Monitoring of modified fine recycled concrete aggregate for mortar production by ultrasound

The demolition waste that is produced by the construction industry is one of the highest generators of solid waste worldwide. Moreover, the construction industry consumes massive amounts of all extracted natural resources. It is thus crucial to encourage more sustainable, environmental and economical construction practices. Nowadays, the proper modification of the recycled aggregates is of high demand because they mitigate the main disadvantages of recycled aggregates, like the increased porosity and water absorption. Although a lot of research has been performed in the modification of coarse recycled aggregates, the modification of fine recycled aggregates has not been adequately investigated. In this study, the outer surface of fine recycled concrete aggregates has been modified by coating them with three different types of modification cement paste, spreadable, elastomeric, water-soluble sealant, and a mixed variety of both modifications. The coated samples were nondestructively examined through the thickness (longitudinal mode), and the ultrasound velocity measurements were processed by a new developing method based on MATLAB that can provide automatically enhanced and high-quality data. The goal is to compare the influence of the cement paste coating of the fine recycled concrete aggregates utilizing ultrasound velocity measurements during the hardening of mortar. Results showed that the coating modification of fine recycled concrete aggregates affects the water absorption, as well as the elastic properties of the mortar. This led to a better understanding of the mechanism of hydration in recycled aggregates mortars, as well as in recycled aggregates concrete.