Study On Degradation Rules Of Polypropylene-basalt Hybrid Fiber Rubber Reinforced Concrete Under Various Environmental Factors

For a"black garbage"said the waste tire,processed into rubber powder can be replaced by the use of fine aggregate in concrete,and the use of basalt fiber and polypropylene fiber mixed into concrete to enhance the effect,in order to achieve the improvement of concrete materials.Buildings in the process of use will face the impact of various environmental factors,such as high temperature,freeze-thaw and salt erosion,which will cause deterioration of concrete,thus endangering the durability of the structure,so improving the deterioration problem is of great significance.This paper takes fiber volume content and rubber replacement rate as research variables and focuses on the analysis of their effects on the physical and mechanical properties of concrete.The main research contents of this paper include:（1）Physical and mechanical tests were carried out on 28 groups of concrete by combining 7 kinds of hybrid fiber volume and 4 kinds of rubber replacement ratio.In terms of physical properties,the apparent density and water absorption of hardened concrete are mainly analyzed.In terms of mechanical properties,compressive strength and splitting tensile strength are mainly studied.The results showed that:Under the same rubber replacement rate,the optimal mixing amount of hybrid fiber in the compressive strength and splitting tensile strength of concrete is V_BF=0.4%,V_PPF=0.2%and V_BF=0.2%,V_PPF=0.1%,respectively.Fiber has a more significant effect on the strengthening of the splitting tensile strength of concrete.High fiber content and rubber powder will weaken the mechanical properties of concrete.（2）Through the comparative analysis of the specimens after mechanical failure,the results show that the fiber has a great influence on the compression and splitting tensile failure modes of concrete,and the failure characteristics change from brittleness to plasticity,and the integrity of the specimens after failure is relatively good.When the rubber powder is added,the small cracks on the surface of the specimen increase rapidly under compression,but it has little effect on the fracture morphology.（3）Carry out high temperature test,successively set the multistage heating temperature,analyze the deterioration law of concrete under different temperature conditions,compare the difference of each group of concrete under high temperature,quantify the strengthening effect of fiber in it.The results show that the influence of high temperature on the splitting tensile strength of concrete is higher than that of compressive strength.The mixing of hybrid fibers can effectively improve the residual strength of specimens after high temperature,and the effect is more significant when the mixing amount is large.The residual strength of rubber powder on specimens after high temperature is increased,but the range is small.（4）Carry out the sulfate erosion-freeze-thaw cycle test to explore the effects of different freeze-thaw cycles and erosion solutions on concrete deterioration,and analyze the improvement effect of mixed fiber and rubber powder on deterioration.The results show that,for the same specimen,the apparent damage is the most serious in5%Mg SO₄ solution under a certain number of freeze-thaw cycles,and the damage in water and 5%Na₂SO₄ solution is similar.The addition of fiber can effectively delay the spalling of surface cement paste and fine aggregate.After the freeze-thaw cycle,the loss rate of splitting tensile strength was generally higher than that of compressive strength.（5）The internal microstructure of concrete before and after high temperature was observed by SEM.The results show that there are two main failure modes of fiber:torsion and tensile fracture.Compared with PPF,BF has stronger bonding effect with concrete matrix.After high temperature,the decomposition of hydration products leads to the serious damage of the interface between aggregate and cement paste,and even the separation of aggregate and cement paste and the phenomenon of cement paste block.In the concrete matrix,it is found that the pores under the PPF melting residue and the pores formed after the final pyrolysis of rubber powder,and there is an obvious gap between BF and the concrete matrix.Figure[100]Table[22]Reference[88]...