Masters Theses

Keywords and Phrases

Cement Paste; Compressive Strength; Fly Ash; Heat of Hydration; Miniature Slump; Setting Time

Abstract

"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.

Advisor(s)

Richardson, David Newton

Committee Member(s)

Volz, Jeffery S
Myers, John

Department(s)

Civil, Architectural and Environmental Engineering

Degree Name

M.S. in Civil Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2012

Pagination

xiv, 235 pages

Note about bibliography

Includes bibliographical references (page 42).

Rights

© 2012 Karl Wehking Beckemeier, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Library of Congress Subject Headings

Fly ash
Concrete -- Additives
Reinforced concrete -- Testing

Thesis Number

T 10085

Electronic OCLC #

828736466

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