| Construction waste is a by-product of the development of the construction industry and has caused severe damage to the ecological environment.Waste concrete accounts for a large proportion of construction waste,which is crushed and sieved to obtain recycled aggregates.An important way to recycle construction waste is to use recycled aggregates as raw materials to prepare recycled concrete.However,due to the characteristics of recycled aggregates such as high crushing index,high water absorption rate and low apparent density,the mechanical properties of recycled concrete specimens are poor,so how to improve the performance of recycled concrete has become the key to solving the problem.In order to prepare high-performance recycled concrete products,the effects of different materials such as straw fiber and graphene oxide on the mechanical properties,water absorption and shrinkage of recycled concrete blocks were explored in this paper;they were determined by modifying the straw fiber with different silane coupling agents The best modifier and concentration;by preparing graphene oxide(GO,the same below),and ultrasonic dispersion with different water reducing agents to obtain a uniform dispersion of GO-water reducing agent;using recycled aggregate,cement,straw fiber,GO-Prepare recycled concrete blocks with water-reducing agent dispersion and compare the effects of different raw materials on the properties of recycled blocks;obtain the mechanism of different materials to improve the mechanical properties of recycled blocks through microscopic characterization.The main research contents are summarized as follows:(1)Pretreatment of experimental materials and analysis of physical and chemical properties: Recycled aggregates were prepared using waste concrete,waste bricks,and waste glass as raw materials,and the physical properties of recycled aggregates were tested experimentally;straw fiber was modified with silane coupling agent The concentration of each modifier on the straw fiber modification effect is 5% KH550,5% KH560 and 2% KH570 respectively;preparation and investigation of the ultrasonic dispersion performance of GO and water reducer,found that polycarboxylic acid water reducer and GO The dispersion effect is the best.(2)Preparation of lightweight straw blocks and performance analysis of construction waste resources: choose the modifier with the best modification effect concentration: 5% KH550,5% KH560 and 2% KH570,pretreatment of straw fiber,And the preparation of recycled blocks;the microstructure shows that the CSH gel formed by hydration of the recycled concrete prepared with KH550-treated straw fibers is easily isolated by impurities such as pectin in the straw fibers,affecting the strength of the recycled concrete.In the recycled concrete prepared by mixing straw fibers treated with silane coupling agents KH560 and KH570,the generated hydrated crystals and straw fibers are intertwined with each other to form a stronger whole,and the strength of the concrete is enhanced.Straw fiber treated with silane coupling agent can increase the compressive strength of recycled concrete by more than 150%.(3)Preparation of high-strength recycled blocks and performance analysis of construction waste resources: choose polycarboxylic acid water-reducing agent and naphthalene-based water-reducing agent with better dispersion effect on GO to prepare recycled blocks;When the water-cement ratio is 0.30,the mechanical properties of recycled blocks increase first and then decrease with the increase of the GO content.When the PGO content reaches the maximum value at 0.06%,the mechanical properties increase by 151.94% and 121.0% The microstructure shows that the incorporation of GO can affect the hydration of cement,adjust the growth and distribution of hydrated crystals in the recycled block,reduce the porosity and void rate of the overall structure of the block,and significantly increase the Mechanical properties. |
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