Experimental investigation of nano-ZnO effect on mechanical properties of cemented clayey sand

To date, various nanomaterials have been used in the literature for soil improvement. However, the application of Nano-ZnO (NZ) to the ultrasonic pulse velocity (UPV) in cement-cured clayey sand soils and the relationship between UPV and unconfined compressive strength (UCS) have not been addressed. A series of UCS and UPV tests were performed to investigate the effects of NZ on the mechanical properties of cemented clayey sand. In addition, the microstructural properties of cemented clayey sand with NZ additive were investigated using a high-resolution field-emission scanning electron microscopy (FESEM). The response surface method (RSM), an experimental technique to reduce the number of tests and the cost of research, was used to design the experiments and evaluate and optimize the results. The results showed that using NZ as an additive enhances the mechanical properties of cemented clayey sand. The correlation with an acceptable determination coefficient between UPV and UCS was suggested at different ages. The correlation with a high determination coefficient between elastic modulus and UCS was also presented. The examination of FESEM images showed that the micro-cracks are reduced in the samples containing NZ. Also, in the samples containing NZ, the calcium hydroxide (CH) size decreased and its orientation is also moderated.