Soil-cement is made by thoroughly mixing soil, portland cement and water by one of the ways described in this article. The most practical soils are those that contain not more than 35 percent silt and clay and that are easily pulverized. If more than 4000 cubic yards are to be constructed, the central-plant mixing method proves easy and economical.
CENTRAL-PLANT MIXING METHOD
Central mixing plants can be either continuous-flow or batch plants. Continuous-flow plants are the more common. Such plants include a bulkhead that confines the soil aggregate, an aggregate feeder, a cement silo and feeder, a main feeder belt, a water supply system and a pugmill mixer. Materials are metered onto the belt and fed to the mixer. In a batch plant the soil aggregate is stored in bins above the batching hopper into which an auger feeds cement. Cement and soil aggregates are batched by weight.
The soil-cement mixture can be compacted initially by a sheepsfoot roller. This should be of sufficient size and weight to compact the bottom of the layer to the required density. Following the sheepsfoot rolling, a heavy pneumatic-tire roller compacts the loose upper portion of the soil-cement layer. Vibratory compaction, using a vibratory steel-wheel roller has been used successfully on several large projects.