Water resistance and compressibility of silt solidified with lime and fly-ash mixtures

Abstract

Silt has poor engineering properties, and lime and/or fly ash are widely used to treat silt. However, very few studies could be found to investigate the water resistance and compressibility of lime and fly-ash mixtures (lime–FA) solidified silt. This paper investigated the unconfined compressive strength (UCS), water resistance and consolidation properties, and the microscopic characteristics of lime–FA solidified silt. In addition, the paper also compared the UCS, water resistance of lime–FA and lime solidified silt in our previous studies. Results reveal that the UCS increased slowly with increasing lime–FA dosage at 7 and 28 days of curing, but increased rapidly at 90 days of curing. However, at 7 days of curing, the soaked UCS was 0, and the water resistance was not improved by increasing lime–FA dosage. As the curing time increased, the UCS gain rate of different dosages of lime–FA solidified silt was largely consistent during 7–28 days of curing, but UCS gain rate became bigger when lime–FA dosage increased during 28–90 days of curing. Meanwhile, the water resistance coefficient increased first and then stabilized with curing time. Compared with lime solidified silt, the lime–FA stabilized silt had superior water resistance and a higher UCS gain rate, and the change trend of water resistance coefficient with curing time was basically the same as that of alone lime. In addition, the compressive modulus increased with curing time increasing, and microscopic analysis shows that the silt had a denser structure and more hydrates were formed with lime–FA dosage and curing time increasing.