Gradation Effects on the Strength Properties of Cement and Fly Ash Stabilized Quarry By-Products

Crushing of aggregates at quarries produce large amounts of waste by-product materials that, if not utilized, pile up or end up in landfills. Current research at the Illinois Center for Transportation has focused on the sustainable applications of by-product materials in transportation infrastructure. Samples of quarry by-products (QB) were collected from several stone quarries in the State of Illinois and characterized for their engineering properties. Due to their low strengths and potential high fines contents, stabilization of QB was necessary for pavement use. Accordingly, the QB samples were stabilized with both 2% Type I portland cement and 10% class 'C' fly ash and tested for the 7-day unconfined compressive strengths. Initially, the unstabilized and stabilized QB specimens from two different crushing stages were tested for their unconfined compressive strengths. Then, the QB samples were sieved, size separated, and the gradations were engineered to match certain gradation curves that are power exponents of the ratio of the sieve size to the maximum particle size. This paper presents findings for the different QB gradations established as a factorial based on the Fuller curve for optimum packing and maximum density. For both stabilizers, the effects of gradation on the unconfined compressive strengths of QB were evaluated. Gradations that produce optimum packing and higher compressive strength are recommended to be utilized in pavement construction to achieve optimal field performance.