EFECTIVE SURFACE AREA OF CEMENT BASED MATERIALS

摘要

Specific surface area of hard end cement paste changes with hydaration and subsequent carbonation, reflecting the change in microstructure of hardened body. Thus the determination of specific surface area is essential in studying the degree of hydration, quality evaluation and durability of concrete. Very few methods that are currently available can determine the specific surface area with ease of execution and rigor of the underlying principle. We derived the equation of state of adsorbing pore water, the general from of Kiselev equation, on the basis of rigorous thermodynamics and, as a consequence, a general concept of specific surface area was proposed. The effective surface area was determined in experiments of water vapor adsorption and compatibility to BET surface areas of hardened cement pastes with different water-cement ratios was examined. Fractal dimension of surface was also obtained from the water vapor adsorption and compared with those obtained another methods to verify the universal applicability of the new concept of effective surface area.