Using isothermal calorimetry, X-ray diffraction, thermogravimetry and FTIR to monitor the hydration reaction of Portland cements associated with red mud as a supplementary material Roberto Cesar de Oliveira Romano 1 • Heitor Montefusco Bernardo 1 • Marcel Hark Maciel 1 • Rafael Giuliano Pileggi 1 • Maria Alba Cincotto 1 Received: 12 June 2018 / Accepted: 14 February 2019 Ó Akade´miai Kiado´, Budapest, Hungary 2019 Abstract This study is part of a global project to find some large-scale application for red mud. A previous work confirmed that the use of RM as partial substitution for cement can affect its rheological properties; however, it is possible to produce cementitious materials without lose mechanical performances at harden state. The main goal of the work was to assess the impact of red mud (RM) as replacement of different Brazilian Portland cements by monitoring the formation of hydrated products over time, by thermogravimetry, X-ray diffraction and FTIR. Results show that the presence of RM increases the induction period, the gypsum and portlandite consumption as well as the amount of ettringite and monosulfoaluminate produced. The formation of sodium silicoaluminate hydrate (NASH) was also observed, regardless the kind of cement, as a result of the reaction with aluminates and silicates from the binder. Keywords Red mud  Portland cement  Hydration reaction Introduction Nowadays, Portland concrete is worldwide the most pro- duced and consumed construction material in modern society. Its yearly production is estimated to be higher than 10 km 3 . Basically, these cementitious products consist of a mixture of aggregates, binder and water. Although it is not possible to obtain an exact value for the volume produced, the value above is estimated in terms of the production of Portland cement. In this case, this hydraulic binder reached the expressive mark of 4 billion tons/year between 2013 and 2014 [1–3]. Currently, the cement industry is under pressure to mitigate the CO 2 emission worldwide, because their cur- rent global release accounts for approximately 7% in global warming [4, 5]. Moreover, the main challenge for the future will be to increase the production of the most important building materials without intensifying the impact of the enormous volumes produced. Considering only the aspects related to materials, dif- ferent routes have been developed to replace clinker with the use of alternative materials such as: 1. A by-product of a few industrial processes (as ground blast furnace slag, fly ash, silica fume, etc.); 2. Inert materials (as limestone filler); 3. A new kind of cement with a lower environmental impact. For this reason, the level of efficiency currently practiced in cement technology has been investigated to identify new opportunities to increase its production without increasing cement production. By the same token, the search for a large-scale appli- cation for red mud, a waste material resulting from the Bayer process to obtain alumina from bauxite ore, poses itself as a great challenge. For a long time, the material has been disposed of into mud lakes, bringing about consid- erable environmental impact [5–15]. In this process, the bauxite ore is crushed, milled and heated at up to 200 °C in a pressure vessel together with a & Roberto Cesar de Oliveira Romano rcorjau@gmail.com 1 Department of Civil Construction Engineering, University of Sa˜o Paulo, Av. Prof. Almeida Prado, trav. 2, n8 83, Sa˜o Paulo, SP CEP: 05424-970, Brazil 123 Journal of Thermal Analysis and Calorimetry https://doi.org/10.1007/s10973-019-08095-x