Properties Of Recycled Coarse Aggregate Concrete Containing Rubber Particles Slope Protection Materials Based On Low Carbon Target

Concrete materials with high safety and stable performance are widely used in the slope protection project of the Yellow River,but the huge demand for concrete increases the carbon footprint.Adding recycled coarse aggregate and rubber particles into concrete as slope protection materials can improve the comprehensive utilization rate of solid waste.However,when recycled coarse aggregate and rubber particles are mixed together and the content is high,the mechanical properties of concrete are significantly reduced,which restricts its application in practical engineering.This paper explores the technology and method of preparing low-carbon slope protection concrete materials with recycled coarse aggregate and rubber particles instead of natural aggregate,so as to provide support for the realization of the "double carbon" goal of hydraulic engineering.The main research contents and results are as follows:(1)The effects of rubber and recycled coarse aggregate replacing natural aggregate on the mechanical properties and impermeability of concrete were studied.Low carbon recycled concrete was prepared by using recycled coarse aggregate100% instead of natural coarse aggregate and rubber particles no more than 30%instead of natural fine aggregate.The compressive strength,flexural strength and impermeability of recycled concrete were tested.The effects of recycled coarse aggregate and rubber particle content on the macro properties of concrete are discussed.The results show that the compressive strength and impermeability of rubber recycled coarse aggregate concrete are significantly lower than that of ordinary concrete;When the rubber content reaches 30%,the 28 d compressive strength of concrete is 62% lower than that of ordinary concrete,and the relative permeability coefficient is about 3 times higher than that of ordinary concrete;It is suggested that the content of rubber particles should not exceed 10% in practical application,otherwise performance improvement measures should be taken.(2)The method of improving the performance of rubber recycled coarse aggregate concrete is explored.The effects of prewrapped slurry and adding polyvinyl alcohol on the basic mechanical properties and impermeability of rubber recycled coarse aggregate concrete were studied.The results show that the two treatment methods have little difference in the improvement of compressive strength;In terms of flexural strength and impermeability improvement,the performance improvement effect after adding polyvinyl alcohol is significantly better than that of pre wrapping method;The content of rubber particles has a direct impact on the performance improvement effect.The higher the content,the higher the strength improvement rate after modification;The relative permeability coefficient of rubber recycled coarse aggregate concrete after pre coating slurry and adding polyvinyl alcohol modification shows a trend of first decreasing and then increasing.When the rubber content is 10% and 20%,it has the strongest impermeability,which is 20.7%and 34.2% lower than that of unmodified concrete.The optimal content of rubber is different for the impermeability of concrete with different performance improvement methods.Comprehensive comparison shows that polyvinyl alcohol is better than pre wrapped slurry in improving the mechanical properties and impermeability of rubber recycled coarse aggregate concrete.(3)The relationship between flexural strength and compressive strength of rubber recycled coarse aggregate concrete is quantitatively analyzed,the conversion formula between flexural strength and compressive strength is given,and the fitting formula between flexural pressure ratio and rubber particle content of rubber recycled coarse aggregate concrete is established.Combined with the micro and macro results of different scales,the mechanism of improving the performance of rubber recycled coarse aggregate concrete is explored.The results show that there is a positive correlation between flexural strength and compressive strength;When the content of rubber particles is 30%,the flexural compression ratio reaches the maximum,and the crack resistance of rubber recycled coarse aggregate concrete is the strongest;Pre wrapped slurry makes the cement particles more evenly dispersed during mixing,and polyvinyl alcohol enhances the interfacial adhesion,so as to improve the performance of rubber recycled coarse aggregate concrete.(4)The calculation model of carbon emission in the life cycle of rubber recycled coarse aggregate concrete is established.Based on the system boundary from "cradle" to "gate",multiple stages from raw material production to concrete construction are comprehensively considered.According to the calculation and analysis,the life cycle carbon emission of rubber recycled coarse aggregate concrete is reduced by about 6%～19% compared with that of natural coarse aggregate concrete,which has the potential to reduce the life cycle carbon emission.Under the condition of meeting the requirements of structural strength and durability,it is recommended to promote the application of low-carbon green concrete,so as to provide support for reducing carbon emission and promoting the improvement of ecological environment.