Waste generation from the production of ready-mixed concrete

In Brazil, ready-mixed concrete (RMC) suppliers are adopting management strategies to reduce waste generation. This is because of the increasing scarcity of adequate places for the deposition of waste, which raises the associated costs. Therefore, it is necessary to know the actual volume production of residues in order to optimize the implementation of the recycling. The waste produced in RMC plants are mainly in the form of leftover concrete and adhered to the internal part of the drum of the mixer truck. The present study analyzed the data and produced an inventory of the amount of waste generated by of one of the largest Brazilian concrete companies. In parallel, an experimental study was performed in the real conditions of an RMC plant in order to measure the influence of concrete characteristics on the volume of concrete adhered to the drum. The results showed that about 3% of all the produced volume returns to the plant, comprising approximately 1.6% adhered concrete and 1.4% leftover concrete. The study proved that the volume of concrete adhered concrete depends on the cement consumption and the slump. The volume of concrete loaded and the region where the RMC plant is located do not influence those results. The inventory showed that the main cause of concrete leftovers is associated to over order and corresponds to 58% of this volume.