Influência de diferentes tipos de materiais cimentícios suplementares nas propriedades de misturas quaternárias para produção de cimentos de menor impacto ambiental

Abstract

Limestone Calcined Clay Cement (LC3), composed of calcined clay, limestone filler, clinker, and gypsum, reduces up to 50% of clinker content, emitting less CO2. Despite research advances, the high cost of calcined clay in Brazil motivates the analysis of agro-industrial waste as partial substitutes in LC3 cements, resulting in quaternary blends with pozzolanic potential. Therefore, in this work, characterization tests of the additions were carried out, namely metakaolin (MK), silica fume (SF), fly ash (FA), and sugarcane bagasse ash (SCBA), regarding their chemical composition through X-ray fluorescence spectroscopy and their pozzolanicity through the modified Chapelle method and mortar compressive strength. Isothermal calorimetry was conducted to verify the kinetics and heat of hydration of the mixes. Rheological properties were evaluated by means of rotational rheometry in pastes, mortars, and concretes produced with quaternary blends, along with the slump test. Mechanical properties were determined by uniaxial compressive strength, diametral tensile strength, and Young’s modulus. Durability was analyzed through electrical resistivity, ultrasonic pulse velocity, and accelerated carbonation tests. In addition, the hydration products were verified by thermogravimetry. Partial replacement of metakaolin in quaternary blends attenuated heat peaks, prolonging the induction period of the pastes. Rheological tests showed LC3 and LC3 SF had higher shear stress and viscosity values, while ordinary Portland cement pastes had lower values. LC3 FA concretes and mortars showed higher torque values, while LC3 had the lowest. In relation to slump, Portland cement concretes presented higher values, and among LC3, the one with silica fume had lower slump. Hardened LC3 concretes showed lower compressive strengths than the reference concrete. LC3 concretes had moderate corrosion risk, while the reference concrete showed a high risk. Portland cement concretes had higher ultrasonic pulse velocity. LC3 SF and LC3 FA concretes reduced the carbonated region. It is concluded that the partial substitution of metakaolin by other supplementary cementitious materials can be beneficial, as long as their pozzolanicity and morphology are evaluated.