| This paper based on the urban road reconstruction and expansion project of Chongqing Metro Line 10.A simple wet cleaning and drying recycled aggregate preparation process is adopted for waste concrete pavement slabs.Pervious concrete gradation is 4.75mm9.5mm single particle size,and the replacement rate of recycled aggregate is uniformly set at 30%.In this paper,the effects of water-binder ratio,design porosity,mineral admixture substitution rate and fiber content on the pavement performance of recycled aggregate pervious concrete are studied.The main work is as follows:1.In this paper,the recycled aggregate is classified as grade III recycled coarse aggregate according to the basic physical properties of aggregate test.It is considered that the recycled aggregate can meet the preparation requirements of pervious concrete.At the same time,according to the construction experience of technicians from the manufacturer,the range of mineral admixtures and fibers is determined,that is,the replacement rate of fly ash is 8%,the replacement rate of silica fume is6%10%,and the content of fibers is 0.9kg/m32.7kg/m3.In addition,the design porosity of recycled aggregate pervious concrete is 15%,20%and 25%.2.Through the workability test of recycled aggregate pervious concrete mixtures,it is found that the cohesiveness of recycled aggregate pervious concrete mixtures is generally good.Wet cleaning and drying of recycled aggregate has little effect on slump,but it is helpful to improve water retention.The slump can be increased by44%85%by adding 8%fly ash instead of cement.The mixing of fly ash and wet cleaning and drying recycled aggregate can make the recycled aggregate pervious concrete obtain good working performance with consideration of water retention,construction and workability.At the same time,in this process,the appropriate water-binder ratio range is determined between 0.29 and 0.35.3.By analyzing the weights of influencing factors on the basic properties of recycled aggregate pervious concrete through range analysis of L9?34?orthogonal experiment,it is found that the highest factor of weight is the design porosity,and the second factor is the water-binder ratio.At the same time,when the design porosity is20%and the water-cement ratio is reduced from 0.35 to 0.32,the 28-day compressive strength increases by 20.36%,the 28-day flexural strength increases by 7.81%,and the permeability coefficient decreases by less than 0.1%.In addition,when the design porosity is 20%,the actual porosity and the design value have the smallest dispersion.Although the 7-day compressive strength can only reach 74%77%of the 28-day compressive strength,the mechanical properties and permeability are the most balanced.4.Through optimization test and blank control test,it is found that the permeability coefficient increases by 3.96%and the compressive strength and flexural strength decrease by 0.5%and 3.57%respectively by adding 30%recycled aggregate.The basic performance of recycled aggregate pervious concrete is the best when the fiber content is 1.8kg/m3.The permeability coefficient of recycled aggregate pervious concrete is not affected by the addition of fibers.The compressive strength of recycled aggregate pervious concrete decreases by 2.59%and the flexural strength decreases by 1.85%with the addition of fibers without silica fume.The permeability coefficient decreases by 3.79%5.26%,the compressive strength increases by7.21%7.72%,and the flexural strength increases by up to 25.35%.The reason is that the composite silica fume can improve the mechanical properties of recycled aggregate pervious concrete.In addition,this paper establishes the correlation fitting relationship among the actual porosity,permeability coefficient,compressive strength and flexural strength,and establishes the binary fitting surface affected by the design porosity and water-binder ratio respectively for the permeability coefficient,compressive strength and flexural strength.5.The mix ratio of recycled aggregate pervious concrete,which meets the requirements of specifications and has similar basic properties,is selected as the research object of frost resistance,sulfate corrosion resistance and wear resistance tests.It is found that the increase of water-binder ratio decreases the frost resistance and wear resistance,but improves the sulfate corrosion resistance;the increase of fiber content improves the frost resistance and wear resistance,but decreases the sulfate corrosion resistance;the increase of silicon powder substitution rate improves the frost resistance,sulfate corrosion resistance and wear resistance obviously.Considering all these factors,the optimum mix ratio of recycled aggregate pervious concrete is 0.29,20%of design porosity,8%of fly ash,10%of silica fume and1.8kg/m3 of fiber. |
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