Statistical evaluation of fracture and mechanical performance of engineered cementitious composites (ECC), containing different percentages of glass, polypropylene, polyvinyl-alcohol fibers, and fly ash

Brittle cracking is one of the most important causes of catastrophic destruction in structures and infrastructures made of cement-based materials. Researchers have tried to reduce the brittleness of plain concretes by adding fibers, and these efforts resulted in the development of cementitious composites. This research aims to investigate the performance of cementitious composite with different types and percentages of fibers (e.g. Polypropylene, polyvinyl alcohol, and glass in 1.5% and 3% of unit weight) and fly ash contents (e.g. 0%, 25%, and 50%). For this purpose, direct tension and mode I fracture behaviors of 21 mixtures were tested. From the results, it can be understood that all the fibers regardless of usage percentage can make the cementitious composite more ductile, however for some of these fibers (i.e. Glass), only strain softening behavior can be seen, whereas for polypropylene and polyvinyl alcohol, in certain percentages, significant strain hardening behavior also can be seen. In studied cases, the polyvinyl alcohol and glass fibers have the most effect on load-bearing indexes (tensile strength and fracture toughness), whereas for the aim of energy absorption indexes, polyvinyl alcohol, and polypropylene fibers are more suited. Results also show that besides the fly ash addition reduces the material strength indexes, the post-failure behavior of composites is also evaded due to the weakening of the bond between the fibers and matrix.