PFI-TT: Development of Scalable Lightweight Aggregate Manufacturing from Waste Coal Combustion Ash

Drexel University, Philadelphia PA

Investigators

Abstract

The broader impact/commercial potential of this Partnerships for Innovation-Technology Translation (PFI-TT) project is to reuse the unused or waste products of burning coal, known as coal combustion ash (CCA); this technology will convert CCA into a type of concrete called lightweight aggregate (LWA). Every year in the United States, nearly 120 million tons of CCA are generated, of which only 40% is reused; few recycling avenues exist for the remaining CCA, affecting the environment and human health. Simultaneously, increased demand for LWA has impacted costs in the concrete and geotechnical industries. Converting CCA to value-added LWA addresses not only the CCA risk, but both these factors at once by developing a product with improved physical performance at lower costs. CCA is abundantly available in the United States, and LWA can be produced near its markets. This project will also encourage students, including underrepresented minorities and females, in engineering. The proposed project will formulate, develop and validate an innovative scalable thermodynamic-based manufacturing technology that can be used to produce sustainable LWA from unused/waste CCA. Using thermodynamic principles and phase equilibria, sintering process of CCA will be tuned to partially melt the oxide compounds of CCA and subsequently combust emitted gas during sintering to create porous CCA-based LWA materials. The developed technology will enable identification of optimized raw material blending, appropriate fluxing agent selections, and the sintering process despite CCA heterogeneity, chemical composition and diversity, allowing conversion of significant amount of unused and waste CCA into value-added CCA-based LWA. This project will develop the technology by (1) looking at the chemical interactions between various types and dosages of CCA and fluxing agents to produce LWA, (2) identifying the thermodynamics of phase equilibria as a function of temperature during sintering as dosage and compositions of CCA vary and (3) preparing a robust technology guideline calibrated with experimental laboratory pilot-scale works. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.