Effect of nano-SiO₂ on flow-ability, setting time and strength properties of controlled low-strength materials using native silt soil

Controlled low-strength material (CLSM) is widely applied in many backfill engineering applications because of its excellent workability and sustainability. However, for CLSM using native soil as fine aggregate and industrial by-products as a binder, the flow-ability and self-leveling performance will deteriorate, and the setting time will be slower, which is unsuitable for construction applications. The addition of additives is regarded as an effective technique for improving the performance of CLSM. Although the effects of nano-SiO 2 on the performance of concrete have been the subject of many studies, little research has been done on its effects on CLSM. The present work investigated the effects of adding nano-SiO 2 as an additive. The flow-ability, hydraulic penetrometer, and unconfined compressive strength (UCS) tests are performed with the increasing nano-SiO 2 content. Lastly, the mercury intrusion porosimetry (MIP) test is carried out to identify the effects of nano-SiO 2 on the morphology of pores. For controlled low-strength materials using native silt soil, significant improvements in setting time and strength are observed with the increase of nano-SiO 2 . A decrease in the average pore diameter and an increase in the percentage of pore diameter below 20 nm are also observed in the specimen with nano-SiO 2 .