ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Influence of borax and citric acid on the hydration of calcium sulfoaluminate cement

Yueyang Hu, Weifeng Li, Suhua Ma, and Xiaodong Shen

College of Materials Science and Engineering, Nanjing Tech University, Nanjing, China

E-mail: yc982@126.com

Abstract: The hydration of calcium sulfoaluminate cement in the presence of borax and citric acid has been studied using isothermal calorimetry, X-ray diffraction, thermogravimetric analysis, Fourier transfer infrared spectrometry and mercury intrusion porosimetry. The results suggest that the formation of complex between calcium and citrate in the solution adsorbed on the solid surface delayed the C₄A₃S and anhydrite dissolution and AFt nucleation. At the same time, the presence of borate replaced sulfate anion in ettringite (AFt) to form B-AFt. These reactions have an effect on the setting times and the mechanical strength values. The setting times of the calcium sulfoaluminate cement increased when the mineral admixtures increased in the cement. The effect of borax and citric acid on the strength development at different hydration stages presented different results, namely a decreased strength in an early stage and an increased strength at 3 and 28 days.

Keywords: Calcium sulfoaluminate cement; Retarders; Setting time; Strength

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-017-0185-9

Chemical Papers 71 (10) 1909–1919 (2017)