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This paper gives the results of an investigation on the performance of high-volume fly ash concrete made with ASTM Class F fly ashes from three different sources. Cementitious materials contents of 300, 370, and 430 kg/m3 were used. The percentage of fly ash used was 58 percent of the total cementitious materials content. All the concrete mixtures were air-entrained and superplasticized. A large number of concrete specimens were subjected to the determination of compressive and flexural strengths, Young's modulus of elasticity, creep strain, drying shrinkage, abrasion resistance, deicing salt-scaling resistance, and resistance to chloride-ion penetration. High-volume fly ash concrete with adequate early-age strengths and excellent later age strengths can be produced with cement and total cementitious materials as low as 125 and 300 kg/m3, respectively. The Young's modulus of elasticity, creep, and drying shrinkage of high-volume concrete are comparable to those of the plain portland cement concrete. The high-volume fly ash concrete shows excellent resistance to chloride-ion penetration and outperforms plain portland cement concrete. The total charge in coloumbs at 91 days, a measure of resistance to the chloride-ion penetration, ranges from 278 to 1078. The corresponding values for reference concrete range from 1003 to 2313. Further research is needed to explain the relatively poor performance of the high-volume fly ash concrete under deicing salt scaling and abrasion tests.

The changes in physical and chemical properties of rice husk ash (RHA) fired at several temperatures from 400 to 800 C at 50 C increments were studied. The noncrystalline of RHA fired below 600 C could not be determined by x-ray diffraction (XRD), but it could be expressed by Luxan's method, which determines the variation in electric conductivity in a saturated solution of calcium hydroxide containing RHA. The effect of RHA on the properties of mortar, such as strength, drying shrinkage, resistance to acid attack, freeze-thaw resistance, and carbonation, was also determined. It was found that the compressive strength of RHA blended mortar with respect to that of plain mortar corresponded to the variation in conductivity. The RHA in mortar improved resistance to acid attack and developed the same degree of resistance to freeze-thaw action as that with silica fume, while it increased the drying shrinkage.

Expansion of mortar bars with and without selected pozzolans exposed to saturated calcium hydroxide and sodium chloride solutions at 50 C has been measured up to 20 weeks of exposure. The mixes contained a Danish low-alkali sulfate-resistant cement or a French high-alkali cement, and inert quartz sand added 2 and 6 percent of synthetic cristobalite and varying amounts of pozzolans. Additions were 5, 15, and 25 percent fly ash; 3, 5, and 7 percent silica fume; 5 percent silica fume plus 15 percent fly ash; and 35 percent slag. Both fly ash and silica fume were found to prevent deleterious alkali-silica reactions. The amount of pozzolan necessary to prevent expansion increased with the amount of reactive aggregate and varied with the type of pozzolan. Additions of 5 percent fly ash or 3 percent silica fume were enough to suppress deleterious reactions in the mixes with 2 percent synthetic cristobalite during the period of testing. Twenty-five percent fly ash or 5 percent silica fume plus 15 percent fly ash were found to prevent deleterious reactions in the mixes with 6 percent synthetic cristobalite until 15 weeks of exposure.

Reports research on the beneficial utilization of waste husk from rice production. The husk was burned in the furnace at two different temperatures, 400 and 500 C for « hr, and it was observed that all the silica obtained was amorphous at both burning temperatures. The mortars were prepared by substituting cement with husk at 10, 20, and 30 percent by weight. The ratio of (water + superplasticizer)/(cement + ash) was kept constant at 0.57 for all batches. The mortars were stored in sodium sulfate solution until the testing date after the initial 28 days normal curing in water. Compressive and flexural strength tests were carried out on the mortar specimens at 4, 8, and 12 week periods of storing in solution. It was observed that durability and strength of mortars were increased by using rice husk ash.

Gypsumless Portland cements (GPC) are inorganic binders, which may be described aas system of: ground Portland clinker (specific surface of 400-500 m2/kg - Blaine), a surface-active agent with hydroxyl groups and a hydrolyzable alkali metal salt (carbonate, bicarbonate, silicate). New cements, developed in recent years, are able to reach both higher strengths and fracture toughness than ordinary Portland cement (1,2,3). New developments in the making of very strong cements have resulted from modifying cement compositions and manipulating the microstructures (4).