Improving carbonation resistance, strength, and microstructure of concrete through compression casting

This study addresses the significant issue of steel corrosion in reinforced concrete structures, which incurs billions of dollars in annual costs globally, with a substantial portion attributed to concrete carbonation. Rising CO 2 emissions from urbanization, industrialization, and population growth worsen concrete durability. Prior attempts to enhance carbonation resistance face energy, cost, efficiency, and environmental challenges. Compression cast concrete (CCC) is an innovative precast concrete solution for enhancing the mechanical performance of concrete. However, CO 2 absorption, carbonation resistance, and post-carbonation compressive strength of CCC remains unexplored in prior studies. This pioneering research examines eight concrete mixtures with varied water-cement ratios (0.36, 0.43, 0.53) and compression pressures (0, 5, 10, 15 MPa). Accelerated carbonation resistance, compressive strength, and microstructural analysis (x-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry) are conducted. Results show CCC samples outperform traditional concrete, with a 55–122 % increase in compressive strength. CCC specimens show higher post-carbonation compressive strength, reduced carbonation depth (i.e., 87–93 %), denser microstructure, and lower porosity than traditional concrete. Therefore, CCC offers improved strength, reduced carbonation depth, and superior microstructural properties compared to conventional concrete, making it suitable for CO 2 -rich settings and leading to durable and corrosion-free concrete structures.