Experimental Study on Engineering Properties and Microstructure of Expansive Soils Treated by Lime Containing Silica Nanoparticles Under Various Temperatures

Abstract

In this study, improvement rate of engineering properties of expansive soils caused by the effect of varying curing temperature together with the addition of Silica Nanoparticles on lime was evaluated utilizing a series of macro and micro-structural tests. Based on the results, as the temperature decreases (especially temperatures below 20 °C with storage duration shorter than 28 days), pozzolanic activities as well as growth process of cementitious mixtures (e.g. CSH and CAH Nanostructures), is disrupted and after the addition of lime, the improvement process will be majorly affected by short-term reactions (Cation-exchange capacity and increase in Osmotic pressure). Under such circumstances, it was found that an increase in the content of the mentioned additives can just control the expandability and the other geotechnical characteristics such as bearing capacity and settlement potential are negligibly improved. On the other hand, the results indicate that when the mixture of lime-silica nanoparticles (LNS) is added, undesirable effect of temperature loss on the engineering parameters is leveled down and unlike the limitations of lime performance, the compressive strength of improved specimens follows an increasing trend in proportion to the rate of increase in the additives content. Based on the X-ray diffractions as well as SEM images, the reason behind less susceptibility of specimens containing LNS to temperature and storage duration and consequently, a better behavior in comparison with those including just lime, arose from a greater number and faster process of pozzolanic reactions and compaction of the mixture’s structure. Conclusively, application of LNS (especially in cold weather and short curing duration) intensifies the lime’s effect and in addition, reduces the consumption of additives by 50%.