ABSTRACT

Corrosion represents one of the most important problems affecting the global behaviour of reinforced concrete (RC) buildings; in presence of aggressive environmental conditions reinforcing steel bars, as well as concrete, suffer from relevant modifications of the mechanical performance. Steel rebars show a high decrease of the deformation capacity, with reduction of the elongation to maximum load up to the 50% in case of TempCore® grades. This can cause unexpected brittle failures related to the premature achievement of ultimate rotation or, even worst, shear capacity of structural elements. To mitigate these problems, actual European standards for constructions foresee the adoption of specific precautions such as the increase of concrete strength class, of the concrete cover, of higher diameter; these tools allow to reduce the effects of corrosion without deleting the origin of the matter. During the last years, otherwise, another typology of reinforcing steel – characterized by a typical Dual-Phase (DP) microstructure – was developed with the aim of directly preventing corrosion initiation. Due to their microstructure, in which martensite is embedded in the ferrite matrix, Dual-Phase steels are less exposed to corrosion; on the other hand, being characterized by a not-defined yielding stress-strain plateau, specific rules need to be elaborated for their employment in civil applications. In the present paper, the experimental test campaign performed on reinforced concrete internal and external joints with Dual-Phase steel rebars is deeply described together with results’ critical discussion. The paper is preparatory for the elaboration of technical models to be used in the design of RC-DP structures.

摘要

腐蚀是影响钢筋混凝土 (RC) 建筑整体性能的最重要问题之一；在恶劣的环境条件下，钢筋和混凝土都会受到相关机械性能的影响。钢筋的变形能力显着降低，在 TempCore® 等级的情况下，最大载荷的伸长率降低高达 50%。这可能会导致与过早实现极限旋转有关的意外脆性失效，或者甚至最坏的情况下，结构元件的剪切能力。为了缓解这些问题，实际的欧洲建筑标准预见到采用特定的预防措施，例如增加混凝土强度等级、混凝土覆盖层、更大直径；这些工具可以在不删除物质来源的情况下减少腐蚀的影响。在过去的几年中，另一种类型的钢筋——以典型的双相 (DP) 微观结构为特征——被开发出来，旨在直接防止腐蚀开始。由于其微观结构，其中马氏体嵌入铁素体基体中，双相钢较少受到腐蚀；另一方面，以未定义的屈服应力-应变平台为特征，需要制定具体规则以使其在民用应用中的应用。在本文中，深入描述了用双相钢筋对钢筋混凝土内外接头进行的实验测试活动以及对结果的批判性讨论。