Development of low-carbon UHPC based on recycled oyster shell powder and wollastonite microfibers: Autogenous shrinkage reduction, strength improvement, and carbon emission reduction

초록

Although ultra-high-performance concrete (UHPC) has excellent mechanical properties and durability, it is generally associated with significant autogenous shrinkage and carbon emissions. To address these challenges, this study incorporated wollastonite fiber (WF), oyster shell powder (OSP), and metakaolin (MK) to develop a UHPC mixture with reduced autogenous shrinkage and environmental impact. A series of tests were conducted to comprehensively evaluate the effects of WF on hydration behavior, autogenous shrinkage, mechanical properties, microstructure, and sustainability on the basis of carbon emissions and performance efficiency metrics. The evolution of the hydration products was characterized using isothermal calorimetry, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT–IR) and scanning electron microscopy (SEM). Macroscopic properties were assessed via workability, autogenous shrinkage, mechanical properties, and surface resistivity measurements. The results indicate that the bridging and dilution effects of WFs increase volume stability and significantly reduce autogenous shrinkage. Moreover, the mechanical properties of UHPC are slightly increased, and carbon emissions are effectively reduced because of the partial replacement of conventional cementitious materials. Microscopic analysis revealed that the combination of MK and OSP enabled the formation of carboaluminates and increased matrix densification. Furthermore, carbon footprint analysis confirmed the environmental benefits of the WF-UHPC system. This approach not only enables the resource utilization of waste OSP but also increases internal water retention, structural integrity, and interfacial synergy via the fibrous nature of WF. Overall, this study presents a UHPC design strategy that reduces autogenous shrinkage and carbon emissions while improving mechanical performance, providing theoretical and technical support for low-carbon, high-performance cementitious materials. © 2026 Elsevier Ltd

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