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ECAUSE of their low cost, CaCl,, NaCI, and KCI are the deicing agents most frequently used. These salts, in combination with freezing and thawing, are, however, the principal cause of surface deterioration on concrete highways and bridge decks.'Z2 In addition, in the presence of oxygen C1-ion can corrode steel in reinforced concretes.In the present work, penetration of CaCl, into cement pastes and concretes was studied. In particular, the effects of the type of cement used, the method of preparing the concrete, and the temperature of the environment on the penetration rate of the C1-ion were examined.Portland cement (ASTM type 11) and pozzolanic cement were used to prepare the pastes and concretes. The pozzolank cement was obtained by mixing the portland cement with 35 wt% of Salone pozzolana. About 4.5 parts by weight of aggregate were used for 1 part of cement. Chemical analyses of all materials used and the particle size distribution of the aggregate (maximum size 12 mm) were described previously.3Immediately after the cylindrical test samples were prepared, the pastes (water/cement ratio= 0.4) were evacuated (P=10 cm Hg) for a few minutes to eliminate air bubbles; some of the concretes (those with the lower w/c ratios) were prepared by vibration. Both the pastes and the concretes (w/c=0.5 or 0.6) were cured at 25°C under wet sand for 2 months. After an additional month of air-curing, the test Supported by an IAEA Fellowship to M. S. Abdel-Azim. The writers are with the Department of Metallurgy, Atomic 1972.Energy Establishment, Cairo, United Arab Republic. Fig. 2. Electron micrograph illustrating dispersion of UO, particles obtained by flotation method ( X 5000).

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