| Calcined Clay Blended Cements For Sustainable Cement Production Ran Li1; Marlene Schmid1; Aleksandar Jaglicic1; Tongbo Sui2; Johann Plank3; 1TECHNICAL UNIVERSITY OF MUNICH (TUM), Garching, Germany; 2SINOMA INT’L & SINOMA RESEARCH INSTITUTE, Chaoyang District, Beijing, China; 3TECHNICAL UNIVERSITY OF MUNICH, Garching, Germany; PAPER: 141/Nonferrous/Regular (Oral) SCHEDULED: 14:50/Tue. 29 Nov. 2022/Arcadia 2 ABSTRACT: This paper presents that the CO<sub>2</sub> footprint of cement can be reduced significantly by blending Portland cement clinker with thermally activated (calcined) clays (CCs). Investigations on pure meta phases obtained via calcination of kaolin, montmorillonite, illite and muscovite reveal that they increase water demand and decrease workability of the cement. The effect depends on fineness and internal porosity of the calcined clay and the chemical composition of the native clay, with illite and kaolin behaving much less favorably than montmorillonite or muscovite. A comparison of three industrial calcined samples of mixed layer clays originating from natural clay deposits in Germany, India and China confirmed the increased water demand of composite cements holding up to 40 wt. % of these calcined clays. The increase in water demand correlates well with the amorphous part and the content of meta kaolin in the calcined mixed layer clay. For one sample holding ~ 50 % meta kaolin, an increase in superplasticizer dosage of ~ 400 % as compared to neat OPC was recorded. Whereas, a high content of meta kaolin proved to be favorable with respect to early strength development as a result of its high pozzolanic reactivity. It can be concluded that calcined clays offer the potential of significant CO<sub>2</sub> reduction in cement manufacture, however this comes at the price of higher admixture dosages for superplasticizers. Still, a substantial savings in CO<sub>2</sub> emission can be realized, and the cement industry can progress into an era of more eco-friendly binders. References: K. Scrivener, F. Martirena, S. Bishnoi, S. Maity, Calcined clay limestone cements (LC3), Cem. Concr. Res. 114 (2018) 49–56.<br />S. Ferreiro, D. Herfort, J.S. Damtoft, Effect of raw clay type, fineness, water-tocement ratio and fly ash addition on workability and strength performance of calcined clay – Limestone Portland cements, Cem. Concr. Res. 101 (2017) 1–12.<br />T. R. Muzenda, P. Hou, S. Kawashima, T. Sui, X. Cheng, The role of limestone and calcined clay on the rheological properties of LC3, Cem. Concr. Compos. 107 (2020), 103516.<br />R. Fernandez, F. Martirena, K.L. Scrivener, The origin of the pozzolanic activity of calcined clay minerals: A comparison between kaolinite, illite and montmorillonite, Cem. Concr. Res. 41 (2011) 113–122.<br />S. Krishnan, A.C. Emmanuel, S. Bishnoi, Hydration and phase assemblage of ternary cements with calcined clay and limestone, Constr. Build. Mat. 222 (2019) 64–72. |
