Adding dry ice into ultra-high-performance concrete to enhance engineering performances and lower CO2 emissions

• Published in: Construction & building materials 2023-08, Vol.392, p.131858, Article 131858
• Main Authors: Xuan, Mei-Yu, Lee, Si-hwan, Hu, Hui-qin, Wang, Xiao-Yong
• Format: Article
• Language: English
• Subjects: Carbon neutral; CO2 utilization; Dry ice; Micro-meso-macro; ultra-high-performance concrete (UHPC)
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2023.131858

•The microscopic CO2 bubbles generated by the dry ice underwent carbonation with Ca(OH)2.•Dry ice reduced the accumulated hydration heat and promoted ettringite production.•Dry ice improved the strength and electrical resistivity of UHPC for 28 days.•Dry ice is an effective way of carbon utilization.•Dry ice can promote carbon neutrality in the concrete industry. Developing low-carbon cement-based materials is crucial to address the pressing sustainability concerns the construction industry faces. This study elucidates the effect of adding dry ice on the micro-meso-macro properties of ultra-high-performance concrete (UHPC). The main original points of the method were summarized as follows: simple operation, low technical difficulty, no specific equipment required, and solving the problem that the carbonation curing method is difficult to use in low water-cement ratio concrete. The results show that adding dry ice generates microscopic CO2 bubbles that react with the carbonation of Ca(OH)2 and improve the later-stage strength and electrical resistivity. And adding dry ice reduces the heat of hydration and promotes ettringite formation. The results of microscopic analyses confirmed that increasing the dry ice content results in a decrease in Ca(OH)2; hence more calcium carbonate is formed. It was also observed that the carbon conversion effect became more apparent when the curing period was 28 days. And optical micrograph analysis showed that adding dry ice increased the total bubble content of the matrix and decreased the average bubble diameter, thus affecting the change in macroscopic properties. Moreover, as the addition of dry ice increased from 0 to 15%, the CO2 emission per unit strength decreased from 6.5 to 4.5 kg·CO2·m−3·MPa−1 (30% reduction in CO2 emission). Therefore, adding dry ice to UHPC is an effective way to utilize carbon and is crucial to achieving carbon neutrality in the concrete industry.