Research On Mechanical Properties Of Recycled Aggregate Thermal Insulation Concrete By Physical Properties Of Recycled Aggregate

Study on Recycled Aggregate Thermal Insulation Concrete(RATIC)played an important role in actualizing the comprehensive utilization of resources,energy saving and emission reduction in China.However,for the sake of complex recycled coarse aggregate(RCA)source and the large discreteness of recycled aggregate,the application of RATIC was limited.In addition,due to the dual influence of RCA and thermal insulation aggregate,the interior of RATIC contained a variety of interface structures.This feature resulted in a random internal damage parts caused by the destruction.Therefore,it had important theoretical significance to establish concrete stochastic damage model of this kind of interior containing a variety of interface structures.In this background,this paper focused on the influence of the physical properties of RCA on basic mechanics of RATIC,the stress-strain test was carried out to obtain the stressstrain relationship equation of RATIC.On this basis,stochastic damage constitutive model of RATIC under compression was established,failuremechanism of RATIC under uniaxial compression was revealed.The main conclusions of this paper were as follows:1.The influence of different RCA gradations,different RCA raw strength and different initial moisture contents of RCA on performance of RATIC was studied,it concluded that: the initial slump of RATIC increased with the aggregate size increasing,while the aggregate raw strength and moisture content had an unobvious influence on the initial slump,however the RCA moisture content on the slump had a huge influence on timing slump: while the moisture content of RCA was 0%,with the growth of time,the concrete slump decreased sharply,the slump loss reached 76.7% in 30 mins,while the moisture content was 100%,the slump loss reached only 37.6% in 30 mins.2.Effect of these three factors above on mechanical properties of RATIC was studied,and research showed that the RATIC strength made by RCA of natural gradation was the lowest.After the artificial deployment the compressive strength was increased,while the gradation was A/B=2/8,RATIC had the maximum compressive strength which was increased by 27.3%.The higher the raw strength of RCA,the higher the strength of RATIC.With the increase of initial moisture content of RCA,the strength of RATIC decreased gradually.The changing of elastic modulus was familiar to the strength,but there was no obvious effect on the elastic modulus of concrete with different RCA gradations from 2.36×104MPa to 2.42×104MPa.Elastic modulus of RATIC increased with the increase of the raw strength of RCA,it also decreased with the increase of initial moisture content,but the overall change was slight from 2.31×104MPa to 2.86×104MPa.The elastic modulus of RATIC was lower than that of ordinary concrete.Based on the RATIC trength analysis of three kinds of different factors,the common relationship between cubic compressive strength and axial compressive strength was obtained.The ratio of fc/fcu basically remained constant under different conditions,and it was higher than the ordinary concrete.Therefore,based on the experimental data,the ratio of fc/fcu for RATIC was recommended to take 0.93.3.As for the stress-strain relations,several conclusions were obtained as follows: first,the peak strain of RATIC was greater than that of ordinary concrete with the same strength.The peak strain with different RCA gradations was between 0.002307 to 0.002863,the peak strain with different RCA raw strength was between 0.002080 to 0.002399,the peak strain with different recycled aggregate initial moisture contents was between 0.001647 to 0.002340.Second,the ratio between ultimate strain and peak strain of RATIC increased with the particle size of RCA increasing,it decreased with the increase of raw aggregate strength,and RCA size of the initial moisture content had no significant effects on this ratio.This was to say that the ductility of RATIC was better than ordinary concrete.Third,based on the test data,the constitutive equation under uniaxial compression was under regression analysis,the fitting of regression analysis curve and test data was high.Fourth,the randomness of different RATIC composition material physical properties and recycled aggregate were considered,micro stochastic damage model of RATIC was proposed,the micro damage mechanism of RATIC with different RCA raw strength was analyzed,stochastic damage constitutive equation of RATIC under uniaxial compression was concluded based on micro spring model.The stochastic damage constitutive equation of compression was in well agreement with the experimental and stress-strain curves.