Effects of exposure to atmospheric moisture and CO2 on the performance of a ternary binder system and chemical admixtures in a self-levelling underlayment

Abstract

• Hydration of a model SLU after exposure of different components was examined. • Combined TBS reacted stronger to exposure than OPC, CAC and anhydrite individually. • Main exposure product of TBS was ettringite, exhibited seeding effect in hydration. • Admixtures present during TBS exposure suffered performance loss in hydration. • Impact of exposure on TBS rheology/strength worsened by admixture presence. The reactions with atmospheric moisture and CO 2 which cause a limited shelf life of self-levelling underlayments (SLUs) require a better understanding. Different components of a model formulation based on a ternary binder system (TBS) with admixtures (accelerator, retarder, and superplasticizer) were exposed to high humidity air above ambient temperature. Changes in the material composition, hydration behavior and engineering properties were investigated. The combined TBS possessed significantly higher hygroscopicity than its individual components, resulting in premature ettringite formation which exhibited a seeding effect that eliminates the dormant period during hydration. Admixtures present during exposure accelerated the TBS’s reaction with atmospheric moisture and suffered from performance losses in hydration. This negatively affected both setting and compressive strength development and unbalanced the hydration behavior of formulations with a mix of fresh and aged admixtures. The study highlights the importance of proper storage of dry-mixes to preserve their functionality over time.