Durability performance of self-compacting concrete produced using CO2 as an admixture

Abstract

This research investigates the fresh characteristics and durability of self-compacting concrete (SCC) made using CO2 as an admixture. In the existing practice, CO2 is added to concrete mainly through accelerated carbonation curing. That has many limitations, such as low diffusion rate, requirements of the large airtight chamber, and use in precast concrete only. To overcome these limitations, the current study employed a CO2 mineralization approach. As cementitious materials hydrate during mixing, CO2 reacts with it and produces more hydration products. In addition, calcium carbonate particles are formed in situ, filling the minute pores and densifying the SCC matrix. The present research results reveal that a small quantity of CO2 mineralization improves the SCC compressive strength and durability; the best durability is achieved at 0.3% mineralization of CO2 by the weight of the cement used. Compare to normal SCC, a 4.3% higher compressive strength of CO2 mineralized SCC was noticed at 28 days of testing. 0.05 % lowers weight gain and 1.88 % higher compressive strength was noticed in CO2 mineralized SCC at 180 days of 5% sodium sulfate exposure condition. Similarly, the rapid chloride penetration test result shows that 11.35% lesser chloride ions pass from CO2 mineralized SCC compared to normal SCC. The fresh characteristics of the SCC as a result of CO2 mineralization behave similarly to reference SCC with small degradation that is considered acceptable. Hence, thepresent study demonstrates that CO2 can be used beneficially in concrete to enhance its properties and lower CO2 emissions into the atmosphere.