Physico–Chemical Processes Limiting CO₂ Uptake in Concrete during Accelerated Carbonation Curing

Abstract

Accelerated curing of fresh concrete using CO 2 is a possible approach for value-added, high-volume usage products from waste CO 2 emitted from stationary sources. The extent of CO 2 uptake and the spatial distribution of the CaCO 3 (s) precipitates formed during accelerated carbonation curing of compacted, 4-h hydrated cement mortar (fresh concrete mixture with fine aggregates) samples were investigated in this study. The maximum carbonation efficiency achieved was 20% of the theoretical uptake. Microprobe imaging was used to analyze the composition of the compacted cement mortar microstructure and showed extensive filling of pores of diameters 4 μm and smaller, with CaCO 3 (s). The carbonation efficiency, however, reached 67% when an aqueous suspension of cement was carbonated in a completely mixed reactor, where interparticle pores do not exist and a higher surface area of cement particles is exposed to dissolved CO 2 . The theoretical efficiency was not achieved because all reactive cement surfaces were saturated with carbonation products, as indicated by equilibrium concentrations of dissolved calcium, silica, inorganic carbon, and pH. This study shows that both deposition of CaCO 3 (s), on reactive surfaces, and pore filling may regulate the extent of CO 2 uptake during accelerated carbonation curing of concrete.

Mixture design and treatment methods for recycling contaminated sediment

“…Based on preliminary tests, the demoulded sediment block samples (after 24-h initial casting) was pre-dried at 50 • C for 24 h to reduce the moisture content to 4% for ensuring sufficient pathway for gas penetration, because the dissolution of CO 2 gas and deposition of CaCO 3 on the porous surface could be the limiting factors [41,42]. However, it was noted that elevated temperature may accelerate cement hydration and affect final strength [43], thus the moisture content should be controlled by curing in a drying chamber at room temperature in future studies.…”

Mechanical properties, durability characteristics and shrinkage of plain cement and fly ash concretes subjected to accelerated carbonation curing

“…Many factors affect the effectiveness of ACC, such as the concentration of CO 2 , temperature, relative humidity, pressure in the carbonation chamber, exposure duration to CO 2 , the age of concrete when exposed to CO 2 , type and amount of binders, and water/cement ratio (Fernández Bertos et al 2004;Chen et al 2011;El-hassan et al 2013;Mohammed et al 2014;Shao & Monkman 2006;Zhan et al 2013a;Zhan et al 2013b). Kashef-Haghighi and Ghoshal (2013) found that CO 2 uptake could be increased significantly through the use of cements having higher amounts of reactive minerals and more fineness, which would provide a higher reactive surface area. Carbonation shrinkage resulting from ACC can be reduced by incorporating mineral admixtures such as slag (Monkman & Shao 2010).…”

Influence of Wind Pressure on the Carbonation of Concrete

“…So it is hard to validate the proposed penetration-reaction carbonation model using existing theoretical and numerical models. With regard to experiments, some research has been conducted though experimental investigations in order to develop a carbon dioxide mitigation technology [25,26]. The concrete is used to store carbon dioxide under high CO 2 pressure.…”