Use of class C fly ash for stabilization of soft subgrade

Abstract

This paper represents the results of a study aimed at using self-cementing Class C fly ash for the stabilization of soft subgrade of a city street in Cross Plains, Wisconsin, U.S.A. Both strength and modulus-based approaches were applied to estimate the optimum mix design and to determine the thickness of the stabilized layer. Stabilized soil samples were prepared mixing fly ash at three different contents at varying water contents. The samples were subjected to unconfined compression test after seven days of curing to develop water content-strength relationship. To evaluate the impact of compaction delay that commonly occurs in field construction, one set of the samples was compacted just after mixing with water, while the other set after two hours. CBR and resilient modulus tests were conducted and used to determine the thickness of the stabilized layer in pavement design. Some field tests were also performed after the construction, which showed that the fly ash stabilization improved the engineering properties significantly.