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The results of studies on the contributions of alkalies in fly ash, slag, and silica fume to the expansion of concrete due to alkali-silica reaction are presented and discussed. A wide range of concrete mixtures was made. Each mixture contained a different amount of cement and different proportions of one type of fly ash, one type of slag, or one type of silica fume. All mixtures were made with amorphous-fused silica as a synthetic reactive aggregate. The alkalilevel of some mixtures was increased by sodium hydroxide to study the effects of pozzolans or slag mixtures at higher concentrations of alkalies. Concrete prisms were made and stored in water at 38 C. The test results indicate that the effectiveness of these supplementary cementing materials in reducing or increasing expansion due to alkali-silica reaction varies widely. The results also indicate that the supplementary cementing materials can contribute significant quantities of alkalies to the reaction, under particular replacement and test conditions employed.

Paper presents extensive test data on the shrinkage and creep behavior of high fly ash-content concrete made with ordinary portland cement and 50 percent by weight cement replacement with low-calcium Type F fly ash. The concrete mixes were designed to have 20, 40, and 60 MPa 28 day cube strength with high workability and low water-to-composite cement ratio. The other variables were the exposure condition for the shrinkage tests and stress-strength ratio for the creep tests. The results showed that for structural concrete of 40 to 60 MPa, the ultimate shrinkage strain ranged from 400 to 500 x 10-6 m/m. The swelling strain amounted to 40 to 55 percent of the shrinkage value and indicated the importance and continued water curing for effective realization of full pozzolanic action of the fly ash. For the same concrete strength of 40 to 60 MPa, the specific creep and the creep coefficient were remarkably low ranging from 40 to 100 x 10-6 /MPa and 1.20 to 2.50, respectively. The data clearly confirm that the time-dependent deformations of well-designed high fly ash-content concrete compare extremely well with those of portland cement concrete.

Presents experimental results on the use of concrete incorporating condensed silica fume and fly ash to reduce cement content, to lower temperature rise due to hydration, and to enhance early strength, and gives a case history on the application of this type of concrete in the construction of turbine shells in China. Studies were done on the effect of adding different amounts of silica fume and fly ash on strength, the effect of addition of both silica fume and fly ash on the total heat of hydration, and properties of concrete, including setting time, slump loss, modulus of elasticity, ultimate elongation, impermeability, and resistance to abrasion. Experimental and field studies indicated that the concrete mixture containing condensed silica fume and fly ash helped save 38 percent cement, lower the heat of hydration by 40 percent, and showed a slight increase in strength and durability. In placing over 200 mý of concrete of this type in hot weather, no abnormal phenomena occurred during the operation. A 90-day compressive strength of 30 MPa and a 98 percent strength were obtained, meeting the design strength requirements. No crack has been found in the surface of the shells since they were completed half a year ago.

In the Federal Republic of Germany, adequate pozzolanic activity of fly ash as a concrete additive has so far been insured by requiring cement mortars containing fly ash to reach a certain compressive-strength ratio as compared to a reference mortar. Test results are known to be sensitive to other influencing factors, especially composition and properties of cement. A series of tests was conducted to establish the usefulness of various testing methods. Under investigation were the respective influences of cement, fly ash content, and preparation on the basis of constant water content or constant workability. Mortars were stored according to the German test guideline, to BS 3892, and to ASTM C 311. Certain physical and chemical properties of the fly ashes were also determined. This paper discusses the effects of cement, i.e., alkali content, fineness, and slag content, on the pozzolanic activity index at different ages. Also demonstrated is the suitability of accelerating strength testing methods. Finally, the strong influence of fly ash fineness on workability and strength is shown.

Usability of rice husk ash was investigated as a siliceous material for calcium silicate products manufactured by hydrothermal reaction. It is concluded that rice husk ash can be used as a superior siliceous material for manufacture of calcium silicate insulating materials with good thermal durability up to 1000 C. Characteristics of rice husk ash, namely, high SiO2 content, reactive silica phase comprising amorphous silica, cristobalite and/or tridymite, and high surface area, are favorable to the formation of well-grown xonotlite which forms bodies of insulating materials. Trial products with bulk densities ranging from 0.11 to 0.41 g/cm3 prepared from rice husk ash using glass fiber for reinforcement not only satisfied all the requirements in the industrial standards (JIS A9510) but also gave 1.4 to 2 times higher bending strength than commercial products prepared from conventional siliceous materials, such as finely ground quartz sand, silica fume, and diatomaceous earth. A variety of rice husk ashes with different crystallinity are usable for manufacture of calcium silicate products, but the hydrothermal reaction condition should be optimized according to the crystallinity or amorphousness of the ash.