Avaliação de um método alternativo para o ensaio de perda ao fogo empregado na caracterização de cimento

Abstract

One of the main forms of chemical analysis that has the objective to guarantee cement quality is the loss on ignition test, a normative analysis that evaluates the loss of mass at a temperature of 950°C which also measures the thermal decomposition related to residual moisture, oxidation, and descarbonation. However, for cements that add blast furnace slag, also known as CPIII, during the loss on ignition test, some phases start fusing and mass gains begin to occur starting at 800°C due to the transformation from the vitreous phase to the crystalline phase, which is a result of the oxidation of sulfide present in the slag. Thanks to this, the need arises to perform the corrected loss on ignition test for CPIII cements, in which a correction of sulfide oxidation is calculated taking into account the variation in sulfuric anhydride content. However, one of the issues with this test is the handling of reagents with dangerous characteristics such as concentrated hydrochloric acid and barium chloride and the consequent generation of hazardous waste. Under the precepts of Green Chemistry, this study aims to present a new proposal for the normative corrected loss on ignition test for CPIII cements, with the intent of eliminating consumption of used reagents and, consequently, the generation of waste in laboratories. In order to achieve this, corrected loss on ignition tests were conducted following the technical standard NBR NM16 to evaluate and compare the results with the proposed loss on ignition analyses, which were based on thermogravimetric tests to study the behavior of CPIII cement at different temperatures. Thus, the indicated alternative without the use of reagents, employing only a muffle furnace with temperatures of 700°C to 720°C. The obtained results were better with the 720°C tests than with the 700°C tests, correlating the importance of prioritizing Green Chemistry in cement tests, aiming for more sustainable practices in the industry.