Doubling the coating-substrate pull-off strength by growth of CaCO3 nano-crystals.

• The coating-substrate pull-off strength increased by up to 112.2% with carbonation curing. • Interfacial debonding was altered to substrate failure after ACC treatment. • Pure physical adhesion had limited contribution to the strength rises. • Pillar-like CaCO 3 nano-crystals provided the crystals anchoring adhesion. Strong coating-substrate adhesion is crucial for ensuring long-term durability and performance of protective coatings in various applications. The growth of nano crystals on the substrate may be a preferable way to enhance the coating-substrate interactions. Here, an accelerated carbonation curing (ACC) scheme (0.5 MPa CO 2 gas pressure) was designed to grow calcium carbonate (CaCO 3) nano-crystals on a mortar substrate at early age before coated with a waterborne epoxy resin (WER). Microstructures of the ACC-treated mortar specimens and the coating-substrate interfaces were characterized by multiple microscopic tests, and the compressive strength of the carbonated substrate and the pull-off coating-substrate strength were measured. Results showed that the ACC treatment not only increased the mortar strength (by up to 17%), but also greatly improved the pull-off strength (by up to 112.2%). Substrate failure took place in the mortars after the ACC treatment. The mechanisms of physical adhesion, surface roughness, and crystals anchoring caused by the growth of pillar-like CaCO 3 nano-crystals may account for the largely raised pull-off strength. The findings would deepen the understandings of interfacial adhesion mechanisms between polymer coatings and cement-based substrates and provide new insights into developing stronger coating-substrate adhesions. [ABSTRACT FROM AUTHOR]