Study On Freeze-thaw Damage Of Fiber Reinforced Cementitious Composite Containing Waste Ceramics

Ceramic waste is a major type of solid waste,and its application in cement-based materials has certain environmental.Fiber-reinforced cementitious composites are susceptible to freeze-thaw damage in cold regions,which leads to reduced strength and durability.This thesis aims to explore the freeze-thaw damage laws of fiber-reinforced cement-based materials containing waste ceramics.A kind of fiber-reinforced cementitious material containing ceramic wastes was prepared.The replacement ratio of fine ground ceramic powder to Portland cement was0%-30%,crushed ceramic sand was used as fine aggregate,and the volume fraction of PVA fiber was 1%-2.2%.Then The freeze-thaw experiment was conducted.The freeze-thaw damage was described by mass loss rate,relative dynamic modulus loss rate,and equivalent circuit parameters of electrochemical impedance spectroscopy(EIS)tested.The effect of PVA fiber content on frost resistance was studied using analytical methods such as elasticity and damage mechanics.The main research content and results are as follows:(1)The mass loss rate and relative dynamic modulus loss rate of the materials of different freeze-thaw cycle times were obtained through experiments with a 180-day curing age.The results indicate that the addition of PVA fibers or the increase in ceramic powder substitution rate can improve the frost resistance of fiber-reinforced cementitious materials.Adding PVA fibers or increasing the replacement rate of ceramic powder is an effective way to improve the frost resistance of fiber-reinforced cementitious materials containing waste ceramics.(2)After 100 freeze-thaw cycles,the microstructure was observed and analyzed by scanning electron microscopy.The results showed that the freeze-thaw damage caused PVA fibers to peel off from the surface of the matrix and even completely detach from the matrix.Even with hydrophilic fibers such as PVA,the interfacial transition zone is still a weak link in mechanical properties.The freeze-thaw damage developed rapidly due to the loss of the bridging effect of PVA fibers.(3)Performing exchange impedance spectroscopy testing on fiber-reinforced cementitious materials.An equivalent circuit model was introduced to investigate the influence of freeze-thaw cycles on the internal structure and conductivity path of the fiber-reinforced cementitious material.The changes in specimen resistance,connected pore resistance,and non-connected pore resistance with freeze-thaw cycles were obtained,and two freeze-thaw damage description indicators were established to analyze the effects of PVA fiber content and ceramic powder replacement on the frost resistance of the fiber-reinforced cementitious material.(4)A combined analysis using hydrostatic pressure theory and the Cai Hao model was conducted to investigate further the impact of PVA fibers on the freeze-thaw performance of fiber-reinforced cementitious materials containing waste ceramics.The relative dynamic modulus loss rate variations were analyzed with PVA fiber content and freeze-thaw cycle number as variables.The strengthening effect of PVA fibers on the frost resistance of cementitious materials was examined while emphasizing the influence of the freeze-thaw cycle number on the frost resistance of the material.