Study On Basic Properties And Modification Of PVA Fiber Recycled Concrete

With the continuous expansion of urban scale and renovation of buildings,the annual growth of urban construction waste is also accelerating.Waste concrete is an important kind of construction wastes which accounts for more than half of the construction waste.How to effectively treat and utilize the waste concrete has become a barrier in the development of society.Hie recycling of waste concrete can not only protect the ecological environment,but also carry out the sustainable development strategy of our country.The recycled coarse aggregate in PVA(Polyvinyl alcohol)fiber recycled concrete studied in this paper is obtained by simply crushing waste concrete.The influence of water-binder ratio,fly ash replacement rate,recycled coarse aggregate replacement rate and PVA fiber content on the strength of recycled PVA fiber concrete is studied by orthogonal test The basic properties of PVA fiber recycled concrete was studied by single factor test,considering the influence of recycled coarse aggregate substitution rate and length-diameter ratio of PVA fibers.The recycled coarse aggregate was modified by hydrochloric acid solution,sodium silicate solution,polyvinyl alcohol solution,silane coupling agent solution and cement mixed with fly ash slurry,which made up for the deficiency of recycled coarse aggregate's own performance.The degree of comparison and analysis provide a theoretical basis for the popularization and application of PVA fiber recycled concrete in practical projects.The results show that:(1)The compressive strength and splitting tensile strength of recycled concrete with PVA fibers of 12 mm increase from 0 to 0.05%,0.1%and 0.15%respectively,and then decrease.When the content of PVA fibers is 0.1%,the two kinds of strength reach the peak.When the content of PVA fiber is 0.1%,the compressive and splitting strength of recycled concrete with PVA fiber increases first and then decreases as the ratio of length to diameter increases from 0 to 1945 290 and 387s respectively.(2)The compressive strength of recycled concrete with PVA fiber can be reduced by adding fly ash,and the compressive strength will decrease with the increasing replacement rate of fly ash.When the replacement ratio of fly ash is 10%,the splitting tensile strength of the specimens reaches the highest value.(3)The continuous increase of recycled coarse aggregate substitution rate leads to the development trend of compressive and splitting tensile strength of recycled concrete with PVA fibers,which first decreases,then increases slightly and then decreases.When the aggregate substitution rate reaches 70%,the strength of the specimens shows a wave peak.In general,the addition of recycled coarse aggregate reduces the strength and frost resistance of PVA fiber reinforced concrete.(4)The comprehensive physical properties of recycled coarse aggregate obtained by the secondary modification test with five kinds of solutions or slurries are better than the corresponding single modification,and the compressive and splitting tensile strength of the secondary modified PVA fiber recycled concrete is slightly higher than that of the corresponding single modification.