Use of construction and demolition wastes as raw materials in cement clinker production

Abstract

The aim of the present paper was to investigate the possibility of utilizing Construction and Demolition (C&D) wastes as substitutes of Portland cement raw meal. The C&D wastes that were so used, were the Recycled Concrete Aggregates (RCA) and the Recycled Masonry Aggregates (RMA) derived from demolished buildings in Attica region, Greece. RCA and RMA samples were selected because of their calcareous and siliceous origin respectively, which conformed the composition of the ordinary Portland cement raw meal. For that reason, six samples of cement raw meals were prepared: one with ordinary raw materials, as a reference sample, and five by mixing the reference sample with RCA and RMA in appropriate proportions. The effect on the reactivity of the generated mixtures, was evaluated on the basis of the free lime content (fCaO) in the mixtures sintered at 1350°C, 1400°C and 1450°C. Test showed that the added recycled aggregates improved the burnability of the cement raw meal without affecting negatively the cement clinker properties. Moreover, the formation of the major components (C 3S, C 2S, C 3A and C 4AF) of the produced clinkers (sintered at 1450°C) was corroborated by X-Ray Diffraction (XRD).