Influence of natural zeolite on fresh properties, compressive strength, flexural strength, abrasion resistance, Cantabro-loss and microstructure of self-consolidating concrete

This study aimed to evaluate the effect of natural zeolite (NZ) on some fresh and hardened properties of self consolidating concrete (SCC). For this purpose, eight mixtures containing 0, 5%, 10%, and 15% NZ as partial replacement of portland cement with two water to binder ratios (w/b) were studied. In order to evaluate the mechanical properties of concrete, compressive strength and four-point bending tests were performed at the ages of 7, 28, and 90 days. The abrasion resistance and Cantabro-loss tests were performed according to ASTM C779-A (procedure A-revolving discs) and ASTM C1747, respectively at the ages of 28 and 90 days. The results indicated that the HRWR demand of SCC mixtures increases with NZ content. However, the viscosity and stability of the mixtures were improved by NZ. Overall, the mechanical properties of SCC mixtures were improved by using NZ. The optimum rate of NZ was found to be 10%. Although the reduction of the w/b ratio had a more significant effect on improving the mechanical properties compared to using NZ, the reduction of the w/b ratio along with the partial replacement of cement with NZ enhanced this effect. In addition, regression analysis showed a strong correlation between the results of abrasion resistance and Cantabro-loss tests. The results of SEM analysis showed a significant reduction in the width, length and number of micro-cracks in the bulk binder paste and the ITZ of 10% NZ mixtures compared to the plain portland cement mixtures. High peak intensities of C-S-H gel and low intensities of ettringite were also observed by XRD analysis in the ITZ of NZ-containing concretes due to pozzolanic reaction.