Improvement of mechanical strength of mortars by different morphological zinc oxide nanoparticles

Abstract

This study presents novel nano-mixtures containing zinc oxide (ZnO) nanoparticles (NPs) to enhance the mechanical properties of cement mortars. Different morphological ZnO NPs were synthesised through the green sonochemical method, using tragacanth gum/Kappa carrageenan (TG/κ-C) and tragacanth gum/chitosan (TG/CS) as biopolymer matrices. The ZnO NPs were characterised using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, X-ray diffraction, Zetasizer and Brunauer–Emmett–Teller techniques. The intrinsic viscosities of TG/κ-C-ZnO and TG/CS-ZnO NPs were investigated to determine the miscibility of the polymeric blends in aqueous solution as affected by sonication time and composition ratios. The average diameters for the spherical and prism-like ZnO NPs were around 266 nm and 355 nm, respectively. Seven different cement mortar specimens containing TG/κ-C-ZnO and TG/CS-ZnO NPs were prepared in ratios of 0, 0.1, 0.5 and 1% by weight, and the flexural and compressive strengths of the specimens were determined at the ages of 7 and 28 days. The results indicate that there is a significant improvement in the mechanical performance of different morphological ZnO NP-based cement mortar composites. In comparison, it was observed that specimens containing TG/κ-C-ZnO NPs had much better results than TG/CS-ZnO NPs. Moreover, the workability problem encountered by using only ZnO NPs has been overcome with the presented biopolymers used in this study.