Effects of different mixing ratio parameters on mechanical properties of cost-effective green engineered cementitious composites (ECC)

ECC is an advanced construction material with tensile strain hardening characteristics and multiple cracking behavior, which is very attractive to the construction industry. However, the oiled polyvinyl alcohol (PVA) fibers and fine silica sand widely used in traditional ECC lead to high cost, and high cement content will lead to high carbon footprint. In order to reduce the cost and severe environmental concern, the paper develops a low-cost green ECC. The means adopted is to replace oiled PVA fibers and fine silica sand with hybrid local fibers (unoiled PVA fibers and basalt fibers) and river sand, respectively and thus decreases the ECC cost, and replace the cement with the high-volume fly ash and silica fume and thus improve the green. And then the influences of river sand particle size, sand-binder ratio, water-binder ratio and fiber content on mechanical properties of ECC are studies by some macro experiments. Furthermore, a new method which can comprehensively evaluate the flexural toughness of ECC from two aspects of energy and strength is proposed. In addition, the microstructure of the samples was studied by scanning electron microscopy. Test results showed that the low-cost green ECC can be developed by using local materials, but the grain size of river sand should not exceed 0.85 mm, the sand-binder ratio should not exceed 0.5, and the water-binder ratio should not be less than 0.3. Although the basalt fiber can effectively reduce the average crack width, the strength of basalt fiber decreases according to the fiber orientation, resulting in its low contribution to flexural toughness.