Experimental Study On Physical And Mechanical Properties Of Recycled Aggregate Pervious Concrete

At present,China is advocating the concept of green development,and recycled aggregate pervious concrete can not only solve the problem of utilization of urban construction waste effectively,but also alleviate the "heat island effect" and noise pollution caused by impervious roads.In order to promote the concept of recycling and reuse of construction waste as well as the concept of "sponge city" effectively,the "recycled aggregate" and "pervious concrete" are combined as recycled aggregate pervious concrete and various aspects were considered to improve its performance.Based on the research at home and abroad,this paper mainly studies the mixing ratio of recycled aggregate pervious concrete(RPC),and conducts experimental research were studied on its mechanical properties and permeable performance.The main research contents are as follows:(1)The performance of the tested raw materials(cement,aggregate,admixture,admixture)is measured to determine its feasibility for making RPC.According to the characteristics of RPC,the mode of stirring,forming and curing processes are determined based on theirs permeability coefficients measured by a self-made water permeability instrument.The experimental mix design was carried out by a method suitable for this study.(2)The strength and permeable performance of RPC are studied based on the basic characteristics of the raw materials.Aggregate gradation,water-cement ratio,replacement rate of recycled aggregate,and mineral admixture are regarded as variable parameters to make recycled aggregate pervious concrete.The compressive strength,flexural strength,effective porosity,and permeability coefficient of the specimens which have been cured for 28 days were tested and analyzed to investigate the relationship between the four variable parameters and the variation law of RPC performance.(3)The recommended mix ratio of RPC in terms of strength is: aggregate gradation is 4.75~9.5mm,water-cement ratio is 0.31,recycled aggregate replacement rate is 32%,and silica fume content is 6%.Because at this time,the mechanical properties of the specimen can reach the best performance.The recommended blending ratio of RPC in terms of water permeability is: Aggregate gradation is mixing the recycled aggregates with a particle size of 4.75~9.5mm and 9.5~15mm in a ratio of 1:2,and the water-cement ratio is 0.31.Both the replacement rate of recycled aggregate and the increase of silica fume content will reduce the permeability of permeable concrete.Therefore,it is recommended not to add recycled aggregate and silica fume when onlythe permeability is considered.(4)After the systemization and the contrastive analysis of the experimental data of the mechanical test and the water permeability test,the optimal test combination for RPC is theoretically given as follows: Aggregate gradation is mixing the recycled aggregates with a particle size of 4.75~9.5mm and 9.5~15mm in a ratio of 3:2,the water-cement ratio is 0.31,the replacement rate of recycled aggregate is 30%,and the amount of silica fume is 6%.To optimize the mix ratio of recycled aggregate permeable concrete and to test the mechanical properties and water permeability of the optimized specimens.When the water-cement ratio is 0.31,the silica fume content is 6%,and the superplasticizer content is 0.25%,in order to improve the utilization rate of recycled aggregates,the recycled aggregate concrete with sufficient strength and good permeability coefficient can be obtained by adopting double gradation.To study out composite-graded RPC which has a high-recycled aggregate replacement rate and were developed in accordance with the industry code CJJ/T253-2016 "Technical Regulations for the Application of Recycled Aggregate Pervious Concrete".