Air-cooled slag derived from municipal solid waste (MSW) and sewage sludge as coarse aggregate for sustainable construction

• Main Author: Tan, Jun Ying
• Other Authors: Grzegorz Lisak
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; Environmental Engineering
• Online Access: https://hdl.handle.net/10356/177434
• Institution: Nanyang Technological University

This final year project explores the potential of utilizing air-cooled slag from municipal solid waste (MSW) and sewage sludge as substitutes for traditional coarse aggregates in concrete production, addressing environmental concerns like air & water pollution and solid waste generation within the construction industry. This project analyses the physical properties, chemical compositions, and environmental impacts of incorporating air-cooled slag into concrete mixtures. Through crushing and sieving, the slag is classified into three particle size fractions: 10-20 mm, 5-10 mm, and less than 5 mm in diameter. The study encompasses six different concrete mix formulations, primarily investigating three distinct cooling methods (Control, Fan-Cooled, and Insulated) applied to two types of samples (municipal solid waste (MSW) and sewage sludge derived slags). Chemical tests like XRF, XRD, ICP-OES and ICP-MS and physical tests like LA abrasion, slump and compressive strength test were conducted in order to evaluate the suitability of air-cooled slag as replacement for coarse aggregates. X-ray fluorescence (XRF) analysis reveals that the composition of MSW and sewage sludge exhibits relatively similar percentages of oxides, including CaO, SiO2, Al2O3, and FeO. Additionally, ICP-OES and MS analyses were conducted, indicating that MSW slag samples exhibit lower occurrences of elements surpassing NEA reference values, suggesting a safer profile as a construction material. To evaluate resistance to abrasion and wear, the samples underwent Los Angeles (LA) abrasion tests, demonstrating compliance with road base material requirements for both MSW and sewage sludge slag. Notably, the slump height of sewage sludge slag in concrete was observed to be lower compared to MSW slag, attributed to its higher water absorption and resulting in drier mixtures. Further assessment of crystallinity through X-Ray Diffraction (XRD) testing revealed higher levels of crystallinity in MSW slag compared to sewage sludge slag. Moreover, compressive strength testing indicated that fan-cooled samples exhibited the highest compressive strength among the three cooling rates, indicating the influence of elevated iron content and slag morphology on this phenomenon. In conclusion, this study advocates for the viability of sewage sludge slag as a substitute for gravel in coarse aggregate applications and MSW slag as a feasible alternative to sand for fine aggregate applications. These findings present a compelling case for a more environmentally sustainable approach to concrete production.