Performance of sustainable 3D printed binary mixes subjected to carbonation induced corrosion environment

Abstract

Concrete 3D printing is emerging as a transformative approach in construction, providing rapid execution and unparalleled geometric flexibility. To practically apply this technology in load-bearing structural elements, reinforcement integration is crucial, which aggravates its vulnerability towards corrosion. Additionally, high binder content in printable mixes necessitates use of supplementary cementitious materials (SCMs), which makes the corrosion performance under carbonation conditions even more critical. Therefore, this investigation aims to evaluate carbonation induced corrosion behaviour of 3D printed concrete (3DPC) mixes having limestone calcined clay cement (LC2) and fly ash (FA) as alternative binders and further compare it with conventional mould-cast (MC) concrete. For this, migration characteristics in concrete and electrochemical parameters in reinforced concrete are examined followed by evaluation of corrosion mitigation by using a corrosion inhibitor. Carbonation depth surpassed the concrete cover in LC2 concrete and initiated corrosion at around 18–22 weeks, while FA concrete persisted in the passive state throughout the exposure attributed to the formation of denser matrix in FA mix. This indicated that concrete composition and type of SCM was crucial in influencing the corrosion performance. Extrusion of concrete under pressure led to densification of deposited layers which reduced CO₂ ingress and improved corrosion resistance in 3DPC, yielding an estimated extension of approximately 10 years in service life of 3DPC as compared to MC concrete. Inhibitor mitigated corrosion through the combined effect of pore blocking and protective film formation on steel surface which helped in increasing the expected lifespan by about 20 years under natural carbonation conditions.