Fiber-reinforced alkali-activated cements from ceramic waste and ladle furnace slag without thermal curing

• Published in: Journal of Materials in Civil Engineering
• Main Authors: Gaibor, Norma, Leitão, Dinis, Miranda, Tiago F. S., Cristelo, Nuno, Fernandes, Lisete, Pereira, E. N. B., Cunha, Vitor M. C. F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Society of Civil Engineers (ASCE) 2023
• Subjects: Ambient curing; Industrial wastes; Physical and mechanical properties; Polyacrylonitrile fiber; Workability; Engenharia e Tecnologia::Engenharia Civil; Indústria; inovação e infraestruturas; Norway; Iceland
• Online Access: https://hdl.handle.net/1822/86431; https://doi.org/10.1061/JMCEE7.MTENG-14776

Alkaline-activated cement, as an alternative to conventional portland cement, is being increasingly studied due to its environmental advantages and engineering properties. However, research on the feasibility of using both uncommon precursors and curing at ambient temperature is still limited. This study aims to investigate the potential of ceramic wastes, specifically from brick and tile production and ladle furnace slag, as precursors in alkaline activated cement reinforced with polyacrylonitrile fibers cured at 20°C. Sodium silicate, in solution form, was used to activate the precursors, and three different fiber contents were tested, namely 0%, 0.5%, and 1%, by volume. Physical properties, such as capillarity and porosity, were assessed. Moreover, the mechanical behavior was thoroughly characterized by uniaxial compressive, flexural, and elasticity modulus tests. In addition, a thorough microstructural characterization, including scanning electron microscopy, X-ray energy dispersive analyzer, X-ray diffraction, and Fourier transform infrared spectroscopy was conducted at 14, 28, and 90 days. The results revealed that environmentally friendly alkali-activated binders were produced from wastes with limited industrial recycling possibilities. The mixture with 0.5% fibers was the one that presented better results, i.e., a flexural strength of 8.84 N/mm2 and compressive strength of ∼29 MPa at 90 days. The mechanical performance of this material is relevant, especially considering that a relatively low curing temperature was applied. The results also showed that calcium aluminum silicate hydrate (C-A-S-H) was detected as the main reaction product. This work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020, and the research project CirMat: CIRcular aggregates for sustainable road and building MATerials (ref. 16_Call#2) is funded by Iceland, Liechtenstein and Norway ...