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Dissertation
Engineering lightweight aggregates from waste coal combustion ash and waste glass: influence of composition and sintering parameters
Doctor of Philosophy (Ph.D.), Drexel University
Aug 2025
DOI:
https://doi.org/10.17918/00011186
Abstract
Waste coal combustion ash (WCCA) and soda-lime waste glass (WG) are abundant industrial byproducts that are often landfilled, posing environmental and economic challenges. This thesis explores the sustainable conversion of WCCA and WG into engineered spherical lightweight aggregates (LWAs), with the goal of reducing waste disposal, conserving natural aggregate resources, and providing locally sourced construction materials. A thermodynamics-guided framework was adopted to predict successful sintering conditions to produce WCCA/WG-based LWAs; the sintering conditions were predicted as slag content of 45-60 wt% and slag-solid suspension viscosity of 1×10⁴-2×10⁵ Pa·s to achieve desirable LWA properties. Rapid sintering trials in a stationary furnace demonstrated that Fe₂O₃ and carbon contents in WCCA, in combination with sintering temperature, directly influence gas generation, melt viscosity, and, consequently, the porosity and strength of LWAs. Various types of WCCAs with different chemical and mineralogical compositions were tested with WG replacement up to 50 wt%. WCCAs containing high Fe₂O₃, high loss on ignition (LOI), and high amorphous content, combined with low mullite content, produced well-bloated WCCA/WG-based LWAs even with low WG content. These characteristics of WCCA enhanced iron oxide reduction, promoted partial melting of the WCCA and resulted in WCCA/WG-based LWAs with promising properties for concrete applications. The primary function of WG in LWA acts as a molten binder during sintering rather than as a fluxing agent (due to its high content of Na₂O and CaO). Furthermore, alkali-silica reaction (ASR) performance of WCCA/WG based LWAs was assessed under accelerated and semi-realistic alkali exposure conditions to evaluate the potential application for concrete applications. No visible cracking was observed in the ASR evaluation, which can be attributed to the WCCA's aluminosilicate composition reducing ASR gel formation as well as the porous structure of WCCA/WG-based LWAs providing space for the formed gel. Overall, the study demonstrates that WCCA/WG blends can be used synergistically to engineer valuable LWAs that meet ASTM specifications for concrete applications, with performance comparable to commercial LWAs. The proposed framework provides a practical approach for selecting suitable WCCA compositions for industrial-scale WCCA/WG LWA production, offering a sustainable solution for managing WCCA from diverse landfills and WG from municipal waste.
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Details
- Title
- Engineering lightweight aggregates from waste coal combustion ash and waste glass
- Creators
- Sharaniya Visvalingam
- Contributors
- Yaghoob Amir Farnam (Advisor)Yick Grace Hsuan (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xiv, i, 149 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Civil (and Architectural) Engineering [Historical]; College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991022093252504721