Effect of Silicate Fume -Based Activating Solution on Mechanical Properties of Fly Ash/Silica Fume Geopolymer Concrete

Abdel Aziz, Yasmin Hefni; El Malky, Abeer

doi:10.21608/jesaun.2025.383265.1506

Effect of Silicate Fume -Based Activating Solution on Mechanical Properties of Fly Ash/Silica Fume Geopolymer Concrete

Document Type : Research Paper

Authors

¹ Civil Engineering Department, Faculty of Engineering, Modern University for Technology &amp; Information, Cairo, Egypt

² Civil Engineering Department, Faculty of Engineering, Modern University for Technology & Information, Cairo, Egypt

10.21608/jesaun.2025.383265.1506

Abstract

This study introduces a novel approach by entirely substituting commercial Soduim Silicate (Na₂SiO₃) with silica fume (SF), an industrial by-product, to create economical and eco-friendly GC. Fly ash (FA) was partially substituted with SF at proportions of 20%, 25%, 30%, and 35% of the total binder weight to assess its impact on mechanical performance. The alkaline activator solution was employed at 30%, 35%, and 40% of binder weight, with different SF/NaOH ratios (0.75, 1.5, and 2.0) to enhance the activation process. Treated rubber fibers (0.3% by binder weight) were included to improve ductility. The workability and mechanical properties were assessed using slump, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity tests. Test results indicated that higher SF replacements diminished workability and strength, with a 25% substitution yielding optimal results. The SF-based activator demonstrated comparable strength to traditional methods, attaining optimal performance at an SF/NaOH ratio of 1.5. The inclusion of rubber fibers enhanced the elastic modulus by 10.8%. Microstructural analysis using SEM and EDX confirmed the formation of a denser matrix with fewer cracks and improved bonding. This research presents a viable alternative to commercial activators and proposes a sustainable GC mix design utilizing industrial by-products, contributing to more eco-friendly construction materials.

Keywords

Main Subjects

Civil Engineering: structural, Geotechnical, reinforced concrete and steel structures, Surveying, Road and traffic engineering, water resources, Irrigation structures, Environmental and sanitary engineering, Hydraulic, Railway, construction Management.

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