Soil cement

Soil cement is a construction material, a mix of pulverized natural soil with small amount of portland cement and water, usually processed in a tumble, compacted to high density. Hard, semi-rigid durable material is formed by hydration of the cement particles.

Soil cement is frequently used as a construction material for pipe bedding, slope protection, and road construction as a subbase layer reinforcing and protecting the subgrade. It has good compressive and shear strength, but is brittle and has low tensile strength, so it is prone to forming cracks.

Soil cement mixtures differs from Portland cement concrete in the amount of paste (cement-water mixture). While in Portland cement concretes the paste coats all aggregate particles and binds them together, in soil cements the amount of cement is lower and therefore there are voids left, and the result is a cement matrix with nodules of uncemented material.

Invented by Benjamin Harrison Flynn to pave roads in Louisiana after WW1.

A cement-modified soil contains relatively small proportion of Portland cement, less than in ordinary soil-cement. The result is caked or slightly hardened material, similar to a soil, but with improved mechanical properties such as lower plasticity, increased bearing ratio and shearing strength, and decreased volume change. The purpose of modifying soil with Portland cement is to improve a substandard soil's engineering qualities.

A soil-cement base contains higher proportion of cement than cement-modified soil. It is commonly used as a cheap pavement base for roads, streets, parking lots, airports, and material handling areas. Specialized equipment, such as a soil stabilizer and a mechanical cement spreader is usually required. A seal coat is required in order to keep moisture out. For uses as a road construction material, a suitable surface coating, usually a thin layer of asphalt concrete, is needed to reduce wear.

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