Sustainable Portland Limestone Cement–Based Ultrahigh-Performance Concrete

This paper investigates the development of sustainable (ultra)high-performance concrete (UHPC) mixtures by replacing ordinary portland cement (OPC) with widely available materials, including portland limestone cement (PLC) and industrial by-products such as ultrafine limestone, fly ash, and slag, and by partially or fully replacing steel fibers with polyethylene fibers. Although UHPC is recognized for its excellent mechanical and durability performance, conventional mix designs remain cost-prohibitive and are not aligned with recent sustainability-driven changes in clinker and concrete production. This study addresses this gap by evaluating the fresh, mechanical, and flexural performance of PLC-based (ultra)high-performance concrete mixtures reinforced with steel, polyethylene, and hybrid steel–polyethylene fibers, and by comparing them with a commercially available UHPC. The mixtures are referred to as “(ultra)high” and not “ultrahigh” to reflect the targeted performance level under practical curing conditions because UHPC mixtures designed for such conditions may not always reach traditional UHPC strength thresholds. Mixtures with steel fibers exhibited flowability comparable to the commercial UHPC, while polyethylene fiber–reinforced mixtures showed reduced but still adequate flow for practical applications. A compressive strength of 120 MPa was achieved for a steel-fiber PLC-UHPC mixture under standard curing; however, mold material and specimen shape influenced the measured strength. Polyethylene fiber mixtures developed lower compressive strength but exhibited high flexural toughness, and the PLC-UHPC with hybrid fibers showed excellent flexural response but relatively lower compressive strength. A sustainability analysis indicated that the PLC-based mixtures can reduce the concrete carbon footprint relative to the commercial UHPC. The work aims to promote sustainable PLC-based UHPC as a practical solution toward more environmentally responsible and broadly deployable (ultra)high-performance concrete for infrastructure applications.