Porous Concrete & Asphalt: Pervious Pavement

Soil Cement

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Soil cement is a highly compacted mixture of soil, or other salvaged aggregate, Portland cement, and water. Soil cement and Portland cement differ in several ways, including their general physical compositions and appropriate uses. It is cost effective, since as much as 90% of its materials are obtained on-site. Existing soil, deteriorated roads, cinders, foundry sands, and screening from quarries and gravel pits can all be utilized as mixing materials. Virtually any inorganic soil can be used, though granular soils are favored over clay soils. Using site soils in the soil cement can improve the visual and physical connection between the existing landscape and the new intervention.

In general, soil cement has good compressive and shear strength, but low tensile strength and some brittleness, making it prone to forming cracks. Because soil cement forms a very rigid material with slab-like characteristics, the required thicknesses for roads and other surfaces are less than those required for granular bases. It can also be designed to be virtually impermeable, making it particularly resistant to freeze-thaw and suitable for high-intensity hydrological uses. Simple laboratory tests establish the cement content, compaction, and water characteristics required to achieve structural performance. Specimens taken from roads show that the strength of soil cement actually increases with age; some specimens from roads were four times as strong following four years of traffic.

Mixing soil cement with on-site materials is a simple multi-step process. The proper amount of cement is spread over the existing soil, then the cement, soil, and water are mixed by any of several types of mixing machines. Next, the mixture is heavily compacted with common machines to obtain the maximum benefits associated with the material. Finally, it is cured. When off-site materials are used the soil cement can be mixed off-site in a concrete plant and hauled to site and spread, compacted, and cured.

Soil cement is commonly used in a wide range of applications. In addition to serving as a general-purpose paving surface, it is often used for stream bank protection, channel liners, drop structures, pond liners, and retaining walls. Its impermeability, stiffness, and economical characteristics have made it an ideal material for large-scale hydrological infrastructure projects. The material’s more naturalistic finish is ideal for blending hydrological reinforcements into the existing landscape. Soil cement can also be mixed directly in the ground with lower concentrations of Portland cement to create a material akin to soft rock; these ground modification techniques are useful for foundations, retaining structures, or temporary support.

Source: Portland Cement Association

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