Search

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. [ABSTRACT FROM AUTHOR]

Finding a method to optimize the design of the polyethylene fiber-engineered cementitious composite (PE-ECC) mix proportion is an urgent endeavor. The analytic hierarchy process (AHP) is an efficient decision-making tool for complicated problems with multiple variables and uncertainties. In this study, initial cracking strength, ultimate tensile strength, tensile displacement, and test age, as influencing factors of the PE-ECC optimum mix design were considered. The weightings of the factors were quantified through the AHP method according to the tensile test results of 14 groups of specimens with different mix proportions. The water to binder ratios (0.25, 0.27, 0.29, 0.31), the mineral admixtures (30%, 40%, 50%, and 60%), and the PE ratio (2%) were the three main test parameters for the factors of the PE-ECC tensile properties. The weight of each influence factor was calculated by constructing a matrix, which confirmed that the judgment matrix satisfies the consistency test. The optimum mixture ratio of 30% fly ash and 0.27 water-binder ratio were obtained. The results demonstrate the applicability and rationality of the AHP theory. The findings from this study can be used as a guideline for the optimized design of PE-ECC mix proportions. [ABSTRACT FROM AUTHOR]

• We explored the effects of different ions on the self-healing performance of PE-ECC. • WE setting two evaluation methods: tensile strength recovery rate and resonance frequency recovery rate. • We used two sampling methods to compare and analyze the self-healing products of PE-ECC. • Combining SEM, XRD, and EDS methods, the self-healing products and self-healing process of PE-ECC were summarized. This study applied pre-damage of 1 % tensile strain and 75 % failure loads to tensile and prismatic specimens of desert sand polyethylene fiber (PE) engineered cementitious composite (ECC) specimens at different ages (3 and 28 days), respectively. Self-healing was applied to the pre-damaged PE-ECC under 5 % Na 2 SO 4 and 3 % NaCl, 5 % Na 2 SO 4 , and water environments. The mechanical properties of the PE-ECC after self-healing, the changes in the number and width of cracks, tensile strength and resonance frequency recovery rate were analyzed. Then, the self-healing products and self-healing process of the PE-ECC were further examined by SEM, EDS, and XRD microscopy. Results showed that self-healing PE-ECC could complete the process within 10 days in different environments and found the self-healing process involved the continuous generation and consumption of self-healing products. The 3-day-old self-healing PE-ECC was stronger than its 28-day-old counterpart. The self-healing performance was strongest in 5 % Na 2 SO 4 , whereas it was weakest in water. The main self-healing product of the PE-ECC was CaCO 3 , which was the result of the coupling effect of carbonization, secondary hydration, and erosion product fillings. [ABSTRACT FROM AUTHOR]