Measuring permeability of cementitious materials

At present, it is well-known that permeability is a more fundamental parameter for characterizing concrete durability than the standard compressive strength. Permeability governs the penetration of aggressive substances responsible for degradation and, thereby, has an important effect on the durability of cement-based materials. Despite the importance of permeability, a lot of confusion exists on a wide range of available experimental techniques for quantifying the permeability. This work aims at reviewing existing methods to measure the hydraulic conductivity. In addition, a new method was proposed based on the technique which is used to measure permeability of clay materials at the Belgian Nuclear Research Centre. A constant flow rate was applied to a permeability cell. When steady state was reached, gradient pressure was then determined to calculate permeability. The pressure and water flow was controlled by precise Syringe pumps. Tests were performed on hardened cement pastes with w/c ratio ranging from 0.5 to 0.6 in a temperature control chamber. The tests showed that the proposed method gave reliable results within a reasonable experimental time