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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 18 Abstracts search results
October 1, 2004
Leonard Pepper and Bryant Mather
Twenty materials, representing eight different classes of mineral admixtures, were evaluated, using both chemical and mortar-bar test methods, for their effectiveness in preventing excessive expansion of concrete due to alkali-aggregate reaction. It was found that the chemical tests cannot be used with reliance to evaluate effectiveness. Each of the replacement materials evaluated will prevent excessive expansion if a sufficient quantity is used. Correlations were found between effectiveness and: fineness, dissolved silica, and percentage of alkali retained by reaction product. Five of the materials tested (a fly ash, a tuff, a calcined shale, a calcined diatomite, and an uncalcined diatomite) showed a reduction in alkalinity of 40 percent or more when tested by the quick chemical test. All of these except the fly ash met the requirement proposed by Moran and Gilliland for the relationship between reduction in alkalinity and silica solubility. Six of the materials tested (two slags, a fly ash, a pumicite, and two calcined shales) reduced mortarbar expansion at least 75 percent with high-alkali cement and Pyrex glass aggregates when used as 50, 45, 35, and 30 percent replacements of the cement. Calculations were made that suggest that the minimum quantity of each material required for effective prevention of excessive expansion ranged from 10 percent for the synthetic silica glass to 45 percent for one of the slags. By groups, these calculated minimum percentages were: calcined shales, 19 to 29; uncalcined diatomite, 22; volcanic glasses, 32 to 36; slags, 39 to 45; and fly ashes, 40 to 44. The investigation of mineral ad-mixtures as cement-replacement materials was initiated by the Office of the Chief of Engineers in 1950 as part of the Civil Works Investigations Program with the purpose of ascertaining the degree to which portland cement may be advantageously replaced by other materials, considering cost and the quality of the resulting concrete. This paper deals with that part of the investigation that was concerned with the ability of these materials to prevent excessive expansion of concrete due to alkali-aggregate reaction.
Concrete will be immune to the effects of freezing and thawing if (1) it is not in an environment where freezing and thawing take place so as to cause freezable water in the concrete to freeze, (2) when freezing takes place there are no pores in the concrete large enough to hold freezable water (i.e., no capillary cavities), (3) during freezing of freezable water, the pores containing freezable water are never more than 91 percent filled, i.e., not critically saturated, (4) during freezing of freezable water the pores containing freezable water are more than 91 percent full, the paste has an air-void system with an air bubble located not more than 0.2 mm (0.008 in.) from anywhere (L = 0.2 mm), sound aggregate, and moderate maturity. Sound aggregate is aggregate that does not contain significant amounts of accessible capillary pore space that is likely to be critically saturated when freezing occurs. The way to establish that such is the case, is to subject properly air-entrained, properly mature concrete, made with the aggregate in question, to an appropriate laboratory freezing-and-thawing test such as ASTM C 666 Procedure A. Moderate maturity means that the originally mixing water-filled space has been reduced by cement hydration so that the remaining capillary porosity that can hold freezable water is a small enough fractional volume of the paste so that the expansion of the water on freezing can be accommodated by the air-void system. Such maturity was shown by Klieger in 1956 to have been attained when the compressive strength reaches about 4,000 psi.
No one could question the appropriateness of "Research on Concrete" as a topic for a Stanton Walker Lecture on the Materials Sciences. Research, according to Webster’s Dictionary, is "critical and exhaustive investigation or experimentation having as its aim the discovery of new facts and their correct interpretation; the revision of accepted conclusions, theories, or laws, in the light of newly discovered facts; or the practical applications of such new or revised conclusions." Dr. Bates noted, in the first of these lectures in 1963,1 that it had recently been said that "concrete is not a material, it is a process." However, in 1967, when the American Concrete Institute finally got around to publishing an official definition of concrete,2 hat definition read: "A composite material which consists essentially of a binding medium within which are embedded particles or fragments of aggregate; in portland cement concrete, the binder is a mixture of portland cement and water."
Douglas Southall Freeman’s authoritative biography of Robert E. Lee has a chapter on the building of Fort Carroll in the middle of Baltimore Harbor in 1849-1852. In the spring of that year, Lee established that there was a stable hard surface 45 ft below low water and began to work on the construction. These preliminary activities, as recounted by Freeman, included the following: "He experimented in the laying of concrete under water with a tremie." Lee continued with the work until August 1852 when he was sent to be Commandant at West Point. By then some concrete had been placed in Fort Carroll. Lee received information from General Totten on 22 June 1849 on placing concrete with a tremie. Lee replied on 25 June, "I shall make experiments to test the tremie preparatory to laying foundations." These experiments are among the earliest bits of concrete research done in the USA.
Editors: Celik Ozyildirim and Shuaib Ahmad
"In October 2000, the American Concrete Institute’s Technical Activities Committee approved publication of a commemorative compilation honoring Bryant Mather for his significant contributions to concrete technology. This publication, Investigating Concrete—Selected Works of Bryant and Katharine Mather, is the result of a cooperative effort by Mather, Celik Ozyildirim, and ACI Chief Engineer Shuaib Ahmad. It is divided into seven parts: potential of concrete; cementitious materials; aggregates; durability of concrete; petrographic examination of aggregates and concrete; specifications for use of concrete in transportation structures; and research and emerging technologies. This publication also includes an appendix with a bibliography of selected works of Bryant and Katharine Mather."
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