Effects of early microwave curing on physical and mechanical properties of slag based geopolymer mortars

This study examines the effect of early microwave curing on the physical and mechanical properties of slag (GGBS) based geopolymer mortars. Rapid strength boosting effect of microwave curing applications on slag based geopolymers promise them to be useful on construction applications including repairing. However, there are two main parameters of microwave curing highly influence the mechanical characteristics of geopolymers: energy level and curing duration. Therefore, prepared specimens were exposed various microwave energy levels (300W-450W-800W) with different curing duration such as 10-15-30-60 minutes just after demolding from molds after 1 day from casting. Firstly, fresh properties such as workability and density were performed at fresh state. Both cured and uncured specimens were kept in laboratory conditions until the day of compressive strength testing. Furthermore, SEM and EDS analyses were also performed on selected specimens since microwave energy and/or curing duration may affect the chemical and physical properties of geopolymer. It was found that strengths of specimens were exposed to microwave curing increased enormously at early stages especially with longer time of curing such as 300W microwave radiation for 60 minutes. Also, there is almost no color change was relatively observed on these specimens. Although 800W curing increased the strength by 8 times in 1 day even in a very short time as much as 15 minutes, 28 days compressive strength results indicate that 800W energy resulted deleterious and is not applicable.