Effects of perlite/fly ash ratio and the curing conditions on the mechanical and microstructural properties of geopolymers subjected to elevated temperatures

This paper investigated the mechanical and microstructural properties of geopolymer mortars before and after elevated temperature exposure. The mortars were based on blends of finely ground raw perlite (RP) and Class F fly ash (FA). RP-FA blends were alkali-activated with 10 M NaOH solution. The synthesis of geopolymer mortars was conducted at 90 degrees C during 4, 8, and 24 h, with different RP/FA mass ratios (100/0; 75/25; 50/50; 25/75; 0/100). Several experiments regarding the hardened properties were performed after curing for 7, 28 and 90 days. After curing, the geopolymer mortars were heated up to elevated temperatures of 400 degrees C, 600 degrees C, and 800 degrees C, separately. Influence of elevated temperature on the geopolymer properties were determined in terms of the mass loss, strength loss, and alterations in the microstructures after exposure to elevated temperatures. The best results were observed on the geopolymer mortars made with the RP/FA mass ratio of 25/75. The flexural and compressive strength values of the mortars after exposure to 800 degrees C were higher than the values after exposure to 600 degrees C. New crystalline phases were detected in the mortars after being subjected to 800 degrees C.

Automated summary

This paper investigated the mechanical and microstructural properties of geopolymer mortars made from RP and FA blends before and after exposure to elevated temperatures. The results showed that the mortars with a RP/FA mass ratio of 25/75 exhibited better performance after high temperature exposure, with higher flexural and compressive strength values at 800 degrees C compared to 600 degrees C.