Experimental Study On The Effect Of Freeze-thaw Cycles On Mechanical Properties Of Recycled Concrete

In the past 20 years,many cities demolish old buildings of the last century,a lot of construction waste is produced,which is difficult to solve effectively.Recycling and crushing these construction waste into recycled concrete is one of the important ways to solve this kind of problem.Buildings in northern China are often damaged by freezing and thawing in winter,Fully studying the freeze-thaw destroy mechanism of recycled concrete is one of the important preconditions for popularizing recycled concrete materials.In this test,gravel and crushed stone are selected as natural coarse aggregates,by adding recycled coarse aggregate with different replacement rate.After 25,50,100 and150 freeze-thaw cycles,detection of frost resistance of recycled concrete,And the compressive and tensile strength properties of recycled concrete after freeze-thaw.To explore the influence of different sand ratios on the performance of crushed stone recycled concrete in freeze-thaw environment.The results show that the performance of crushed stone recycled concrete is good,the higher the replacement rate,the worse the performance of recycled concrete.Natural crushed stone mixed with 30% and 50% replacement rate recycled coarse aggregate,within the range of reasonable sand rate,the lower limit is 36% and the upper limit is 40%.After 25,50,100 and 150 freeze-thaw cycles,detection of frost resistance of recycled concrete,And the compressive and tensile strength properties of recycled concrete after freeze-thaw.To explore the influence of different sand ratios on the performance of crushed stone recycled concrete under freeze-thaw environment.The results show that increasing sand rate can effectively enhance the frost resistance and mechanical properties of recycled concrete in freeze-thaw environment.Using ABAQUS finite element software to build cube temperature field model under freezing and thawing environment,analyze temperature change cloud diagram and temperature change curve.Completed the numerical simulation of the thermal stress field,take the substitution rate and the number of freeze-thaw cycles as parameters,analyze thermal stress and thermal strain clouds,study the curves of thermal stress and thermal strain with time.Completed the numerical simulation of the cube loading test in the freeze-thaw environment,take the substitution rate and the number of freeze-thaw cycles as parameters,analyze the stress and strain cloud diagram of the cube model,study the stress-strain curve of the cube model.Comparing the development of destroy cracks between numerical simulation and research results,simultaneously compare the load-displacement curve and compressive strength loss rate of the two.