Nanoscale insights on the interface between passive film of steel and cement hydrate: Diffusion, kinetics and mechanics

• Published in: Applied surface science Vol. 514; p. 145898
• Main Authors: Hou, Dongshuai, Xu, Xiaoqian, Wang, Muhan, Chen, Zheng, Zhang, Jinrui, Dong, Biqin, Miao, Jijun, Liu, Caiwei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2020
• Subjects: Bonding strength; Interfacial properties; Mechanical properties; Micro-scale; Molecular dynamics; Reinforced concrete; Molecular dynamics; Mechanical properties; Bonding strength; Interfacial properties; Micro-scale; Reinforced concrete
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2020.145898

•Molecular dynamics simulation is used to observe the microstructure of concrete and steel interface.•The relationship between interfacial bonding and mechanical properties is revealed.•Interfacial water changes the bonding properties of interfacial region, which reduces the strength of reinforced concrete. The interfacial region between concrete and steel reinforcement (SCI) determines strength and durability of reinforced concrete structure. In this work, the molecular dynamics simulations were employed for understanding the bonding mechanism of SCI region. In the interfacial region, the calcium ions play the mediation of bonding CSH surface and the passivation film by combing the oxygen atoms and hydroxyl groups of CSH in the nearest neighbors. The hydroxyl groups in the γ-FeOOH and the unbinding O atom in the CSH provide enough oxygen sites to form the hydrogen bonds and hydration, which also improve the bond strength of the interlayer region. Furthermore, introducing single-layer water results in the hydrated Ca2+-water cluster formation, weakening the CaO connectivity between CSH and passive film. Double-layer water can significantly increase the diffusion of interfacial components and decrease the stability of interfacial bonds. In addition, simulated pull-out test and uniaxial tensile test were performed to evaluate bond strength of CSH and γ-FeOOH. Hydrolytic weakening is found due to water ingress in the interfacial region. Double-layer water penetration results in reduction of interfacial shear strength from 0.53 GPa to 0.38 GPa. Also, the Young’s modulus and cohesive strength reduced by more than 50% percentage. This work is expected as an important reference for design and development of reinforced concrete in engineering application.