Optimal screening method for dosage of calcium-based nanosilica modified expansive soils improver based on cost-effectiveness

Abstract

Under complex natural environments, the properties of lime-modified expansive soil may deteriorate. This facilitates the need for newer materials to develop composite modifiers to improve the anti-deterioration performance. Nanosilica (NS), which is a highly reactive material, is a good promoter of reaction systems with volcanic ash. In this paper, lime is mixed with NS according to a specified ratio to form calcium-based nanosilica (NS-C). NS-C significantly increased the unconfined compressive strength, cohesion, and internal friction angle and decreased the plasticity index, free swelling ratio, and permeability coefficient. The optimum ratio of nano-silica to lime in compound modifier was determined to be 1:8. NS can facilitate the production of a large amount of hydration products in the early stage of the reaction of stabilized soil, thus strengthening the connection between soil particles. In addition, NS exhibits good filling effect on the tiny pores between soil particles. The properties of NS-C stabilized soils with different ratios and curing times were determined to evaluate the modification effect and mechanism of composite modifier and obtain the optimal dosage for Hefei expansive soils in road-base edging technology. The optimum content of the compound modifier for expansive soils in the Hefei area should be 6 %, and the curing time should be at least 14 days.