###### Abstract  
In 2021, approximately 4.1 billion tonnes of cement were globally produced and the annual CO\({}_{2}\) emissions from cement plants reached almost 2.8 billion metric tonnes. In recent years, many efforts have been made to manufacture low-CO\({}_{2}\) cements. In this regard, great consideration has been given towards calcium sulfoaluminate (CSA) binders for both their technical features and sustainable properties, principally connected to their industrial process. The use of blended cements composed by CSA binders and supplementary cementitious materials (SCM\({}_{\text{S}}\)) can be an effective way to (a) reduce the CO\({}_{2}\) footprint and (b) produce greener binders. This scientific work studied the utilization of different amounts (15-35 wt%) of calcined reservoir sediments (RS) as SCM\({}_{\text{S}}\) in blended CSA binders, where the binders were cured for up to 56 days and characterised by various analytical techniques. It was found that thermally treated RS were particularly noteworthy as their utilization allowed for a dilution of the CSA linker, thus implying a decrease in CO\({}_{2}\) emissions and a reduction in costs related to their production. However, compared to a plain CSA cement, the blended systems showed rather similar volume stability levels, whilst their compressive strength and porosity values were, respectively, lower and higher at all the investigated aging periods. calcium sulfoaluminate cements; thermally treated reservoir sediments; supplementary cementitious materials; hydration; expansion; mechanical strength +
Footnote †: journal: Applied Sciences  
At present, there are several CO\({}_{2}\)-reducing cements, including belite-rich cements, alkali activated binders, geopolymers, magnesia cements, and calcium sulfoaluminate (CSA) binders [15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46]. In this regard, there is noticeable interest in calcium sulfoaluminate (CSA) cements for their relevant technical properties [47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58] coupled with their environmentally friendly features [59; 60]. CSA cements are obtained by mixing a clinker (derived from heating a meal composed of natural gypsum, bauxite, and limestone) with a source of calcium sulfate (e.g., anhydrite or natural gypsum). CSA binders contain calcium sulfoaluminate (3 CaO\(\cdot\)3 Al\({}_{2}\)O\({}_{3}\)-CaSO\({}_{4}\), ye'elimite) as a principal constituent and, on the basis of the burning temperature and the type and proportion of the raw materials, calcium sulfates, dicalcium silicate (2 CaO\(\cdot\)SiO\({}_{2}\), belite), calcium aluminium ferrite (brownmillerite, 4 CaO\(\cdot\)Al\({}_{2}\)O\({}_{3}\cdot\)Fe\({}_{2}\)O\({}_{3}\)) calcium sulfosilicate (sulfospurrite, 4 CaO\(\cdot\)2 SiO\({}_{2}\)-CaSO\({}_{4}\)), and several calcium aluminates. CSA cement's technical features (e.g., its rapid hardening, high impermeability, and excellent dimensional stability) are mainly due to the ye'elimite's hydration with CaSO\({}_{4}\), which leads to the formation of 3 CaO\(\cdot\)Al\({}_{2}\)O\({}_{3}\cdot\)3 CaSO\({}_{4}\cdot\)32H\({}_{2}\)O (ettringite). Compared to ordinary Portland cement, CSA cements display the following sustainable characteristics: (1) reduced synthesis temperatures (<1350 \({}^{\circ}\)C); (2) lower limestone demand (usually <35%) in the clinker-generating raw meal; (3) lower energy requirements for the cement milling; and (4) a wider utilization of industrial wastes in the cement manufacturing process [61; 62; 63; 64; 65; 66; 67; 68; 69; 70; 71]. In order to further decrease the generation of CO\({}_{2}\) and reduce their high costs (mainly depending on the utilization of bauxite), CSA cements can be blended with SCMs [72; 73; 74; 75; 76; 77; 78; 79; 80].