Original paper

Syntheses, properties and solid solution of ternary lamellar calcium aluminate hydroxi salts (AFm-phases) containing SO42, CO32 and OH

Pöllmann, Herbert


The addition of gypsum, hemihydrate or anhydrite to OPC is necessary for the control of setting and hardening. The reaction of the aluminate phase leads to the formation of AFt (Ettringite) and AFm-phases in the course of hydration. The primary Aft-phase (ettringite) is transformed to AFm-phases. A natural analogue of AFm-phases containing sulfate ions was named Kuzelite.In this investigation ternary solid solutions containing sulfate, carbonate and hydroxide of lamellar calcium aluminium hydroxi salts (AFm phases) were synthesized and characterized.The synthesis of ternary AFm-phases containing SO42−, CO32− and OH− was performed using pure chemicals. The influence of temperature, water content and additional carbonate for carbonation reaction is discussed. The X-ray patterns of different hydration stages at 100 % r. h. and 35 % r. h. were studied. Transformation reactions of ettringites and lamellar salts can be caused by sulfate deficiency, carbonation reactions or transformation reaction with additional C3A. The following ternary solid solutions of AFm-phases with single phase compositions could be established:Lamellar calcium aluminum hydroxi salts (AFm-phases)3CaO·Al2O3·(x)CaCO3·(y)Ca(OH)2·(z)CaSO4·nH2O0.33 < x < 0.660.17 < y < 0.50 x + y + z = 10 < z < 0.17Two new distinct ternary phases were determined:1. 3CaO·Al2O3·1/6CaSO4·1/2Ca(OH)2·2/6CaCO3·nH2O2. 3CaO·Al2O3·1/6CaSO4·1/6Ca(OH)2·4/6CaCO3·nH2O


afm-phasessulfatecarbonatizationtransformationsolid solutionettringitekuzeliteternary phaseslamellar phases