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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 geological characteristics of Mexico permit an important number of materials to be considered for use as pozzolans in the construction industry. These materials have great importance, due to the relevance to problems of concrete durability. This situation has caused an increase in the use of pozzolanic cement. This increase of use of pozzolanic cement creates a need for characterization of these products and evaluation of their performance based on the specifications related to their use in concrete. Mexican natural pozzolans meet the requirements of the specification, with some deficiencies in some pozzolans. The objective of this work was a detailed characterization of all pozzolans actually used in Mexico and evaluation of their use as an admixture in concrete, using for this purpose ASTM C 311 and C 618. Those particular points of the specifications that are not satisfied completely and the elements that contribute to the fact are discussed in this paper.

Due to increasing volumes of fly ash production each year, new utilization areas must be found. A new application had been developed at Bogazici University. Fly ash with various weight percentages of rubber tire chips were mixed and compacted at a water content wet side of optimum. Sealed single ring infiltrometer and falling head permeability tests were conducted on these specimens with water and gasoline as the permeants. Unconfined compression and split tensile strength tests were conducted to evaluate the mechanical behavior of the proposed liner material. When gasoline was permeated through rubber-fly ash specimens, a decrease was observed in the permeability as compared to that measured during water permeation. This decrease is due to the physical characteristic of rubber, expansion upon contact with gasoline. The expanded rubber holds some portion of the gasoline in itself, while sealing the voids and blocking the passageways for further leakage. For the above-mentioned technique, patent protection has been applied. This technique has a good application in the field because the liability for the underground petroleum storage tanks will decrease considerably when this technique is used.

Three reactive aggregates from New Brunswick, Canada, a greywacke, a gneiss, and a meta-volcanic rock were evaluated for their potential alkali reactivity (AAR) in concrete mixtures incorporating 420 kg/m 3 of cementitious materials. The concrete mixtures consisted of the control made with CSA Type 10 low- and high-alkali cements and mixtures incorporating ASTM Class F fly ash at 20, 30, and 56 percent replacement levels of the high-alkali cement. The susceptibility of the concretes to AAR was evaluated by casting test prisms and subjecting these to various accelerated curing conditions in the laboratory. For comparison purposes, mortar bars were also made and tested according to the ASTM C 1260-94 Accelerated Mortar Bar Test procedure. The AAR concrete prism tests performed in this study have shown that none of the test prisms cast from concrete mixtures incorporating 20, 30, and 56 percent fly ash showed significant expansion after two years of testing at 38 C and relative humidity >95 percent. These results were in good accordance with those obtained in the accelerated mortar bar test. Some alkaline immersion tests results would indicate, however, that concrete incorporating 20 percent fly ash might not offer adequate protection against potential deleterious expansions with highly reactive aggregates.

Presents the results of a joint project between CANMET, Ottawa, Canada, and NORCHEM Concrete Products, Inc., Hauppauge, New York, on the performance of concretes incorporating various forms of silica fume. Eleven different product forms of silica fume were used in four series of concrete with water-cementitious materials ratio of 0.40, 0.35, 0.30, and 0.22. Test specimens from the above concretes were subjected to varying curing conditions and were tested for compressive and flexural strengths, drying shrinkage, and rapid chloride permeability. It was found that, in general, the performance of the silica fume concretes in terms of mechanical properties was comparable, regardless of the silica fume product form used and the SiO 2 content of the fumes. The Rapid Chloride Permeability values, in coulombs at 41 days, a measure of the resistance of concrete to the penetration of chloride ions (AASHTO T277) for all the silica fume concretes tested except those made with silica fume blended cements, ranged from 94 to 346 coulombs, indicating very low permeability of the concretes. The values for concretes made with the blended silica fume cements were slightly higher.