The connectivity of the porosity in cement-based materials has an impact on material durability, the interpretation of experimental measurements such as chemical shrinkage, and the timing of curing operations. While several techniques have been used to assess the connectivity of the microstructure (porosity), the interpretation of certain procedures is complicated due to the effects of specimen processing or the addition of chemical admixtures. This paper discusses capillary porosity depercolation in cement pastes as determined from measurements of chemical shrinkage, low-temperature calorimetry, electrical impedance spectroscopy, and x-ray attenuation. The experimental results are interpreted to identify the time of depercolation and parameters which influence the interpretation of each technique. The evidence provided by the experiments is that there exists a capillary porosity depercolation threshold around 20% capillary porosity in cement pastes. Further, the influence of capillary depercolation is demonstrated in terms of the reduction of the fluid transport properties of the material. Finally, special attention is paid to understand the influence of shrinkage reducing admixtures (SRAs) on the freezing behavior of cement-based materials.
Citation: Cement and Concrete Research
Pub Type: Journals
chemical shrinkage, fluid-transport, depercolation, capillary porosity, hydration, shrinkage-reducing admixture