Study On Influence Factors Of Self-Healing Of Tailing Sand Cementitious Composites

The tailings sand cement-based composite material is a high-performance,green fiber-reinforced cement-based composite material developed by using tailings sand as a substitute for fine aggregate in cement-based composites,adding PVA fibers,and using a large proportion of fly ash.The material has a good prospect of engineering application.At present,great progress has been made in the study of the self-healing properties of cement-based composites at home and abroad.However,there have been few reports on the self-healing properties of PVA fiber-reinforced cement-based composites with tailings.Therefore,based on the existing research works of the research group,this study carried out self healing performance of tailings sand cement-based composite material.From the point of material component and environmental factors,this subject uses the strength recovery method and ultrasonic testing to study the volume of PVA fiber,the substitution rate of tailings sand and the content of fly ash,as well as the effect of different environment on the self healing properties of the tailings sand cement-based composite material.The orthogonal experiment was designed to analyze the significance of each component on the self-healing property and the mix ratio with optimal self-healing properties of the material.Through the above studies,the influence of different factors on the self-healing properties of tailings sand cement-based composite material is revealed.The research content and main conclusions of this paper are as follows:(1)Carry out self-healing test of prefabricated crack specimens for material components.According to the strength recovery rate and ultrasonic wave velocity of the damaged specimen after self healing,the influence of the material component factors on the self healing properties of the tailings sand cement-based composite material is studied.The results show that the self-healing properties of the tailings sand cement-based composite material with PVA fiber are better than those of the materials without PVA fiber.Reasonable use of tailings sand to replace the fine aggregates in the material can improve the self-healing properties of the material;When the self curing age is relatively short,the lower the amount of fly ash is,the better the self healing performance of the material is.With the growth of self-healing curing age,the use of certain amount of fly ash can improve the self-healing properties of tailings sand cement-based composite material,and fly ash will gradually take part in the self-healing curing process.(2)Conduct self-healing test in view of the environmental impact.In the standard curing environment and different concentration of sulfate solution curing environment,the self-healing maintenance test of prefabricated crack specimens was carried out.The results showed that the low-concentration sulphate solution can improve the self-healing properties of the material,and it is superior to the self-healing properties of the material under standard self-healing curing.The self-healing performance in the high-concentration sulfate environment is better at the initial stage of curing,but with the increase of curing age,the self-healing property of the material gradually decreases,and is lower than other groups,and even corrosion damage occurs.(3)Orthogonal experiments were designed based on the selected material composition factor.The variance and range analysis of the strength recovery rate obtained from the test were used to infer the significance of the effect of each component on the self-healing properties of the tailings sand cement-based composite material,and then the optimal mix ratio of the self-healing properties of the material was investigated.The results show that the volume content of PVA fiber has a significant effect on the self-healing properties of tailings cementitious composites.Fly ash content has a significant effect,and its significance increases with the increase of self-healing and curing age;Tailings sand replacement rate has an effect on self-healing properties.Tailings sand replacement rates have a slight effect on self-healing properties.In the range of parameters selected in this study,the volume ratio of PVA fiber is 1.5% and the tailings replacement rate was 1/2 when the mix ratio is optimal,and the optimum mixing amount of fly ash varies with the age of self Healing curing.