Estudos dos parâmetros ambientais, químicos e mineralógicos dos agregados reciclados oriundos da construção civil

Abstract

This study aimed to analyze environmental, chemical and mineralogical parameters of Recycled Aggregates (RA), classified as Recycled Concrete Aggregate (RCA), generated at the Plant for Improvement of Construction Solid Waste (USIBEN), in João Pessoa / PB, as well as some Natural Aggregates (NA). Environmental analyses were performed, through solubilization and leaching tests, as well as the characterization of its chemical and mineralogical composition by X-ray fluorescence, X-ray diffraction, differential thermal and thermogravimetric analyses, and infrared spectrometry. In Step I, for the solubilized extract, the aggregates Gravel 12 RA, Gravel 25 RA, Fine Aggregate RA, Gravel 12 NA and Stone Dust NA had values above the limits set out in Annex G of the standard ABNT NBR Nº 10004/2004 for some chemical parameters, such as sulfate (250 mg / L), iron (0.30 mg / L) and aluminum (0.20 mg / L). This study also investigated the presence of heavy metals (As, Cd, Cr, Ni, Al, Cu, Fe, Ni, Se, Zn), and, in accordance with the aforementioned standard, Gravel 12 RA exceeded the allowable limit for Cadmium. According to these results, the aggregates mentioned above changed their classification from Class II B – Inert – to Class II A – Non-Inert. In Step II, only four aggregates were selected to continue the study: Sand NA and RA; Gravel 12 NA and RA. The pH behavior of the aggregates chosen was investigated, and all of them suffered decay, stabilizing at alkaline pH (pH> 7). The chemical and mineralogical analyses (XRF, XRD, DTA / TG and IV) revealed the presence of quartz (SiO2) in the four samples, being the greater quantity in the NA ones. It was confirmed that the RA samples had compounds also found in mortar and concrete, such as calcium carbonate (CaCO3), alumina (Al2O3), iron oxide (Fe2O3), magnesium oxide (MgO) and cement hydration products, such as portlandite [Ca(OH)2] and plaster [CaSO42H2O]. It was concluded that the RA studied are viable for several uses, in relation to environmental, chemical and mineralogical analyses, since most compounds found in them are also part of NA used daily in civil construction.