Degradation and service-life prediction of silicone rubber in a highly alkaline environment simulating concrete

• Silicone membrane’s alkaline durability was evaluated by solution aging. • Aging conditions (time, temperature, pH of solution), influenced silicone deterioration and caused changes in its properties. • Harsher aging conditions caused more discolouration, non-uniformity of the surface, and micro-cracking. • Short- and long-term structural properties of the silicone showed different trends upon alkaline solution aging. • Failure time was estimated using the Dakin-Arrhenius model. This research investigates the aging resistance of a silicone product exposed to highly alkaline conditions. A silicone membrane was immersed in a pH 13.5 solution and aged up to 30 days at four temperatures between 40 °C and 70 °C. The effects of alkaline aging on morphology, mechanical properties, thermal properties and surface chemistry of the alkaline-exposed silicone membranes were scrutinized by various techniques. On alkaline solution aging, both surface and bulk morphology and chemical structure were found to evolve as the silicone membrane experienced toughness deterioration. After failure criteria were established based on practical considerations, the service life of the silicone product was estimated using the Dakin-Arrhenius model, which provided for a cross-linking activation energy of 60 kJ/mol. The calculated service life of over one year for silicone membranes revealed alkaline immersion provides significant aging acceleration, although prediction of silicone performance in contact with concrete in field situations requires further investigation.