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Effective Soil Stabilisation

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  • 8/4/2019 Effective Soil Stabilisation

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    ?Effective

    Soil Stabilization

    & Dust Control

    For Roads

    Displaces bound water

    and improves the bearing ratio of clay & silty soils

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    Soil Analysis

    Soils are classified in accordancewith the AASHTO classification.

    CBR PLUS chemists analyse a200g sample to determine thesoil reactivity with CBR PLUS .

    Using this information and thechart on the back of thisbrochure the correct amount andmethod of application is deter-mined. CBR PLUS reacts differ-ently with different soils.

    Site preparation

    Shape the surface to final

    levels. Allow for proper drainage. Scarify soil to depth of 150mm

    (6 inches). Break down lumps of material. For heavy clays remove top

    half and windrow.

    CBR PLUS Application

    Pour prescribed amount ofPLUS into water tanker.

    Apply diluted CBR PLUS solutevenly to soil surface, addingenough water to achieve a soilmoisture content 1% of optimu

    Mix CBR PLUS into soil and blainto final shape.

    Compaction

    Commence compaction withmaterial at 1% of optimummoisture content.

    There is no maximum time limit

    between application of CBRand commencing compaction.

    A vibratory, sheeps foot orsmooth drum roller compactorcan be used for the initialcompaction and the section isthen finished off with a pneu-matic compactor.

    Vehicle traffic will furthercompact treated section.

    Untreatedsoil

    CBR PLUStreated soil Density gradient graph

    0

    100

    200

    300

    400

    500

    600

    1

    8 0 0

    1

    9 0 0

    2

    0 0 0

    Dry density kg/m 3

    D e p

    t h b e

    l o w r o a

    d s u r f a c e

    ( m m

    ) Untreated Moisture

    content optimum

    Slightincrease

    in densitygradient

    CBR P

    ImmediatcompactiMoistureless than free wate

    Large impdensity g

    Absorbed WaterFurther compaheavy traffic fo

    Road with compaction& large traffic forces

    Stabilized

    Water RepellentRoad Surfaces

    CBR PLUS has been in use for over twenty years.

    The North American Formulation, CBR PLUS SUPER, has

    been specially blended for our soil and climaticconditions. CBR PLUS SUPER is a dark brown, viscous,highly concentrated liquid soil stabilizer, with double the

    reactive component of the other blends of CBR PLUS .CBR PLUS SUPER has high penetration capabilities andquick curing characteristics.

    CBR PLUS is a stabilizer for anionic soils that improvesthe load bearing performance of a variety of clays and

    silty soils. It has been used worldwide for over twentyyears to control dust and improve compaction.

    CBR PLUS is a synthetic thio compound which formsprotective, oily layers on the surfaces of soil and clay

    particles. It reduces ion mobility and ion exchange andsimultaneously makes the material hydrophobic by

    eliminating the adsorption of water. The result is a soilmaterial that is much less sensitive to moisture, more

    workable and can be compacted to a better particle-interlock state by equipment and traffic forces.

    Better particle-interlock means higher internalfriction and improved bearing capacity.

    CBR PLUS will treat materials ranging from clays to siltysands and some gravels. Non-cohesive materials such assand can be treated only after they have been

    modified by mixing them with a suitable clayey material.

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    Working in

    96 Countries Worldwide

    Curing

    After compaction, spray surfacewith clean water at daily intervals

    for seven days or as required toavoid rapid drying out.

    In the event of rain fall aftercompaction, the road surfacemay become slippery and form amud crust. This is normal.

    Do not grade. Allow the surfaceto dry and traffic to smoothenthe surface.

    If sealing of the surface isdesired, the in situ moisturecontent of the treated section

    must be allowed to stabilize atbetween 50% to 60% ofoptimum moisture content.Normal sealants or asphalt canthen be applied.

    Results

    Cost saving use local soils. Increased workability saves

    time, machine effort and fuelduring construction.

    Increase performance ofin-situ soils.

    Improved trafficability andbetter driving conditions inwet weather.

    Dust reductions up to 90%create safer driving conditions.

    Treatment is permanent does not require retreatmentof surface.

    Key Benefits

    Increase bearing capacity Increase soil workability Long term stabilization Reduces readsorption of water Reduces gravel loss Control dust Increase trafficability in wet

    conditions

    Primary Uses

    Economical road construction

    Upgrading of roads Maintenance on unpaved

    roads Rehabilitation of failed roads Construction roads Parking areas Air strips Mass fills

    CBR PLUS treated road surface shown here at actual size.

    (L) Road surface is prepared by scarifying and grading to final levels.

    (C) CBR PLUS is completely non-toxic and requires no special handling.

    (R) Treated road is compacted with rollers or vehicle traffic.

    CBR PLUS was developed in South Africa, and is backed

    by a team of professional soil specialists, chemists, androad construction engineers. CBR PLUS (also sold un

    the name CON-AID) is manufactured under the strictestquality batch control to ensure consistent performance.

    It is used in more than 96 countries to build low cost, all-weather roads using in-situ materials and is biodegrad-

    able, non-toxic and environmentally friendly.

    What differentiates CBR PLUS from most other similar

    products is its permanent change to the soil. Roadsrequire little or no re-treatment, so the resulting benefits

    are long term. Roads constructed over 20 years ago

    (without re-treatment) are still in excellent condition today.

    Over 30,000 km of roads have been successfully con-

    structed using CBR PLUS . This technology is today oneof the preferred methods used by the WORLD BANK in

    developing countries for building roads in rural areas.In certain countries we are assisting in the development

    of the countrys whole road infrastructure.

    Detailed soil analyses determine the correct application

    rates and professional construction methods ensure

    successful results and consistent increases in soilstability and CBR values.

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    ?OK, but what about costs?

    A. Application of CBR PLUS modifies the compactability oflocally available soils for road construction. The cost ofCBR PLUS is usually significantly less than the cost of

    hauling gravel to modify the local soils.

    prep time?

    A. There is a distinct improvement in the workablilty ofthe soil after applying CBR PLUS . This saves time whengrading and placing the soil. During the compaction stage,the number of passes required with the variouscompactors is reduced often up to 50%.

    wet conditions?

    A. The treated soil or road surface becomes hydrophobic or water repellent. The soil does not deteriorate in wet

    conditions, resulting in improved trafficability.

    dust?

    A. Dust diminishes by up to 90% depending on soil type.This reduces the need for frequent grading and othermaintenance, resulting in cost savings and safer drivingconditions.

    application to an existing road?

    A. CBR PLUS can be applied to an existing road surfaceto prevent rutting, gravel loss and provide dust controlwithout rebuilding the road. The correct amount ofCBR PLUS is applied with a water tanker in three or fourapplications. It penetrates the soil and reacts sufficientlyto correct these problems.

    the need to repeat the treatment?

    A. The reaction of CBR PLUS with the clay particles in thesoil is permanent. Some existing roads have been in usefor over 20 years and have shown little or no deteriorationover this period. If re-treatment is required at all, it wouldonly be if additional material is imported.

    regrading or repairing a treated road?

    A. To repair damage in a road that was previously treatedwith CBR PLUS , merely wet the surface, regrade andensure that the material pushed to the side is replacedonto the road. Provided no new untreated material isplaced onto the road, the soil will recompact as if freshlytreated. The repaired surface can be compacted bymachine or by traffic forces.

    Adsorbed water(weak cation)

    clay particles

    CBR PLUS

    (strong cation)

    Absorbed water

    How does it work?The Stabilizing Process for Anionic Soils

    CBR PLUS was developed to enhance the expulsion ofadsorbed water in clay particles, to achieve maximumdensity, with less mechanical effort and to prevent the

    re-adsorption of water. This results in a permanentlystabilized construction material.

    Most clay minerals are made up of stacks of silica andalumina sheets. The arrangement of these sheets result indifferent clay minerals such as kaolinite, montmorilloniteand illite.

    Simply stated, these clay minerals inherently have apredominantly negative electrical or anionic charge. Thiscauses the clay minerals to have a strong attraction forany cations that are present. The negative clay mineralsattract cations like iron filings to a magnet and will reactwith water when present. (The electrostatic forces aregreater in close proximity to the clay molecule or particle,resulting in very strong bonds). Normal temperatures andcompaction pressures will not remove them. This layer ofwater is known as the electrostatic diffused double layeror adsorbed water.

    Further away from the clay particle, the water moleculesare no longer in an attracted or orientated state. Thiswater is known as pore water or absorbed water.

    Certain clays, like montmorillonite, have spaces betweenthe plates or layers, that can absorb water causing themto expand. These are known as expansive or swellingclays and are the cause of many failures in foundations orroad layers.

    The obvious solution is to reduce the adsorbed layer ofwater surrounding the soil particle. If powerful positivemolecules (such as the 4 + charge in CBR PLUS ) can besupplied, the negative charge of the clay minerals can besatisfied or balanced out. At the same time any weakercations, such as water can easily be disassociated andreplaced, and/or occupation of the vacant ionic sites onthe clay surface can take place.

    Large cations such as sodium, calcium and water cannoteasily fit into these sites and are easily disassociated orreplaced. Small cations, on the other hand, fit firmly intothese vacated sites, balancing the clays negative chargewith positive ions that cannot be removed. The clay isnow relatively inert to water and the soil mass is perma-nently stabilized.

    This is precisely what CBR PLUS does.

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    Group Sub Soil Purpose % Passing Sieve (mm) CBR PLUS ***Group Description of 2.00 0.425 0.075 Liquid Plasticity application

    CBR PLUS #10 #40 #200 limit index Rate litre/m 2

    A-1 Well graded gravel or sand, not applicable NAmay include fines

    A-1-a Largely gravel but can include Facilitate 50 max 30 max 15 max 6 max 0,003sand and fines compaction

    A-1-b Gravelly sand or graded sand; Facilitate 50 max 25 max 6 max 0,005may include fines compaction

    A-2 Sands, gravels with excessive fines

    A-2-4 Sands, gravels with elastic silt fines Facilitate 35 max 40 max 10 max 0,003compaction &stabilize fines

    A-2-5 Sand, gravels with elastic silt fines Facilitate 35 max 41 min 10 max 0,005compaction &stabilize fines

    A-2-6 Sands, gravels with c lay fines Stabilize clay fines 35 max 40 max 11 min 0,006

    A-2-7 Sands, gravel with highly plastic Increase clay 35 max 41 min 11 min 0,008

    A-3 Fine sands N/A 51 min 10 max Non-plastic N/A

    A-4 Low compressibility silts Facilitate 36 min 40 max 10 max 0,010

    sand and fines compaction

    A-5 High compressibility silts, Stabilize clays 36 min 41 min 10 max 0,010micaceous silts

    A-6 Low to medium compressibility Stabilize silty 36 min 40 max 11 min 0,012clays clays

    A-7 High compressibility clays Increase CBR 36 min 41 min 11 min 0,012

    A-7-5** High compressibility silty clays Improve 36 min 41 min 11 min 0,013workability

    A-7-6** High compressibility, high volume Stabilize clay 36 min 40 min 11 min 0,015change clays

    A-8 Peat, highly organic soils N/A N/A

    1. Group A-2 includes all soils having less than 35% passing a 0.075 mm sieve that cannot be classed as A-1 or A-3.2. Plasticity index of A-7-5 subgroup is equal to or less than LL-30. Plasticity index of A-7-6 subgroup is greater than LL-30.3. The classification is supplemented by Group Index, or GI: GI = 0.2a + 0.005ac + 0.01bd where:

    a = percentage passing the No 200 sieve greater than 35 and not exceeding 75; expressed as a whole number {0 to 40}b = passing No 200 sieve greater than 15 and not exceeding 55; expressed as a whole number {0 to 40}c = that portion of the liquid limit greater than 40 and not exceeding 60; expressed as a whole number {0 to 20}d = that portion of the plasticity index greater than 10 and not exceeding 30; expressed as a whole number {0 to 20}

    ** Surface may be slippery after treatment. Allow for 25mm (1") layer of gravel and sand to dress surface.*** Soil tests are conducted to determine specific application rates for each soil type.

    CBR PLUS (North America Inc.)

    Suite 640, 580 Hornby Street Vancouver, BC Canada V6C 3B6T: 604.683 .0430F: 604.68 3.0450E: [email protected]: http://www.cbrplus.com/

    For further technical information, material safety data sheets (MSDS) or testing services to determine product suitability for material and correct application rates andconstruction methods contact your nearest distributor.

    The statements, data and information contained in this brochure are based on data which is considered to be accurate and reliable, but is presented without guarantee,warranty or responsibility, express or implied. The product is intended for use by persons having requisite knowledge and skill, and are utilized at their own risk. Anyloss incurred during storage, handling, transportation, use, resultant from its use or disposal is expressly disclaimed.

    AASHTO Classification Table & Nominal Application Rates.


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