The relationship between compressive strength and age for soils stabilized with four types of cement

Abstract

Summary: The relationships between unconfined compressive strength and age up to 28 days have been determined for soil-cement specimens made with a sand, a silty clay and a clay, stabilized with four different cements. A comparison has also been made of the effects on compressive strength of coating test specimens with wax and of placing them in a humid atmosphere during the curing period. High-alumina cement was found to give the highest strength after 24 hours, wirh all three soils, but afier 28 days it gave lower strengths than the other cements. Rapid-hardening cement was found to give strengths 20-40 lb per sq. in. greater than normal Portland cement with the two cohesive soils, while super-rapid-hardening cement generally gave strengths about 40 lb per sq. in. lower than those obtained with the other two Portland-type cements. The setting of normal Portland and rapid-hardening cement mixed with the sand was retarded for seven days, due to an organic impurity, but the setting of high-alumina cement was not affected. The addition of lime, or calcium chloride (e.g. in super-rapid-hardening cement) was found to reduce the retardation, the latter being the most effective. The action of calcium chloride in this respect was confirmed with three other soils containing deleterious organic matter. Coating test specimens with paraffin wax during the curing period was found to result in considerably smaller differences in moisture content among similar specimens in a batch than was obtained by storage in a humid atmosphere. This was accompanied by a reduction in the differences in the unconfined compressive strength of specimens only in the case of the sand-cement. The average limits of error of the mean compressive strengths based on ten independent measurements were calculated to be between ±10 and ±20 lb per sq. in. for strengths ranging between 200 and 400 lb per sq. in.