Abstract
Abstract : The generation of construction and demolition waste (C&DW) worldwide keeps on escalating due to growth in infrastructure and the related refurbishment or replacement of existing structures. Numerous researches have been conducted towards utilizing C&DW materials for production of new concrete, from which it has been well-established that their use in concrete mixtures generally leads to inferior mechanical properties of the resulting concrete. As such, the general acceptance and conventional utilization of C&DW in the construction industry, is undermined. In this paper, the concept of triple layered interfacial transition zone (3ITZ) is suggested to be the main reason for the inferior mechanical properties exhibited by recycled aggregate concrete. The present paper reviewed past researches on re-activation of hydrated cement paste and on improving the quality of recycled aggregates by using different treatments. It is shown that a combination of mechanical grinding and thermal treatment at temperatures of 500 to 800oC, is an effective means of activating the cementitious properties of hardened cement paste. Adhered mortar removal and mortar fortification are the main approaches for enhancing the properties of recycled aggregates. Mechanical abrasion and/or thermal treatment at a temperature of 500oC, are the most effective techniques for improving the properties of recycled aggregates.