Properties and microstructure of concrete and cementitious paste with liquid carbon dioxide additives

This study verified the effect of liquid CO2 admixture on fresh, hardened, and durability properties of concrete insitu. It was found that the overall compressive strength of the concrete increased by approximately 5% after 7 days and by about 3% after 28 days. The t-test, however, revealed no statistically significant difference between the two groups of samples in terms of 28-day compressive strength for concrete mixes. Therefore, using liquid CO2 admixture may not help with significant strength improvement and consequently, with reducing cement content within the mix design. In addition, results showed that liquid CO2 does not significantly affect the fresh, hardened, or durability properties of concrete. In addition, XRD and SEM techniques were performed on paste samples to evaluate the chemical effect of CO2 admixture on hydrated cement, and hydration products.