With the rapid development of China’s economy and the acceleration of urbanization,how to deal with construction waste has become the focus of attention from all walks of life.The recycling of construction waste is mainly the preparation of cementation materials and recycled coarse aggregate,of which the most widely used is recycled coarse aggregate.However,due to the characteristics of high water absorption,high needle like content and large crushing value of recycled coarse aggregate,its application in concrete products is limited.Therefore,most recycled coarse aggregate is used in roads or buildings with low strength requirements,However,since the domestic mineral resources,the mining cost of natural stone is high,the aggregate resources are more and more scarce,and the coarse aggregate used in concrete is less and less,which urges us to broaden the application field of recycled coarse aggregate.In the water transport engineering,the concrete structure mostly adopts gravity structure,and the amount of concrete is large.The application of recycled coarse aggregate in the concrete structure of water transport engineering not only solves the problem of large amount of construction waste,but also reduces the overall cost of the project.Therefore,it only needs to solve the key problem of the application of recycled coarse aggregate in the concrete structure of North Water Transport Engineering,The main contents and conclusions of this paper are as follows:(1)Determine the basic index of adhesion rate of recycled coarse aggregate mortar.The adhesion rate of recycled coarse aggregate mortar was detected by image method Through the image analysis function of MATLAB,the threshold segmentation of the recycled coarse aggregate image is carried out to realize the division of the special area of the image.After the statistics of the pixels in the special area,the detection of the mortar adhesion rate on the surface of the recycled coarse aggregate is realized.Through the physical performance index test of recycled coarse aggregate with different mortar adhesion rate,when the adhesion rate is not more than 30%,it basically meets the technical requirements of the current specification,but the water absorption rate of recycled coarse aggregate is still greater than the index required by the specification(2)Under the condition that the adhesion rate of recycled coarse aggregate mortar meets the requirements,the mix proportion of recycled concrete is adjusted through the influence of replacement rate of recycled coarse aggregate,water binder ratio of recycled concrete and fly ash content on the work-ability and mechanical properties of recycled concrete.The results show that when the replacement rate of recycled coarse aggregate is30%,the water binder ratio is 0.4 and the content of fly ash is 30%,the strength of recycled concrete is the best,but the work-ability of recycled concrete mixture is slightly poor.(3)Three kinds of strengthening agents(dilute sulfuric acid(concentration 5%),sodium silicate(concentration 10% modulus 2.8)and cement-based permeable crystalline material)were used to strengthen the recycled coarse aggregate.Through the test on the physical properties of recycled coarse aggregate,the results show that the physical properties of recycled coarse aggregate strengthened by sodium silicate are the best.(4)The mechanical properties and durability of recycled concrete were studied by strengthening,preset wetting and strengthening preset wetting combination.The results show that The recycled concrete reinforced by dilute sulfuric acid has the worst freeze-thaw resistance and chloride ion permeability resistance.Combined with economy and experimental operative,the recycled coarse aggregate improvement by the combination of water glass strengthening and cement-based permeable crystalline material slurry preset wetting is more suitable for the recycled concrete in the northern marine environment. |