Study On The Graded Resource Utilization Method Of Waste Aerated Concrete

Aerated concrete is widely used in wall materials because of its light weight,good thermal insulation performance and other advantages.However,with the rapid development of urbanization,the number of waste aerated concrete is increasing.It not only occupies a large number of land resources,but also pollutes the soil and groundwater,and the recycled problems have attracted more and more attention.In view of the above problems,this paper put forward some methods of classified and resource utilization of waste aerated concrete.Based on the crushing and screening treatment of waste aerated concrete,the products were divided into recycled powder,recycled fine aggregate and recycled coarse aggregate according to the particle size and different uses,and the effect and mechanism of activation excitation and inert substitution on the properties of recycled products were systematically studied,aiming to develop products which met the engineering requirements and provide a feasible way for large-scale recycling of waste aerated concrete The main research and conclusion of this paper are as follows:The recycled powder of waste aerated concrete with particle size less than 0.15mm was taken as the research object to study its optimal activation system and the feasibility of using activated recycled powder as cement admixture to prepare mortar.The flow properties,physical properties and mechanical strength of mortar with equal quality of recycled powder replacing cement(10%、30%、50%)were tested,where the recycled powder was activated under different modes(calcination and grinding)and the micro mechanism of excitation activation was analyzed by TG/DSC and XRD.The results show that with the increase of the replacement rate of recycled powder,the fluidity,harden density and mechanical strength of mortar gradually decrease,while the water absorption and porosity gradually increase.The activity of recycled powder is the highest after calcination at 750℃ or grinding for50min.Micro analysis show that calcination can change the material composition of the recycled powder,while grinding will reduce the crystallinity of the material,which will promote the hydration reaction.The way to make mortar and pavement concrete was explored,which used waste aerated concrete with particle size between 0.15mm and 4.75mm as recycled fine aggregate.The flow properties,physical performance,mechanical strength and shrinkage performance of mortar with equal volume of recycled fine aggregate replacing river sand(10%、30%、50%)were tested,and the “internal curing” effect of recycled fine aggregate and the intrinsic relationship between macroscopic properties and microstructure evolution was analyzed by XRD and BSEM.On this basis,the slump,mechanical strength,wear resistance and frost resistance of pavement concrete with equal volume of recycled fine aggregate replacing river sand(10%、20%、30%、40%、50%)were tested.The results show that with the increase of the replacement rate of recycled fine aggregate,the hardening density of mortar decreases,while the water absorption and porosity increase,and it has negative impact on shrinkage property when the replacement rate exceeds 10%,and the mechanical strength will not decrease when the substitution rate is less than 30%.Micro analysis show that the “internal curing” effect can promote the hydration of cement and improve the interface transition zone.For pavement concrete,when the replacement rate is less than 30%,the mechanical strength,the wear resistance and the frost resistance can meet the requirements of engineering practice.The feasibility of making coarse aggregate foamed concrete was explored,which used waste aerated concrete with particle size between 4.75mm and 26.5mm as recycled coarse aggregate.At first,the reference mix proportion of coarse aggregate foam concrete was determined,and then the foam content,recycled coarse aggregate content and water binder ratio were studied by single factor study.On this basis,orthogonal tests were designed,and the influence of multi factor coupling on the basic properties were evaluated by means of extreme difference analysis and variance analysis,and the optimal mixing quantity of each factor was determined.The results show that the foam content has a significant effect on the compressive strength,dry apparent density,softening coefficient and water absorption of the coarse aggregate foam concrete,and the recycled coarse aggregate content has no significant effect on the basic properties,and the water binder ratio has only a significant effect on the softening coefficient.On the basis of the previous test results,the optimum mix ratio of A09 grade coarse aggregate foam concrete was determined.