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The sticking of the concrete on metallic formworks during building construction generates many concrete wall defects. Several solutions have been proposed, among which surface lubrication and polymeric coatings are commonly applied. In this paper, the main functional signatures of a steel formwork skin and a polymeric coating were determined to understand their effect on the concrete sticking. The topographical, chemical and mechanical signatures of the surfaces were characterized at near-surface regions. The top of the steel formwork a 10 µm-thick layer is constituted of two oxides each one having specific tribological properties. Adding the polymeric coating on the formwork skin surface lowers its surface tension, which lowers the sticking by reducing the wettability. Moreover, the smaller roughness of the coating limits the susceptibility of mechanical anchoring. Nevertheless, scratch testing suggests a short durability of the polymeric coating due to its weak resistance to abrasion.

Concrete, a commonly used material in the construction industry, interacts with metallic surfaces such as formwork during pouring and reinforced bar during lifespan. Formworks are designed to minimize hardened concrete adherence in order to avoid wall defects after formwork removal. In opposite, reinforced bar designs aim at maximizing their adherence to concrete for optimizing the transmission of mechanical solicitations. The present review investigates the surface properties that govern bonding of freshly poured concrete onto metallic surfaces. Identifying the underlying mechanisms of adhesion highlighted the importance of substrate characteristics (roughness, composition), concrete curing and compaction), and interfacial additives (release agents, wetting). This paper addresses the basic requirements in designing a functional surface interacting with concrete and emphasizes today challenges.