Comparative Environmental Impact Assessment of 3D Concrete Printing and Precast Techniques in Bridge Construction: A Case Study Analysis

This study conducted a comparative environmental impact assessment specifically investigating three-dimensional (3D) concrete printing (CP) and precast construction techniques applied to bridge construction. Using a cradle-to-site life-cycle assessment (LCA), including both Intergovernmental Panel on Climate Change (IPCC) 2013 global warming potential (GWP) indicators and ReCiPe Midpoint (H) impact assessment methods, the study evaluated key sustainability metrics such as GWP, human toxicity, particulate matter formation, freshwater ecotoxicity, material efficiency, and energy consumption. A case study of an 8-m-long pedestrian bridge constructed using 3DCP was compared directly with an equivalent precast concrete bridge modeled with identical dimensions. The results demonstrated that 3DCP offers substantial environmental advantages, reducing total CO2 emissions by 64.3% compared with precast techniques. This significant reduction is attributed primarily to the elimination of formwork, reduced steel reinforcement requirements, and precise material placement, which contribute to lower environmental impacts across multiple stages of construction. Conversely, precast construction results in higher emissions due to heavier structural components, increased material usage, and energy-intensive formwork production and handling processes. However, the continuous operation of 3D printing equipment leads to greater energy consumption during the off-site construction phase, presenting a notable challenge. Overall, this research specifically highlights the environmental advantages and limitations of 3DCP and precast methods, emphasizing the potential of 3DCP to substantially enhance sustainability in construction through improved material efficiency, reduced emissions, and innovative design approaches. The primary contributions of this research include quantifying the precise environmental benefits and challenges associated with 3DCP, offering insights into targeted optimization opportunities, and providing foundational evidence to guide sustainable construction decision-making.