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Describes the performance of a cement-based grout recommended for possible use to control brine inflows in potash mines. The grout consists of Type III high-early-strength cement, fly ash, and sodium saturated brine. Specimens were prepared and submerged in containers filled with brine to cure under confining pressures of 0, 3.40, and 6.9 MPa (0, 500, and 1000 psi). The isotropic confining pressures were designed to simulate different mining environments and to accelerate penetration of brine into the specimens so that long term performance could be evaluated. Tests were conducted at different ages to determine the compressive strength, splitting tensile strength, and static and dynamic modulus of elasticity. The performance of grout mixtures containing brine with zero and 40 percent fly ash over the three-year test program seems to be in an acceptable range. Confining pressure can adversely affect the physical properties results of grout over time. This investigation found that a reduction in the physical properties was occurring after two years, especially when the grout was subjected to a confining pressure. The grout with fly ash exhibited a more scattered data under different confining pressures than grout with no fly ash; however, it showed a better long term performance. Generally, fly ash grouts stored under zero confining pressures were found to perform better than those subjected to high confining pressures.

SP-153 In 1995, CANMET, in association with ACI, U.S.A. Electric Power Research Institute, Canadian Electrical Association, and several other organizations in Canada and the United States, sponsered the Fifth International Conference on fly ash, ferrous and nonferrous slags, and silica fume was held. The two volume proceedings of the Fifth CANMET/ACI Conference contains 62 papers from 23 countries.

The increasing construction of high-rise buildings in recent years had led to a demand for lightweight, high-strength concrete. In this study, the compositions of the matrix and the air void structure of aerated mortar containing silica fume were investigated as the basis for manufacturing lightweight, high-strength concrete. Mortars made with cement containing silica fume and fine or ultra-fine silica stone powder, having a particle size between that of cement and silica fume, were tested; the properties of cement paste in fresh and hardened conditions were improved. The compressive strength and the air void structure of prefoamed aerated mortars were determined and their relationship studied. Based on the results, it was confirmed that lightweight, high-strength concrete could be made with an effective combination of aerated mortar containing silica fume and lightweight coarse aggregate.

As part of a series of experiments designed to develop binary and ternary blended cements for use in structures exposed to freezing and thawing cycles in the presence of deicer salts, 39 mortar mixtures were made. Five different portland cements (two Canadian Type 10 cements, two ASTM Type I cements, and one Canadian Type 30 cement), seven fly ashes (three Class F fly ash, one Class CF fly ash, and three Class C fly ash), and two blast furnace slags were used as cementitious materials. The water-cementitious material ratio of all mixtures was fixed at 0.40; the amount of supplementary cementitious material (as a percentage of the total mass of binder) was zero percent for the five portland cement reference mixtures, 20 percent for nine mixtures, and 40 percent for the other 25 mixtures. The compressive strength of all mortars was measured after seven, 28, and 90 days of curing in water. The pore size distribution (with mercury intrusion porosimetry) and the chloride ion permeability of all mortars were determined after 28 days of curing. The results of the tests carried out to analyze the portland cements, the fly ashes, and the slags are also given in this paper. It was found that certain mixtures containing 40 percent of supplementary cementitious material had an excellent 28-day strength, a very low chloride ion permeability, and a very small average capillary pore size.

Partial replacement of a moderately sulfate-resistant cement with a high-calcium fly ash may result in either increased or decreased sulfate resistance for concrete. These effects of fly ash have been related to, among other factors, changes in the permeability of concrete and changes in the stability of hydrated calcium aluminates in the presence of sulfate-bearing solutions. The objective of this study was to investigate the effects of using anhydrous sodium sulfate as a chemical admixture in concrete made with Class C fly ash. The sodium sulfate admixture was expected to influence the sulfate resistance of concrete by increasing the availability of sulfate ions during the hydration of calcium aluminates. The admixture was also expected to increase the rate of pozzolanic reactions by increasing the concentration of alkali ions in solution. In addition to studying the effects of the sodium sulfate admixture on sulfate resistance, its effects on mixing water requirements, compressive strength, and permeability were also examined. The fly ash was introduced into the concrete by two methods: partialre placement of portland cement with fly ash at the time of mixing concrete and intergrinding of fly ash with portland cement clinker and gypsum, as in the production of blended cements. A commercially available ASTM C 150 Type II cement and five ASTM C 618 Class C fly ashes were used. The fly ashes replaced the portland cement (or the cement clinker plus gypsum) at a level of 35 percent by volume. For each source of fly ash, 14 concrete mixtures were produced; seven mixtures included Type II cement and fly ash with various amounts of the sodium sulfate admixture and seven mixtures included blended fly ash cement with various amounts of the sodium sulfate admixture. The use of sodium sulfate as a concrete admixture, in amounts ranging from two to five percent by mass of cement, resulted in improved sulfate resistance for concrete containing Class C fly ash. In many cases, sulfate resistance exceeded that of Type II cement concrete without fly ash. Additional effects of the sodium sulfate admixture included increased compressive strengths at early ages and lower permeabilities at early ages.