Modal Characteristics of Fly Ash-Based Geopolymer Reinforced Concrete Columns under Dynamic Impact Loads

Abstract

Geopolymer concrete (GPC) stands out as an environmentally friendly, sustainable structural material with superior mechanical and thermal properties, as an alternative to ordinary Portland cement (OPC) concrete. Due to this, investigating the dynamic properties of GPC materials is particularly crucial for structures subjected to vibration loads such as earthquakes. Therefore, eight heat-cured class F fly ash-based GPC and two OPC column specimens were subjected to modal tests using the Experimental Modal Analysis (EMA) method. Thus, the modal characteristics of columns produced from GPC were investigated and compared regarding reinforcement ratio, alkali activator ratio, and curing method. Furthermore, the dynamic properties of GPC and OPC columns were also compared. Additionally, the relationship between these columns' resonance frequencies, damping ratios, mode shapes, and mechanical properties was evaluated. The results show that although the resonance frequencies of OPC columns are 8.19% higher than those of GPC columns, their damping ratios are 13.01% lower. For GPC columns, the alkali activator ratio and curing method had a greater impact on the modal characteristics of the column samples than the reinforcement ratio. Besides, the relationship between strength and resonance frequency was closely related. In contrast, the damping ratio was closely related to the static modulus of elasticity and rigidity values. In particular, it was concluded that GPC columns had higher energy dissipation capacities, which was an important design parameter, under dynamic loads due to the high damping ratio.