Effects of steel slag fineness and MEROS ash on GGBFS-based geopolymers

Mahfuz Pekgöz; İlker  Tekin

doi:10.7764/RDLC.24.3.582

Authors

Mahfuz Pekgöz Civil Engineering Department, Karabük University, Karabük (Turkey)
İlker Tekin Civil Engineering Department, Karabük University, Karabük (Turkey)

DOI:

https://doi.org/10.7764/RDLC.24.3.582

Keywords:

Steel slag, MEROS® ash, ground granulated blast furnace slag, geopolymer, microstructure.

Abstract

In this study, magnetic and non-magnetic steel slag (SS) and ground granulated blast furnace slag (GGBFS) with two different fineness levels were utilized in the production of geopolymers. In the synthesis of geopolymers, a triple alkaline activator comprising MEROS® ash (MA), a by-product of the iron and steel industry, in combination with Na₂SiO_3(aq) and NaOH, was employed. Workability was conducted on fresh geopolymers, while compressive strength, water absorption, shrinkage, and microstructural analyses were performed on hardened geopolymers. The experimental findings demonstrate that the physical, mechanical, and microstructural properties of geopolymers produced with coarse (<1 mm) and fine (<125 µm) SS particles were comparable; however, the grinding process for coarse SS was approximately 9.6 times more energy-efficient than that for fine SS, thereby demonstrating a significant advantage in energy savings. The presence of magnetic and non-magnetic steel slag, with particle sizes smaller than 1 mm, has been shown to reduce shrinkage in geopolymers. The MA significantly enhances compressive strength and workability. The highest compressive strengths were obtained on the Mc2s, which was produced using magnetic steel slag with a size of less than 1 mm and 5% sintering ash, reaching 48.85 MPa at 2 day and 62.0 MPa at 28 day. The microstructure analysis indicates that geopolymer gels, such as C-S-H and C(N)-A-S-H, contain sulfur forms derived from the MA. This work differs from previous SS/GGBFS geopolymer studies by systematically comparing magnetic and non-magnetic steel slag at different fineness levels and by quantifying the energy savings achieved through the use of MEROS® ash in a ternary activator system.

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