Experiment And Meso-scopic Mechanism Analysis On Mechanical Properties Of Recycled Aggregate Concrete

The pollution of construction waste was a severe problem that attracted little public attention.Most of the construction waste consists of scrap concrete which comes from the removal of old buildings or other force majeure.The waste pollutes the air,water,and soil.And it is not biodegradable.This research fulfills the following four tasks:(1)The cylinder compressive strength and modulus of elasticity of C30 waste contained recycled concrete are tested;(2)With the aid of MATLAB curve fitting toolbox,predictive formulas of compressive strength and modulus of elasticity with different recycled coarse aggregate replacement rate(RCARR)are devised;(3)Calculations made by theory of micro-mechanics based on Mori-Tanaka method and homogenization theory are compared with experimental results and simulated curves from MATLAB;(4)Summarization and expectation of the paper are set forth.In this paper,the specific work is as follows:1.Through tests of 36 cylindrical specimens of C30 waste contained recycled concrete,the performance numbered A of compressive strength and elastic modulus of recycled concrete at age of 28 days with different RCARR(i.e.,0%、20%、40%、60%、80%、100%)were investigated;According to A performance,54 cylindrical specimens of C30 waste contained recycled concrete were tested,the performance numbered B of compressive strength and elastic modulus of recycled concrete with different RCARR(i.e.,0%、20%、40%、60%、80%、100%)and different ages(i.e.,7d,14 d,28d)were investigated.The experimental result shows:(1)with the increase of the RCARR,the water quantity of concrete keeps increasing and the compressive strength and elastic modulus is decreasing;(2)the higher compressive strength of recycled coarse aggregate is,the higher compressive strength of recycled concrete is;(3)the impact of ages of recycled concrete on compressive strength is relatively greater than that of elastic modulus of recycled concrete.2.Three common mathematical models selected from MATLAB curve fitting toolbox were used to fit the trend of experimental results.Based on the comparison of the fitting precision,the predictive formula between the RCARR and the cylinder compressive strength from experimental results was devised.Another predictive formula between RCARR and the modulus of elasticity was also derived from experimental results.Two predictive formulas were proved as a valuable reference through comparative analysis of the calculated results and experimental data.3.The calculations of C30 waste contained recycled concrete’s elastic modulus was established by theory of micro-mechanics based on Mori-Tanaka method and homogenization theory.With comparative analysis of the calculations,experimental results and simulated curves from MATLAB,all results of simulation are consonant with the experiment.The analysis shows:(1)when the elastic modulus of cement mortar is less than the elastic modulus of recycled coarse aggregate,elastic modulus of recycled concrete increases with RCARR.Otherwise it decreases with RCARR;(2)20%-40% of RCARR is a suitable range.