Utilization of paper mill lime mud to partially replace fillers in cementless ultra-high performance concrete (UHPC)

Abstract

This study investigates the impact of incorporating lime mud (LM) as a filler material to develop sustainable, cementless ultra-high performance concrete (UHPC) by replacing silica powder (SP) and silica sand (SS) at varying percentages. Flowability analysis reveals that LM, with its distinctive particle size, influences flow characteristics differently at different replacement levels. Compressive strength was improved by 5.4% with 30% SP replacement, showcasing the role of LM in nucleation, as well as its particle size advantage. The heat of hydration analysis indicates that LM likely influences the early curing stages, enhancing reactivity and nucleation. TGA analysis also confirms that LM plays a role in hydration reaction, influencing weight loss and hydration peaks. The mercury intrusion porosimeter results show the impact of LM on pore distribution, with 30% for SP and 50% for SS replacements, favoring denser matrices. Life cycle assessment (LCA) demonstrates reduced CO2 emissions and favorable environmental performance, highlighting the sustainability potential of LM replacements. Overall, the incorporation of LM in UHPC shows promise in terms of enhancing its mechanical properties and environmental sustainability.