MEASUREMENT OF THE PORE WATER PRESSURE OF EARLY-AGE CEMENT-BASED MATERIALS: SIGNIFICANCE, TECHNIQUES AND ENGINEERING OUTLOOKS

Cement-based materials are essentially porous media. Their physical properties are largely influenced by the thermodynamic state of the internal pore water. Measuring pore water pressure of early-age cement-based materials helps not only to study the driven force of their early-age shrinkage behavior but also to investigate their early-age microstructure evolution. This paper gives an overview of the measuring techniques of pore water pressure in very early-age cement-based materials. In particular, the air leakage problem exists in the measurement of the previous research, which is thoroughly discussed. A modified measuring system, which adopts a special ceramic head referenced to soil research, is introduced to improve the air-tightness and prevent the pressure recovery error. The experimental results of the pore water pressure development also give promising outlooks for further engineering application in the construction site.