Square-root law prediction of chloride penetration rates in stabilized cement pastes

The chloride penetration rate in a cementitious system characterizes its ability to resist chloride-induced corrosion. Assessing this property involves determining a diffusion coefficient obtained from diffusion or migration tests, or from models. The evolution of penetration depth can be used to predict the durability of a cementitious system, as it follows a linear relationship with the square root of time, known as the square root law. However, given the many assumptions behind this law, it remains unclear when and how it can be used to predict future penetration depths. This study investigates the applicability of the law for seven binders and shows that it can be used to monitor the evolution of penetration depth before the stabilization of the properties of the specimen, except when glass powder is used. However, predicting future penetration depths is more accurate when both the microstructure and surface content are stable. • The square root law enables rapid chloride ingress prediction on stabilized systems. • Microstructure stabilization time is a key concept for long-term chloride ingress. • Conductivity ratio and hyperbolic law can provide microstructure stabilization times.