Steel Corrosion And Cracking Due To Corrosion In Recycled Aggregate Concrete

Development and utilization of recycled aggregate concrete can save natural resources and reduce construction waste, is an effective measure of sustainable development strategy. At present, research on durability of recycled aggregate concrete is still insufficient, which greatly hinders application of recycled aggregate concrete. This paper studied steel corrosion and cracking process induced by corrosion in recycled aggregate concrete, experimental study, theoretical analysis and numerical simulation were used.Firstly, the replacement ratio of recycled coarse aggregate and water cement ratio were two main control variables,15 types of concrete were designed and 45 specimens were made. The law of steel corrosion in recycled aggregate concrete was studied by the wetting and drying cycles, the process of corrosion-induced cover cracking was studied by the way of accelerating corrosion. The research results show that the ability of recycled aggregate concrete to resist the steel corrosion is worse than that of ordinary concrete, with the increase of the replacement ratio or the increase of the water cement ratio, the reinforcement protection property is decreased. Improving the replacement rate or water cement ratio fails to result in a significant increase the amount of rust in the porosity of concrete, so that can’t delay the cracking due to corrosion. The critical corrosion rate is influenced by the replacement ratio and water cement ratio, and its measure depends mainly on the strength of concrete. Cracks induced by corrosion tend to propagate through interfacial transition zones(ITZ), crack paths are affected by mechanical properties of new ITZ and old ITZ.Secondly, with the help of some reasonable assumptions, the whole process from corrosion initiation to cover cracking was analyzed by elastic theory, the theoretical predictive model of critical corrosion rate in recycled aggregate concrete structure was established, filling amount of rust in cracks and damage of cracking concrete were considered, the theoretical analysis agrees well with the experimental results, the predictive model can be used to analyze corresponding corrosion rate in recycled aggregate concrete structure. The effect on steel corrosion and cracking process due to corrosion in recycled aggregate concrete were analyzed, the results show that enhancing the impermeability of concrete, reducing the rust volume expansion rate and the thickness of reinforced-concrete interface gap, improving the strength of concrete, increasing the thickness of cover, and using the small diameter steel bars are conducive to improve the durability of recycled aggregate concrete structures.Finally, from the perspective of micro perspective, the random aggregate model of recycled aggregate concrete was established by ABAQUS software, the mechanical properties of old adhered mortar, new mortar, old ITZ and new ITZ were described by the plastic damage model of concrete, the displacement induced by rust expansion was simulated by applying the radial displacement. The research results show that the random aggregate distribution model based on the plastic damage property can simulate the failure pattern and complex stress state in recycled aggregate concrete, the failure pattern induced by corrosion and the critical corrosion expansion force are influenced by the replacement ratio and water cement ratio, the critical corrosion rates obtained by analysis have a good agreement with the available test data.