Strength evaluation of soil stabilized with nano silica- cement mixes as road construction material

•CBR values of soil treated with nano silica and cement increased with the increase in concentration of nano silica and cement.•UCS values increased with increase in concentration of nano silica, cement and age of curing.•Resilient modulus value for the optimized mix increased with the increase in cement content.•Soil stabilized with nano silica and cement satisfied the standard code provisions as chemically stabilized subbases in pavement practices. In pursuit of replacing the conventional GSB courses by stabilizing locally available soil and reconciling it for road constructions, an experimental investigation was undertaken by treating silty sand with colloidal nano silica in three different concentration grades of NS-20, NS-30 and NS-40. Each proportion was further treated with 2%, 4% and 6% of cement. Experiments were conducted to study the effect of nano silica on modified proctor compaction, CBR and UCS tests. XRD and SEM tests were conducted to discern the latent mechanisms to study the physico- chemical changes within the soil matrix. The results demonstrated that the increase in cement content with different grades of nano silica treated soil played an indispensable role in improving the mechanical properties of soil. Optimal results were obtained for soil treated with NS-40 and 6% cement. Soaked CBR values of soil mixes were substantially enhanced by 240.76%, 268.62% and 312.90% and 7-days UCS results were observed to be enhanced by 20.98%, 43.93% and 80.19% on addition of 2%, 4% and 6% cement in case of optimized soil mixes. XRD and SEM results postulated the evidences of the furtherance in cementitious activity within the soil matrix. The paper also discusses about Resilient Modulus parameters for optimized samples by cyclic triaxial tests under different cell pressures. Results demonstrated that nano silica-cement reinforced soil satisfied the criteria for chemically stabilized bound sub bases as per codal provisions.