Utilization of waste silty soil as fine aggregate in controlled low-strength material

Abstract

Abstract Silty soil excavated in construction projects is usually considered waste material. This work pioneers a high-value utilization of waste soil by exploring the feasibility of repurposing silt soil to prepare controlled low-strength materials (CLSMs). For sustainable purposes, alkali-excited fly ash and waste glass powder are used instead of pure cement, and the necessary additives are introduced to improve the performance of CLSM. Laboratory tests are performed on CLSMs with different mixture ratios to evaluate the flowability, unconfined compressive strength, and setting times. The effects of two critical parameters: the water content (W/G), i.e., the mass ratio of water to solid in CLSM mixtures, and the stabilizer content (S/MLd), i.e., the mass ratio of stabilizer to dry silty soil are studied. Experimental results indicate that the increase of water content has a favorable effect on flowability, but significantly increases setting time and reduces the compressive strength. Furthermore, when the water content is over 0.4, the initial setting time may exceed 4 hours, limiting the application of CLSMs. The increase of stabilizer content is beneficial to the increase of flowability and strength and markedly accelerates the final setting time. The predictive equations of flowability and compressive strength and 7 days of the silty soil-based CLSM have been developed with W/G and S/MLd, and the predicted results are compared with the results on the contour map. Based on the prediction model, the recommended intervals of W/G and S/MLd are given to meet the strength and flowability targets of different applications.