DEGRADATION OF A SULFOCALCIC BINDER IN A MIXTURE WITH CEMENT DUE TO FREEZING AND THAWING

The paper deals with the freeze-thaw (F-T) resistance of pastes prepared from a mixture of Portland cement (CEM) and a new clinker-free calcium sulfate binder (SCB) based on sulfocalcic fly ash (FBC ash). Pastes with varying ratios of these two binders were prepared and their F-T corrosion resistance in water and a 3 % NaCl solution was investigated. Furthermore, the paste aeration effect on the F-T resistance and the change in the phase composition of the paste during F-T cycling was studied. The results showed that the F-T resistance of the CEM-SCB mixtures was higher compared to the pastes prepared from the unmixed binders alone. All the mixed CEM-SCB pastes showed an undisturbed or slightly disturbed surface in both the water and 3 % NaCl environments, i.e., excellent F-T corrosion resistance after 100 and 200 F-T cycles in an environmental test chamber. A change in the ettringite content over time was observed.