Residual strength of geopolymer mortars under high temperature and freeze-thaw cycles: Effect of silica fume and alkali activator
Next Materials, cilt.13, 2026 (ESCI, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 13
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.nxmate.2026.103550
- Dergi Adı: Next Materials
- Derginin Tarandığı İndeksler: Emerging Sources Citation Index (ESCI), Scopus
- Anahtar Kelimeler: Durability effects, Geopolymer, NaOH molarity, Silica fume content
- Yıldız Teknik Üniversitesi Adresli: Evet
Özet
For this research, the influences of different silica fume (SF) incorporations (5–15%) and NaOH concentrations (8 M and 16 M) on the strength properties and durability of different ambient-cured geopolymer mortar specimens were studied under high-temperatures of 300, 600, and 900 °C and freeze-thaw attacks (100 cycles). For this aim, flowability, initial and final setting time, void ratio, and water absorption of the geopolymer mixes were determined. Compressive strength (CS), flexural strength (FS), ultrasonic pulse velocity (UPV), and weight change results were evaluated after exposure to elevated temperatures and freeze-thaw cycles. In addition, SEM, XRD, and TGA-DTA analyses were applied to observe the variations in the microstructure. The results revealed that the flowability of the mixes increased up to 10% in replacements but decreased at 15%. The initial setting time, final setting time, void ratio, and water absorption results were reduced with higher SF replacements and NaOH molarity. Also, CS, FS, and UPV values of the ambient-cured specimens enhanced with time, and these improvements were more with high SF contents and NaOH molarity. At 300°C, CS slightly enhanced (~5%), while FS significantly decreased (~50%). The losses became about 50% for CS and 70% for FS at 600°C, while 85–90% for both strengths at 900°C. Meanwhile, there was no favorable influence of SF and high NaOH molarity found on residual CS; however, residual FS was more with higher SF incorporations and NaOH molarity at elevated temperatures. After freezing-thawing cycles, the remaining performances were found to be higher with higher SF incorporations and NaOH molarity due to enhanced pore microstructure.