Nanosilica as an Auxiliary Additive in Behaviour Enhancement of Weak Soil Subgrade

Nanosilica has enormous potential for applications in pavement engineering. The present study evaluated the contribution of nanosilica as a secondary additive towards enhancement of the compressive strength of soil for its application in the construction of roads and embankments with lime as the primary additive. Considering both short-term and long-term curing, unconfined compressive strength tests were performed on soil modified with lime and the soil-lime mixture with the optimal proportion of nanosilica for curing periods of (0, 7, 14, 28, 90 and 120) days. Though lime-modified soil had good strength characteristics, the present study revealed an elevated compressive strength with the addition of the optimum dosage of nanosilica (0.75 % by mass of soil) in a short-time span. Strength improvement of 11.05 times and 17.57 times that of the virgin soil were achieved in the case of lime-modified soil without and with nanosilica, respectively. Durability tests were conducted to evaluate the effective contribution of nanosilica to the strength retention of soil subgrade subjected to wetting-drying and freeze-thaw cycles. The increase in the California bearing ratio (CBR) of the lime-modified soil without and with nanosilica by 4.23 times and 5.36 times that of the virgin soil demonstrated the efficacy of nanosilica in the reduction of pavement thickness. The study thus provided an improved assessment of the use of nanosilica for strengthening weak soil subgrade.