Understanding the environmental, economic, and social impact of fly ash utilization on early-age high-strength mass concrete using life cycle analysis

Abstract

High-strength mass concrete mixtures are a crucial component of numerous structures nowadays. However, concrete greatly impacts the environment, economy, and society. The impact of employing fly ash in early-age, high-strength mass concrete mixtures has not yet been quantified and documented in the literature. This study aims to evaluate the impact of early-age, high-strength mass concrete mixtures and provide insight into how the current practice might be enhanced to promote sustainability. The research examines concrete mix utilized in two bridges in the Philippines with the following design compressive strengths: 55 MPa at 7 days (7OPC), 55 MPa at 28 days (28OPC), and 55 MPa at 7 days with 20% fly ash as cement substitute (7FA20). Using SimaPro 9.3, a cradle-to-gate life cycle analysis was conducted to quantify their effects based on 18 midpoint and 3 endpoint categories. Results show higher impact of 7OPC on 17 midpoint and 3 endpoint indicators was observed than on 28OPC. The most significant midpoint impacts based on normalization are fossil resource scarcity, global warming potential, ozone formation, human carcinogenicity toxicity, and terrestrial ecotoxicity. The global warming potential of 7OPC was quantified to be 636 kg CO2 eq compared to 549 kg CO2 eq of 28OPC concrete. Utilizing fly ash decreased the damage to resources (11%), human health (16%), and the environment (16%). Analysis of concrete constituents indicated that using chemical admixtures to obtain early high strength contributed significantly to fossil resource scarcity and resource damage . The framework presented in this study may be used for assessing the sustainability of utilizing other waste materials in concrete production.