Performance Enhancement of Concrete Produced with two-step CO2 Mineralization

This paper presents a beneficial use of CO2 as an admixture in concrete made with ordinary Portland cement. In current practice, accelerated carbonation is the primary method of adding CO2 to concrete. This method has several drawbacks, including low CO2 diffusion, which is applicable only to precast construction, CO2 diffusion to the immediately surrounding outer surface of the concrete element, the need for a carbonation chamber, and high handling costs. This study suggests using CO2 as an addition directly mixed with concrete using a two-stage procedure to overcome the drawbacks of earlier methods. Through the in-situ generation of calcium carbonate particles in the nano- to submicron range in fresh concrete, densifying the concrete improves its performance. At 28 days of testing, the compressive strength of M20 and M40 grades with 0.25% and 0.20% of CO2 is 21.98% and 20.59%, higher than that of corresponding conventional M20 and M40 grades of concrete, respectively. The improved performance can be used to develop concrete mixture proportions that better use Portland cement and CO2 to reduce concrete’s carbon footprint. The suggested method can save 6 to 7.5% of Portland cement, resulting in about an 8% reduction in carbon emissions. In brief, the present method is cost-effective for CO2 mineralization in concrete, offering double benefits, improving concrete properties and making beneficial use of the recovered CO2, hence resolving the problem of greenhouse gas emissions.