Experimental Study On Physical And Mechanical Properties Of Fluid Fiber Reinforced Recycled Concrete

Recycled concrete is made from recycled aggregate instead of natural aggregate.The self-defects of recycled aggregates make the work ability,mechanical properties and dry shrinkage performance of recycled concrete different from that of ordinary concrete.The engineering application of recycled concrete is limited to a certain extent.In this paper,different proportions of fluid fiber reinforced recycled concrete were obtained by changing the content of recycled aggregate,sand content,the amount of water-reducing agent,and the content of steel fiber and polypropylene fiber.The experimental study on the work ability,mechanical properties and dry shrinkage properties of fluid-reinforced recycled concrete was conducted.The main findings are as follows:(1)C60 recycled concrete with 30%,40% and 50% recycled aggregate was selected as research objects.By changing the sand rate and the water-reducing agent to match the fluidity of the recycled concrete,an appropriate increase in the sand rate and the amount of the water-reducing agent are obtained,and the flow ability of the recycled concrete mix is increasing.With the mechanical properties as the discriminant index,increasing the sand rate causes inconsistent changes in the mechanical properties of fluid recycled aggregates with different proportions proportions show inconsistent changes When water-reducing agent is between 0.65% and 0.75%,the fluid-recycled concrete with different proportions is more enhanced than the initial ratio mechanical properties.(2)Through the incorporation of steel fibers or polypropylene fibers,the work ability and mechanical properties of the flow-reinforced fiber reinforced recycled concrete were experimentally studied and analyzed.The results show that the incorporation of steel fibers or polypropylene fibers reduces the flow ability of recycled concrete mixes.When the content of steel fiber is about 1.2%,the compressive strength of different steel fiber content recycled concrete increases by 7.0%~14.5%,the tensile strength increases by 7.6%~24.9%,and the flexural strength increases by 34.3%~60.5%.When the content of polypropylene fiber is about0.15%,the tensile strength of different polypropylene fibers mixed recycled concrete increases by 6.3% to 9.8% and the flexural strength increases by 16.5% to 38.2%,which significantly improves the bending and pulling performance of recycled concrete.(3)Through the incorporation of steel fibers or polypropylene fibers,the dry shrinkage properties of the flow-reinforced recycled concrete were studied and analyzed.It is concluded that with the increase of the amount of recycled aggregates,the dry shrinkage ratio of the fluid recycled concrete with different ratios tends to increase.Recycled concrete with 50% recycled aggregate shrinks to 0.1%.When the content of steel fibers is 1.2% and the content of polypropylene fibers is 0.15%,the amount of recycled aggregates can be suppressed to no more than 30%.The dry shrinkage ratio of the flow-reinforced fiber-reinforced recycled concrete reaches the level of flow-based concrete.