Impact of in-situ CO2 injection on natural and accelerated carbonation performance of aerial lime mortar

Aerial lime is a well-known carbonatable binder. To address some limitations of slow carbonation speed and low initial strength, this study proposes an internal carbonation technique for field-casting aerial lime mortar using in-situ CO2 injection. The technique was found to be significantly effective in accelerating the carbonation and strength development of the mortar. For the first 28 days, the mortars mixed with CO2 injection showed 1.25–1.68 times faster carbonation and 1.5–2.3 times higher compressive strength than the mortar mixed without CO2 injection. This improvement can be explained by the internal carbonation effect, which effectively refines the pore structure while providing a nucleation site for subsequent carbonation. The early refinement of the pore structure also increased later carbonation performance under both natural and accelerated conditions. •The internal carbonation technology by CO2 injection is proposed for on-site lime mortar manufacturing.•In aerial lime systems, the internal carbonation effect is instantaneous and significant.•The submicron-sized calcite particles serve as nucleation sites for subsequent carbonation.•The internal carbonation effect makes subsequent external carbonation up to 3.2 times more efficient.