Experimental Study On Mix Proportion And Basic Mechanical Properties Of Recycled Brick Aggregate Concrete

With the advancement of urbanization and the transformation of old cities,China produces a large amount of construction waste every year.If these construction wastes are not effectively treated,it will have an adverse impact on the cities we live in.On the one hand,it will cause environmental pollution and land resource occupation and other problems;on the other hand,it will excessively consume natural aggregate resources.Using construction waste instead of natural aggregate to prepare recycled concrete can effectively alleviate these problems.In this paper,the research on the recycling of waste sintered clay bricks widely distributed in a large number of construction wastes is carried out.The physical and mechanical properties of recycled brick aggregates are determined through experiments.Concrete.The main research contents and conclusions of this article include are as follows:(1)The physical and mechanical performance indexes such as crushing index,mud content,apparent density,bulk density,water absorption rate and water content of recycled brick aggregate and natural aggregate are measured,and the difference between the two is compared and analyzed to obtain recycled brick aggregate The level of aggregate performance and recommendations for the preparation of concrete.The test results show that although the aggregate strength of recycled brick aggregate is low,it meets the performance requirements of class III recycled coarse aggregate,and at the same time meets the density level of class 1000 light coarse aggregate,and can be directly used to prepare lower strength grade lightweight recycled concrete.(2)The mix proportion design of recycled brick aggregate concrete with strength grade of C20 and C30 is carried out by using broken brick as coarse aggregate.The regression coefficient A = 0.53 and B = 0.50 are obtained by mix proportion calculation and trial mixing.After the adjustment and determination of the mix,the recycled concrete with these two strength grades of brick aggregate is prepared,and the corresponding laboratory mix proportion is obtained.The test results show that the cube compressive strength of recycled brick aggregate concrete of these two strength grades can reach 30.7MPa and 41.6MPa respectively,which can meet the required strength value for the construction of middle and low-rise buildings.(3)Based on the C30 recycled brick aggregate concrete mix ratio,the orthogonal test design method was used.The water purification ratio,volumetric sand ratio,fly ash content,and recycled brick coarse aggregate volume replacement rate were 4 factors.The cube compressive strength and splitting tensile strength are the performance indicators,and the orthogonal test design with 4 factors and 3 levels of mix ratio is designed.Through analysis of variance and range analysis,we explored the four factors affecting the performance order of the performance index and the degree of significance,and obtained the strength level of recycled brick aggregate concrete corresponding to an optimal performance ratio under a certain performance index.The test results show that for the cube compressive strength and splitting tensile strength,the primary and secondary order of each factor is: brick aggregate volume replacement rate> fly ash content> water purification rubber ratio> volume sand rate;cube compressive strength The optimal combination of strength is 0.40 water purification glue ratio,0.36 volume sand rate,15% fly ash content,30% replacement rate of recycled brick coarse aggregate,the optimal combination of splitting tensile strength is water purification glue The ratio is 0.40,the volumetric sand rate is 0.44,the fly ash content is 15%,and the recycled aggregate coarse aggregate replacement rate is 30%.