Bearing Capacity of Corrosion-Damaged Bending Reinforced Concrete Elements Exposed to Fire

Abstract

One of the main reasons for the repair and restoration of residential buildings is the corrosion of reinforced concrete structures. This study aims to provide experimental data on the fire resistance of corroded high-strength reinforced concrete. For this, 18 samples of reinforced concrete beams were prepared from three different concrete mixtures (of different strengths) together with concrete prisms for compressive strength tests (GOST 10180-2012).

After curing, all beams were corroded in two stages using electric current, then corrosion cracks were evaluated, after which 50% of the samples were exposed to fire, following the time-temperature curve GOST 30247.0-94 (ISO 834-75) using a gas furnace.

Fire damage was assessed and compared between samples using the Ultrasonic Pulse Diagnosis (UPD) method. All samples were tested for bending strength using GOST 10180­2012. The effect of fire exposure on corroded beams was analyzed by the level of corrosion. The bearing capacity loss of the bent corroded beams ranged from 78% to 84% depending on the integrity of the corroded beam after exposure to fire, which had a compressive strength of 70MPa and an average corrosion rate of 9.3%. Such a large loss of bearing capacity is the result of severe cracking of concrete due to the combined action of corrosion and fire exposure. In addition, cracked specimens generally show a linear relationship with the level of corrosion of steel reinforcement associated with mass loss.