Hexagonal ice in hardened cement

Neutron diffraction from nearly saturated cement paste (made from D2O, wate r/cement ratio = 0.36, hardened 3 months under lime-saturated D2O) has show n that the pore water transformed mainly to hexagonal ice (Ih) upon slow co oling below the (bulk) equilibrium freezing point of heavy water (276.8 deg rees K). The amount of ice increased continuously upon cooling to 227 degre es K, and then decreased continuously upon heating. At every temperature be low 276.8 degrees K, the ice content was greater upon heating than upon coo ling. The results were used to calculate the pore size distribution, which ranged mainly between a diameter of 3 and 30 nm. (C) 2000 Elsevier Science Ltd. All rights reserved.