Study On Sub-high Temperature-Cooling Performance Of Building Waste Recycled Pervious Concrete

In order to study the influence mechanism of the synergistic effect of sub-high temperature and the cooling way on the performance of recycled pervious concrete,the recycled coarse aggregates were made by C20 waste concrete pavement fragments,based on literature research and preliminary experiments,the preparation process of recycled pervious concrete was determined.The entropy method and the gray correlation analysis method are used to optimize the mix ratio of the recycled pervious concrete.Based on this,the pervious concrete specimens required for the test were prepared,and the mass loss rate,compressive strength and splitting tensile strength of the specimens under sub-high temperature,different cooling state and sub-high temperature-cooling cycle test were determined.On this basis,the strength prediction model for sub-high temperature-cooling of recycled pervious concrete is established based on BP neural network.The results show that:(1)The synergistic effect of heating temperature and cooling way has a great influence on the performance of recycled pervious concrete.The rate of mass loss increases with the increase of heating temperature,and the strength increases first and then decreases.The influence degree of different cooling way on the compressive strength of recycled pervious concrete is as follows: water immersion cooling > cool air cooling > natural cooling,the influence degree on the splitting tensile strength is as follow: natural cooling > cool air cooling > water immersion cooling.(2)In the sub-high temperature-cooling cycle test,the compressive strength of the recycled pervious concrete increases with the increase of the number of cycles under the cool air cooling condition,and the same time,the splitting tensile strength first decreases and then increases.But the strength of the recycled pervious concrete decreases first with the increase of the number of cycles under the immersion cooling condition.When decreasing to a minimum value,it increases with the number of cycles increases.(3)There is a functional relationship between the six input parameters(density,heating temperature,cooling way,age,number of cycles,mass loss rate)and the strength of recycled pervious concrete.The overall prediction effect is good,and the correlation coefficient between the measured value and the predicted value of the compressive strength of recycled pervious concrete is 0.981,and the average relative error is 11.01%;the correlation coefficient between the measured value and the predicted value of the split tensile strength of recycled pervious concrete is 0.881,and the average relative error is 11.95%.