Calcium silicate phases, alite and belite, are among the main components of modern portland cements. Alite reacts relatively rapidly with water and is responsible for most of the early strength development of concretes. Belite is less reactive at early ages, but can contribute appreciably to strength at later ages.
The MIT Concrete Sustainability Hub’s Concrete Science Platform is studying alite and belite phases starting at a fundamental level, that of electrons and atoms, through rigorous computer modeling. The primary goal of the program is to enhance our knowledge about the reactivity of these two phases in order for potential improvements to be developed and implemented. Thus far, the potential impacts on reactivity of substitutions of different elements into alite and belite crystal structures have been evaluated as well as reactivity of their various crystal faces. This work alone would have required decades of research to have been achieved experimentally. Further refinement of these models and validation of model predictions—using alites and belites from commercial clinkers with realistic compositions—is underway.