Manufacturing engineering cementitious composites (ECC) with available materials in Iran and reinforcing them using glass grids

Engineered cementitious composite is a cement-based composite material that exhibits significantly higher flexural, tensile, and compressive strength compared to ordinary concrete. The initial tensile strain capacity of ECC within the first two days of concreting is approximately 5%. However, as time progresses, the tensile strain capacity decreases to stabilize at a constant value of 3%, a level considerably higher than that of ordinary concrete. Moreover, ECC exhibits exceptional durability in sulfate, chloride, tropical environments, as well as resistance against freeze-thaw cycles. Its significance characteristics, including strain-hardening behavior, multiple cracking, and ductile behavior, distinguish it from the other types of concrete. To produce engineered cementitious composite, special materials such as fly ash and polyvinyl alcohol (PVA) fibers are required, but they are not available in the country. In this research, 13 different engineered cementitious composite mix designs were developed using locally available materials such as slag, limestone powder, industrial pozzolan, silica fume and polypropylene fibers. Then, the mechanical properties of different engineered cementitious composite mix designs, including compressive strength, modulus of rupture, energy absorption, and toughness indices have been investigated. The experimental results showed that optimizing the use of silica fume, and slag at rates of 10% and 28% by weight of cement, respectively, along with the inclusion of industrial pozzolan at a rate of 22% by weight of cement, improves the mechanical properties of engineered cementitious composite. Finally, the best engineering cement composite mix design was reinforced with glass grids (one and three layers) and subjected to a four-point bending and direct tensile tests. According to the results obtained from the four-point bending test of glass grid reinforced engineered cementitious composite panels, it can be concluded that increasing the number of glass grid layers enhances flexural strength, the area under the load-deflection curve, and energy absorption. For instance, the flexural strength of engineered cementitious composite panel reinforced with three layers of glass grid increased by 47.5% and 275%, respectively, compared to the flexural strength of an engineered cementitious composite panel reinforced with one layer of glass grid and an unreinforced engineered cementitious composite panel.