Bonding performance between high-early-strength high-ductility concrete (HES-HDC) and existing concrete

To investigate the interfacial bonding performance between high-early-strength high-ductility concrete (HES-HDC) and existing concrete, 108 bonding specimens were used to study the effects of concrete substrate roughness, the content of silica fume, hydroxypropyl methylcellulose (HPMC), and polyethylene (PE) fiber in HES-HDC, as well as curing age and testing methods on the interface failure mode, load-slip curve, and interfacial bonding strength between HES-HDC and concrete. The results show that the interfacial bonding strength at 2 h of all bonding specimens exceeded 1.2 MPa, with the interfacial bonding strength at 1 day reaching 60% of that at 28 days, demonstrating significant high-early-strength properties, meeting the requirements for rapid repairs. The concrete substrate roughness significantly influenced the interface failure mode and the characteristics of the shear load-slip curve. The interfacial shear strength increases with increasing concrete substrate roughness, HPMC content, fiber content, and curing age. HES-HDC with 6% silica fume exhibits higher interfacial shear strength with existing concrete. Based on the experimental results, a formula for the interfacial bonding strength between HES-HDC and concrete was proposed, considering interface properties and material strength, which could be applicable for predicting bonding strength using different interface testing methods.