addition of 3%

lime as shown in Figure 12. The results CBR value exceeds well over 120 indicating an ideal

mix for either road base .and sub base.

Figure 12: Variation CBR with addition of 3% lime

Material Properties

LL PI CBR Remarks

Original Soil 22 8 11 Not Comply

Improved Material

(30% bottom ash ) 23 6 38 Comply

Improved Material (30%

Bottom ash + 1% cement) 25 9 72 Comply

Improved Material (30%

Bottom ash + 3% lime) 36 7 142 Comply

Table 10: Properties of marginal material mix with 30% bottom ash with lime and cement

6.1.2 Plasticity

Plasticity of original soil mix decreases with the addition of bottom ash and become non plastic

generally in excess of 40% bottom ash. The reduction in plasticity index to comply with

standard is important particularly for road subbase and subgrade.

Specification limits

Below limits are given in RDA specification for road pavement layers and embankment.

Specification Limit <40 < 15 >30

Specification Limit <40 <15 >30

Embankment

26

110

142

0

20

40

60

80

100

120

140

160

Natural Soil Soil + 3% Lime Soil + 3% Lime + 30% Ash

CB

R %

Specification Limit <50 <25 >7

Sub Base (upper layer)

Sub Base (lower layer/capping)


7. Quality control

Sand cone tests are accurate but, cumbersome and time-consuming. The field density test shall

be carried out in accordance with test 15A of BS 1337 – part 9 -1990 or ASTM D1556 -90.

A test pad using bottom ash shall be constructed with a combination of roller passes. On the

basis of the results of dynamic cone penetration and LWD tests conducted in the test pad, in

conjunction with a combination of roller passes, the criteria for compaction control of bottom

ash shall be established. The subsequent construction monitoring and post construction

evaluation of the bottom ash embankment will be very effective using this criteria.

8. References

1. Syakirah Afiza Mohammed and Mohamed Rehan Karim - Application of coal

bottom ash as aggregate replacement in highway embankment, acoustic absorbing wall

and asphalt mixture, Department of Civil Engineering, Faculty of Engineering,

University of Malaya, 50603 Kuala Lumpur, Malaysia.

2. Esteban López López, Ángel Vega-Zamanillo, Miguel A. Calzada PérezAlberto

Hernández-Sanz - Bearing capacity of bottom ash and its mixture with soils, May2015.

3. Wei-Hsing Huang – The use of bottom ash in highway embankments, subgrades and

sub base joint highway research project, Feb 1990.

4. John K.W. Chan, Roger P.K. Lee – The use of furnace bottom ash as road sub-base

material in Hong Kong, 1996.

5. Syakirah Afiza Mohammed and Mohamed Rehan Kari - Application of coal bottom ash

as aggregate replacement in highway embankment, acoustic absorbing wall and asphalt

mixtures, International Technical Postgraduate Conference, 2017.

6. AbdusSalaamCadersa,1 AkshayKumarSeeborun,2 and Andre Chan Chim Yuk – Use

Of Coal Bottom Ash as Mechanical Stabiliser in Subgrade Soil, Hindawi Publishing

Corporation Journal of Engineering me, July 2014

technical notes - volume 1 - road development …(modified). for road pavements the thickness of...

Documents