Chemically Stabilized Soft Clays for Road-Base Construction

Soft clays are widely distributed in Missouri, United States. Due to their relatively low strength and high compressibility, subgrade construction in soft clays has encountered many difficulties. In recent practice, the use of fly ash (FA) along with lime to tackle soft subgrade problems has shown promising results. The effectiveness of Class C FA and lime kiln dust (LKD) in clay subgrade stabilization is examined in this research. Scanning electron microscopic (SEM) analysis, proctor compaction tests, unconfined compression tests, and resilient modulus tests were carried out on the FA and LKD modified soil mixtures. Test specimens were prepared at optimum water content and tested at various curing periods. The test specimens were reconstituted by static compression. Test results revealed that the addition of Class C FA could increase the dry unit weight of the FA treated soil, enhance the unconfined compressive strength, and improve the resilient modulus. Regression equations were developed to correlate the resilient modulus with curing time. The mechanism of FA stabilization was discussed based on the SEM results and the measurement of the electrical conductivity of the FA-soil-water system. Correlations between the unconfined compressive strength and resilient modulus were developed. It is concluded that subgrade stabilization with Class C FA and LKD are cost-effective for road-base construction.