Research On The Effect And Machanism Of Nano-strengthening On The Properties Of Cement-based Products With Recycled Fine Aggregate

In this paper,use nano-polymer composite liquid to reinforce recycled fine aggregates,which can not only make use of properties of nano-materials,like small particles,strong activity and high permeability,but also can use filming and adhesive characteristics of polymer to fill micro-cracks and micro-pores on the surface of recycled aggregates well,in order to improve nature properties of aggregates.By comparing the basic properties of recycled aggregates(such as water absorption,apparent density and microstructure)before and after strengthening,analyze the strengthening mechanism of nano-polymer composite strengthening fluid.Evaluate the effect of nano-polymer composite on strengthening recycled aggregates.And then make cement products with strengthening and no strengthening recycled aggregates,do reasearches on their mechanical properties,shrinkage and deformation properties and analyze strengthening mechanism by XRD,MIR and SEM.Finally,based on the actual application and recycled wallboard produced by Hangzhou Fu Lihua Building Material Co.,Ltd.,prepare the large recycled concrete wallboard with the same ratio.Do reasearches on the basic properties of recycled concrete wallboard before and after strengthening to evaluate the effect of nano-polymer composite material in practice engineering.The following conclusions are obtained through experiments.1.Compared with no-strengthened recycled fine aggregates,the water absorption of the recycled fine aggregates strengthened by the nano-polymer composite decreases by 11.8%.By observing the microstructures of recycled fine aggregates before and after strengthening with SEM,it is found that the surface pores of the recycled fine aggregates are significantly reduced after being strengthened by the nano-polymer composite.There is a layer of polymer film on the surface of the recycled fine aggregates,and the pores of surface of the fine aggregates is remarkably reduced,and the surface state of the recycled fine aggregates is effectively improved.2.The use of nano-polymer composite reinforced fine aggregates can improve mechanical properties and shrinkage deformation of cement mortar.In the case of recycled fine aggregate cement mortar,strengthening can significantly increase the rate of early hydration of cement,affect the form and internal structure of hydration products,and increase compressive strength by 10%,flexural strength by 6%,and compressive strength and flexural strength for 28 days both by about 10%.At the same time,it can also significantly improve the dry shrinkage performance of recycled cement mortar.For the standard curing of recycled cement mortar,the early shrinkage decreases and decreasing range of early shrinkage significantly increases,shrinkage for 3d decreases by about 17%,decreasing range of late shrinkage gradually stabilizes,and shrinkage for 21d stably decreases by about 20%.3.The compressive strength and flexural strength for 3d of the recycled wallboard mortar under autoclave curing condition are increased by 30%;the compressive strength for 7d is improved by about 34%and flexural strength for 7d is increased by 40%,and both compressive strength and flexural strength for increase by about 50%,while the static elastic modulus does not change,indicating that strengthening the recycled fine aggregates can improve the compressive strength of mortar while ensuring that its crack resistance and deformation capacity is not reduced.The shrinkage of the recycled wallboard mortar is also obviously reduced after the strengthening,and the decreasing range shows the state of first increasing,then decreasing and finally being stable.The decrease of shrinkage is obvious.The decrease of shrinkage for 3d is about 40%,and the decrease of late shrinkage decreases gradually and finally stabilizes.The decrease of shrinkage is stable at about 10%after 14 days.4.The basic properties of large-scale wall panels made from recycled concrete,such as area density,water absorption,compressive strength and softening coefficient,before and after strengthening have been improved.