Research On Pilot Production Of Recycled Total-fine Aggregate By Waste Concrete And Its Application In Concrete

The preparation of waste concrete from construction waste into recycled fine aggregate can alleviate the increasing number of construction wastes and the shortage of building materials.Recycled total-fine aggregate is made from all waste concrete to 5mm recycled fine aggregate.Compared with the traditional recycled fine aggregate,it has high apparent density and low water absorption.The laboratory small test results of recycled total-fine aggregate have achieved good results.For further popularization and application,it is necessary to carry out pilot study.View of this problem,this article first carried out the purchase of pilot production equipment and the technology Optimization of recycled total-fine aggregate,and then carried out the research of recycled total-fine aggregate concrete admixture and mix proportion design method.The main work and conclusions of this paper are summarized as following:(1)Through the analysis of the working principle of the crushing equipment and the requirements of the pilot production,the PE250*400 type jaw crusher and the PCX8040 type high efficiency sand making machine are selected.By comparing the aggregate performance,mortar and concrete performance of recycled total-fine aggregate,which producted by different strength waste concrete and different pilot production processes,the production processes of one ? grade jaw breaking and circulating sand making is relatively superior.(2)By the aggregate performance test of recycled total-fine aggregate which producing by the optimized technology.The results show that the aggregate performance of the recycled total-fine aggregate produced in pilot scale is superior,and it is feasible for mass production in pilot production process of recycled total-fine aggregate.The whole aggregate performance is much better than the traditional recycled fine aggregate,but compared with the river-sand,the characteristics of the edges and corners are more,and the high water absorbency and high content micro powder still exist.Through the macro and micro analysis test,it can be observed that the aggregate have many edges and corners.there are some porous mortar or mortar and stone combination in the aggregate and the micro powder,which is the important reason for the high water absorbability of the aggregate.the fineness of some micro powder is similar to the cement fineness,and it may replace the cement to fill the aggregate void.(3)By studing the influence of different admixtures on the performance of recycled total-fine aggregate concrete.The results show that the problem of low slump-loss of concrete can be improved by the compound admixture,which based on the slump reducing agent,adding 0.3% modifier agent and 0.2% anti mud agent.(4)By studing the mix proportion design method of recycled total-fine aggregate concrete.Based on the close packing mix proportion design method of mechanically interlocked skeleton,the mix proportion design method of recycled total-fine aggregate concrete is formed by making full use of the micro powder in the recycled total-fine aggregate.By the influence of different mix ratio parameters on the performance of recycled total-fine aggregate concrete with different water binder ratio.The specific range of mix ratio parameters is further clarified,the recycled total-fine aggregate saturation coefficient in the added water content should be between 0%~60%,and the high water binder ratio concrete should choose low added water content.The concrete surplus coefficient suitable for 1.1~1.3.The coefficient of cementitious material should be between 0.90~1.00.Sand ratio should be between 38%~44%.(5)Under the same water binder ratio and the same workability,comparing the recycled total-fine aggregate concrete with the river-sand concrete.The results show that the compressive strength of the high water binder ratio recycled total-fine aggregate concrete is lower than the river-sand concrete,but the compressive strength of low water binder ratio recycled total-fine aggregate concrete is higher than that of river-sand concrete.Using the micro powder replace the cementitious material can save the amount of cementing material and reduce the cost of materials.