Novel method for evaluating water absorption and retention of waste-based stabilizers using suction filtration to predict treatment effects on soft clay soils

Abstract

In this study, a novel testing method was developed to evaluate the water absorption and retention of waste-based stabilizers using suction filtration. Suction filtration was seen to remove most of the unabsorbed and unretained water from the waste-based stabilizer without losing any waste-based stabilizer particles. Therefore, oven-drying of the wet stabilizer, which can deteriorate the stabilizer, was not necessary. In addition, a formula was introduced to estimate the residual free water in the stabilizer after suction filtration based on the particle size. This estimate was used as a correction to determine the water absorption and retention rate (Wab) of the stabilizer. Subsequently, newly developed tests were conducted on fly ash (FA), a paper sludge ash-based stabilizer (PSAS), biomass ash (BMA), and the PSAS–BMA hybrid to evaluate Wab. The results show that the PSAS exhibited the highest Wab, followed by the BMA and FA. This is attributed to the CaO content of each stabilizer, which may have initiated hydration reactions. The Wab of the PSAS–BMA hybrid was similar to that of the PSAS, which is attributed to the synergistic effects of the components of each type of waste. Finally, the strength development of the FA, PSAS, BMA, and PSAS–BMA hybrid-treated clays was investigated via cone index tests. In addition to the stabilizer addition ratio (A), the Wab of the stabilizers is suggested to be an essential indicator for predicting the strength development of clays treated with waste-based stabilizers. Parameter β, which is the product of Wab and A, governs the cone index qc of the treated clays instead of A and Wab. Thus, the modified water content, w*, which considers the absorbed and retained water as a solid instead of a liquid, was applied to the cone index test results. The results show that the qc of the treated clays is more correlated to w* than to the measured water content. An empirical relationship for predicting cone index qc using w* was also proposed.