Sudarshan Assignment 1 Insitu Stabilisation

608/658 Insitu Stabilisation Assignment 1 Question 1

Sudarshan Maharjan ID: 839025 of 1

Question 1

The use of in-situ stabilisation is helping lessen a number of environmental issues. The

environmental benefits of using these techniques in comparison to using other rehabilitation

techniques are quite substantial.

The list of key environment factors makes in-situ stabilisation a better option than other

construction methods are as follows:

1. Recycling of existing material: The in-situ stabilisation make use of existing pavement

material helping preserve the natural resources. Recycling also reduces the need for landfill

which often saves large areas of land from clearing and contamination.

2. Construction Time: In-situ stabilisation often drastically reduces the construction time and

lane closures. In soft and moist clayey sub grade, in-situ stabilisation by use of lime can

drastically reduces the excess moisture without the need for drying out the sub grade.

Construction time directly affect the road users and fuel consumption by vehicles waiting in

traffic.

3. Greenhouse Gases: Minimal usage of construction equipment helps reduces the production

of greenhouse gases. The raw material transportation and energy used will be greatly

minimised. Vehicle emissions are also reduced as less material haulage occurs. Sometimes it

becomes necessary to clear vegetation to build an access to get to the quarry site. Using in-

situ stabilisation helps reduce our carbon footprints.

4. Use of Industrial By-products: Industrial by-products like slag and fly ash were traditionally

been considered as waste materials however, these days it’s an important constituent of the

blended cement used for pavement stabilisation. Rather than dumping these produces in

the landfill it can recycled for good of environment and human beings.

References:

AustStab (2011) Pavement Recycling and Stabilisation Guide, AustStab, North Sydney, NSW.

Austroads (2006) Guide to Pavement Technology Part 4(D): Stabilised Materials Austroads Project

No: TP1089, Sydney NSW


Sudarshan Maharjan ID: 839025 Page 1 of 1

Question 2

The major problem associated with the construction of pavement layer with two stabilised layer is

failure of bonding between two layers. The consequences are that the fatigue life of smooth

interface between the two layers is approximately 100 times less than the fatigue life of rough

interface or bonded layers. This usually happens when significant delay between the placement of

lower and upper layers occur. The shrinkage cracking on the surface of the upper layer may

terminate at the interface of the two layers. Which in turn may allow the water to enter from

surface to the interface & consequently laterally along the interface. This may caused rapid and

further more de-bonding. Once the layers act as separate layers, the fatigue life of the pavement

diminishes quiet rapidly.

In general, the bond strength between the cemented layers was observed to decrease with an

increased time delay in placement of the second layer (Cameron & Mathias 2001). Minimising the

time delay between placements of second layer to the same day or as soon as possible can have very

good results. Some road agencies have tried using chemical bonding agent between the stabilised

pavement layers, but the more studies have to be done before we have the definitive answers.

Techniques that can be used to attempt to bond cementitiously-bound pavement layers include the

use of cement slurry or bituminous seal Interlayer (Kadar et.al. 1986). In the mean time, the

preferred construction method for two stabilised layer is to remove the top existing pavement

material to allow stabilisation of lower layer with the stabilising binder. This is then followed by

replacing the top material and stabilising this layer together with the uppermost 50mm of the lower

layer in the final phase. This may ensure the bonding between the two stabilised layers.

References:

Mathias C.L, Cameron D.A (2001) Bonding of Cement treated pavement Layers, 20th ARRB

Conference Melbourne Australia, ISBN 0-86910-799-2

AustStab (2011) Pavement Recycling and Stabilisation Guide, AustStab, North Sydney, NSW

Austroads (2006) Guide to Pavement Technology Part 4(D): Stabilised Materials Austroads Projects




Question 3

a. When lime is added to the clayey soil, the lime reacts with poozzolanic material in clay like

silica and alumina to form calcium aluminates and calcium silicates. The silicate compounds

in treated soil decreases plasticity, increases cohesion and strength.

b. For the lime stabilisation to be effective, the plastic index of the soil should be equal to or

greater than 10%. High plastic soil indicates the presence of pozzolanic material in soil such

as alumina and silica. The presence of pozzolanic material in high alkaline environment

promotes formation of silicate and aluminates.

c. Lime, particularly quicklime, is an alkaline material that is reactive in the presence of

moisture (National Lime Association, January 2004). Workers handling lime must be trained

and wear proper protective equipment. Soil applications can create exposure to airborne

lime dust, which should be avoided. The list of safety precautions required during

stabilisation are as follows:

Eye Protection - Lime can cause severe eye irritation or burning, including

permanent damage. Eye protection (chemical goggles, safety glasses and/or face

shield) should be worn where there is a risk of lime exposure. If lime comes in

contact with the eyes, they should first be flushed with large amounts of water. Seek

medical attention immediately after administering first aid.

Skin Protections - Lime can cause irritation and burns to unprotected skin, especially

in the presence of moisture. Prolonged contact with unprotected skin should be

avoided. Protective gloves and clothing that fully covers arms and legs are

recommended. Particular care should be exercised with quicklime because its

reaction with moisture generates heat capable of causing thermal burns. If skin

contact occurs, brush off dry lime and then wash exposed skin with large amounts of

water. If skin burns occur, administer first aid and seek medical attention, if

necessary.

Respiratory Protections - Lime dust is irritating if inhaled. In most cases, nuisance

dust masks provide adequate protection. In high exposure situations, further

respiratory protection may be appropriate, depending on the concentration and

length of exposure (MSDS should be consult for applicable exposure limits). For

inhalation, remove exposed person to fresh air. Seek medical attention immediately

after administering first aid.

d. Cementitious Binders like Slag/Lime (85/15) allows the contractors to have longer setting

time. This gives more time to achieve compaction and possibility to reduce shrinkage cracks.

In such cases this binder is useful. This blend has also been tested thoroughly and accepted

throughout Australia.

e. Fly Ash and Slag are the pozzolans i.e. it contains siliceous or alumina siliceous material.

These materials themself cannot form an expected cementitious material. These pozzolans



need calcium hydroxide released from the hydration lime to form silicates and aluminates.

Lime act as an activator for slag and fly ash. That is why in Triple blends it is essential to

have lime.

For the Triple blend, a minimum of 10% hydrated lime is required to activate slag and usually

one part of lime for every 2 part of Fly Ash is necessary. If these proportions are maintained,

various Triple blends could be made and used.

f. Blended Cement (Hydraulic Cement) is a cement which contents one or both of

Greater than 5% of Fly Ash or Ground Granulated iron blast furnace slag, or both.

Up to 10% silica fumes.

The list of Blended Cement type used in our region (Central West NSW) are as follows:

SSC40 (60% Slag / 40% Cement)

SSC50 (50% Slag / 50% Cement)

RoadPozz (75% Cement / 25% Fly Ash)

RoadPozz 50 (50% Cement / 50% Fly Ash)

622 Cement Triple Blend (60% Cement / 20% Slag / 20% Fly Ash)

g. Both bitumen emulsion and foamed bitumen use bitumen as a major component however,

the way they interact with the pavement material differs. Where the traffic has to be

opened immediately foam bitumen are better suited as foam bitumen treated material can

be placed, compacted and opened to traffic immediately.

Foamed bitumen can be used to stabilise the marginal quality pavement material with

relatively high plasticity. Bitumen emulsion can only be used in the comparatively better

material. Foam bitumen encapsulates only the fine particle and creating a bitumen rich

mortar that binds the matrix together. In the other hand bitumen emulsion separate and

breaks leaving bitumen. Then the bitumen provides a thick coat of binder to the aggregate in

the pavement without excessive bitumen drain off.

In urban area the supply and delivery cost generally does not varies much between bitumen

emulsion and foamed bitumen. However, in rural area foamed bitumen has edge over

bitumen emulsion as contractor does not have to carry extra water to rural place.

h. In bitumen emulsion the bitumen is in the state of dispersed droplets in a continous water

phase. The surface active agent (an emulsifier) is used in bitumen emulsion to prevent

rejoining of bitumen droplets.

The bitumen in suspension of water helps it become easy to mix with the pavement

material. Bitumen emulsion is designed to break or remove from water leaving solid

bitumen at or near the time of primary compaction. This frees bitumen than coat the

pavement materials that needs to be stabilised.



It would be necessary to incorporate secondary binder into the bitumen emulsion if the

traffic is to open shortly after the stabilisation (in this case 3 hrs). The supplementary binder

like cement makes the stabilised pavement to improve the early strength rapidly without

significantly reducing the fatigue life of pavement. The study shows that up to 2% of General

Purpose cement is considered to be suitable (Wirtgen, 1998).

i. Soluble synthetic polymers are in granulated or liquid form. During in-situ stabilisation it is

mixed with water to form the polymer chain which forms acrylimide or urethane copolymer.

These polymers then encapsulate soil particles with the thin film of polymer. When the

polymer dries it bonds with the pavement material reducing permeability and minimising

the water absorption into the clayey soil.

j. It is usual practice to keep stabilised pavement layer damp to help cure for 4 to 7 days.

However, over watering the layer will create a slurry on the surface of the stabilised layer

and it can cause delamination of the upper zone of stabilised layer.

References:

National Lime Association (January 2004), Lime-treated Soil Construction Manual, Lime Stabilisation

and Lime Modification, Bulletin 326

AustStab (2011) Pavement Recycling and Stabilisation Guide, AustStab, North Sydney, NSW.

Austroads (2006) Guide to Pavement Technology Part 4(D): Stabilised Materials Austroads Project




Question 4

We have, No. of heavy vehicles = 200 For calculating the Design Traffic (NDT) we have equation as follows:

NDT = 365 x AADT X DF x % HV/100 X LDF x CGF X NHVAG

Where,

AADT = 200 DF = 0.5 % HV = 100% LDF =1 CGF = 29.8 (assuming annual growth rate of 4%, 20 years design life) (Austroads 2008, Table 7.4) NHVAG = 2.8 (for rural road, Austroads 2008 Table 7.5)

Design Traffic = 3.05 X 106 ESAs DESA = 2.75 X 106 ESAs DESA = 3.0 X 106 ESAs (rounded)

Laboratory Test indicates that the pavement material throughout the studied section is similar with around 40% passing 425 micron and PI in between 7 to 9 %. The existing pavement is 180 mm thick and the subgrade CBR ranges from 2% to 5%. On the basis of the laboratory test results for pavement material, the following stabilising binders have been chosen in top to bottom rank:

1. RoadPozz (Cement 75% / Fly Ash 25%) (http://www.boral.com.au/ProductCatalogue/product.aspx?product=2345

2. Stabilment (Slag 85% / Lime 15%) (http://www.boral.com.au/ProductCatalogue/product.aspx?product=2269)

3. Cement Triple Blend 622 (Cement 60% / Slag 20% / Fly Ash 20%) (From BCSC – Stabilisation Product Range)

The most preferred binder would be RoadPozz as it contains both Cement which is suitable for granular material and FlyAsh for finer material. In this case, there are 40% passing 425 micron sieve which justify the need of Fly Ash in stabilising binder. RoadPozz is a proven binder as it has been used successfully used in NSW Central West for local council roads. Fly Ash is the byproduct of Power Generation Company. Using Fly Ash as a component of binder helps reduce the environmental impact as the waste material like Fly Ash can be used. In rural areas in NSW, Fly Ash based binder is more readily available. Stabilment is another option for the stabilisation; however slag cost more than cement in this region. GGBFS Slag is produced by steel industries and due to the lack of steel producing industries in this region and even in Australia the Slag has to be imported from other countries. This makes it costlier than other binders like RoadPozz. Long Haulage to the rural Area is not viable.

http://www.boral.com.au/ProductCatalogue/product.aspx?product=2345

http://www.boral.com.au/ProductCatalogue/product.aspx?product=2269



RoadPozz (Cement 75% / Fly Ash 25%) has been used for the design of this pavement. Using CIRCLY 5TM as the design tool pavement has been designed as follows.

Option 1

Depth (mm) Descriptions

2 coat bitumen seal

000mm – 150mm 150mm thick unbound granular base (specified by RTA 3051)

150mm – 350mm 200mm thick modified existing pavement including additional 20mm of base material (modulus = 500MPa anisotropic) (use RoadPozz)

350mm – 650mm 300mm thick 4% hydrated lime stabilised Subgrade (minimum CBR = 10%)

Subgrade In-situ Subgrade (CBR = 2%)

Construction Methodology

1. As the road cannot be closed during the rehabilitation, the construction shall be done in

single lane at a time. This method needs longer time to finish the job.

2. Excavate and stockpile the existing 180mm of pavement material for reuse.

3. The CBR value of the subgrade is quiet low which indicate the soil must me CLAYEY in

nature. For clayey soil lime based binders are suitable (AustStab 2011 Table 3.2). Stabilise

300mm of in-situ CBR with approximately 4% of hydrated lime and compacted to required

density ratio and moisture ratio. Let the stabilised pavement cure for 4 to 7 days. Required

hydrated lime percentage shall be determined in lab using Lime Demand Test on the

subgrade material.

4. Place 200mm thick existing pavement material that has been stockpile. Place extra unbound

granular base material as the exiting pavement material wouldn’t be sufficient to make

200mm of stabilised subbase.

5. Modify 200mm of subbase layer with RoadPozz and perform the required compaction. The

percentage of binder shall be determined by stabilisation trials in the laboratory. The testing

includes Unconfined Compressive Strength (UCS) trials and Stabilised California Bearing

Ratio (CBR) trials using different % by mass of the binders.

6. The UCS of the sample tested in lab should be less than 1 MPa (for modified pavement)

7. Lay and compact 150mm of base layer (specified by RTA 3051)

8. Carry out sealing with 2 coat bitumen seal (Which is the economical and better option for

traffic <107 ESAs, Austroads 2009).

The 150mm of unbound granular base has been laid to stop the possible crack from stabilised layer

to transfer on to the top of the pavement.



Foamed bitumen stabilisation of pavement including certain design depth of subgrade and existing

pavement could be another option which takes much lesser time than the option devised above.

This method also allows the traffic on the pavement immediately after the construction. However,

the subgrade seems to be clayey and upon mixing with the pavement material will increase the PI of

the soil matrix greater than 10. In this case, it is necessary to pre-treat the soil with lime to reduce

the PI. And because the subgrade CBR is low it will be difficult to compact the stabilised layer to

required density ratio.

Deep lift stabilisation could have been another option however, presence of weak subgrade would

have made it difficult for the compaction of the pavement layer and in many instant it is impossible

to compact the pavement to the right compaction ratio which will lead to even thicker pavement.

CIRCLY Analysis

CIRCLY Version 5.0s (30 May 2011)

Job Title: Assignment-1-Q4

Damage Factor Calculation

Assumed number of damage pulses per movement:

One pulse per axle (i.e. use NROWS)

Traffic Spectrum Details:

ID: 2004-1 Title: Austroads 2004 - Example 1 - Unbound Granular Pavement

Load Load Movements

No. ID

1 ESA75-Full 3.00E+06

Details of Load Groups:

Load Load Load Load Radius Pressure/ Exponent

No. ID Category Type Ref. stress

1 ESA75-Full SA750-Full Vertical Force 92.1 0.75 0.00

Load Locations:

Location Load Gear X Y Scaling Theta

No. ID No. Factor

1 ESA75-Full 1 -165.0 0.0 1.00E+00 0.00

2 ESA75-Full 1 165.0 0.0 1.00E+00 0.00

3 ESA75-Full 1 1635.0 0.0 1.00E+00 0.00

4 ESA75-Full 1 1965.0 0.0 1.00E+00 0.00

Layout of result points on horizontal plane:

Xmin: 0 Xmax: 165 Xdel: 165

Y: 0

Details of Layered System:

ID: Aust2004-1 Title: Austroads 2004 - Example 1 - Unbound Granular Pavement

Layer Lower Material Isotropy Modulus P.Ratio

No. i/face ID (or Ev) (or vvh) F Eh vh

1 rough Gran_300 Aniso. 3.00E+02 0.35 2.20E+02 1.50E+02 0.35

2 rough Cem500A Aniso. 5.00E+02 0.35 3.70E+02 2.50E+02 0.35

3 rough StasubCB10 Aniso. 1.00E+02 0.35 7.40E+01 5.00E+01 0.35

4 rough Sub_CBR2 Aniso. 2.00E+01 0.45 1.38E+01 1.00E+01 0.45

Performance Relationships:

Layer Location Performance Component Perform. Perform. Traffic

No. ID Constant Exponent Multiplier

4 top Sub_2004 EZZ 0.009300 7.000 1.600

Reliability Factors: Not Used.

Details of Layers to be sublayered:

Layer no. 1: Austroads (2004) sublayering



Layer no. 3: Austroads (2004) sublayering

Results:

Layer Thickness Material Load Critical CDF

No. ID ID Strain

1 150.00 Gran_300 n/a n/a

2 200.00 Cem500A n/a n/a

3 300.00 StasubCB10 n/a n/a

4 0.00 Sub_CBR2 ESA75-Full 1.03E-03 9.60E-01

Note: I used Macquarie Geotechnical Pty Ltd facilities to prepare this assignment. All the RTA

Standard and Specification and CIRCLY software were provided by Macquarie Geotechnical

Pty Ltd, Bathurst NSW 2795.

References:






Question 5

The pavement materials need to be tested for the index properties to determine the suitability of

the three possible binders.

The laboratory test programs to assess the suitability of the binder are as follows:

Flow Chart for selecting suitable binder and it proportion in the material to be stabilised

Determine the Particle Size

Distribution (PSD) of the

pavement material

Determine Plasticity Index (PI)

Determine the suitable binder

types

Cement TBlend 622 Stabilment RoadPozz

Perform UCS Test

(Pair) at 2%, 4% &

6% binder

Perform UCS Test

(Pair) at 2%, 4% &

6% binder

Perform UCS Test

(Pair) at 2%, 4% &

6% binder

Select Suitable Binder

and Percentage binders

(two possible

proportions of binders

like 2% & 4%)

Perform Compaction Test on

material with 2% binders and

Perform CBR Test

Perform Compaction Test on

material with 4% binders and

Perform CBR Test

Select the suitable %

binder



The testing can be done either using Australian Standard or RTA standard; however, RTA is more

rigorous and detailed. This is the reason why I chose RTA method of Testing.

The list of test methods that have to be used to determine the suitable binders are as follows:

1. RTA T106 & T107 – Coarse & Fine Particle Distribution of road construction material.

Particle size distribution test helps determine the % fine particles and % coarse particles in

the materials (pavement material in this case).

2. RTA T108 & T109 – Liquid Limit, Plastic Limit & Plasticity Index of the soil.

This testing determines the plasticity of the soil. The plasticity is used to determine the

suitable binders that will work for the given material. If the plasticity is low cement based

binder is suitable whereas for high plastic soil lime based binder is suitable.

The Acceptance value for Plasticity Index test for pavement material is < 10%.

Note: both of above tests won’t be needed as the testing results are already available in the

question.

3. RTA T111 – Dry Density/Moisture Relationship of road construction material

This test determines the optimum moisture content and maximum dry density of the road

construction material.

4. RTA T117 – California Bearing Ratio of remoulded specimens of road construction material

This test determines the CBR value of remoulded sample of road construction material

without binder so that it can be compared with the Stabilised CBR value to identify where

the binder has done the job or not.

5. RTA T116 – Unconfined Compressive Strength test of remoulded road construction

materials. Accelerated Curing at 65 °C for 7 days.

This test method is used to determine the suitable proportion of binder in the construction

material to give the desired compressive strength. For this assignment, I have chosen

modified layer i.e. UCS shall be less than 1 MPa.

The Acceptance value for UCS test for remoulded pavement material with the appropriate

binder is <1 MPa.

6. RTA T130 – Dry Density/Moisture Relationship of Road Construction Materials (Blended in

the laboratory with cementitious binders)

This test determines the optimum moisture content and maximum dry density of the road

construction material with binder mixed in.

7. RTA T132 – Determination of California Bearing Ratio of road materials modified or

stabilised with proportions of cement, lime or other cementitious materials.



This test determines the CBR value of remoulded sample of road construction material with

binder. It determines the whether the addition of binder has produced the required CBR in

the material.

The Acceptance value for Stabilised CBR test for remoulded pavement material with the

appropriate binder is ≥ 50% CBR. The designated stabilised layer in Assignment Question 4

is the subbase layer.

The quantities of pavement material required from each Test pit are as follows:

S. No

Description of test Qty

/ Test

number of test

Sets of binders (2%, 4% and 6%)

Total Amount Remarks

1 RTA T111 - MDD & OMC 8kg 1 - 8kg quantity passing 19mm sieve

2 RTA T117 - CBR Test 6kg 1 - 6kg quantity passing 19mm sieve

3 RTA T130 - MDD & OMC 8kg 1 3 24kg quantity passing 19mm sieve

4 RTA T132 - CBR Test 6kg 1 3 18kg quantity passing 19mm sieve

5 RTA T116 - UCS Test

(pair) 3kg 2 3 18kg quantity passing 19mm sieve

6 RTA T108 & T109 - Atterberg's Limit

- - - - Already Provided

7 RTA T106 & T107 - PSD - - - - Already Provided

Total Sample required from each test pit = 74 kg.

Samples were taken from 20 test pits, however due to the similarities in the material based on PSD

test and plasticity Index result we shall do the laboratory testing on only 10 Test Pit samples evenly

spread along the road.

The total cost for laboratory program is calculated as follows

S. No

Description of test no. of test per sample

Sets of binders (2%, 4% and 6%)

Total no. of

Sample

Unit Rates

Total Amount

Remarks

1 RTA T144 – Lime Saturation Point Test

1 10 120 $1200 For subgrade

material

2 RTA T111 - MDD & OMC

1 1 (@ lime

saturation) 10 100 $1000

For subgrade material

3 RTA T117 - CBR Test

1 1 (@ lime

saturation) 10 150 $1500

For subgrade material

4 RTA T111 - MDD & OMC 1 - 10 $100 $1000

5 RTA T117 - CBR Test 1 - 10 $150 $1500

6

RTA T130 - MDD & OMC (Stabilised)

1 3 10 $150 $4500 binder cost inclusive

in the unit rates

7 RTA T132 - CBR Test (Stabilised) 1 3 10 $200 $6000

binder cost inclusive in the unit rates

8 RTA T116 - UCS Test (pair) 2 3 10 $150 $9000

binder cost inclusive in the unit rates

9 RTA T108 & T109 - Atterberg's Limit - - - - - Already Provided

10 RTA T106 & T107 - PSD - - - - - Already Provided

Note: unit rates are provided by Macquarie Geotechnical Pty Ltd. (Exclusive of Tax)



The total laboratory cost = $ 25,700.00 (does not include site investigation cost)

The total construction cost provided = $ 525,000.00

Therefore, the proportion of total cost spends on the testing = 4.9 %.

References:

RTA T106 – October 2011 “Coarse Particle Size Distribution of road construction material (by dry

sieving)

RTA T107 – October 2011 “Fine Particle size distribution of road construction material”.

RTA T108 – April 2007 “Liquid Limit of road materials”

RTA T109 – November 2007 “Plastic Limit & Plasticity Index of road construction material”.

RTA T111 – May 2011 “Dry Density/moisture relationship of road construction materials”.

RTA T116 – May 2011 “Unconfined compressive strength of remoulded road construction

materials”.

RTA T117 – October 2011 “California bearing ratio of remoulded specimens of road construction

material”.

RTA T130 – January 2010 “Dry density/moisture relationship of road construction materials (blended

in the laboratory with cementitious binders)

RTA T132 – February 2001 “Determination of the California bearing ratio of road materials modified

or stabilised with proportions of cement, lime or other cementitious materials

RTA T144 – February 2001 “Determination of the lime saturation point of roadmarking materials by

the pH method”.




Sudarshan Assignment 1 Insitu Stabilisation

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