In recent decades, much research on new materials for civil engineering has emerged. The aim of those research studies is to replace Portland cement due to its high environmental cost. Materials with high performance for that matter are alkali-activated materials [
1]. These new types of binder material have obtained good results in terms of mechanical strength and durability [
2], but their properties depend on raw materials used and their provenance.
In this study, a comparison was made between the uses of different slags as raw materials: black steel slag, ladle furnace slag, copper slag, and ferrosilicon slag. One-hundred percent of slag was used as a precursor, and the activator was a mixer with different proportions of KOH (8M) and K2SiO3: 35–65, 50–50, 65–35, and 75–25 (% KOH-% K2SiO3). The precursor and activator were mixed in a mixer, and they were poured into prismatic (10 × 10 × 60 mm) and cylindrical (diameter 25mm) molds. After one day, pastes were demolded, and they were cured in climatic chamber for 7, 28, and 90 days for testing. In addition, at 28 days of curing, pastes were attacked by different solutions in order to verify the durability of pastes.
Pastes manufactured were characterized after and before attack by mechanical strength, thermal conductivity, ATR-FTIR (Vertex 70 Bruker, Billerica, MA, USA), XRD (Empyrean equipment with PANalytical PIXcel-3D detector, Malvern, UK), and SEM-EDS (JEAL model SM 840, Peabody, MA, USA).
The optimal activator was different for each precursor, highlighting copper slags such as the precursor. The same behavior was verified with durability tests by comparing the percentage losses of properties.
Author Contributions
Conceptualization, M.Á.G.C. and D.E.-Q.; methodology, M.Á.G.C.; investigation, M.Á.G.C.; resources, D.E.-Q.; data curation, M.Á.G.C.; writing—original draft preparation, M.Á.G.C.; writing—review and editing, M.Á.G.C., L.P.-V., P.J.S.-S. and D.E.-Q.; supervision, D.E.-Q.; project administration, D.E.-Q.; funding acquisition, D.E.-Q. All authors have read and agreed to the published version of the manuscript.
Funding
This work has been funded by the project PID2020-115161RB-I00: Applying the circular economy in the development of new low carbon footprint alkaline activated hydraulic binders for construc-tion solutions (CongActiva), MCIN/AEI/ 10.13039/501100011033 FEDER “A way of making Europe”. M.A. Gómez-Casero acknowledges support of MINECO (PRE2018-084073).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The datasets generated during and analysed during the current study are available from the corresponding author on reasonable request.
Acknowledgments
The authors thank Siderúrgica Sevillana Company, Atlantic Copper Company, and Ferroatlántica (XEAL) Company for supplying slags. M.A. Gómez-Casero acknowledges the support of MINECO (PRE2018-084073). Technical and human support provided by CICT of University of Jaén (UJA, MINECO, Junta de Andalucía, FEDER) is gratefully acknowledged.
Conflicts of Interest
The authors declare no conflict of interest.
References
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