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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.

The thermodynamic properties of the dilute solutions of the chromium chlorides were determined in the solvents NaC1, KC1, CsC1, or their equimolar mixtures between approximately 973 and 1173 K using an EMF technique. Galvanic and redox cells with Ag-AgC1 reference electrodes were used. The cells are described by (-)Cr/CrC12 -AC1//asbestos diaphragm//AgC1 -AC1/Ag(+) and (-)Ag/AgC1 -AC1//asbestos diaphragm//CrC12 -CrCI~ -AC1/Pt(+) where AC1 represents the alkali chloride solvent. The thermodynamic properties imply high]y nonideal systems in which the formation of complex species is indicated. A reacting system consisting of Cr metal immersed in a CrC13-KC1 solution was studied potentiometrically. It was found that when the redox reactions were completed, all potentials assume a common value. This potential could be calculated using a simple mass balance and the formal potential for Cr/Cr 2+ and Cr2+/ Cr 3 § systems determined in this study.

For concrete produced in a commercial ready mix operation, the compressive strengths were fitted to Weibull and normal distributions. It was found that the Weibull distribution successfully describes concrete compressive strength failure data. This information is useful in the theoretical description of concrete failure. Furthermore, based on chi-squared, Anderson–Darling and Kolmogorov-Smirnov goodness-of-fit tests, the difference between the Weibull and normal distribution is not large enough to make a clear distinction regarding which distribution definitively fits the experimental data better. Key words: compressive strength, normal distribution, Weibull distribution, goodness-of-fit.

The thermodynamic behavior of CoC12, NiC12, FeC12, CuC1, FeC13, and CuC12 was investigated in NaC1, KC1, CsC1, or the equimolar mixtures of these salts between 700~176 using galvanic or redox cells with a silver-silver chloride reference electrode. The results indicate solutions which are reactive and nonideal. ExperimentalThe metal chlorides and CsC1 were anhydrous and they were received in sealed ampuls packed under argon gas.