Comparison of recycled aggregate treatment methods on the performance for recycled concrete

Abstract

The effect of different aggregate treatment methods on the properties of both the recycled aggregate and the recycled concrete was studied. In this work, the compressive strength, dynamic elastic modulus, dry shrinkage rate, and chloride ion migration coefficient for five types of recycled concretes were investigated. Moreover, the Vickers hardness index and micro-morphology of new and old interfaces were analyzed. The results showed that “carbonation” significantly improved the mechanical properties and the dry shrinkage resistance of the recycled concrete. However, “slurry wrapping” greatly enhanced the chloride ion penetration resistance. Different aggregate treatment methods had different mechanisms to strengthen the interface. The influence of “carbonation” on the old interfacial zones (ITZ) was more significant than that on the new ITZ. A contrary influence of the “slurry wrapping” on both old and new ITZs was observed. The old interface had an obvious effect on the compressive strength and dynamic elastic modulus, while the new interface with different treatments had a non-negligible influence on the chloride penetration resistance. Besides, in this study, two optimization methods were proposed based on the improvement of “carbonation” and “slurry wrapping” treatment, respectively. These optimized methods can further improve the quality of recycled aggregate and the performance of recycled concrete.