Incorporação de gesso alfa, oriundo de resíduos da indústria salineira, e de gesso beta reciclado em pastas para revestimento de construção civil

Abstract

Plaster is a material widely used by several industries, ranging from cement to dental, with civil construction as its biggest consumer. The search for the technical and economic feasibility of recycling waste, as well as for new mineral sources that are capable of alleviating the intense soil exploitation resulting from this activity, has become increasingly important. In this context, the possibility of recycling its waste has been studied in recent years as well as the possibility of new sources of gypsum, among which is the salt industry, by discarding waste known as “raw carago” or “malacacheta”. In view of this, this work aims to evaluate the influence of recycled plaster and alpha plaster produced from the calcination of the “carago”. The experiments involved chemical and mineralogical characterization, through the following techniques: X-ray diffraction (XRD), X-ray fluorescence (FRX), thermogravimetric analysis (TG / DTG) and scanning microscopy (SEM). The mechanical and workability properties of the plaster were evaluated from the analysis of the start and end time of setting, mini-slap, resistance to axial compression, resistance to pullout by traction and mass constancy. In the experimental planning, the symplex lattice model was used and for obtaining the response surfaces, the complete cubic model. The recycled plaster was obtained by calcination under atmospheric pressure, temperature of 150 ° C and cycle time of 1.5 hours. The “raw carago” was processed in an autoclave, under a pressure of 1.8 Bar, at a temperature of 129 ° C and a cycle time of 2 hours. A lattice symplex planning matrix was used and later with the use of the complete cubic mathematical model. The analyzes allowed to observe that the pastes formulated with 25% of alpha salgesso and 75% of recycled plaster showed satisfactory results of mechanical resistance besides presenting the longest open time of the paste.