Effect of Thermal Activation of Powders Obtained from Multi-Recycled Concrete on the Performance of Cementitious Materials

Utilizing supplementary cementitious materials to reduce cement usage is a promising solution to mitigate carbon emissions in the cement industry. Generally, the powder generated during the recycling process of concrete (i.e., recycled concrete powder, RCP) has an unfavorable effect on the performance of cementitious mixtures due to its low activity, but it can be improved by dehydration at high temperatures. In this study, RCP obtained in the crushing process of repeatedly recycled coarse aggregate concrete was thermally activated at various temperatures (200–800 °C), and its effect on the properties of cementitious mixtures as a partial cement replacement was discussed. The results showed that the properties of cementitious mixtures containing RCP heated at 200 °C and 400 °C did not show significant differences with those containing unheated RCP, whereas RCP activated at 600 °C and 800 °C contributed to the improvement of mechanical strength, drying shrinkage, and water absorption of cementitious mixtures than non-heated RCP, proving that thermal activation of RCP at these temperatures is effective for the utilization of repeatedly recycled concrete powder.