A novel approach for revealing the strength evolution mechanism of limestone-calcined clay cement with self-ignition coal gangue and shell powder

Abstract

Limestone Calcined Clay Cement (LC3) plays a pivotal role in the transition of cement industry toward lower carbon emissions. However, the reliance on limited, non-renewable limestone and expensive, high-grade kaolinite presents notable challenges for LC3, requiring a balance between using lower-quality materials and maintaining high performance. To address this challenge, this study introduced an innovative LC3 mix by incorporating shell powder and self-ignition coal gangue as substitutes for traditional ingredients. The study found that shell powder significantly increased the early-age compressive strength of LC3 at 3 days, raising it to 20.4 MPa, although it restricted the space for further hydration product development. In contrast, introducing self-ignition coal gangue fine-tuned the hydration process, resulting in enhanced compressive strengths of 34.3 MPa and 45.2 MPa at 7 and 28 days, respectively. Additionally, Backscattered Electron (BSE) analysis revealed notable microstructural heterogeneity and introduced a new image processing-based method for evaluating microstructure, emphasizing the importance of adjusting phase compositions around inert particles and reducing inter-particle overlap to optimize LC3 performance.