Formulation of concrete to remove adhered cement paste from recycled aggregate by comminution

Abstract

The circular economy is based on increasing the reuse and recyclability of materials. Currently, at the end of its life cycle, concrete cannot be fully recovered in cement and natural aggregates, even after recycling. After crushing, recycled concrete aggregates contain cement paste adhered to natural aggregates. This material does not have the same performance when used again in concrete and requires adaptations (content dilution, surface treatment) to not lose performance when new mixtures are produced. Thus, this research seeks to increase the recyclability of concrete, by obtaining natural aggregate, without adhering cement paste. For this, the concrete formulation will be controlled (adding limestone filler, others) and the comminution process in order to parameterize, in different situations, the necessary energy for efficient removal of adhered cement paste. It is initially proposed to mold cementitious pastes with and without limestone filler to investigate their cracking process. Pastes containing aggregate will be also studied. The second stage of the study deals with the analysis of energy for fragmentation of particles from the pastes evaluated in the first stage. Finally, concrete will be molded with the studied filler formulations, which will undergo different comminution processes and have analyzed the characteristics of the produced aggregate particles. Thus, a relationship between comminution energy and concrete formulation will be performed, seeking to obtain a recycled natural aggregate that meets the concepts of circular economy. (AU)