Long-term durability assessment of 3D printed concrete

Concrete 3D printing can be described as a revolution conquering the modern construction field. However, additive manufacturing is still confronted with many challenges and several limitations, such as the absence of building codes that regulate this construction approach. This technology is known to be environmentally friendly and its market is widening its horizons by implementing 3D printed concrete in harsh environments, such as bridges, infrastructures, and maritime applications. In this regard, the durability of those structures should be assessed to ensure sustainability. This study consists of assessing the durability of 3D printed concrete by comparing printed and casted samples aged by sulfuric acid attack. Three mixes were subjected to 0.5% sulfuric acid solution over 142 days. In addition to visual inspections of the samples, the mass loss was recorded periodically. Moreover, the total water porosity and the mechanical performance were evaluated. Both printed and casted samples showed degradation when placed in acid solutions, but the printed ones slightly resisted better during the first 84 days. However, after that date, both printed and casted samples presented comparable resistance. In addition, the mechanical performance came in accordance with the mass loss to prove that printed samples resisted well the acid attack by not losing much strength. In contrast, the strength drop rates in degraded printed samples were higher than those in the degraded casted elements between days 112 and 142. Moreover, the water porosity test showed that printed elements have a denser concrete matrix which protects the elements against chemical ingression.