Study On Composition Detection And Strength Range Of Recycled Aggregate From Construction Waste

The recycled aggregate of construction waste has complex composition and unstable quality,which leads to the discrete performance of recycled products and hinders the efficient utilization of the recycled aggregate.Recycled aggregate of construction waste in China mainly include recycled concrete & brick aggregate(RCBA)and recycled concrete aggregate(RCA).The content of brick aggregate in RCBA and the strength of RCA primary concrete have the greatest influences on their quality.At present,there is no simple method to detect the mass ratio of brick and concrete aggregate in RCBA and the strength of RCA primary concrete.Therefore,it is of great significance to research the image recognition method for detecting the mass ratio of brick and concrete aggregates in RCBA and the drop weight impact test for detecting the strength of RCA primary concrete.The following work results are obtained:(1)The concentrated distribution characteristics of the color components of brick aggregate,concrete aggregate,and background in the two kinds of color models in RCBA images are studied.and the replacement of the background of the picture and the accurate sorting of brick and concrete aggregate are achieved.The watershed algorithm based on Euclidean distance transformation is used to realize the accurate segmentation of the bonded particle image,and to read the pixel area and shape data of brick and concrete aggregate in the two-dimensional image.(2)According to the shape data of brick and concrete aggregate in RCBA,brick and concrete aggregate are equivalent to cylinder,sphere,and ellipsoid.And the total mass ratio of brick and concrete aggregate in the mixture is calculated according to the volume of the equivalent stereoscopic and the density of brick and concrete.The test conditions are designed to verify the test results of the mass ratio of brick and concrete aggregate in RCBA images with different particle size.The test results show that the volume of recycled aggregate is equivalent to an ellipsoid with the smallest error.The smaller the regenerated aggregate particle size in the test conditions is,the larger the error of the test results is.The error of the RCBA mixed particle size detection result is larger than that of the single particle size.(3)A method for testing the strength interval of RCA primary concrete by the drop weight impact test is proposed.The mortar attached to the surface of RCA was peeled off and crushed by the drop weight impact instrument.Linearly fit the proportion of RCA detritus with a particle size less than 4.75 mm and the strength of its primary concrete.The fitting equation for testing the strength of RCA primary concrete by the drop weight impact test is obtained.The influence of sieving times and impact energy on the composition of exfoliated debris is studied.(4)A recycled aggregate testing software is designed.Its functions include detecting the mass ratio of brick and concrete aggregate in the RCBA picture according to the method described in this paper,recording the data of the drop weight impact test,and calculating the test results.