Jang, J.; Jang, J.; Barbato, M.; Gutierrez-Wing, M.T.; Rusch, K.A., and Jung, J., 2021. Effects of fluorogypsum and quicklime on unconfined compressive strength of Kaolinite. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 126–130. Coconut Creek (Florida), ISSN 0749-0208.

Coastal areas have environmentally and economically important roles but tend have weak soft ground, which is often vulnerable by waves and unsuitable for coastal construction, such as ports and waterfront areas. Hence, this soft ground, which usually contains large amounts of clays, needs to be ameliorated by using appropriate soil improvement techniques. A common approach to improve soft ground is soil–binder injection techniques to enhance its strength. When avaialbe, binders from industrial wastes can be used instead of commercial products, such as cement and lime, to reduce construction costs and minimize environmental disturbance. Reusing industrial wastes mitigates environmental pollution and reduces the costs of waste management. Construction materials, such as sand and cement, can be partially replaced with industrial wastes if the wastes are granular and induce cementation effects. Fluorogypsum (FG), a by-product obtained during the production of hydrofluoric acid, satisfies these conditions, as it is capable of binding granular materials. Approximately 894,000 metric tons are annually produced in the U.S. However, data on the mechanical strength of clay–FG mixtures are unavailable. In this study, we conducted unconfined compressive strength tests to investigate the mechanical behavior of kaolinite, which represented clay in soft ground, at different FG and quicklime contents. The effects of FG on the compressive strength of kaolinite–FG–quicklime mixtures depend on the curing time and weight ratios of the constituent materials. The composition of the mixture with the highest compressive strength was 30% FG, 5% lime, and 65% kaolinite. We infer that the stoichiometric ratios of mixtures control the chemical reactions for the maximum compressive strength at different quicklime contents based on a series of compressive tests.