Januarti Jaya Ekaputri, Yusak Nurrizki, Ferian Anggara, Puput Risdanareni, Ipung Fitri Purwanti, I.D.A.A. Warmadewanthi, Min-Chih Liao
Employing FA in large proportionsis economically and environmentally more sustainable than regular concrete. However, a challenge arises from the non-uniform quality of FA, containing oxides that are not beneficial to concrete. This study explores low-grade FA quality enhancement through iron removal and subsequent application in green concrete. We removed iron elements from the original FA (ORI) containing 17% iron oxide. The wet magnetic separator divided the ash into low-iron fly ash (LIFA) containing 9.9% iron oxide and high-iron fly ash (HIFA) containing 21.1% iron oxide. We applied a different sequence of mixing materials as a pivotal method for HVFA concrete where alkali and CaCO3 were incorporated. A cylindrical concrete specimen with a 10 × 20 cm shape was used, featuring two variations: without bottom ash (BA) and with 50% BA as a fine aggregate substitution. The concrete strength with a target strength of 45 MPA was tested at 3, 7, 28, 56, and 90 days by replacing 50% cement with FA, using three variations: ORI without BA, ORI with BA, and LIFA with BA. Additional tests were conducted for splitting tensile strength, heat of hydration, and shrinkage. Results indicated that using low-iron fly ash (LIFA) to replace the original fly ash in HVFA increased the compressive and splitting tensile strength. It led to superior strength at both 7 and 28 days. Despite containing BA, LIFA reduced shrinkage but decreased workability. This is attributed to the smoother physical properties of LIFA, characterized by a lower specific gravity than the original fly ash, as well as the higher silica and alumina content and lower iron oxide content in LIFA © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.
Department of Civil Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia; Department of Geological Engineering, Universitas Gadjah Mada, Yogyakarta, Indonesia; Department of Civil Engineering and Planning, Universitas Negeri Malang, Malang, Indonesia; Department of Environmental Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia; Civil and Construction Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan
