Thermal Decomposition and Carbonation of Tetracalcium Aluminate Monosulfate

Abstract

In this paper, thermal stability and stability for a carbonate reaction were examined to investigate the use of monosulphate (tetracalcium aluminate monosulphate 12-hydrate, 3CaO Al₂O₃·CaSO₄· 12H₂O) as a filler for papermaking. Monosulphate was synthesized by the use of chemical reagents in liquid-liquid systems. The product material was characterized by XRD, DTA-TG and IR after thermal decomposition and the carbonation reaction were carried out under humidity conditions from R.H.40% to R.H.90%. Obtained results suggest following.
There are two endothermic peaks on the DTA curve from the dehydration of monosulphate through heating up to 300°C. A change in the crystal shape of Monosulfate is not observed during the heating up to 800°C.
Calcium carbonate, gypsum, and aluminagel are formed, when monosulphate was carbonated in the wet condition. However, the progress of the reaction is slow in R.H.40% and R.H.70%, and there is only small change detected in the crystal shape.
Results indicate that it is possible for monosulphate to be used as a filler for the paper.