PERMEABILITY AND SUCTION IN SETTING CEMENT

A new method is presented for measuring permeability evolution during the rapid hydration phase of cement set. The method exploits the hydra tion-induced pore pressure decline in the cement by using it as a driv ing force for fluid dow and thus minimises damage to the delicate evol ving matrix structure. This represents an improvement on traditional m easurement techniques, where a pressure gradient is imposed on the sam ple, which can cause much greater damage to the matrix. Cement is mode lled as an elastic frame filled with a diffusing pore fluid, with flui d consumption represented by an effective universal sink, or suction, term. This sink term is proposed as a fundamental material property of a setting cement, which is independent of curing conditions. Results are compared with early-time measurements of permeability made using a more conventional test scheme where water is forced through a sample.