Environmental implications of the manufacture of calcium sulfoaluminate-based cements

Interesting environmentally friendly features are associated with the manufacturing process of calcium sulfoaluminate (CSA) cements. Compared to Portland cements, a lower limestone requirement and synthesis temperature as well as a larger clinker dilution and waste utilization can be achieved. In this work a CSA clinker was successfully synthesized in a laboratory electric oven by burning for two hours at 1250°C a raw mix composed by 58.5% anodization mud (a waste generated by the manufacturing process of anodized aluminium), 27.2 % limestone and 14.3% natural gypsum. In comparison with a Portland clinker, the synthesized CSA clinker enables a 70% reduction of limestone/clinker mass ratio as well as 42% and 59% savings of specific fuel consumption and CO2 emission, respectively. The hydration properties of the related CSA cement were similar to those shown by industrial CSA cements. The investigation was carried out by means of X-ray diffraction analysis, differential thermal-thermogravimetric analysis and scanning electron microscopy.