Soil Cement project, eng. ssekamatte denis













Soil Cement

Content

•   Introduction

•   What is Soil Cement?

•   WhyUseSoil-Cement?

•   Howis Soil-Cement Built?

•   Objectiveof theWork

•   SoilCement Road

•   Performanceof Soil Cement

•   Types

•   Advantages

•   Disadvantages

•   References



Introduction


Soilcement isfrequentlyused as a construction material forpipebedding,slope protection, and road construction asasub baselayer reinforcingand protectingthesubgrade.It hasgood compressive and shear strength, butis brittle and has low tensilestrength,so it is proneto forming cracks.

Soilcement mixtures differfrom Portland cementconcretein the amountofpaste (cement-water mixture). Whilein Portland cement concretes thepaste coats all aggregateparticles andbinds them together, in soilcements theamountof cement is lower and thereforetherearevoids left and the resultis a cementmatrixwith nodules of uncemented material.

WhatisSoilCement?

Soilcement is a construction material, a mixof pulverized naturalsoilwith small amount of portlandcement and water, usuallyprocessed in atumble, compacted to high density. Hard, semi-rigid durable material is formed byhydrationof thecement particles.



WhyUseSoil-Cement?

Failing granular-basepavements, with or without their old bituminous mats,can besalvaged, strengthened, andreclaimed as soil-cement pavements. This is an efficient, economical wayof rebuildingpavements. Since approximately90 percent percent of the material used is alreadyin place, handlingand haulingcosts arecut to aminimum. Manygranular andwaste materials from quarries andgravel pits can also be used to makesoil-cement; thus high-gradematerials are conservedforother purposes.

Highwayand cityengineers praise soil-cement’s performance, its low firstcost, longlife,and high strength. Soil-cement is constructed quicklyand easily– afact appreciated byownersand users alike.

Howis Soil-Cement Built?

Beforeconstruction begins, simplelaboratorytests establish the cement content, compaction, and waterrequirements of thesoil material to be used.During construction, tests aremadeto seethat the requirements arebeingmet. Testingensures that themixturewillhavestrengthand long-
term durability. Noguesswork is involved.

Soil-cement can bemixed in placeor in acentral mixingplant. Central mixingplants can beused whereborrow material is involved. Friablegranular materials areselectedfortheirlow cement requirements andeaseofhandlingand mixing. Normallypugmill-typemixers areused. The mixed soil-cement is then hauled to the jobsite and spread on the preparedsubgrade.
Compaction and curingprocedures arethe samefor central-plant and mixed-in-placeprocedures. Thereare foursteps in mixed-in-placesoil-cementconstruction; spreading cement, mixing,
compaction, and curing.Theproper quantityof cement is spread on the in-placesoil material.
Then the cement, thesoil material, and the necessaryamountof waterare mixed thoroughlyby anyof several types of mixingmachines. Next, themixtureis tightlycompacted to obtain maximum benefit formthe cement. No special compaction equipment is needed; rollers of various kinds, depending on soil type, can beused. Themixtureis cemented permanentlyat a high densityand the hardened soil-cement will notdeform or consolidate further under traffic.

Curing, the final step, prevents evaporation ofwater to ensuremaximum strength development through cement hydration. A light coat of bituminous material is commonlyusedto prevent moistureloss; it also forms part of thebituminous surface. A common typeof wearingsurface forlight traffic is asurfacetreatment of bituminous material and chips .5-to .75-inch thick. For heavy-dutyuseand in severeclimatesa1.5-inchasphalt mat is used.

Contractors biddingon soil-cement jobs know that construction willbe relativelyeasyand problem-free; weatherdelays rare;and reworking of completed sections unnecessary.



Objectiveof theWork

To studyabout soilcement roads.
To studyabout construction methods.
Discuss about various properties ofsoil cement roads.
Discuss about advantages anddisadvantages of soilcement roads.




SoilCementRoad

Soil-cement is ahighlycompacted mixtureof soil/aggregate, Portlandcement, and water. Soil- cement differs from Portland cementconcrete pavements in severalrespects. One
significant differenceis themanner in which the aggregates or soil particles areheld together. APortland cement concrete pavements mixcontains sufficient paste (cement and water mixture) to coat the surface areaofall aggregates and fill the void between aggregates.In soilcement mixtures, the paste is insufficient to fill the aggregate voids andcoat all particles, resultingin acement matrix that binds nodules ofuncemented material.It is widelyusedas a low-cost pavement basefor roads, residential streets,parking areas, airports, shoulders, and materials-handlingand storage areas.Itsadvantages ofgreat strength and durabilitycombinewith low firstcost to makeitthe outstandingvalue in its field.

A thin bituminous surfaceis usuallyplaced on thesoil-cement to completethe pavement. material used for soil cement aresoil cement andwater. Theuse of soil-cement can beofgreat benefit to both owners and users of commercial facilities.Its cost comparesfavorablywith that ofgranular-basepavement. When built for equal load carryingcapacity, soil-cement is almost always less expensive than otherlow-costsitetreatment or pavement methods. Theuse or reuse ofin-placeor nearbyborrowmaterials eliminatesthe need for haulingof expensive, granular- basematerials;thus both energyand materials are conserved.



PerformanceofSoilCement

Soil-cement thicknessesareless than thoserequired forgranularbases carryingthe same traffic over thesamesubgrade.This is because soil-cement is a cemented,rigid material that distributes loads over broad areas.Its slab-like characteristics andbeam strengthareunmatched bygranular bases. Hard, rigid soil-cement resists cyclic cold, rain, and spring-thawdamage. Cement stabilizes soilin two ways. First, it reduces soil plasticity, especiallyforthesoil in which thereis high amountof clayparticles.

Thesecond is cementation which is veryimportant becauseclayis not its main composition.In finegrained siltyand clayeysoils, the hydration of cement develops strong linkages between the soilaggregates to formamatrixthat effectivelyencases the soil aggregates.Old soil-cement pavements in allparts ofthe continent arestillgiving good serviceat low
maintenancecosts.Soil-cement has been used in everystatein theUnited States andin all Canadian provinces.

Specimens taken fromroads show that the strength of soil-cement actuallyincreases with age; some specimens werefourtimes as strong as test specimens madewhen the roads were first opened to traffic. This reservestrengthaccounts in part forsoil-cement’sgood long-term performance.



Typesofsoilcement



Cement-modified soils (CMS)

A cement-modified soil contains relativelysmall proportion ofPortland cement. The resultis caked or slightlyhardened material, similarto a soil, but with improved mechanicalproperties - lower plasticity, increased bearingratio and shearingstrength,and decreased volume change.

Soil-cement base (SCB)

A soil-cement basecontains higher proportion ofcement than cement-modified soil.It is commonlyused asa cheap pavement basefor roads, streets, parkinglots, airports,
 and material handlingareas. Specialized equipment, such asasoil stabilizer and amechanical cement spreader is usuallyrequired. A seal coat is required in order to keep moistureout. Foruses as a road construction material, a suitable surface coating, usuallyathin layer ofasphalt concrete, is needed to reducewear.
Incomparison withgranularbases, soil cement bases can bethinner for thesame road load, owingto their slab-likebehavior that distributes load over broaderareas.In-placeor nearby located materials can beusedfor construction-locallyfoundsoil, stone, orreclaimedgranular base from aroad being reconstructed. This conserves both material andenergy.
Thestrength of soil-cement bases actuallyincreases with age, providing good long-term performance.

Cement-treated base (CTB)

A cement-treated baseisamixof granularsoil aggregates or aggregate material with Portland cement and water.It is similarin use and performancetosoil-cement base.

Acrylic copolymer (Rhino Snot)

Developed for theU.S.Militaryin desert conditions and commerciallytrademarked,"Rhino Snot"is a watersolubleacrylic copolymerappliedto soilor sand which penetrates andcoats the surface. When dry, itforms a waterproof, UV-resistant, solid bond which binds thesoil together reducingdust.In higherconcentration itcreatesadurable surfacethat canwithstand heavytraffic allowingexistingsoil to beused forroads, parkinglots, trails andother heavytraffic areas.



Advantages

Economic andEnvironmental Benefits

1.LowFirst Cost
Soil-cement is often more economical to construct than bases through theuse of soil material on ornear the commercial pavingsite.anyin-placenon-organic,low plasticitysoils can be used.Also,nearbyborrowsoil can provide anexcellent material source,requiringlower cement contents than clayand silt soils.Borrowsoils do not haveto be expensive base-course material;almost anygranularmaterial issuitable.




2. Fast Construction
Modern methods and equipment makesoil-cementprocessingsimple and efficient.In-placesoils areprocessedat thepavingsite.When borrow soil is used,itn is usuallymixed in a central plant the borrowsource,thehauled to the pavingsitetobe compacted. Finishedto grade,andcured.Thereis no mellowingperiod or other delays in the construction process.Inaddition,soil- cement is stable immediatelyafterconstruction and gains strength rapidly.




3. Recyclingof Existing Materials.
Making good soil-cement outof old flexiblepavement is nothingnew;ithas been done for years.Failed flexiblepavements contain materialsthat can besalvaged economicallyby recycling-breakingthemup,pulverizingthem,andstabilizingthem aminimum quantityof Portland cement to makeanew soil-cement base.Thereis no disposal problem as is commomly foundwhen old pavements aredugout.Since approximately90%of thematerial used is already in place,handlingand haulingcostsare cut to aminimum.Manygranular and waste materials from quarries andgravelpits can also be usedtomakesoil-cement,thusconservinghigh-grade materials forother purposes.




Engineering Benefits

1.Stiffness
Soil-cement is alow-costpavement baseofferingthe feature mostessentialforlong-lasting parking and storage areas-stiffness.Largepaved areas must maintain their originalgradeand mustnot develop depressions or potholes if theyareto drain freelyduring rains,thereby preventingpuddles and damagefrom water that seeps throughand weakensthe underlying soil.Thestiffness of acement-stabilized base actsto distributeloads over a wider area,reducing subgradestresses and allowingthe maintain its originalgrade formany years without costly resurfacingor repairs.

StabilizedBase vs. UnstabilizedBase






















Soil-cement does not rut or consolidate.As acemented material,itdoes not soften when exposed to water.When ruttingoccurs in an unstabilized basematerial or theunderlyingsubgradesoil,a simple overlayof thepavement surfaceis insufficient to correct the causeof therutting.With a stabilized base,ruttingis confined to the asphaltsurfacelayer and is relativelysimple and less expensive to correct.




2. Great Strength

















Cores taken from soil-cement pavements furnishproof of its strength. Samples taken after 15 to
20years showconsiderablygreaterstrength thansampletaken when thepavement was initially built. Becausethe cement in soil-cement continues to hydrate formany years, soil-cement has “reserve”strength and actuallygrows strength andactuallygrows stronger.




Soil-cement thickness requirements areless than those forgranularbases carryingthe same traffic over thesamesubgrade. This is because soil-cement distributesloads over broadareas.Its



slab-like characteristics and beam strength areunmatched bygranular bases. Strong, stiffsoil- cement resists cyclic cold, rain and spring-thaw damage.




3. SuperiorPerformance



Morethan 70years ofcollective experiencehavedemonstrated that different kinds of soil- cement mixtures can betailored to specific pavement applications,allachievingsuperior performanceas a resultof soil-cement’s strength.Thousands of miles of soil-cement pavement in everystatein theUnitedStates and in all theCannadian provincesarestillproviding good serviceat low maintenance costs.




Cement-treated bases are designedto be virtuallyimpermeable,so thatevenunder frost conditions no icelenses can form in the baselayer.With agranular,unboundmaterial,if poor drainageexists or groundwaterrises,thebasecan easilybecome saturated,causingsignificant strength losses.The cement-stabilized layer,on theotherhand,willmaintain significant strength even in theunlikelyevent it becomes saturated.




Thehigher stiffness of cement-treated bases leads to lower pavement deflections and lower asphalt strains,resultingin longerfatiguelife forthe asphalt surface.Theuseof soil-cement actuallyreduces the occurrenceof fatiguecracking,acommon pavement failure.



Disadvantages

1. Need to follow thestandard strictly. if not, theresultMaynot work properly.

2. Waterstillbe able to penetrate if Capillaryvoid too big.

3.If thepercentageof Cement too high, it’ll createcrack.Dueto less flexibility(too brittle)
Normallythe optiumpercentageof cement shall belesser than 7%byweight of drysoil.

4.It’s not suitable for some typeof soils.

5. Thehomogeneouslymixis strictlyconcened,then this process needexperienced supevisoror qualityequipment to process.

6. Can not operate if moistureof soil above10%.



References

www.google.com
www.wikipedia.com













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