The Effect of Combined Nanosilica and Lime on the Improvement of the Marl Soil Engineering Properties

Marls are problematic soils, which easily erode if they are exposed to water flow and problems in the stability of the bedding of construction projects can be occurred. One of the methods for soil chemical modification is the use of additives such as lime, cement and nanoparticles. The effect of adding nano-SiO2 on the lime performance on the enhancement of the improvement process of the marl soil engineering properties and the formation of new compounds due to the stabilization process has been investigated in the present study. In this regard, after determining the geotechnical properties of Marl soil, improvement of engineering properties of samples stabilized with various percentages of lime and nano-SiO2 after the end of the curing period was analyzed by performing large-scale experiments (Atterberg limits, aggregation, deposition and unconstrained compressive strength (UCS), and microstructure ((pH) and X-ray diffraction (XRD)). According to the results of this study, the presence of nano-SiO2 in the marl-lime soils system has led to increased pozzolanic activities and growth of calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H) nanostructures and uniform distribution of these nanostructures. The compressive strength of the modified samples with the combination of nanosilica and lime proportional to the increased nano-silica additive has a quite ascending trend. Based on the results of the present study, the development rate of improvement of marl soil engineering properties in a modified specimen with 6% lime and 1% nano-SiO2 increased the compressive strength in the first 7 days by 18.45 kg/cm2 and the compressive strength increased by 18 times compared to the reference specimen.