A coupled hygro-thermal model for the performance evolution of mineral admixture concrete subjected to variable environmental conditions

Fly ash and slag have received widespread attention as mineral admixtures for their capacity to improve concrete properties and effectively reduce pollution. In this study, a model for predicting the compressive strength of concrete with fly ash and slag under complex environmental conditions is proposed. The model is based on the principles of hydration kinetics and the concept of maturity. A unified theoretical framework for predicting hydration and strength of concrete is developed, which takes into account the influencing factors such as mix proportion, mineral admixtures and environmental conditions. The exothermic and drying behaviors of the reactions of cement and mineral admixtures are clarified, while temperature and humidity are selected as the primary parameters to achieve the coupling of environmental influence and hydration mechanism. And drying experiment was conducted at 40 degrees C with 35 % relative humidity to improve the permeability part of the model. The development of compressive strength is modeled by integrating an improved maturity method. Through the verification of simulation cases under complex curing environments, it is found that the model could accurately simulate the early hydration characteristics and effectively predict the development of short-term and long-term compressive strength. The theoretical framework proposed in this study possesses clear physical meaning compared to the existing methods and allows accurate prediction of properties along with simplicity of structure. The findings are expected to provide a new research perspective for further studies on the application of mineral admixtures in cement-based materials.