Experimental Study On The Mechanical Properties And Anti-permeability Of PVA-SHCC After High Temperature

Fire is one of the potential factors which will damage buildings. Once fire, theproperty of building materials will be deteriorated significantly, the performance of thestructure will be weakened greatly and the economic losses will be very huge.Polyvinyl Alcohol Fiber reinforced Strain-Hardening Cement-based Composites(PVA-SHCC) possess high toughness, compatibility with the interface of the concretesubstrate, high tensile strength, high power consumption characteristic, highimpermeability and burst-resistance performance. Which will be applied to majorconstruction projects, structural durable protection or repair of damaged parts havebeen reinforced, which will be of great significance to improve the durability of thestructure. Now, many scholars at home and abroad on PVA-SHCC has carried out alarge number of experimental studies, and obtained a lot of achievement. However,these studies mainly focus on PVA-SHCC the basic mechanics, at room temperatureon the permeability resistance and durability, currently no the performance ofPVA-SHCC after fire. Based on these problems, this paper mainly carried out thefollowing work.（1）Observation and record the change in appearance and quality of PVA-SHCCafter different temperature, discovery that the color of the specimens graduallybecome shallow with temperature rising. After800℃high temperature, specimensare grey, try a large number of irregular small crack on the surface, but not burst. Asthe temperature rising continually, the quality of specimen reduced. After800℃hightemperature, the quality loss percentage rate is about20%.（2） Through flexural, compressive, three-point bending, four-point bendingexperiment study on the mechanical performance change rule of added with two kindsof PVA fiber SHCC after high temperature. Results indicated that at room temperaturethe flexural strength of PVA-SHCC improved about twice times than the cementmortar, and compressive strength of PVA-SHCC increased slightly than the cementmortar. After200℃,400℃,600℃and800℃, in addition to the residual compressivestrength of added Beijing fiber PVA-SHCC increase at200℃,and the residual flexural strength, residual compressive strength, three-point bending property, toughnes,four-point bending property and fracture energy of the rest specimen appear differentdegrees reduced under different temperature. In addition, after high temperature thedamage form of SHCC from plastic damage changed into brittle failure, and thespecimen does not appear strain hardening stage.（3）Through the capillary water absorption experiment study on the variation ofimpermeability of PVA-SHCC after different high temperature. Results indicated thatthe porosity and pore radius of PVA-SHCC increases as the temperature increases,and leading to the capillary water absorption, capillary absorption coefficient andcapillarity absorbed energy can be increased. Especially when the temperatures ishigher than400℃, two specimens of capillarity absorbed energy increased suddenly,and the porosity of specimen rising rapidly at this time, the PVA-SHCCimpermeability reducing.