| With the development of urban construction,the amount of construction waste increases rapidly.In order to improve the resource utilization rate of the construction industry and alleviate the pressure of construction waste on the environment,this article refers to the treatment method for construction waste in China and prepares the construction waste into recycled crude Aggregate is added to concrete,and the mix ratio of recycled concrete is designed reasonably.Considering the problem of acid rain and the effects of freeze-thaw,this paper analyzes the basic mechanical properties and anti-freezing performance of recycled concrete after being eroded by acid rain on the basis of experimental research,and uses micro-electron microscopy scanning and energy spectrum analysis tests for mechanism analysis.In addition,this paper uses the parameter recognition method in the least square method to reprocess the data to obtain more reasonable parameter values.The following is the main research content of the full text:(1)By analyzing the current commonly used production process of recycled coarse aggregate,the production process and grading standards suitable for this experiment are selected for the preparation of recycled coarse aggregate,and the basic properties of natural coarse aggregate and recycled coarse aggregate are compared and studied.It shows that the particle gradation curve of the recycled coarse aggregate prepared in this experiment is in good agreement with the natural coarse aggregate.The apparent density,crushing index and water absorption rate of the recycled coarse aggregate are significantly greater than that of the natural coarse aggregate.The recycled coarse aggregate meets the national Class II recycled coarse aggregate standard.(2)The compressive strength of recycled concrete was tested,and the effects of the replacement rate of recycled coarse aggregate,fly ash and slag powder content on the conditions of single and double admixture were analyzed.The results show that:(1)Under the same conditions,the compressive strength of recycled concrete is lower than that of ordinary concrete,the greater the ratio of recycled coarse aggregate replacement,the smaller the compressive strength of recycled concrete;(2)The compressive strength of recycled concrete varies with fly ash and slag powder The increase in admixture shows a trend of increasing first and then decreasing.That is,there is an optimal admixture.When the single admixture is 30%,the compressive strength of recycled concrete is the largest;The effect of slag powder on the compressive strength of recycled concrete is stronger than that of single admixture.(3)An experimental study was conducted on the resistance of the recycled concrete to chloride salt corrosion.Through the electrical flux test,the electrical flux value of the recycled concrete specimen was measured and converted into a chloride ion diffusion coefficient through an empirical formula.The effect of aggregate replacement rate,fly ash and slag powder content on the conditions of single and double admixture.The results show that:(1)The ability of recycled concrete to resist chloride salt corrosion is weaker than that of natural concrete,and it decreases with the increase of the replacement rate of recycled coarse aggregate;(2)The appropriate amount of fly ash and slag powder can effectively enhance the resistance of recycled concrete to chloride salt corrosion.Under the condition of 30% doping,double doping is better than single doping.(4)Experimental research was conducted on the frost resistance of recycled concrete,and the replacement rate of frost resistance of recycled concrete by recycled coarse aggregate,the content of fly ash and slag powder under single and double admixture conditions,and the number of freeze-thaw cycles were analyzed.The law of influence.The research results show that:(1)recycled coarse aggregate is not conducive to the frost resistance of recycled concrete,the greater the replacement rate,the worse the frost resistance of recycled concrete;(2)the single addition of fly ash and slag powder can effectively enhance the frost resistance of recycled concrete There is an optimal amount of both.When the dosage is 30%,the effect of enhancing the frost resistance of recycled concrete is the most obvious;(3)The effect of double-mixed fly ash and slag powder on the frost resistance of recycled concrete is better than that of single admixture.On the premise that the total dosage is 30%,the 1: 1 mixing effect of fly ash and slag powder is the best.(5)Numerical simulation study of chloride ion attack on concrete based on COMSOL.In this paper,the COMSOL finite element simulation software is used to establish a chloride ion erosion concrete model.The effects of erosion time,recycled coarse aggregate replacement rate,fly ash content,and penetration depth on the concentration distribution of chloride ions in concrete are analyzed.The results show that COMSOL can better simulate the process of chloride ion eroding concrete,and the simulation calculation results are in good agreement with the test results,and the conclusions are basically consistent.The depth of chloride ion erosion increases with the erosion time.Recycled coarse aggregate is not conducive to the resistance of concrete to chloride ion erosion,and fly ash can effectively enhance the resistance of concrete to chloride ion erosion.There are 60 figures,26 tables and 127 references in this article. |
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