Abstract

This study explored the behaviour of laboratory-synthesised calcium sulphoaluminate (C(4)A(3)S) in alkaline media. C(4)A(3)S was hydrated in three liquid media: water, 8-M NaOH and 4 (wt.%) Na2CO3 added to the C(4)A(3)S + water mix. Hydration kinetics were studied via isothermal conduction calorimetry and 2- and 28-day mechanical strength values were found. The reaction products were characterised with XRD and FTIR. The findings showed that whilst C(4)A(3)S hydration kinetics were accelerated in the presence of alkalis, the resulting pastes had lower mechanical strength than the pastes hydrated with water and exhibited severe decay in some cases. An analysis of the hydration products revealed the presence of ettringite in the water-hydrated C(4)A(3)S pastes, whereas under alkaline conditions the main calcium sulphoaluminate hydrate detected was U phase. (C) 2013 Elsevier Ltd. All rights reserved.