Soil Stabilization

Submitted by, DINESH.R

The soil stabilization means the improvement of stability or bearing power of the soil by the use of controlled compaction, proportioning and/or the addition of suitable admixture or stabilizers. Basic Principles of Soil Stabilization. Evaluating the properties of given soil Deciding the lacking property of soil and choose effective and economical method of soil stabilization Designing the Stabilized soil mix for intended stability and durability values

Need for Soil StabilizationLimited Financial Resources to Provide a complete network Road System to build in conventional method Effective utilization of locally available soils and other suitable stabilizing agents. Encouraging the use of Industrial Wastages in building low cost construction of roads.

Methods of Soil StabilizationMechanical StabilizationSoil Cement StabilizationSoil Lime StabilizationSoil Bitumen StabilizationLime Fly ash StabilizationLime Fly ash Bound Macadam.

Mechanical StabilizationThis method is suitable for low volume roads i.e. Village roads in low rainfall areas.This method involves the correctly proportioning of aggregates and soil, adequately compacted to get mechanically stable layerThe Basic Principles of Mechanical Stabilization are Correct Proportioning and Effective Compaction

Factors Affecting Mechanical Stabilization Mechanical Strength of aggregates Gradation Properties of the Soil Presence of Salts Compaction

Mechanical Strength When the soil is used in small proportion to fill up the voids the crushing strength of aggregates is importantGradation A well graded aggregate soil mix results in a mix with high dry density and stability valuesProperties of soil A mix with Plasticity Index, results poor stability under soaking conditions. Hence it is desirable to limit the plasticity index of the soil

Presence of Chemicals Presence of Salts like Sulphates and mica are undesirable Presence of Calcium Chloride is BeneficialCompaction Effective Compaction is desirable to produce high density and stability mix

Soil Cement Stabilization

Soil Cement is an intimate mix of soil, cement and water, compacted to form a strong base courseCement treated or cement modified soil refers to the compacted mix when cement is used in small proportions to impart some strengthSoil Cement can be used as a sub-base or base course for all types of Pavements

Factors affecting soil cement stabilization

Soil Cement Pulverisation and Mixing Compaction Curing Additives

Soil THE PHYSICAL PROPERTIES

Particle Size Distribution Clay content Specific Surface Liquid limit and Plasticity Index Cement A increase in cement content generally causes increase in strength and durability

Pulverisation and MixingBetter the Pulverisation and degree of mixing, higher is the strengthPresence of un pulverised dry lumps reduces the strengthCompactionBy increasing the amount of compaction dry density of the mix, strength and durability also increases

Curing Adequate Moisture content is to be retained in order to accelerate the strengthAdditives There are some additives to improve properties Lime Sodium hydroxide Sodium Carbonate Calcium Chloride

Soil Lime Stabilization Soil- Lime has been widely used as a modifier or a binder Soil-Lime is used as modifier in high plasticity soils Soil Lime also imparts some binding action even in granular soils

Soil-Lime is effectively used in Expansive soils with high plasticity index.

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Factors affecting Properties of Soil-LimeLime ContentGenerally increase in lime content causes slight change in liquid limit and considerable increase in Plasticity indexThe rate of increase is first rapid and then decreases beyond a certain limitThe point is often termed as lime fixation point This is considered as design lime content

Type of Lime

After long curing periods all types of limes produce same effects. However quick lime has been found more effective than hydrated limeCalcium Carbonate must be heated at higher temperature to form Quick lime calcium oxide( CaO)Calcium oxide must be slaked ( by the addition of water) to form Hydrated lime

CompactionCompaction is done at OMC and maximum dry density.

CuringThe strength of soil-lime increases with curing period upto several years. The rate of increase is rapid during initial periodThe humidity of the surroundings also affects the strengthAdditivesSodium metasilicate, Sodium hydroxide and Sodium Sulphate are also found useful additives

Soil- Bituminous StabilizationThe Basic Principles of this stabilization are Water Proofing and BindingBy Water Proofing inherent strength and other properties could be retainedMost Commonly used materials are Cutback and EmulsionBitumen Stabilized layer may be used as Sub-base or base course for all the roads

Factors affecting properties of soil-bitumenSoil The particle size, shape and gradation of the soil influence the properties of the soil-bitumen mix.Types of BitumenCutbacks of higher grade should be preferred Emulsions generally gives slightly inferior results than Cutback.

Amount of MixingIncreasing proportion of bitumen causes a decrease in dry density but increases the stability after a certain bitumen contentThe optimum bitumen content for maximum stability generally ranges from 4 to 6%MixingImproved type of mixing with low mixing period may be preferred

CompactionEffective Compaction results higher stability and resistance to absorb waterAdditivesAnti stripping and reactive chemical additives have been tried to improve the properties of the mixesPortland cement can also be used along with the soil bitumen

The End..Thank you.