Study on mechanical properties of secondary recycled concrete
In order to promote the secondary recycling of recycled concrete,the effect of secondary recycled coarse aggregate replacement rate on the mechanical properties of secondary recycled concrete was studied.Six groups of specimens with replacement rates of 0,20%,40%,60%,80%and 100%were prepared.The slump,compressive strength,splitting tensile strength and compressive deformation were measured,and the pore structure and microstructure were analyzed by scanning electron microscopy.The results show that with the increase of the replacement rate of the secondary recycled coarse aggregate,the slump gradually decreases,and the maximum decrease reaches 100 mm when the secondary recycled coarse aggregate is completely replaced.The analysis of pore structure shows that with the increase of the replacement rate of secondary recycled coarse aggregate,the proportion of small pores in the test block gradually decreases,the proportion of large pores gradually increases,and the volume of pores in the concrete gradually increases,resulting in the uncompacted concrete structure.Secondly,the proportion of aggregate in the test block gradually decreases,and the proportion of aging mortar and bubbles gradually increases,which is not conducive to the development of strength.The secondary recycled concrete generally meets the C35 strength requirements.With the increase of the replacement rate,the overall strength shows a downward trend,and the overall deformation shows an upward trend.In addition to the large aggregate crushing index,the pore structure analysis is related to the gradual decrease of the aggregate ratio in the secondary recycled concrete and the gradual increase of the proportion of aging mortar and bubbles,which reduces the strength of the test block and makes it more prone to deformation.The microstructure observation of secondary recycled concrete confirms the macroscopic measured data and cause analysis of the compressive strength and compressive deformation of the test block.Combined with the macroscopic measured data and microstructure observation,the application of secondary recycled concrete is feasible.