Chemical and Mechanical Characterization of Ternary Cement Pastes Containing Calcined Clay and Nanosilica

Research regarding new SCMs (supplementary cementitious materials) is in constant progress, aiming to improve cement properties, reduce its operational costs and make it more sustainable. One such material is calcined clay, which reduces CO₂ emissions and overall cost when blended with cement. Nanosilica is also an SCM, highly reactive. While the benefits of both are well established, their combined effect in a ternary mixture with cement still demands more research. Therefore, the present work evaluates that mixture, aiming to contribute to the cement industry and environmental sustainability. Four cement pastes were studied: OPC (100% Portland cement), 2NS (2% substitution by nanosilica), 25CC (25% replacement by calcined clay produced in the laboratory) and 23CC2NS (replacement by 2% of nanosilica and 23% calcined clay). w/b (water/binder) ratio was fixed in 0.35 and superplasticizer admixtures were used to keep the same workability. fc (compressive strength), XRD (X-ray diffraction) and TGA (thermogravimetric analysis) were performed in the pastes. Results show that the calcination process of the raw clays was efficient, with conversion of kaolinite and that both binary and ternary pastes showed fc equal to or higher than the reference, demonstrating the viability of the calcined clay for clinker substitution at high contents.