Bituminous Soil Stabilization

Описание: Bituminous soil stabilization is a widely employed and effective technique. It involves the use of bituminous materials such as bitumen, asphalt, and tar. Bitumen, a nonaqueous system of hydrocarbons, is completely soluble in carbondisulphide. Asphalt primarily consists of natural or refined petroleum bitumens, while tar is a bituminous condensate derived from the destructive distillation of organic materials like coal, oil, lignite, peat, and wood.

Bituminous materials stabilize the soil either by binding particles together or by protecting the soil from water damage (i.e., waterproofing), or both. The former mechanism is applicable to cohesionless soils, while the latter is more suitable for cohesive soils. Among bituminous materials, asphalt is predominantly used for stabilization, hence soil stabilized with asphalt is often termed soil-asphalt.

Asphalt production involves three main processes: vacuum distillation, high-temperature pyrolysis, and high-temperature air blowing. Straight-run asphalt, with its low softening temperature and melt viscosity, is commonly utilized for soil stabilization. However, due to its high viscosity, it cannot be directly added to soil. Methods such as heating, emulsification in water (emulsions), or dilution with solvents like gasoline (cutbacks) are employed to increase its fluidity. Both emulsions and cutbacks find application in soil stabilization, with soil-asphalt commonly used in highway and airfield pavement bases.

Various factors influence the effectiveness of asphalt stabilization. Soil properties such as particle size distribution, liquid limit, plasticity index, and organic matter content affect the suitability of stabilization. Optimal asphalt content is crucial, as excessive amounts can result in a mixture that is difficult to compact. Thorough mixing of asphalt with soil is essential for proper stabilization.

Compaction conditions, cure conditions, and construction procedures also impact the stability of soil-asphalt. Lower volatiles content generally leads to higher strength, and curing conditions affect the loss of volatiles and water pickup, which inversely affect strength. Proper construction sequence, including mixing, compaction, curing, and surface protection, is critical for achieving desired stabilization results.

Chemical stabilization, involving bonding soil particles with cementing agents, is another method used. Lime, a traditional stabilizer, alters soil properties through chemical reactions. It increases soil strength, reduces plasticity, and improves handling characteristics. Lime-stabilized soil bases follow similar construction procedures as soil-cement, with additional time allowed for lime-soil reactions. Proper care must be taken to prevent lime carbonation during construction.