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.