Influence Of Recycled Aggregate Content On Carbonation Performance Of Concrete

Due to the shortage of natural building materials reserves,the increasing amount of waste construction waste,the earth’s environmental burden pressure is too large,recycling waste concrete has become an important direction of concrete research.In order to promote the application of recycled concrete in the future,it is necessary to conduct a more comprehensive study on the durability of recycled concrete.It is known that the concrete structure is corroded by carbon dioxide in the environment for a long time,which will cause the corrosion of internal reinforcement and reduce the reliability of the structure.Therefore,the anti carbonation performance is an important part of the durability research of recycled concrete.In this paper,the influence of recycled aggregate replacement rate on carbonation depth and compressive strength of concrete is studied by preparing concrete with recycled aggregate replacement rate of 0%,30%and 50%(RC0,RC30 and RC50 respectively).Meanwhile,the micro interface morphology and micro hardness of concrete are used to verify the analysis,and the carbonation depth prediction model of recycled concrete is established,The service life of recycled concrete is predicted.The conclusions are as follows:(1)After 28 days of carbonation,compared with RC0,the carbonation depth of RC30 and RC50 increased by 13.1%an d 31.2%respectively.The higher the content of recycled aggregate,the lower the carbonation resistance of recycled concrete.(2)The compressive strength of RC30 and RC50 is 15.5%and 24.1%lower than that of RC0 under standard curing conditions,respectively.The larger the recycled aggregate content is,the higher the loss rate of compressive strength is.After 28 days of carbonation,the compressive strength of RC0,RC30 and RC50 recycled concrete increased by 2%,14%and 15%respectively.(3)After 28 days of carbonation of RC30 and RC50,the transition zone widths of the old aggregate old paste interface,the new aggregate paste interface and the old paste new paste interface are 30μm、47μm、39μm and 31μm、50μm、41μm.The results show that the interface structure of concrete with 30%recycled aggregate replacement rate is denser and the carbonation resistance is stronger.(4)The more recycled aggregate content,the lower carbonation resistance life of recycled concrete components.According to the requirements of different design service life of general environmental action level,when the design service life is more than 50 years,the recycled aggregate content should not exceed 30%.