Strength mechanism and electrochemical characterization of cement-bonded calcareous sand in different water environments

Abstract

Cement-bonded calcareous sand (C-BCS) can effectively enhance the strength of calcareous sand, which is widely in infrastructure construction on islands in the South China Sea, and can fulfil the engineering requirements of island pavement subbase. However, the enhancement mechanisms and meso-generalized structural characteristics of C-BCS under different water environments and cement dosages are unclear. In this study, we consider the unconfined compressive strength as an evaluation index to quantify the degree of hydration reaction, change of hydration products, and meso-generalized structure of C-BCS in freshwater and seawater. We performed analyses using electrochemical impedance spectroscopy, X-ray diffraction, and scanning electron microscopy. The results demonstrate that C-BCS can satisfy the strength requirements of highway and airport runway subbases with 10% and 15% cement admixture, respectively. Furthermore, the corrosion deterioration phenomenon occurs and spreads in C-BCS in seawater. The internal hydration process of C-BCS can be continuously monitored using the electrochemical impedance spectroscopy test, and a correlation between the electrochemical and mechanical parameters at different ages is proposed. The meso-generalized structure inside the C-BCS can be densified by the bridging and pore filling effects of hydration products on calcareous sand particles, thereby improving the strength of calcareous sand. Additionally, we provide a concrete mechanistic explanation underlying the forming strength of C-BCS, and an optimized design approach of C-BCS considering several complex engineering properties.