Study On Strengthening Technology Of Recycled Aggregate Of Construction Waste And Pavement Concrete Performance

A great deal of sand and stone materials are needed to build a strong transportation country.At the same time,most cities have experienced the phenomenon of "construction waste besieging".If construction waste is recycled for road works,the supply channel of sandstone material can be widened and a large amount of construction waste can be consumed.At present,the composition of recycled aggregate in China is complex,and there are many mortar and cracks left on the surface of the aggregate.The poor quality stability and low performance of the product restrict its promotion and application.In addition,there is limited research on the use of recycled aggregates from construction waste as aggregates for pavement concrete,lacking corresponding research results and theoretical support.In view of this,based on the composition characteristics and image processing technology of recycled aggregates of construction waste,this paper proposes a method for proportion identification and performance evaluation of recycled aggregate bricks and concrete.Meanwhile,the modification effect of several single strengthening methods was studied.Based on this,the research and optimization of composite strengthening technology are carried out.Secondly,the mix ratio design of CWRAC is optimized.On this basis,explore the impact of different strengthening technologies and substitution rates on the road performance of CWRAC.Finally,the reinforcement mechanism of recycled aggregates of construction waste is revealed by means of micro-test methods such as phase analysis and micro-morphology analysis.The main research results are as follows:(1)Brick content image recognition program can quickly and accurately identify the proportion of brick and concrete in recycled aggregate and give performance evaluation.The identification error of the proportion of brick and concrete is within 3%.The apparent density,water absorption and crushing index of the strengthened recycled aggregate have been improved to some extent.And the comprehensive modification effect of cement silica fume-organosilicon and sodium silicate-organosilicon is the best.(2)The optimum additional water use method in CWRAC mix design is is pre wetting and water absorption for 1440 minutes.Both composite strengthening methods can improve the performance of CWRAC.The mechanical properties,impermeability,and chloride ion permeability of CWRAC strengthened by cement silica fume-organosilicon composite are more excellent.The dry shrinkage of CWRAC strengthened by sodium silicateorganosilicon composite is better.The mechanical properties of CWRAC prepared from unreinforced recycled aggregates are poor.The recycled aggregate needs to undergo composite strengthening before it can be used in road engineering,and the replacement rate should not exceed 15%.(3)The appearance and morphology of the recycled aggregate after being coated with cement silica fume have been reshaped.C-S-H gel and silica powder particles of the slurry fill the cracks in the aggregate and improve the density and strength of the aggregate.After strengthened by sodium silicateorganosilicon,C-S-H gel in the surface of recycled aggregate increased.It can effectively fill the pore and crack in aggregate and improve the pore structure.The active groups “ OR ” and “ OH ” in organosilicon molecule react with the active groups “ OH ” on aggregate surface to form a hydrophobic membrane,which reduces the water absorption.The interfacial properties of composite reinforced recycled aggregates are improved.The interfacial properties of composite reinforced recycled aggregates are improved.It can promote cement hydration to produce more C-S-H gel,which can enhance the compactness of the interfacial transition zone of concrete.