Effect of Nano-calcium carbonate on the Geotechnical and Microstructural Characteristics of Highly Plastic Paddy Clay

Construction on temporary wetlands like paddy fields is a necessity due to rapid urbanisation. A sustainable ground improvement practice mitigating negative impacts on the geological genesis of fields is crucial. The novel approach of soil treatment using nano-stabilisers could be a feasible solution. The present study investigated the effect of nano-CaCO3 on the plasticity, compressibility, strength, and shrinkage characteristics of paddy clay. The efficiency of nanomaterial in altering the geotechnical properties was studied by adding 0.5%, 1%, 1.5%, and 2% of nano-CaCO3 per unit weight of dry soil. The unconfined compressive strength of paddy clay samples treated with an optimal amount of 1.5% nano-CaCO3 increased 3.5-times compared to untreated samples after 28 days of curing. There was 20% decrease in the plasticity index value and 46% decrease in the liquid limit of the specimen after treatment. The shrinkage limit of highly plastic clay was found to have increased from 18 to 28% with the addition of optimum nano-content. The compression index value dropped from 0.33 to 0.26, and the coefficient of permeability decreased by nearly two orders of magnitude after nano-treatment. The microstructure of treated soil samples was assessed by X-ray powder diffraction analysis (XRD), Scanning electron microscopy (SEM), Fourier Transform Infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) surface area analysis. The laboratory findings and microstructural studies have shown that nano-CaCO3 treatment is a viable method to improve the physical and engineering behaviour of paddy clay.