Machine learning-based apparent activation energy estimation for cementitious composites incorporating phase change materials

Phase change materials (PCMs) have emerged as a promising solution to reduce the operational energy consumption and carbon emissions of buildings in recent years. Concrete, as the most-consumed construction material, has been widely used as the host medium to incorporate PCMs. Despite integrating latent heat thermal energy storage (LHTES) capacity, microencapsulated PCMs (MPCMs) have proven to impact the hydration process and strength development of cement mortars and concretes due to several probable mechanisms proposed in the literature. Yet, the effect of MPCM addition on the maturity of cement-based composites needs further investigation. Therefore, this study employs a machine learning (ML) model to study the effect of diverse MPCMs having different thermophysical properties on the strength development of cement mortars and concretes cured under various temperatures. For this purpose, a dataset of mixture designs for MPCM-integrated concretes was compiled and a powerful ML model was developed. Results indicated that the ML model successfully captured the effect of MPCM incorporation on the strength development of mixtures cured at different temperatures. Furthermore, the predictor model was utilized to calculate the apparent activation energy of MPCM-integrated cement-based composites to enable the prediction of compressive strength using maturity curves. It was found that the addition of MPCMs reduced the apparent activation energy of the composites which is indicative of lower sensitivity of strength development to curing temperature. Accordingly, the addition of MPCMs at 10 and 15 wt% of cement reduced the apparent activation energy by approximately 25 and 32%, respectively. Additionally, the most influential parameters contributing to the strength gain of such composites were identified which can further assist the optimization of mixture design. The obtained results can be deployed to study the cracking behavior of hydrating MPCM-integrated concrete exposed to temperature variations in future research.