Soil Cement


Soil-cement is a highly compacted mixture of soil/aggregate, cement, and water. It is widely used as a low-cost pavement base for roads, residential streets, parking areas, airports, shoulders, and materials-handling and storage areas. Its advantages of great strength and durability combine with low first cost to make it the outstanding value in its field. A thin bituminous surface is usually placed on the soil-cement to complete the pavement.

Soil-cement is an engineered material designed and constructed for various pavement applications or material characteristics. The best soil-cement product is the one best suited to the specific application. Each of these cement-based pavement materials are engineered specifically for their intended purpose as follows:

Cement-Modified Soil (CMS)
Many problems can occur during construction when silt and clay soils are encountered, particularly when they are wet. These soils can be soft, plastic, and difficult to compact. Cement-Modified Soil is used to improve the engineering properties and construction characteristics of silt and clay soils by reducing the plasticity and enhancing the compaction and strength of the material. With 3 – 5 percent (by dry weight) of cement used to modify the soil, the final product is an improved construction material.

Cement-Treated Base (CTB)
Cement-Treated Base a general term that applies to all hardened soil-cement that meets the project specified minimum durability and strength requirements. The soil-cement can be mixed-in-place (like Cement-Modified Soil) using on-site soils or mixed in a central plant using selected aggregate. However, CTB uses more cement than CMS resulting in a strong, durable, frost resistant layer for the pavement structure. Typical cement contents range from 3 – 10 percent cement, resulting in 7-day unconfined compressive strengths from 300 – 800 pounds per square inch (psi).

Full-Depth Reclamation (FDR)
A special case of cement-stabilization is Full-Depth Reclamation, where aggregate for the cement-stabilized base is obtained by pulverizing and recycling the old asphalt surface and base material. This construction procedure is very similar to mixed-in-place construction, except that there is an aggregate specification for the blend of the pulverized asphalt and old base material. FDR commonly uses 4 – 6 percent cement and results in 300 – 400 psi unconfined compressive strengths in seven days.

The four major variables that control the properties and characteristics of soil-cement are (1) the nature of the soil material; (2) the proportion of cement in the mix; (3) moisture conditions; and (4) the degree of compaction. It is possible, simply by varying the cement content, to produce mixes ranging from those which result in only modification of the compacted soil to those which result in hard soil-cement that will meet durability and strength requirements.

Benefits of Soil Cement

Reduces CostsImproves soil without replacement and hauling expenses

Eliminates wasteNo removal or replacement of inferior soils is necessary

Reduces plasticity/cohesivenessImproved constructability of marginal on-site soils

Improves strengthTreated soils are stronger than native soils

Improves performanceBetter support and bearing capacity

Resists leachingChemical and physical improvements of the soil are permanent

Decreases volume change characteristics

Adaptable to any type of soilImproves strength and durability from poorly graded sands to highly plastic clays