Experimental Research On Basic Properties Of Actual Production Of Recycled Fine Aggregate Concrete

As a new kind of green building material,it has environmental protection and economic values to use the recycled fine aggregate(RFA)concrete.The basic properties of the RFA concrete are related to safety of concrete structures directly.It has practical value for experimental research on basic properties of the RFA concrete.For the actual production of RFA,adopting the mixture ratio design method which based on free water-cement ratio,the RFA concrete was successfully produced.According to five different values of water-cement ratio and six different values of RFA replacement ratio,tests of workability,mechanical properties and durability of the RFA concrete were conducted respectively.The main conclusions in this study as follows:1.The differences of physical properties between RFA and natural sand were analyzed,and the physical properties of RFA were sumarized.The test results show that the physical properties of RFA can only meet the requirements of III,the overall quality is poor,and the physical properties of RFA are less than that of natural sand.2.Adopting the mixture ratio design method which based on free water-cement ratio,the water for concrete was divided into two parts of free water and absorption water,so the problem of large water absorption of the RFA was solved.The results show that when the RFA concrete is produced by this method,the workability of the RFA concrete can basically meet the engineering requirements.3.For different values of water-cement ratio,with the increasing of the replacement ratio,the compressive strength,tensile strength and flexural strength of the RFA concrete are decreased in different degrees.When the replacement ratio is smaller than 20% and the water-cement ratio is equal to 0.7,the compressive strength,tensile strength and flexural strength of the RFA concrete are not lower than those of the ordinary concrete.In this case,the results show that the RFA can replace the natural sand,but the replacement ratio should be no more than 20%.4.When the replacement ratio is smaller than 20%,the impermeability of the RFA concrete reaches up to grade P6,the permeability of the chloride ion is low,and the carbonation resistance is good.The results show that the durability of the RFA concrete can meet the engineering requirements.