The surface free energy of wetting of E-glass by water and benzene vapors was calculated from Bangham and Razouk's free-energy equation. The method of F'u and Bartell for determining specific surface area was used to analyze the microstructure. The surface free energies, which were computed from adsorption isotherms obtained at temperatures from 18" to 2Q"C, had values from -235 to -254 ergs/cm2 and -71.1 to -72.4 ergs/cm* for water and benzene adsorption, respectively, depending on temperature, surface geometry, and sample treatment. The lower affinity of E-glass for benzene, which resulted in a smaller work of adhesion, suggests that active adhesion of hydrocarbons is impossible in the presence of bulk water. Microstructural analysis indicated that the water-modified E-glass surface contains micropores 23 A in diameter.
The physical and chemical properties of fly ash produced at Ottumwa Generating Station have been monitored since April, 1985. The fly ash is produced from burning a low sulfur, sub-bituminous coal obtained from the Powder River Basin near Gillette, Wyoming. One-hundred and sixty samples of fly ash were obtained during the two year period. All of the samples were subjected to physical testing as specified by ASTM C 311. About one-hundred of the samples were also subjected to a series of tests designed to monitor the self-cementing properties of the fly ash. Many of the fly ash samples were subjected to x-ray diffraction and fluorescence analysis to define the mineralogical and chemical composition of the bulk fly ash as a function of sampling date. Hydration products in selected hardened fly ash pastes, were studied by x-ray diffraction and scanning electron microscopy. The studies indicated that power plant operating conditions influenced the compressive strength of the fly ash paste specimens. Mineralogical and morphological studies of the fly ash pastes indicated that stratlingite formation occurred in the highstrength specimens, while ettringite was the major hydration product evident in the low-strength specimens.
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