Evaluation of the Effect of Nano CaCO3 on the Compressive Strength of Sandy Clay Soil with Different Percentage of Clay

Nanoparticles and nano-reinforcement are extensively used in geotechnical engineering and there are various reports on the effect of nanomaterials on the improvement of the engineering properties of various soil types. The effect of nano calcium carbonate (nano CaCO3) on the geotechnical properties of sandy clay (SC) soil containing different levels of clay was investigated. To this end, three types of SC soil containing 10, 20, and 30% clay and 0.3, 0.7, 1.1, and 1.5% nanoparticles were cured for 7, 14, and 28 days and then placed under uniaxial compression test. Also, the experimental results were numerically analyzed by group method of data handling (GMDH) using an artificial neural network. The samples were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests. According to the results, adding nano CaCO3 to SC soils, caused an increase in the uniaxial compressive strength and secant modulus. Moreover, the compressive strength obviously increased over time. An optimum nanoparticle level of 0.7% was obtained for the soils containing 20% and 10% clay. The corresponding nano CaCO3 level for the soil containing 30% clay was 1.1%. The effect of nano CaCO3 as an effective additive on the ultimate compressive strength of the soil was investigated by XRD and SEM evaluations. The results indicated an increase in the crystallinity of particles after adding CaCO3 nanoparticles. Finally, based on numerical analysis of the experimental result, a correlation was obtained to predict the uniaxial compressive strength of the improved SC soil with a mean error of 4%.