Experimental modal analysis of fly ash-based geopolymer concrete specimens via modal circles, mode indication functions, and mode shape animations

The polymerization process of geopolymer concrete is entirely different from the hydration process of ordinary Portland cement concrete. Therefore, it is necessary to re-examine this new material's engineering properties from the ground up. To date, researchers have investigated many engineering properties, but in the whole literature, the available information about the modal characteristics is minimal. Additionally, since the evaluations in the literature are made only on the A ratio (sodium silicate to sodium hydroxide ratio), no significant relationship has been reported between damping and activators. So, this study is conducted to draw attention to this gap in the literature and examine the effect of fundamental geopolymer concrete component ratios on modal characteristics. For these purposes, large-scale heat-cured low-calcium fly ash-based geopolymer concrete mix variations are produced and investigated by performing experimental modal analysis via the advanced modal circle method and mode indication functions. It is found that individually analyzing the total amount of water from the activators and the pure chemical dosages provides more meaningful results than the traditional A ratio. According to the analysis from this perspective, increasing the dosage of pure sodium silicate in the mixture generally increases the damping; on the other hand, it decreases the resonance frequency and dynamic elasticity modulus. Obtained findings of this study reveal some of the methods and benefits of appropriately designing this sustainable material against dynamic loads. [Display omitted] •Experimental modal analysis (EMA) technics are described in detail.•Dynamic modulus of elasticity (DMOE) obtained with EMA & ANSYS FEA back-analysis.•A3.5-W0.7 coded variation achieved a 36% higher damping ratio and a 30% lower DMOE.•New categorization method for correlating activator dosages and modal parameters.•Effect of Na2O and SiO2 on modal parameters discovered via new categorization.