Traditional and Alternative Methods of Assessment of Carbon Dioxide Sequestration Process by Recycled Concrete Aggregates

One of the way of carbon dioxide sequestration is concrete carbonation process. In this paper an assessment of the CO absorption abilities of the recycled concrete aggregates is presented. Analyses have been carried out both with an accelerated method, wherein the concrete aggregates placed in closed chambers under controlled conditions were exposed to the air composed of 8% CO2, and at the ambient atmospheric carbon dioxide concentration. This is the first innovative study where the intensity of the carbonation process was assessed at the ambient CO2, concentration level by means of the closed dynamic chamber technique which is commonly applied in studies of greenhouse gases exchange between the ecosystem and the atmosphere. The recycled aggregates made from concretes with different water to cement ratio (0.40, 0.50, 0.55 and 0.65) and grain sizes (2/4, 6/8, 12/16 and 4/6, 8/12, 12/16 mm) were tested in our study. The results confirmed that carbonation rate increases with increasing water to cement ratio, whereas decreases with an increase of the aggregates fraction size. As determined by measurements carried out with the closed dynamic chamber system, the recycled concrete aggregates absorbed from 1.48 to 3.56 mg kg-1 s-1 of CO2, at the ambient carbon dioxide concentration level dependently on the aggregates characteristics