Fixated flue gas desulfurization scrubber sludge-ground granulated blast-furnace slag blends as one-part sustainable binders

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Seyedian Choubi S., Akgül Ç.

Construction and Building Materials, vol.462, 2025 (SCI-Expanded) identifier

  • Publication Type: Article / Article
  • Volume: 462
  • Publication Date: 2025
  • Doi Number: 10.1016/j.conbuildmat.2024.139517
  • Journal Name: Construction and Building Materials
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, CAB Abstracts, Communication Abstracts, Compendex, INSPEC, Metadex, Veterinary Science Database, Civil Engineering Abstracts
  • Keywords: Fixated flue gas desulfurization scrubber sludge, Ground granulated blast-furnace slag, Mechanical performance, Microstructural characterization, One-part binders, Setting time, Water stability
  • Middle East Technical University Affiliated: Yes

Abstract

This study investigates the performance of one-part sustainable binders composed of fixated flue gas desulfurization scrubber sludge (FSS) and medium-quality ground granulated blast furnace slag (BFS), both of which are underutilized industrial by-products. FSS, an inexpensive and sustainable sulfate source, enhances the reactivity of medium-quality BFS, enabling the development of 100 % waste-based binders without the need for chemical activators or thermal treatment. The inherent alkalinity and rich composition of calcium, silicon, aluminum, and sulfur in FSS effectively compensate for the shortcomings of medium-quality BFS, particularly its low early reactivity. Blending BFS with FSS yielded higher pH levels, shorter setting times, and significantly improved long-term compressive strengths. Blends with over 50 wt% FSS achieved 90-day compressive strengths of 50–55 MPa, compared to only 6 MPa for BFS-only mixes, although higher FSS contents reduced early age strength and water stability. Microstructural analysis using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) revealed ettringite and C-S-H/C-A-S-H as the primary hydration products. Thermal exposure tests revelated a decrease in strength due to the decomposition of these phases. The synergistic utilization of these underused waste materials enhanced their potential for reuse and supports a circular economy in the construction industry.