Study On Effect Of PVA Fiber Modification On Carbonation Resistance Of Concrete

Due to its high strength and low cost,concrete is widely used in bridges,houses,dams and other engineering structures.Durability is an important aspect of the reliability of concrete structures.For concrete exposed to air for a long time,carbonization is the focus of its durability research.In order to improve the tensile and flexural performance of concrete,various fibers,such as polyvinyl alcohol(PVA)fiber,are added into it.Therefore,the study of the carbonation resistance of PVA fiber concrete becomes a very important problem.In order to study the effect of PVA fiber on the carbonation resistance of concrete,the rapid indoor carbonation experiments are carried out on the ordinary concrete specimens and PVA fiber concrete specimens with different fiber lengths of 3 mm,6 mm,12 mm and18 mm and volume contents of 0.1%,0.3%,0.5%,0.75%,1.0% and 1.5%.It is found that the carbonation depth of concrete is obviously dispersed due to the randomness of the internal composition and structure of concrete.The Anderson-Darling(AD)tests prove that compared with lognormal distribution and Weibull distribution,the normal distribution function is more suitable to describe the dispersion of concrete carbonation depth.The experimental study also indicates that the carbonation gradually develops inside concrete with the extension of time,and the addition of PVA fiber could significantly delay the development of carbonation,so it improves the ability of concrete to resist carbonation.Within the experimental range of fiber length and volume content,with the increase of PVA fiber length and volume content,the carbonation depth showed a trend of first decreasing and then increasing.According to the experimental results,the carbonation coefficient is described by the linear or quadratic function of PVA fiber length and volume content,and a time-dependent model of the carbonation evolution of PVA fiber concrete is proposed.Compared with the experimental data,it is found that the prediction accuracy is higher by using the quadratic function.Finally,according to the similarity between concrete carbonation analysis and thermal analysis,the carbonization process of PVA fiber concrete under the conditions of indoor rapid carbonization experiments is simulated with the diffusion model based on the experimental data.By comparison with the experimental results,the rationality of the numerical simulation is validated.The influence of added PVA fibers on the carbonization life and durability of concrete component is further studied.The results show that compared with the ordinary concrete component,the durability of PVA fiber concrete components is significantly improved.