Enhancing the properties of UHPC with recycled concrete powder and iron ore tailings sand, and evaluating the environmental impact

• Published in: Construction & building materials 2024-11, Vol.452, p.138769, Article 138769
• Main Authors: Luan, Chengwen, Liu, Jun, Zhao, Shuo, Li, Yao, Yang, Yuanquan
• Format: Article
• Language: English
• Subjects: Environmental benefits; Iron ore tailings sand (IOTS); Nanoindentation; Recycled concrete powder (RCP); Ultra-high performance concrete (UHPC)
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2024.138769

Currently, cement-based materials, known for their relatively inferior mechanical properties and significant carbon footprint, have emerged as a major challenge to human survival and progress. Concurrently, the production of enormous quantities of construction and demolition debris, along with discarded materials stemming from iron ore tailings, has wrought considerable damage and impact on both human society and the environment. To tackle this predicament, our study has devised an innovative, economically viable, and eco-friendly cement-based material that utilizes recycled concrete powder (RCP) sourced from construction and demolition debris, as well as iron ore tailings sand (IOTS). This novel material strives to strike a balance between cost-efficiency, environmental sustainability, and ultra-high performance. A comprehensive and methodical assessment of this material was conducted through macro-scale mechanical characterization methods, nano-micro phase analysis, and hydration kinetics techniques. The findings reveal that, although the integration of RCP and IOTS diminishes the workability of Ultra-High-Performance Concrete (UHPC), it elevates its compressive capabilities. Specifically, the introduction of 10 % RCP and 45 % IOTS resulted in a 7.4 % boost in compressive strength, surpassing 144 MPa after 28 days. Nano-scale mechanical analysis further uncovered that this precise combination augmented the volume fraction of ultra-high-density hydrated calcium silicate gel by 5.8 %. Furthermore, the observed decline in calcium hydroxide content amidst the hydration products suggests that moderate amounts of RCP and IOTS have the potential to amplify pozzolanic activity and filler effect. Additionally, when compared to the control group, the incorporation of 30 % RCP and 45 % IOTS led to a noteworthy reduction in carbon emissions by 28.5 % and a decrease in non-renewable energy consumption by 25.4 %. In summary, the advancement of UHPC materials incorporating RCP and IOTS presents a promising avenue to significantly curtail costs while delivering exceptional performance and exhibiting environmentally friendly attributes. This groundbreaking material blazes a trail for future possibilities in the evolution of green building materials. [Display omitted] •A method combining sodium silicate nonahydrate with mechanical grinding was developed to activate RCP.•A model was designed for preparing ultra-high-performance concrete utilizing waste concrete and iron ta