A CALORIMETRIC STUDY OF EARLY HYDRATION OF ALKALI-SLAG CEMENTS

This paper examines the early hydration of alkali-slag cements activated by different sodium compounds, such as NaOH, Na2CO3, Na2SiO3.5H(2)O, Na3PO4, Na2HPO4 and NaF, at 25 and 50 degrees C. A conduction calorimeter was used to monitor hydration kinetics. It was found that the initial pH of activator solution has an important role in dissolving the slag and in promoting the early formation of some hydration products. However, further hydration of alkali-slag cements is dominated by the reaction of the anion or anion group of activator and the Ca2+ dissolved from slag rather than the initial pH of the activator solution. Finally, three models were proposed to describe the early hydration of alkali-slag cements based on heat evolution measurements.