Experimental Study On Performance Of Recycled Concrete By Construction Waste Pretreatment

With the development of economy,the speed of urbanization in China is accelerating,and the construction waste is also growing rapidly in this process.How to reduce the adverse effects caused by the rapid increase of construction waste,and how to recycle these materials is of great significance,but is usually only to simple processing of recycled coarse aggregate,lead to strength generally is not high,not batch used in the construction market.This thesis intends to use theoretical analysis and experimental methods to explore the mechanical properties of recycled coarse aggregate from construction waste after pretreatment.Firstly,the construction waste materials in this region are crushed,and then the recycled coarse aggregate is obtained by screening and classification.The influence of different temperature,humidity and physical effects on the recycled coarse aggregate of construction waste is studied.The microstructure analysis and corresponding mechanical properties analysis of the pretreated construction waste aggregate;The pretreated construction waste aggregate is prepared with concrete products and its basic mechanical properties are studied,and the strength improvement value of reclaimed coarse aggregate concrete is compared before and after pretreatment to provide a basis for its feasibility in reinforced concrete structure engineering.(1)The working performance of recycled aggregate was studied through slump and extension tests.(2)Through the mechanical property test,it is found that the recycled aggregate concrete is weaker than the reference concrete in terms of compressive strength and tensile strength.With the increase of the replacement rate of recycled coarse aggregate,the mechanical properties of concrete gradually decrease.(3)Through sulfate corrosion test,it is concluded that the sulfuric acid corrosion resistance of recycled aggregate concrete is lower than that of reference concrete.The sulfuric acid resistance of reclaimed coarse aggregate concrete decreases with the increase of replacement rate of reclaimed coarse aggregate,and the sulfuric acid resistance of reclaimed fine aggregate concrete also decreases with the increase of replacement rate of reclaimed coarse aggregate.(4)Through the physical strengthening method,the strengthened reclaimed coarse aggregate was compared with the simple crushing reclaimed coarse aggregate to find an effective way to prepare recycled concrete products with high strength.Finally,the treatment effect of reclaimed coarse aggregate at 300℃ and wet grinding time of 15 min was the best,and the improvement range of material properties was obtained.Eighteen blocks and three groups of 150×150×300mm prisms were prepared,and mechanical tests were carried out on them.The variation ranges of stress and strain,elastic modulus and peak strain under different replacement rates of recycled coarse aggregate were obtained,which provided basis for practical engineering.(5)Through THE VIC-3D technology,it is proved that the digital speckle method is still effective for the measurement accuracy of recycled concrete.(6)By physical method using the treatment temperature of 300 ℃,wet milling time after 15 min by strengthening recycled concrete cube block experiment,according to the movement of the speckle to get the corresponding two-dimensional strain,and through the stress and strain cloud observation specimens under the action of external pressure factors such as the specific process and the corresponding mechanical properties of the damage,Then the final failure mode of the specimen is predicted.