Title:
The Re-Use and Beneficiation of Industrial Waste Products into New Sources of Supplementary Cementitious Materials
The Re-Use and Beneficiation of Industrial Waste Products into New Sources of Supplementary Cementitious Materials
Author(s)
Benkeser, Daniel J.
Advisor(s)
Kurtis, Kimberly E.
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Abstract
This research examines the re-use and beneficiation of industrial waste byproducts, primarily for use as supplementary cementitious materials (SCMs). Reducing cement clinker content in concrete is a significant strategy to meet the industry's de-carbonization goals. This combined with the decreasing supply of traditional SCMs, such as coal fly ash, is creating a need for new sources of SCMs at a scale consistent with the 20 billion tons of concrete produced annually. For this purpose certain sources of industrial waste are ideal for this purpose after being processed (via crushing and calcination).
The first half of this work primarily focuses on the potential re-use of two such sources: ponded coal combustion products (CCPs) and dredged river sediment. Potentially reactive phases, primarily fly ash for the CCP and kaolinite/diatoms for the calcined sediment, were identified allowing for the development of processes necessary to activate these phases. The reactivity of these SCMs was primarily determined via heat release and Ca(OH)2 content of blended cement pastes. While performance was measured through comparisons to existing specifications (ASTM C618, Class F fly ash and Class N Pozzolans) and ASR mitigation. Results indicate that both sources are moderately reactive and demonstrate the ability to pass ASTM specifications, but possess numerous physical drawbacks which limit their usability. Primarily their high levels of crystallization and low workability.
The second half of this work focuses on the development of beneficiation techniques, chemi-mechanical grinding and spray drying, to mitigate the negative effects of these materials. Chemi-mechanical grinding improves pozzolanic reactivity through reductions in crystallinity and particle size along with increasing the number of terminal silanol groups in the particles, which act as reaction sites for the pozzolanic reaction.While spray drying improves the workability of SCMs by altering particle morphology into spherical agglomerations. Which helps reduce internal friction similar to the "ball bearing" effect seen in fly ash.
Recommendations were made suggesting potential uses for these industrial waste sources and potential changes to existing standards to make better use of these materials.
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Date Issued
2024-04-02
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Text
Resource Subtype
Dissertation