--- title: "Soil stabilization methods and lime stabilized road" subject: "Transportation Engineering II" chapter: 3 key: "semester_7/transportation_engineering_ii:soil-stabilization-methods-lime-road" source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/soil-stabilization-methods-lime-road site: BCT Engineering --- # Soil stabilization methods and lime stabilized road Transportation Engineering II · Chapter 3: Road Construction Technology - Asked in: 2082 Bhadra, 2+2+4 marks - Video: [What is soil stabilization? || Methods of soil stabilization](https://www.youtube.com/watch?v=BSpDUzRQQZI) — Gurukul of Civil Engineers - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/soil-stabilization-methods-lime-road - Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-3 ## Question List out the various methods of soil stabilization used in highway construction. When each of the method of stabilization is applicable? Discuss the material, and construction procedure of lime stabilized road. ## Short answer Methods: mechanical blending, cement (PI<20), lime (PI>10), bituminous, lime-flyash, chemical, thermal/reinforcement. Lime stabilization uses 3–8% lime mixed with pulverized clayey soil (PI>10); after moistening and optional mellowing, it is compacted to 95–98% MDD and cured for 7 days. UCS of 0.7–1.0 MPa at 7 days is required. ## Answer #### Methods of soil stabilisation and where they apply **Soil stabilisation** is improving the engineering properties of a soil (strength, volume stability, durability, resistance to water) so that it can be used in a road layer. Methods and where each is used: | Method | Principle | Applicable to | |---|---|---| | Mechanical (granular, blending) | Mix two or more soils to get a good gradation and compact | Gravel and sand-clay mixes for base and sub-base on low volume roads | | Cement stabilisation | Cement hydrates and binds the grains | Sandy and gravelly soils, low plasticity (PI below 20); base and sub-base | | Lime stabilisation | Cation exchange and pozzolanic reaction reduce plasticity and give strength | Clayey soils (PI above 10), black cotton soils and sub-grade | | Bituminous stabilisation | Bitumen coats and waterproofs particles | Sands, gravels and low plastic soils; desert/sandy areas | | Lime-flyash / lime-pozzolana | Pozzolanic action | Soils with moderate clay plus fly ash; base and sub-base | | Chemical (calcium chloride, sodium chloride, polymers, enzymes) | Reduces dust and moisture change | Gravel roads, dust control | | Thermal (heat, freezing) and geotextile reinforcement | Dry or reinforce the soil | Special areas, soft grounds | #### Lime stabilised road **Materials**: soil (clay or silty clay, PI above 10); lime (quicklime or hydrated lime) at 3 to 8 percent by dry weight of soil, of high purity (available CaO content as specified, usually not less than 50-70 percent; IS:712, IRC:SP:89); water. **Equipment**: grader/pulveriser (rotavator), lime spreader, water tanker, sheep-foot and smooth-wheel/pneumatic rollers, cutting tools. **Construction procedure** 1. Prepare the subgrade or soil layer: clear, grade and trim it to line and level. 2. Pulverise the soil (all clods below 25 mm) with a rotavator or grader. 3. Spread the lime uniformly at the required percentage (by lorry spreader or from bags). 4. Mix the lime with the soil by rotavator or grader and add water to reach the optimum moisture content. For heavy clays, leave the mix after this first mixing to mellow for 24 to 48 hours. 5. Remix and compact, first with a sheep-foot roller and then with a smooth-wheel or pneumatic tyre roller, to 95-98 percent of maximum dry density. 6. Cure by keeping the layer moist for 7 days (or cover with sand or bitumen emulsion), and protect the surface from rain and traffic; lay the surface course after curing. 7. Quality control: lime content, degree of pulverisation, moisture content, density and unconfined compressive strength (UCS of about 0.7-1.0 MPa at 7 days). ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. For which soils is lime stabilisation most applicable? A. Clayey soils (PI above 10) and black cotton soils B. Clean sands and gravels with no fines C. Rock fill only D. Dusty gravel roads only Answer: A. Lime reduces plasticity by cation exchange and pozzolanic reaction in clays. (Key point: Lime applicability) 2. Cement stabilisation suits which soils? A. Highly plastic clays and organic soils B. Sandy and gravelly soils of low plasticity (PI below 20) C. Peat only D. Pure bitumen-coated sands Answer: B. Cement hydrates and binds grains; clays and organic soils interfere with it. (Key point: Cement applicability) 3. Why is the lime-soil mix left for 24 to 48 hours in heavy clay before final compaction? A. To let the soil dry completely B. To allow the lime to evaporate C. To harden the mix into slabs D. To allow lime to react with the clay (mellowing) before remixing Answer: D. The initial reaction breaks down clay lumps and begins plasticity reduction before remixing. (Key point: Mellowing) 4. How is the compacted lime-stabilised layer cured? A. Flood for 28 days B. Open to traffic immediately C. Keep moist for about 7 days and protect from rain and traffic before the surface course D. Dry in the sun for 1 day Answer: C. Moist curing allows the pozzolanic reaction to gain strength, checked by UCS. 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