Experimental Study On Mechanical Properties And Frost Resistance Of Building Waste Recycled Aggregate Concrete Block

Making concrete block from construction waste can make full use of the inherent advantage of rich construction waste in Jilin and its surrounding areas,and save cost.This paper mainly studies the production of recycled concrete single hole bearing block which are made use of waste construction concrete.It has important reference significance for promoting the innovation of wall materials and the development of building energy conservation in Jilin City.The physical properties of recycled aggregate are studied through experiments,and the basic physical properties of recycled aggregate include:apparent density of recycled coarse,fine aggregate,packing density,void ratio,water absorption rate of recycled coarse,fine aggregate;then a comparative analysis has been made between recycled aggregate and natural aggregate.The results show that the loose?compact?packing density of recycled coarse aggregate is lower than that of natural crushed stone,and the tight porosity of recycled fine aggregate is much smaller than that of natural aggregate,and the water absorption rate of recycled coarse,fine aggregate is higher than that of natural aggregate.In this paper,the substitution rate of recycled coarse,fine aggregate,fly ash content and water-cement ratio are used as the main influencing factors,and the L₉?3⁴?orthogonal test table is used to carry out the test,in order to analyze the influence of these four main factors on the performance of recycled aggregate concrete block,then the relationship curves between four factors and block strength are obtained,and the optimum mix ratio of block compressive strength is determined.From the test results,the best mix ratio of recycled concrete block compressive strength:water/glue ratio is 0.35,the substitution rate of recycled fine aggregate is 30%,the substitution rate of recycled coarse aggregate is 45%and the fly ash content is 20%.According to the optimum mix ratio,a load-bearing block with compressive strength up to MU7.5 can be produced.The basic physical and mechanical properties of recycled aggregate concrete block made with optimum mix ratio can meet the requirements of relevant national codes.Through the analysis of the frost resistance of recycled concrete bearing block and the freez e-thaw cycle test of recycled concrete block with different content of fly ash and recycled coarse aggregate,and the influence of the replacement ratio of fly ash and recycled coarse aggregate on the frost resistance of recycled aggregate concrete block is obtained.The results show that in the range of fly ash from 15%to 25%,the increase of fly ash content will enhance the compressive s trength of block after freeze-thaw.In the range of 35%to 55%of recycled coarse aggregate,the f rost resistance of recycled aggregate concrete block decreases with the increase of aggregate.