Behaviour of Geopolymer Mortars after Exposure to Elevated Temperatures


  • Mehmet KAYA Bozok University
  • Mücteba UYSAL İstanbul Univertsity
  • Kemalettin YILMAZ Sakarya University
  • Cengiz Duran ATIS Prof. Dr. Cengiz Duran ATİŞ Erciyes University, Civil Engineering Department, Kayseri 38280, Turkey.



geopolymer, flexural strength, compressive strength, ultrasound pulse velocity, elevated temperature


In this study it was investigated the behavior of class F fly ash based geopolymer mortars subjected to elevated temperatures. Geopolimer composites were prepared with CEN-sand, water, fly ash as the binder, nSiO2Na2O and NaOH mixture combination as alkali activator. After mixing fresh geopolymer mixture, prismatic specimens were prepared using 40 mm × 40 mm × 160 mm prism molds. After molding, fresh geopolymer mortar samples with their mold were subjected to heat curing at 50 °C, 60 °C, 70 °C, 80 °C, 90 °C and 100 °C temperature for 48 hours in an oven. After 48 hours initial heat curing, the hardened samples were taken out of their mold. Then, they were further cured by leaving them in laboratory environment at about 22 ± 2 °C temperature, until 28 days together with heat curing duration. At the end of 28 days, geopolymer mortar samples developed flexural strength values between 2,9 MPa and 8,51 MPa. Geopolymer mortar samples developed compressive strength values between 7,63 MPa and 50,64 MPa. High temperature experiments were conducted to observe behaviour of geopolymer mortars at elevated temperatures. The control cement mortar mixtures were also prepared and subjected to high temperature exposure in comparison to geopolymer mortar mixtures. Control cement mortars were cured at laboratory environment for 28 days without initial temperature curing. Control cement mortar mixtures and geopolymer mortar mixtures were exposed to elevated temperatures of 200 °C, 400 °C, 600 °C and 800 °C temperature. The unit weight, ultrasonic pulse velocity, flexural and compressive strength of all mixtures were measured before and after high temperature exposure. Scanning electron microscope (SEM) images of the mixtures were taken and X-ray fluorescence (XRF) spectrometer analyses were carried out. It was observed that there was an increase in the flexural and compressive strengths of some geopolymer mortars after high temperature exposure. In general, geopolymer mortars exhibited better performance at elevated temperatures in comparison to control cement mortar mixture.


Author Biographies

Mehmet KAYA, Bozok University

Assist. Prof.Dr. Mehmet KAYA

Bozok University, Occupational Health and Safety Department, Yozgat 66200, Turkey.



Mücteba UYSAL, İstanbul Univertsity

Associate Prof. Dr. Mücteba UYSAL

İstanbul University, Civil Engineering Department, İstanbul 34320 Turkey.


Kemalettin YILMAZ, Sakarya University

Prof. Dr. kemalettin YILMAZ

Sakarya University, Civil Engineering Department, Sakarya 54187, Turkey.