CONTRIBUIÇÃO À AVALIAÇÃO INTEGRADA DO DESEMPENHO MECÂNICO, DO DESEMPENHO AMBIENTAL E DA MICROESTRUTURA DE CIMENTOS COM ELEVADOS TEORES DE ADIÇÕES MINERAIS

Abstract

The synergistic effect of combining supplementary cementitious materials (SCMs) is an alternative to mitigate greenhouse gases (GHG) emissions from cement industry, by decreasing clinker content, while maintaining the technical performance. The integrated assessment of mechanical performance, environmental performance and microstructure is fundamental for multidimensional analysis of new cements formulations, in order to identify cements with better performance. The combined use of calcined clay and limestone filler is widely studied, and, despite blast furnace slag and fly ash are no longer sufficient to keep up with current commercial blended cements, optimized formulations, in combination with calcined clay and limestone filler, is an alternative to obtain cements that meet both technical and environmental requirements. In this research, four blended cements, with maximum clinker content of 50% and composed by the combination of calcined clay and limestone filler with blast furnace slag and/or fly ash were assessed by multidimensional indicators. The compressive strength was determined at 3, 7, 28 and 91 days and the cementing efficiency was calculated in relation to the compressive strength of CP V-ARI at 7 and 28 days of age. The GHG emissions per tonne of cement were calculated and related to compressive strength, enabling the determination of GHG emissions intensity. The clinker intensity, that represents the clinker consumption per 1m³ of mortar related with compressive strength, was calculated at 3, 7, 28, and 91 days. Thermogravimetry and X-ray diffraction analyses were used to microstructures assessment. The outperformed cement was the one composed by 10% blast furnace slag, 10% fly ash, 20% calcined clay and 15% limestone filler, with 40% of clinker content, in which the indicators showed the best results, especially at 28 and 91 days of age. The composition of calcined clay and limestone filler outperformed at 3 and 7 days. The results demonstrate the synergistic effect among SCMs and the importance of using multidimensional analyses for assessing cements' performance. The four blended cements show potential to be used in cement industry, to achieve the challenged targets related to reduction in GHG emissions.