Relation between crack opening and extent of the damage induced at the steel/mortar interface

• Published in: Construction & building materials Vol. 193; pp. 97 - 104
• Main Authors: Ghantous, Rita Maria, François, Raoul, Poyet, Stéphane, L'hostis, Valérie, Bernachy-Barbe, Fabien, Meinel, Dietmar, Portier, Lauriane, Tran, Nhu-Cuong
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 30.12.2018; Reed Business Information, Inc. (US); Elsevier
• Subjects: Analysis; Building materials durability; Chemical properties; Civil Engineering; Concrete cracking; Corrosion; Corrosion (Chemistry); Cracks; Durability; Engineering Sciences; Génie civil nucléaire; Load-induced damage; Materials; Mechanical properties; Reinforced concrete; Steel corrosion; Cracks; Durability; Load-induced damage; Corrosion; Reinforced concrete; corrosion; cracks; reinforced concrete; load-induced damage; durability
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2018.10.176

•Width of load-induced cracks on concrete surface is correlated to those near rebar.•Damage along the steel/mortar interface was developed independently of crack width.•Limiting corrosion risk by defining threshold on crack openings may not be relevant. Cracks are inevitable in reinforced concrete structures and promote the diffusion of aggressive agents towards the reinforcement. In Eurocodes, for some exposure conditions, a threshold not to be exceeded for crack width near the rebar is recommended in order to limit risks of corrosion development and ensure structure durability. On the other hand, several studies show that the steel/mortar interface quality at the intersection with a crack strongly influences corrosion development. The aim of this study was therefore to test whether a relation exists between the extent of mechanical damage at the interface and the corresponding residual crack opening. To this end, specimens were cracked using three point bending test apparatus and the evolution of crack opening was determined on the outer surface and deep within the specimen. It was observed that the crack opening measured on the outer surface of the specimen was very close to that measured at various depths within the specimen at the same height level. In addition, the length of the mechanically damaged interface was determined for each residual crack opening. It was deduced that cracks induced significant steel/mortar interface damage independently of the size of their openings. The length of the mechanically damaged interface increased proportionally to the residual crack opening without showing marked variation after a certain crack opening value. Based on the observed results, it is deduced that defining thresholds on crack openings is logical for esthetic reasons but is not particularly relevant for corrosion risk assessment.