The efficacy of self-curing agents on enhanced internal curing and accelerated carbonation with CO2-steam integrated 3D concrete printing

• The coupling of PEG-6000 with CO 2 -steam integrated 3D concrete printing (3DCP) facilitates enhanced internal curing, thus accelerating early-age carbonation activities while improving mechanical strength developments. • Combined usage of CO 2 -steam integrated 3DCP with PEG-6000 at 1–2 wt. % binder dosage resulted in up to 137 % increase in early-age CO 2 uptake, along with significant improvements in compressive, flexural, and interlayer bond strengths. • Beyond early stages of curing, the incorporation of PEG-6000 progressively limits CO 2 ingress due to its moisture retention properties, contributing to reduced CO 2 uptake at increased dosages and extended curing durations. Construction industry, responsible for a substantial portion of global carbon emissions, faces an urgent demand to adopt sustainable practices. Traditional concrete manufacturing processes contribute significantly to these emissions, underscoring a pressing need for innovative technologies that not only reduce carbon footprint but also improve material performances. This study presents an extension of CO 2 -steam integrated 3D construction printing by incorporating functional self-curing agents, specifically Polyethylene Glycol (PEG-6000), to enhance both early-age carbonation reactions and mechanical strength developments of 3D printed cementitious materials. The presented method aims to suppress moisture loss that delays hydration and carbonation activities during unconfined atmospheric curing, which would otherwise hinder strength developments. The combined usage of in-situ CO 2 -steam printing with PEG-6000 demonstrated improvements in early-age carbon uptake up to 137 %, along with substantial developments in compressive, flexural, and interlayer bond strengths of up to 29.4 %, 51.9 %, and 36.5 %, respectively.