Study On Mechanical Properties Of Polymer Modified Recycled Coarse Aggregate Concrete

With the development of China ’ s construction industry,a large number of sand and stone resources will be consumed every year.At the same time,a large number of construction waste is produced,which leads to the shortage of natural sand and stone resources and the pollution of a large number of construction waste to the environment.It is an important way to solve this problem that the waste concrete is broken into recycled aggregate and reused in buildings.However,due to the high crushing index,high water absorption and low apparent density of recycled aggregate,the quality of recycled concrete is low,so it is particularly important to find an efficient method to improve the performance of recycled aggregate.In this paper,the recycled coarse aggregate was strengthened by polymer MMA.The physical properties of natural aggregate,recycled coarse aggregate and recycled coarse aggregate strengthened by MMA were studied.Effect of modified recycled coarse aggregate on mechanical properties of recycled concrete such as cube compressive strength,axial compressive strength,splitting tensile strength and flexural strength.The main conclusions are as follows :(1)The experimental results show that the optimum polymerization temperature of MMA modified recycled coarse aggregate is 60°C,and the optimum polymerization time is 24 h,which can reduce the water absorption of recycled aggregate by 31 % and the crushing index by 11.1 %.When the aggregate is pre-dried before modification,the water absorption of the modified recycled aggregate decreases by 46 % and the crushing index decreases by 20 %.(2)The cube compressive strength and axial compressive strength of polymer modified recycled concrete are obviously improved.The cube compressive strength,axial compressive strength,splitting tensile strength and flexural strength of 28-day PRAC are 34.6 MPa,27.9 MPa,2.86 MPa and 5.01 MPa,respectively,which are14.9 %,14.3 %,7.9 % and 5.3 % higher than those RAC.(3)The cube compressive strength,axial compressive strength,splitting tensile strength and flexural strength of HRAC reached 37.3 MPa,29.5 MPa,3.04 MPa and5.34 MPa,respectively,which were 23.9 %,20.9 %,14.7 % and 12.2 % higher than those of RAC.It shows that pre-drying and modification of aggregate can obtain better modification effect.(4)The peak stress and peak strain of the constitutive curve were analyzed.Compared with the advantages and disadvantages of the existing constitutive equation,the constitutive equation proposed by Guozhenhai is selected to fit the stress-strain curve.The measured data are in good agreement with the fitting curve.The calculation results show that the higher the concrete strength is,the smaller the a value is.When b value is smaller,the brittleness of recycled concrete is more obvious.