Experimental study on flexural toughness of fiber reinforced concrete beams: Effects of cellulose, polyvinyl alcohol and polyolefin fibers

Flexural toughnesses of concrete reinforced by cellulose fibers (CTFs), polyvinyl alcohol fibers (PFs) and polyolefin fibers (VSs) are studied through notched beam tests. Flexural strength, ultimate strength, residual flexural and tensile strength, fracture energy, the relationship between crack mouth opening displacement and deflection, as well as the synergistic effect of hybrid fibers are investigated. The results show the following. (1) With the increase of fiber dosage, CTFs enhance the flexural strength and ultimate strength of concrete, while high dosages of PFs and VSs weaken the flexural and ultimate strengths. (2) CTF-PF hybrid fibers have a positive synergistic effect on the flexural strength and ultimate strength of concrete. (3) With the increase of fiber dosage, CTFs firstly strengthen and then weaken the fracture energy of concrete, while PFs weaken and then strengthen the fracture energy, and VSs strengthen the fracture energy. CTF1.2PF2.0VS2.0 is considered the optimal combination of hybrid fibers. (4) It is significant that there is a three-stage linear functional relationship between the crack mouth opening displacement and deflection of fiber reinforced concrete.