Gravimetric, volumetric and calorimetric studies of the surface structure of portland cement

Dry cement powder and hardened cement paste were characterised by means of laser granulometry and volumetric measurement of the nitrogen adsorption is otherm at 77 K. Water sorption isotherms at ambient temperature were measur ed stepwise by means of a gravimetric apparatus. The isotherms show a very large hysteresis loop, reaching down to zero relative pressure, which refle cts swelling of the cement gel. Thermoporometric measurements reveal that s welling of that gel consists in water take up within the continuously growi ng structure; no stable pore structure could be observed.