Experimental Study On Influence Of Polyvinyl Alcohol Fiber And Steel Fiber On Mechanical Properties Of High Performance Fiber Reinforced Cementitious Composites

In this thesis, an experimental investigation was conducted on the influences of polyvinyl alcohol fiber and steel fiber on strength, fracture energy, and flexural toughness of high performance fiber reinforced cementitious composites (HPFRCC).A series of HPFRCC was prepared with ratio of water to binder (W/B) (0.26, 0.36 and 0.50), fiber type (PVA fiber and steel fiber) and fiber volume factions (0, 0.5.% and 1.00%). Mechanical properties measured include flexural strength, compressive strength, fracture energy, and flexural toughness at 7th day and 56th day.Flexural strength and compressive strength of steel fiber HPFRCC was higher than that of PVA fiber HPFRCC at the same condition of the ratio of water to binder (W/B) and fiber volume fraction.Flexural strength and compressive strength of steel fiber HPFRCC and PVA fiber HPFRCC was enhanced with the increase of fiber volume fraction at the same condition of the ratio of water to binder (W/B), respectively.Fracture energy, flexural toughness and ratio of flexural strength to compressive strength of steel fiber HPFRCC was higher than that of PVA fiber HPFRCC at the same condition of the ratio of water to binder (W/B) and fiber volume fraction.As PVA fiber is hydrophilic, dispersibility of PVA fiber was higher than that of steel fiber in cementitious matrix. Effect of PVA fiber on the toughness of HPFRCC was enhanced with fiber volume fraction increase from 0 to 1.00% at the ratio of water to binder (W/B) as 0.26,0.36 and 0.50, but the effect of steel fiber was weakened.Fracture energy of PVA fiber HPFRCC declined with age at the same condition of the ratio of water to binder (W/B). In fracture energy test, stress concentration was presented in notch of specimen, where stress distribution was complex. With age increasing, capability of resisting complex stress of PVA fiber declined due to aging. Interfacial bonding strength between PVA fiber and cement matrix reached tensile strength of PVA fiber, failure of fiber could be delayed by yielding. However, mid-span deflection of specimen reached 20 mm-30 mm at the end of fracture energy test, which caused failure for most of PVA fiber by exceeding itself limited elongation, so that energy could not be consumed any more. Fracture energy of steel fiber HPFRCC was enhanced with age at the ratio of water to binder (W/B) of 0.26 and 0.36. Tensile strength of steel fiber was greater than interfacial bonding strength, steel fiber was always pulled out from interface. With the age, interfacial bonding strength was increased, so that more energy was consumed during steel fiber pulled out from the cement matrix.Fiber-type is the key factor influenceing fracture energy, flexural toughness, the ratio of flexural strength to compressive strength of PVA fiber HPFRCC and steel fiber HFPRCC.The ratio of water to binder (W/B) is the key factor influenceing flexural strength and compressive strength of PVA fiber HPFRCC and steel fiber HPFRCC.