Date of Graduation
Bachelor of Science in Civil Engineering
Fly ash is the residue produced from coal combustion in electric generating plants. There are two types of fly ash, Class C and Class F. Approximately 40 percent of fly ash generated from coal combustion can be used as a partial replacement of cement in concrete. Incorporating fly ash improves concrete properties and extends its service life. Alkali-silica reaction (ASR) is an expansive reaction between reactive silica typically found in aggregates (rock and sand) and alkalis in cement. This reaction results in the formation of a gel that absorbs water and swells, which exerts an internal pressure in concrete. This pressure leads to cracking and premature deterioration of the structure. ASR can be prevented by replacing approximately 15 to 25 percent by mass of the cement with Class F fly ash. Class F fly ash is more effective in preventing ASR than Class C fly ash due to its chemical composition. Sources of Class F fly ash are limited in the State of Arkansas, and occurrences of ASR are increasing. Preliminary results show that cement replacement rates, ranging from 20 to 40 percent of Class C fly ash, effectively control ASR.
Dickson, Sydney Marie, "Alkali-silica reaction mitigation using high volume Class C fly ash" (2015). Civil Engineering Undergraduate Honors Theses. 24.