文摘
This study presents a methodology for the characterization of construction and demolition (Cx26;D) waste recycled aggregates based on a combination of analytical techniques (X-ray fluorescence (XRF), soluble ions, semi-quantitative X-ray diffraction (XRD), thermogravimetric analysis (TGA-DTG) and hydrochloric acid (HCl) selective dissolution). These combined analytical techniques allow for the estimation of the amount of cement paste, its most important hydrated and carbonated phases, as well as the amount of clay and micas. Details of the methodology are presented here and the results of three representative Cx26;D samples taken from the São Paulo region in Brazil are discussed. Chemical compositions of mixed Cx26;D aggregate samples have mostly been influenced by particle size rather than the visual classification of Cx26;D into red or grey and geographical origin. The amount of measured soluble salts in Cx26;D aggregates (0.15–25.4 mm) is lower than the usual limits for mortar and concrete production. The content of porous cement paste in the Cx26;D aggregates is around 19.3 % (w/w). However, this content is significantly lower than the 43 % detected for the Cx26;D powders (<0.15 mm). The clay content of the powders was also high, potentially resulting from soil intermixed with the Cx26;D waste, as well as poorly burnt red ceramic. Since only about 50 % of the measured CaO is combined with CO2, the powders have potential use as raw materials for the cement industry.