Effect of Silica Fume and Activator Concentration on Metakaolin Geopolymer Exposed to Thermal Loads
Alaa M. Rashad and Sayieda R. Zeedan
Appears on pages(s):
activator concentration; compressive strength; elevated temperatures; flowability, metakaolin; silica fume
There are inconsistent results of the previous studies that focused on the effect of elevated temperatures on metakaolin (MK) geopolymers. Likewise, some studies reported a positive effect of silica fume (SF) on the compressive strength of MK geopolymers, whilst others reported a negative effect. In this paper, the authors tried to get suitable reasons for these contradictions. Therefore, two different concentrations of sodium silicate and different ratios of SF that affect the Si/Al and Na/Si molar ratios were used. For each concentration of activator, MK was partially replaced with 5-25 wt.% SF. The flowability was measured. The compressive strength of the specimens before and after exposure to 400-1000 °C was recorded. The results were analyzed by different techniques. The results showed higher flowability with the inclusion of SF. The incorporation of SF may increase or decrease the compressive strength before and after heating. This depends on activator concentration (i.e Si/Al and Na/Si).