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Thermodynamic properties of liquid Rb-Pb alloys are deduced from electromotive force measurements using a coulometric titration technique. From a combination of measurements as a function of composition or temperature, Gibbs energies of mixing, entropies of mixing, and excess heat capacities are derived for alloy compositions covering the range from pure lead to 70 at.% Rb. At the equiatomic composition, extrema are obtained in the variations with composition of the Darken excess stability, the entropy, and the excess heat capacity. Recent electrical resistivity, calorimetric, and neutron diffraction measurements indicated an unusual behaviour at the same composition, which was interpreted in terms of polyanionic species. Our results corroborate the presence of structural units that become predominant at the equiatomic composition. A departure from this composition through addition of Rb or Pb leads to a decrease and dissociation of these species into free atoms.

The properties of concrete were studied when the proportions of 37.5 and 19.5 mm stone in the coarse aggregate were varied. With the cement content of 160 kg/m3 and the ratio of water/cement (w/c) greater than 0.9, the compressive strength is maximum at 25 percent by weight (w/o) of 37.5 mm stone. Conversely, for the cement content of 350 kg/m3 and w/c ratios of less than 0.50, maximum compressive strength is substantively reduced. For both 160 kg/m3 and 350 kg/m3 cement contents, workability improves slightly as the proportion of the 37.5 mm stone is increased. For 100 mm fixed slumps and cement content of less than 160 kg/m3, there was little change in compressive strength as the proportion of 37.5 mm stone increased. However, when cement content was increased from 190 to 350 kg/m3, maximum compressive strength was observed, which shifted downward from 50 w/o to 25 w/o of 37.5 mm stone. In general, to maintain a 100 mm slump, water demand decreased as the proportion of 37.5 mm stone in the coarse aggregate fraction increased.Key words: concrete, compressive strength, workability, slump, aggregate, size, cement.