Optimal design of glazed hollow bead thermal insulation mortar containing fly ash and slag based on response surface methodology

Fly ash (FA) and slag could improve the performance of glazed hollow bead (GHB) thermal insulation mortar, but little research touched on how the FA and slag affect its performance and optimize its component contents. In this study, an experimental and statistical investigation is conducted to analyze the influences of FA and slag variables on the performance of GHB mortar based on the response surface methodology (RSM). The predicted model was proved statistically significant in terms of the fluidity, compressive strength, flexural strength, and thermal conductivity. Then, the validated model was used to identify the critical parameters and discuss their mechanisms of action. It can be found that (i) FA plays a significant role in fluidity and compressive and flexural strength owing to its morphological and physical filler effects; (ii) slag has an obvious influence on compressive strength and thermal conductivity due to its microaggregate effect. Finally, optimization design was conducted using the desirability approach of RSM to give the optimal component of 20.73% FA and 21.49% slag. The predicted combination was validated by confirmatory tests within an error of 1.52%. This study provides a feasible and effective solution for optimizing GHB thermal insulation mortar to achieve higher performance.