Effect of Carbonation Mixing on CO2 Uptake and Strength Gain in Concrete

Abstract

Concrete is well known for its capacity to sequester carbon dioxide (CO2) through carbonation curing. If carbonation mixing can be used to introduce CO2 during concrete mixing, the process is able to enhance the carbon capture and storage capacity of concrete and makes the technology available to both precast and cast-in-place concretes. This paper studies the effect of carbonation mixing on CO2 uptake and strength gain of cement paste, which is the key carbon-reactive ingredient in concrete. Three mixing methods were investigated: (1) normal air mixing, (2) carbonation mixing, and (3) hybrid mixing with carbonation mixing first, followed by normal air mixing. Two curing methods, air curing and carbonation curing, were also studied to examine the effect of carbonation mixing on curing. It was found that carbonation mixing could increase the CO2 uptake but decrease the strength gain. The reduction in strength by carbonation mixing was caused by the formation of carbonate coating on cement particles. The property can be improved if air mixing is introduced right after carbonation mixing.