Experimental and numerical analysis of damage and crack behavior in geopolymer and ordinary portland cement reinforced concrete columns

This study evaluates and compares the structural behavior of reinforced concrete columns produced with geopolymer concrete (GPC) and ordinary Portland cement (OPC) under eccentric axial loading, aiming to investigate GPC's potential as a sustainable alternative. A total of twenty columns with varying longitudinal reinforcement ratios, curing methods, eccentricities, and geopolymer formulations were experimentally tested. Displacement measurements at each load increment were obtained using a total station, allowing crack pattern tracking at key stages such as first cracking, yielding, and ultimate failure. These observations were schematically documented using AutoCAD. Additionally, finite element models were developed in ABAQUS using the Concrete Damage Plasticity (CDP) model, with material parameters calibrated based on experimental compressive and tensile strengths, elastic modulus, and fracture energy. Results indicated that increasing eccentricity reduces axial load capacity while increasing lateral deformation. While the reinforcement ratio did not significantly affect axial strength, it increased displacement demand. Due to their distinct microstructural characteristics, GPC columns exhibited greater deformation capacity and narrower, more localized crack patterns than OPC columns. Furthermore, the sodium silicate/sodium hydroxide (SS/SH) ratio and curing duration significantly influenced the structural response of GPC. Numerical simulations showed strong agreement with experimental results regarding load-displacement behavior and damage distribution. These findings demonstrate that GPC can serve as a reliable and sustainable alternative to OPC in structural column applications, provided its specific material properties are considered in design and analysis.