Materiais ativados alcalinamente a partir de formulações à base de caulim, esmectita e dolomita

Abstract

Alkaline activated materials (MAA) are ligands obtained by activating solid particles, rich in aluminum and silicon, through alkaline solutions. When compared to Portland cement, MAA stand out for their lower production energy consumption, greater strength and durability. Currently, kaolin is the most used precursor to obtain MAA. Its wide use is due to its low cost and low energy consumption to obtain the calcined precursor, with excellent properties of the final product. Dolomite, a mineral rich in calcium and magnesium carbonate, is a material with the potential to integrate the composition of refractory products and magnesium cements. The use of dolomite in cementitious materials can bring benefits to the final product such as increased refractoriness, reduced porosity, among others. Although smectite clay has a chemical composition that places it as a potential precursor, studies to prove and consolidate its use for the production of MAA should be expanded. In this work, the feasibility of using dolomite and smectite for the production of MAA was investigated. Feasibility was evaluated mainly through mechanical strength and porosity, since mechanical strength is the main property required for most applications of cementitious materials. The uncalcined clays were characterized through X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), thermal analysis and infrared spectrometry (FTIR). After calcination, the clays were characterized through laser granulometric analysis, XRD and FTIR. The MAA were obtained through formulations containing kaolin, smectite and dolomite, activated by an alkaline solution of NaOH, 15M. After 28 days of curing, the MAA were characterized by compressive strength, apparent porosity, XRD, FTIR and scanning electron microscopy (SEM). Compressive strength and porosity data were statistically analyzed through the design of mixtures. The analyzes showed that kaolin was the precursor that most contributed to the mechanical performance of MAA. Dolomite contributed significantly to the decrease in porosity, but this contribution was not reflected in its mechanical strength. The mixture of kaolin, smectite and dolomite proved to be viable for obtaining MAA.