Water sensitivity of cement‐based materials

Cement‐based materials are the most widely used construction materials on the planet. Cement‐based materials play a fundamental role in modern civilization and will for the foreseeable future. Although great efforts have been devoted to discovering the behaviors and optimizing their performances, several long‐standing controversies persist for the fundamental water‐related properties of cement‐based materials, which hinder theoretical researches and mislead technological developments. Inspired by the decreasing water permeability of clay‐bearing rocks, the term “water sensitivity” in geophysics is borrowed and proposed for cement‐based materials. The lamellar structure of negatively charged nanoparticles is responsible for swelling in clay‐based reservoir rocks. Amorphous calcium silicate hydrate gels in cement‐based materials have similar micro‐structural characteristics. They probably swell upon wetting and contract upon drying, making the pore structure of cement‐based materials dependent on water content. More importantly, several unexplained behaviors of cement‐based materials can be rationalized using water sensitivity. Thorough exploration of both the micro‐structural characteristics and performances validate the use of water sensitivity for cement‐based materials. Because water participates in or regulates almost all physical and chemical processes of cement‐based materials, water sensitivity can be a part of the interpretations of almost all of their properties and performances.