Experimental Study On Deterioration Mechanism And Performance Optimization Of PVA-ECC After Exposure To Elevated Temperature

Engineered cementitious composite(ECC)has been widely used in the world due to its excellent strain hardening and multiple cracking properties.Polyvinyl alcohol(PVA)fiber is widely used in ECC due to its physical,chemical and mechanical properties.The polymer fiber will inevitably melt at high temperature,so it is important to study the high temperature degradation mechanism of ECC for the development of ECC.In this study,PVA-ECC was used as the object of the study.The effects of high temperature on the general strength PVA-ECC were studied by thermogravimetry,X-ray powder diffractometer and field emission scanning electron microscope.The results showed that the high temperature performance of PVA-ECC was affected by the change of chemical components.Meanwhile,the mesh channel formed by PVA fiber melting can reduce the internal pore pressure and prevent the occurrence of explosive spalling.The degradation mechanism of high-strength PVA-ECC at high temperature was studied under the same test conditions,and compared with that of PVA-ECC.The results showed that the high temperature properties of PVA-ECC were different,which was due to the different chemical components and micro morphology.Finally,the optimization of high temperature resistant fibers on high temperature properties of high strength PVA-ECC was studied.The high temperature properties of steel fiber,carbon fiber and basalt fiber hybrid high strength PVA-ECC were compared.The results showed that the effect of steel fiber was the best,carbon fiber was the second,and basalt fiber was the worst.Among them,the performance of high strength PVA-ECC optimized with 1.0%vol steel fiber and PVA fiber respectively were the best.