Combined effects of steel fibers and water to cementitious materials ratio on the fracture behavior and brittleness of high strength concrete

This experimental program investigated the effect of steel fibers and water to cementitious materials ratio (w/c) on the fracture characteristic of plain high strength concrete (HSC) and high strength steel fiber reinforced concrete (HSSFRC). In this research, the w/c ratios of 0.24 and 0.35 as well as four volumetric steel fiber contents of 0.2%, 0.4%, 0.6%, and 1% were examined. Two methods including size effect method (SEM) and work of fracture method (WFM) were applied to determine the fracture properties of concrete. Based on the experimental results, by increasing the steel fibers and decreasing the w/c ratio in HSSFRC, the total fracture energy (G(F)), characteristic length of concrete (L-ch), initial fracture energy (G(f)) and fracture toughness (K-IC) were increased. Also, for steel fiber content greater than 0.2%, the effective length of fracture process zone (C-f) was increased; however, the brittleness number (beta) was reduced. The G(F)/G(f) ratio from 2.53 and 2.5 in HSC was increased to 11.88 and 10.26 in HSSFRC when w/c ratio was increased from 0.24 to 0.35.