Low-carbon ultra-high-performance concrete: raw materials, particle packing optimization, and data-driven performance assessment—a review

Ultra-high-performance concrete (UHPC) offers exceptional mechanical properties and durability; however, its cement-intensive formulations raise concerns regarding environmental sustainability. This study addresses this challenge by establishing quantitative relationships between UHPC mixture design, performance indicators, and embodied CO 2 emissions by coupling a literature survey with data-driven analysis of over 200 mixtures. Unlike previous studies that examine the behavior of raw materials and the resulting performance in isolation, this study leverages data-driven approaches to link mixture design parameters to mechanical performance, durability indicators, and embodied CO 2 emissions, thereby providing useful insights into low-carbon UHPC formulations. The influence of supplementary cementitious materials and mineral fillers is evaluated across rheological, mechanical, durability, and carbon footprint aspects. Machine learning (i.e., Random Forest) analysis demonstrates high accuracy in predicting compressive strength from mixture design parameters, while tensile properties and permeability remain influenced by microstructural factors not captured by mixture design parameters. Heat map correlation reveals strong interdependencies among mechanical and durability performance indicators, with compressive strength highly correlated (95%–98%) across curing ages and inversely related to permeability-related durability metrics. An exponential relationship between cement-to-binder and water-to-cement ratios is established ( R 2 of 95%), providing a strong predictive tool for mixture design. From a carbon footprint perspective, cement is the dominant contributor to CO 2 emissions, as expected. Interestingly, cement content above 800 kg/m 3 has negligible contributions to mechanical properties while significantly increasing the embodied CO 2 emissions. By adopting a data-driven approach, this study provides novel insights into designing UHPC mixtures that foster higher mechanical and durability performance while reducing embodied carbon.