Hydration monitoring and strength prediction of cement-based materials based on the dielectric properties

A nondestructive testing method is developed to monitor the hydration process and predict the strength development of cement-based materials by applying the ground penetrating radar (GPR) and a non-contacting electrical resistivity device. These two instruments allow the measurements of the relative dielectric constant (RDC), the relative amplitude reflected electromagnetic (EM) wave and the electrical conductivity. The RDC and relative amplitude can be measured by calculating the propagation time and the intensity of electromagnetic impulses in material, while the electrical conductivity can be obtained directly by using the non-contacting electrical resistivity device. The results show that both of the relative amplitude and RDC are ideal indicators of the hydration process. The electrical resistivity shifts are well related to the dielectric properties. Linear relationships between the dielectric properties and compressive strength are observed, and a theoretical model is proposed to describe this relation based on the measurements of the dielectric constant and the relative amplitude at early age. This study provides additional theoretical and technical foundations for investigating the hydration progress and estimating the strength, which further helps to have a better understanding of the hydration process and promotes the quality control of cement-based materials.