Effect of Desert Sand on the Section Bonding Properties of Polyethylene Fiber−Engineered Cementitious Composites

Abstract

Xinjiang is in northwest China and has abundant desert sand. Replacing natural sand with sand from deserts is an urgent need and could be used in making polyethylene fiber−engineered cementitious composite (PE−ECC). The interfacial bonding properties of desert sand PE−ECC (DSPE−ECC) were made using the optimal mix proportion (30% desert sand content, 2% fiber volume) and the laboratory’s previous research results. Normal sand PE−ECC (NSPE−ECC) and DSPE-ECC at different test ages (3, 7, 14, and 28 days) were subjected to uniaxial tensile tests, and a method for determining bonding properties is proposed. Scanning electron microscopy and X-ray diffraction were used to analyze the development of PE-ECC fiber and matrix and the formation of hydration products. The results indicated that the cracking loads of the DSPE-ECC at 3, 7, 14, and 28 days increased by 16.72%, 28%, 23.23%, and 10.05%, respectively. Desert sand had low water content and high water absorption, which slowed down the rate of C2S, C3S combining with water molecules to form C−S−H, and had a great influence on the bonding properties of ECC at 3 days. However, the bonding properties of DSPE−ECC were only slightly less than those of NSPE−ECC at 28 days, and the bonding properties had gradually stabilized. Therefore, the addition of desert sand enhanced the fiber/matrix’s bonding properties, and the bonding properties stablized with the increase in curing ages.