Ligantes álcali-ativados à base de metacaulim, cinza de casca de arroz e fíler calcário

Abstract

The increasing population demand, day after day, for greater infrastructure in cities, with more homes, buildings, highways and special works of art, makes concrete one of the most consumed materials in the world. As a result, the production of Portland cement generates high carbon dioxide emissions into the atmosphere. Faced with the need to reduce this environmental footprint, alkali-activated cements have been gaining ground in research and practical applications, as they are based on minimally processed natural materials or industrial solid waste, tending to provide important reductions in carbon emissions. The objective of this research is to analyze the mechanical properties and the appearance of efflorescence in alkali-activated cements produced from the concomitant use of metakaolin (MK), rice husk ash (CCA) and limestone filler (FC). The raw materials were properly processed and defined through chemical and physical tests and the mixtures were evaluated through tests to verify mechanical performance: resistance to axial revision; durability: flower formation; Thermogravimetry (TG/DTG) and Differential Scanning Calorimetry (DSC) tests; Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD). Four mixtures were developed: 100% with metakaolin precursor, two binary mixtures, one with 20% replacement by limestone filler and the other 20% by rice husk ash, a ternary mixture with 10% replacement by limestone filler and 10% % by rice husk ash, using potassium hydroxide (KOH) solution as a chemical activator. The mixtures prepared did not develop resistance to high axial compression for use in structural concretes, with the best averages being the binary mixture of MK+CCA, followed by the ternary mixture with MK+CCA+FC. Regarding the formation of efflorescence, the best results were for the binary mixture of MK+FC and ternary mixture of MK+CCA+FC, which did not show degradation. The TG/DTG, DSC, FTIR and XRD tests and results confirmed the formation of the K-A-S-H amorphous gel, corroborating and assisting in the analysis and understanding of the other results and data obtained.