Keywords and Phrases
Cement Paste; Compressive Strength; Fly Ash; Heat of Hydration; Miniature Slump; Setting Time
"The study of high-volume fly ash (HVFA) concrete mixtures has become popular due to the significant environmental and economic benefits which the material may provide. By including fly ash at 50 percent or greater replacement levels, substantial benefits could be obtained. However, the inclusion of fly ash can have negative effects, including incompatibilities between constituents of a mixture. As the fly ash replacement level increases, the degree and likelihood of these problems increases.
In this study, paste mixtures were made, as part of a larger HVFA concrete study, in order to determine the degree to which varying levels of fly ash would affect the paste mixtures and to determine potential methods of mitigating the negative effects of high volumes of fly ash on concrete mixtures. Five Type I or I/II portland cements were tested in combination with five Class C fly ashes at 0, 25, 50, and 70 percent replacement levels. The effects of gypsum, calcium hydroxide, and rapid set cement additions were evaluated at fly ash replacement levels of 50 and 70 percent, and the effects of a Type A/F water-reducing admixture were examined for all fly ash replacement levels. The paste properties that were evaluated included compressive strength, heat of hydration, consistency, and setting time.
Analysis of the results showed general trends for increasing fly ash replacement levels, such as slower strength gain, decreased heat of hydration, delayed setting times, and increased fluidity of the paste at very early ages. However, there were also many inconsistencies in the results, which were attributable to sulfate imbalances and increased aluminate hydration at early ages. It was found that, in many cases, these sulfate imbalances were lessened by the addition of gypsum. The additions of calcium hydroxide and rapid set cement also showed improvements, such as increased rates of strength gain and accelerated setting times"--Abstract, page iii.
Richardson, David Newton
Volz, Jeffery S
Civil, Architectural and Environmental Engineering
M.S. in Civil Engineering
Missouri University of Science and Technology
xiv, 235 pages
© 2012 Karl Wehking Beckemeier, All rights reserved.
Thesis - Open Access
Concrete -- Additives
Reinforced concrete -- Testing
Electronic OCLC #
Beckemeier, Karl Wehking, "Effects of high volumes of fly ash on cement paste" (2012). Masters Theses. 6942.