The accelerated population growth in Guayaquil has increased the demand for pedestrian infrastructure, emphasizing the need for sustainable, cost-effective materials. This study evaluates three alternatives for pedestrian bridges: A36 structural steel, conventional concrete (OPC), and geopolymer concrete (GPC). These solutions are compared using structural analysis in SAP2000, life cycle assessment (LCA), and cost evaluation through BIM modelling in Revit. Both A36 steel and Ordinary Portland Concrete (OPC) demonstrated superior structural performance, whereas GPC displayed increased deflections due to a lower modulus of elasticity. However, GPC offered significant environmental advantages, with CO₂ emissions up to 67% lower than OPC and potential cost savings of up to 11% at higher strengths. The findings underscore GPC’s promise as a sustainable alternative, offering reduced carbon footprint and competitive costs.