Influence of the pretreatment of recycled aggregates

The physical characteristics of the recycled aggregates (RAs) such as water absorption, abrasion resistance, specific gravity, and gradation greatly affect the resulting concrete properties. Thus, it is highly imperative to improve RA properties prior to the use in concrete. This chapter overviews various pretreatment techniques used to enhance the properties of RA thus influencing the mechanical, interfacial, and durability-related attributes of resulting concretes. Both the physical methods (including mechanical grinding/churning, physical heating, and heat grinding) and chemical pretreatment techniques (including presoaking of RA in various acidic/basic solutions, bio-deposition, chemical grouting, carbonation, polymer treatment, and nano-modification of aggregate surface) have been comprehensively discussed. It has been shown that incorporation of pretreated RA into concrete leads to property enhancement of recycled aggregate concrete (RAC). However, the associated cost, embodied energy, and complexity of the pretreatment technique employed are governing factors while ascertaining the most appropriate methodology for achieving improved properties of RA.