Strength Assessment of Soil Cement Base in Alabama

Abstract

Soil cement is a mixture of soil, portland cement, and water that is compacted and cured to form a strong, durable pavement base. Variances among construction practices and core strength data have led to questions concerning proper quality control practices and strength testing protocol for soil cement base. The major objective of this research is to develop means to reliably assess the strength of soil cement base. In order to develop a method to reliably assess soil cement, a laboratory testing program and a field testing program were developed to evaluate the suitability of using the dynamic cone penetrometer based upon ASTM D6951 (2018) and the plastic mold method to prepare cylinders for compressive strength testing. In the laboratory, molded cylinder strength and the dynamic cone penetrometer results were well correlated between 100 to 930 psi. The effectiveness of the dynamic cone penetrometer was evaluated during an ongoing Alabama Department of Transportation (ALDOT) soil cement project. The results from this research are aimed at providing guidance to the ALDOT when specifying strength assessment parameters of soil cement base. Based on the results of this research, the plastic mold method should be used to produce molded cylinders on-site for compressive strength testing for quality assurance of the soil cement mixture. If the plastic mold compressive strength is less than or greater than the ALDOT requirement for soil cement base, then the dynamic cone penetrometer should be used to determine the in-place strength of soil cement base.