Abstract
Calcium sulfoaluminate clinkers containing ye’elimite (Ca4Al6O12(SO4)) and ternesite (Ca5(SiO4)2SO4) are being widely investigated as components of calcium sulfoaluminate cement clinkers. These may become low energy replacements for Portland cement. Conditional thermodynamic data for ye’elimite and ternesite (enthalpy of formation) have been determined experimentally using a combination of techniques: isothermal conduction calorimetry, X-ray powder diffraction and thermogravimetric analysis. The enthalpies of formation of ye’elimite and ternesite at 25 °C were determined to be − 8523 and − 5993 kJ mol−1, respectively.
Highlights
Calcium sulfoaluminate (CSA) cements, commercially developed in China in the 1970’s, are widely regarded as one of the new generation of ‘‘eco-friendly’’ cements and are currently undergoing optimisation
CSA cements are typically made by clinkering at high-temperature mixtures of limestone, bauxite, clay, and calcium sulphate, forming clinkers consisting primarily of ye’elimite (C4A3S)1 and belite (C2S)
Complete consumption of reactants was not achieved within 72 h; Eq 10 considers the reactivity of ternesite and, will not be an obstacle for calculating the enthalpy of formation
Summary
Calcium sulfoaluminate (CSA) cements, commercially developed in China in the 1970’s, are widely regarded as one of the new generation of ‘‘eco-friendly’’ cements and are currently undergoing optimisation. Because CSA formulations reduce CO2 emissions by approximately 30 mass% [1,2,3,4]. CSA cements are typically made by clinkering at high-temperature mixtures of limestone, bauxite, clay, and calcium sulphate, forming clinkers consisting primarily of ye’elimite (C4A3S) and belite (C2S). Compared with PC, CSA requires less calcium per kg clinker; less limestone needs to be decarbonated, resulting in a lower carbon footprint. CSA clinker is produced at 1250–1300 °C; this is approximately 200 °C less than that of PC clinker manufacture, leading to a reduction in both the quality and quantity of required fuel. The embodied CO2 is reduced due to the friability of CSA clinkers, reducing the energy requirements for grinding [3, 5,6,7,8,9,10]
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