Avaliação das propriedades mecânicas do gesso com incorporação dos produtos da combustão do carvão

Abstract

The accelerated industrial development of recent decades has been touted as one of the most impacting factors on the environmental imbalance. For this reason, research has been developed aiming, among other objectives, the reuse of waste generated by industrial processes as raw materials or inputs in other processes. This study aims to investigate the viability of using waste generated by the combustion of coal in power plants as an additive in the production of gypsum parts for construction. Coal combustion products (CCP) are already being applied in the construction industry as an additive in concrete, but their use in gypsum masses is very limited, which motivated the current reseach project. Initially the influence of water by varying the addition on mass in 5 levels between 10 and 50% was evaluated in order choose the best ratio water / gypsum about the mechanical properties. The materials used were characterized by fluorescence spectroscopy X-ray (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray (EDS) and scanning electron microscopy (SEM). The production process used for making the specimens was the so-called UCOS (portuguese acronym for the initials of wetting, compaction and drying), with pressure of 10 MPa. Then, test pieces were prepared with incorporation of PCC to the mass of gypsum in 5 levels between 10 and 50% to analyze the influence of these additions on mechanical properties, which was evaluated by compression tests, hardness and three point bending. The results determined that the water/gypsum (a/g) that provides the best mechanical properties is 0.2, which is used in the evaluation stage of the specimens with addition of PCC. It was concluded that, in general, increasing the incorporation of the waste was damaging to the mechanical properties of the gypsum block. Nonetheless, the studied conditions meet the requirements of NBR 13207, except for the condition with incorporation of 50% of PCC. In general, the mechanical properties behaved in similarly conditions between 10 and 20% of PCC, but the evolution from 20 to 30% caused a significant decrease in the results. Thus, it is concluded that the condition of 20% PCC in plaster and ratio a/g 0,2 meets the standard, ensures recycling of waste and, due to the pressing process, has better mechanical strength compared to the usual products