Study on Properties of Waste Concrete Powder by Thermal Treatment and Application in Mortar

Waste concrete must be crushed, screened, and ground in order to produce high-quality recycled aggregate. In this treatment process, 15-30% waste concrete powder (<0.125 mm) can be generated. Hydration activity and the reuse of waste concrete powders (WCPs) were studied in this work, and the results illustrated that the particle size changed after a series of thermal treatments at temperatures from 400 degrees C to 800 degrees C. The particle size of waste concrete powder decreased by 700 degrees C thermal treatment, and by 600 degrees C thermal treatment, it increased. More active elements appeared in WCP heated by 800 degrees C. Nevertheless, the activity index (AI) of WCP, measured by the ratio of mechanical strengths between mortar with a 30% replacement of the cement with WCP and normal mortar without WCP, indicated that the WCP by 700 degrees C thermal treatment had an optimal AI value, which meant WCP treated at 700 degrees C could be used in mortar or concrete as an admixture.