Sürdürülebilir Kalkınma Amaçları
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- MakaleAçık Erişim2026Scopus SJRQ1Sustainable hybrid activation: Synergistic effects and optimization of one-part alkali-activated slag using sodium sulfate and sodium carbonate
Orhan, Taha Yusuf; Balun, Bilal; Dener, Murat; Karataş, Mehmet
The development of one-part alkali-activated materials (AAMs) using near-neutral and moderately alkaline salts offers a promising, low-carbon alternative to hazardous two-part systems. However, overcoming delayed reaction kinetics and setting anomalies remains a critical challenge. This study systematically investigates the fresh state, mechanical, and microstructural evolution of one-part slag mortars activated by sodium sulfate (Na2SO4), sodium carbonate (Na2CO3), and their hybrid combinations, adopting a hybrid binder approach through modification with calcium-rich additives (Portland cement, hydrated lime, and quicklime). Results demonstrate that while Portland cement ensures a controlled dissolution rate and balanced setting times across all environments, the incorporation of 7.5% quicklime in pure carbonate media triggers an instantaneous flash set. This extreme reactivity leads to a severe structural collapse, plunging the 90-day compressive strength to 16.11 MPa. Microstructural analyses (TGA and FTIR) suggest a link between this mechanical failure and a massive accumulation of unreacted portlandite (4.51% mass loss) rather than cohesive C-(A)-S-H gel formation, a degradation further corroborated by a drastic attenuation in ultrasonic pulse velocity (UPV). Conversely, the synergistic implementation of hybrid sulfate-carbonate activators effectively mitigates these anomalies. Sulfate ions buffer early-age kinetics to prevent flash setting-recovering the collapsed strength up to 29.16 MPa while carbonate ions facilitate sustained late-age matrix densification. Ultimately, tailoring specific calcium boosters within a hybrid activator framework presents a highly robust and potentially low-carbon framework for developing sustainable binders for practical on-site construction applications.
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İncele - MakaleYalnız künye2024Scopus SJRQ2Factors Affecting the Setting Times of Pumice Based Alkali-Activated Hybrid Cements
Balun, Bilal; Karataş, Mehmet
The environmental impacts of ordinary Portland cement (OPC) production have led researchers to produce alternative binders. Binders with aluminosilicate structure, such as pumice, can be used to produce one of these alternatives, alkali-activated cements. In addition, alkali-activated hybrid cements have become a type of material that combines the positive aspects of geopolymers and Portland cement. Especially in the activation of low CaO containing materials such as pumice with alkalis, the use of a small amount of OPC ensures that the alkali-activated materials can both be produced under ambient conditions and improves its strength properties. In this study, setting times of pumiced based alkali-activated hybrid cements were evaluated based on OPC amount (0%, 5%, 10%, 15% and 20%), alkaline solution/binder ratio (0.47, 0.50 and 0.53) and sodium silicate/potassium hydroxide (1, 2 and 3) ratio. In experiments carried out under ambient conditions, the silica module (2.0) of the sodium silicate solution was kept constant. As a result of the experimental studies, the increase in the OPC amount and the sodium silicate ratio shortened the setting times of the pumiced based alkali-activated hybrid materials while the alkali solution/binder ratio increased the setting times. It was determined that the factor most affects the setting times was the OPC amount. The setting time of the OPC-free pumice-based alkali-activated binders without OPC takes more than one day. As a result, increasing the amount of OPC up to 20% significantly reduced the setting times. A decreasing trend was observed in compressive strengths with increasing setting times.
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