Research On Preparation Technology Of Recycled Concrete

Compared with the developed countries,the utilization rate of waste concrete is less than 50%,and it is repeatedly applied at the low quality level.In order to realize the high quality application of waste concrete and to save natural resources to maximum extent and reduce environmental pollution,and based on the urgent needs of the sustainable development strategy and ecological civilization construction in our country,The high quality recycling of waste concrete has become one of the hot spots of scholars and engineers at home and abroad.Therefore,it is of great significance to carry out research on the preparation technology of recycled concrete.Based on the science and Technology innovation team project of Hunan Science and Technology Innovation Talents Plan"Research and Development and Application Innovation Team of Ecological building Environmental Materials"(2020RC4049),this paper focuses on the change law of the properties of recycled aggregate and recycled concrete before and after modification by using the relevant theories of materials science,physical chemistry,mechanics and other means of micro and macro testing and analysis.The optimum preparation technology of cement-based composite cementitious materials based on high performance of recycled concrete was studied.Based on the principle of grey correlation analysis,the correlation degree between the particle group distribution of cement-based composite cementitious materials and the fluidity of slurry was studied.At the same time,the mechanical properties of the modified and optimized reclaimed concrete were studied.The research results of this paper provide a reliable theoretical basis and practical application value for guiding the recycling and utilization of high-quality waste concrete resources,and also provide a reference for the revision of relevant standards,which has important guiding significance for engineering practice.The research results obtained in this paper are as follows:(1)Taking reclaimed aggregate and reclaimed concrete as the research object,and based on hydrochloric acid solution soaking modification technology,silicone waterproof solution soaking modification technology and hydrochloric acid and silicone composite modification technology,the change rule of three modification technologies on the performance of reclaimed aggregate and reclaimed concrete was studied.The research results showed that:The composite modification technology of hydrochloric acid and organosilicon improved the characteristics of reclaimed aggregate,significantly improved the quality of reclaimed aggregate,and effectively improved the compressive capacity of reclaimed aggregate.At the same time,the modification technology can also significantly improve the mechanical properties of the reclaimed concrete,especially the anti-cracking property of the reclaimed concrete.(2)In order to achieve high performance of recycled concrete,based on powder optimization combination technology and maximum compactness theory,the optimization combination technology of cement based composite cementitious material powder composed of fly ash,silica fume,slag and cement was studied,as well as the relationship between particle group distribution of powder combination system and slurry fluidity.The research results show that:In the optimal combination system of single fly ash,wollastonite,slag and cement powder,when the content of fly ash and wollastonite is 20%,and the content of slag is 15%,the voidage is minimum and the filling degree is maximum after powder combination.When cement:fly ash:silica fume:slag:slag=80:7.3:7.3:5.4,the voidage of powder combination is minimum and the filling degree is maximum.Based on the principle of grey correlation analysis,the correlation degree between particle group distribution and slurry fluidity of cement-based composite cementitious materials was verified.(3)This paper studied the variation rules of the workability and mechanical properties,crack resistance and flexural strength of the newly mixed recycled concrete with different replacement rates of recycled aggregate(0%to 100%).The results showed that the workability of the newly mixed recycled concrete was excellent.The compressive strength,splitting tensile strength and flexural strength of recycled concrete decrease with the increase of the replacement rate of recycled aggregate,but the cracking resistance of recycled concrete is obviously improved.