SEPARABILITY STUDIES ON RECYCLED AGGREGATES FROM DIFFERENT CONSTRUCTION AND DEMOLITION WASTES

Construction and demolition waste constitute the largest portion of municipal solid waste. The prohibition of their disposal in landfill, the increasing demand for aggregates, the environmental restriction for aggregates extraction and the growing requirement for the development of sustainable applications for construction and demolition waste, stimulated the development of applications for this material, particularly in the concrete, which is by far the most important construction material. Different strategies have been established to improve the quality of recycled aggregates (reduce their porosity), such as optimized comminution, heat treatment and others. However, the liberation between the present phases is seldom discussed in the literature. To develop an efficient recycling process, able to separate the cement paste from the aggregates, it is first necessary to know the liberation behavior of the cement paste under crushing along the particles size distribution. In this paper, it is discussed the results of separability studies by heavy liquid separations in recycled aggregates from construction and demolition waste from different sources. The results show that the proportion of heavy products increases specially on factions bellow 12.7 mm. The products differ notably among them, which can be confirmed by the content of binder, loss on ignition and mineralogical composition. These differences reflect directly on recycled aggregates physical properties (water absorption, porosity and mechanical resistance).