Belitic calcium sulfoaluminate cement and its use in the United States

Belitic Calcium Sulfoaluminate (BCSA) cement, has a history of over 30 years of use in North America. To date, more than 2 million tons of BCSA cement have been manufactured in the United States. It has been primarily used in the fast-track rehabilitation of highway and airfield pavement It has also been used widely in high-performance, low carbon footprint mortars. Despite this extensive use in the field, many aspects of the hydration mechanisms have yet to be investigated. The gap between the reactivity of calcium sulfoaluminate and that of belite, for one, has been presented as a challenge to the continuous strength gain of the material. In theory, this gap in reactivity should be reflected in a reduction in the rate of strength gain after hydration of the sulfoaluminate is complete. However, this is not always observed in the field, as was observed in the rehabilitation of the concrete runway of the Seattle-Tacoma Airport.

This paper discusses the hydration of BCSA cement with a particular focus on the intermediate hydration times using quantitative XRD, thermodynamic modeling, TGA and TD-1H NMR. Hydrated BCSA cement contains amorphous phases yet to be defined and characterized, especially in terms of their contribution to strength. The paper discusses these results in the context of the history of the binder in North America, the regulatory aspects controlling its use, and the important opportunities linked to its unique characteristics of speed of construction, durability and low carbon footprint.

Author: E. Bescher, K. Vallens, J. Kim

Section: Science and production

Keywords: belite, calcium sulfoaluminate, cement, hydration, phase composition