Hydration and early-age expansion of calcium sulfoaluminate cement-based binders: experiments and thermodynamic modeling

Abstract

Calcium sulfoaluminate (CSA) cements have been shown to have lower carbon footprint than that of Portland cement. In addition, the expansive nature of CSA-based cement can be utilized to enhance the resistance against shrinkage cracking by inducing compressive stress in concrete. The current paper reports the hydration and early-age volume changes of three OPC-CSA binary cement systems with varying CSA content. Hydration and phase development was monitored through calorimetry and quantitative X-ray diffraction. Expansion characteristics of OPC-CSA blends were monitored in saturated lime water. A geochemical modeling program (GEMS-PSI) was used to estimate the saturation levels of ettringite which had strong correlation with 1 day-expansion. The volume fraction of ettringite in a given pore volume was found to have a stronger correlation with expansion of OPC-CSA blends than the ettringite content. Furthermore, a poromechanical model was used for estimating the tensile stress in OPC-CSA blends.

Keywords:

• calcium sulfoaluminate cement
• early-age expansion
• thermodynamic modeling
• crystallization

Acknowledgements

The authors gratefully acknowledge the financial support provided by Illinois Center for Transportation and Illinois Department of Transportation to conduct part of this research. This study was carried out in part in the Frederick Seitz Materials Research Laboratory Central Facilities, University of Illinois.