The impact of air entraining on frost endurance in 3D-printed concrete: the function of printing orientation and curing process

This study evaluated the freeze-thaw (F&T) resistance of 3D-printed concrete by analyzing the effects of air-entraining agent (AEA) concentrations, curing methods, and core orientations. Concrete specimens (600 x 600 x 150 mm) with 0%, 0.1%, 0.15%, and 0.2% AEA were cured and tested after 28 days. Cores were drilled horizontally and vertically and then subjected to 360 F&T cycles according to ASTM C666/Procedure B. Microstructural analyses (BET, MIP, SEM, XRD) evaluated changes in pore structure. Results showed 25% of the samples endured 300 cycles without significant damage. F&T damage occurred primarily at interlayer bonds. Horizontal cores showed greater durability due to reduced interlayer gaps. AEA at 0.1% significantly improved F&T resistance and increased dynamic modulus by 15%. BET and MIP analyses showed a 20% increase in average pore size, while SEM confirmed air voids. Optimized AEA levels and curing methods improved the durability of 3D-printed concrete in frost-prone conditions.