Investigation on improving the residual mechanical properties of reinforcement steel and bond strength of concrete exposed to elevated temperature

• Published in: Case Studies in Construction Materials Vol. 16; p. e01128
• Main Authors: Kiran, Tattukolla, Anand, N., Mathews, Mervin Ealiyas, Kanagaraj, Balamurali, Andrushia, A. Diana, Lubloy, Eva, G, Jayakumar
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2022; Elsevier
• Subjects: Bond strength; Elevated temperature; Perlite coating; Pull-out behaviour; Reinforcement steel; Yield strength; Bond strength; Perlite coating; Yield strength; Elevated temperature; Reinforcement steel; Pull-out behaviour
• ISSN: 2214-5095; 2214-5095
• DOI: 10.1016/j.cscm.2022.e01128

Concrete and reinforcement steel are essential building materials widely used in composite construction due to their advantages, such as strength, durability and ease of availability. Fire is one of the critical hazards that causes severe damage to the structure and leads to progressive collapse. Due to the intensity of fire exposure, the concrete and reinforcing steel significantly losses their inherent mechanical properties and service life. Minimizing the fire-induced damage and failure are the primary objectives in the design of concrete structures. Therefore, an extensive experimental attempt was undertaken to evaluate the pull out behaviour and also to improve the bond performance of concrete and reinforcement steel when exposed to elevated temperature. A cement based perlite coating was developed as a protective material to safeguard the concrete in the study. All the pull out bond test specimens were heated following the ISO 834 standard fire curve, and subsequently cooled either by air or water. Residual mechanical properties of steel rebar such as yield strength, ultimate strength, elastic modulus, shear and bending capacity were evaluated after the exposure to elevated temperature. Investigations were conducted on pull out specimens to evaluate the bond stress slip behaviour and bond strength of concrete. A detailed physical observation was made on the failed concrete specimens to examine the damage. A drastic reduction in bond strength of concrete and tensile strength of the rebar were observed while increasing the duration of heating. Also, it was observed that the coated specimens exhibited better performance by retaining the bond strength and yield strength of the rebar. •Pull out behaviour of reinforcement steel exposed to standard fire exposure was investigated.•Effect of elevated temperature on residual mechanical properties of Fe500 steel grade was evaluated.•A coating was developed with expanded perlite material to improve the post fire performance of steel reinforcement.•Influence of natural air cooling and forced water cooling on residual mechanical properties was investigated.•Failure and crack pattern of damaged specimens were examined and reported.