Research On Basic Mechanical Properties Of Polyvinyl Alcohol Fiber Nanomodified Recycled Concrete

With the acceleration of urbanization in China,the construction of new buildings and the demolition of existing buildings are generating a large amount of construction waste,while also consuming a large amount of natural resources,resulting in serious problems of resource shortages and environmental pollution.Recycling and reusing concrete and bricks,which account for the majority of construction waste,is an important way to recycle construction waste.Because waste concrete and brick usually coexist in a certain proportion,it is difficult to sort them in actual engineering.Therefore,it is of great theoretical value and practical significance to study the properties of mixed recycled aggregate and recycled concrete.In this paper,nano-silica is used to modify the recycled aggregate of brick-concrete mixtures.The effect and mechanism of different soaking mechanisms on the recycled aggregate are studied and analyzed by testing the physical properties and micro-morphology of the recycled aggregate.The basic mechanical properties of nanomodified recycled concrete were studied by using concrete cast with modified recycled aggregate.On the basis of the above,polyvinyl alcohol fiber nanomodified recycled concrete was designed and cast,and the basic mechanical properties of fiber nanomodified recycled aggregate concrete were studied and analyzed.The main conclusions are as follows:(1)The effects of the concentration of silica sol solution and soaking time on the physical properties of recycled aggregates were studied and analyzed.The relationship between the properties of recycled aggregates and the concentration of silica sol solution and soaking time was established.The results show that with the increase of solution concentration and soaking time,the physical properties of mixed recycled aggregate are improved continuously.The water absorption,crushing index and apparent density of the mixed recycled aggregate were improved by 2%nano-silica sol solution concentration and 2 days immersion.(2)The time-varying regularities of cube Strength,splitting tensile strength,flexural strength and axial compressive strength of nanomodified recycled concreteare studied and analyzed,and the correlation between mechanical indexes is established.The modification mechanism of recycled concrete by nano-silica was discussed based on scanning electron microscopy(SEM).The results show that the cubic strength and axial compressive strength of recycled concrete are increased by13.3% and 19.4% respectively through aggregate modification,while the splitting tensile strength and flexural strength have no significant change.(3)The time-varying regularities of cubic strength,splitting tensile strength and flexural strength of polyvinyl alcohol fiber nanomodified recycled concrete are studied and analyzed.The results show that the compressive properties of nanomodified recycled concrete are weakened by the addition of polyvinyl alcohol fibers,but the splitting tensile properties and flexural properties can be improved effectively.The modification effect of polyvinyl alcohol fiber is better than that of polypropylene fiber.