Influence of water amount in efflorescence formation of the Geopolymers based on metacaulim

Abstract

Geopolymers are susceptible to efflorescence formation, which is a pathological manifestation that affects the mechanical properties and durability of geopolymers. The aim of work was to evaluate the influence of the water amount on compressive strength and efflorescence formation in the fresh state of a metakaolin-based geopolymer. Sodium hydroxide and sodium silicate were used as activators and a type of metakaolin was used as a precursor. Geopolymer materials were developed varying the total molar ratio of H2 O/Na2 O with values of 15.0, 15.5, 16.0, 16.5 and 17.0. The results showed that the water amount has a significant influence on the formation of efflorescence on the surface of geopolymers in the fresh state, i.e., the greater the molar ratio H2 O/Na2 O, the greater the area of efflorescence. Highest rate of efflorescence growth occurred approximately between 500 and 1000 minutes, after which time growth tended to stabilize. Compressive strength results showed that the water amount and the curing time significantly influenced, and the higher the molar ratio of H2 O/Na2 O, the lower the average compressive strength.