Behavior of Epoxy Repaired Beams under Fire

Epoxy injection techniques are widely used to repair concrete or masonry structural components damaged by earthquakes, wind, or other types of overloads. When properly performed, the effectiveness of such epoxy injection techniques has been demonstrated by numerous laboratory experiments and a multitude of successful field applications. Except for elevated temperature, fire, and creep effects, most strength properties of epoxy repaired concrete components exceed those prior to damage. Since epoxy adhesives are organic thermosetting resin systems, they are highly susceptible to softening and pyrolysis at elevated temperatures. The effects of temperature and fire on epoxy repaired concrete beams is discussed herein with a presentation of test results of both small- and large-scale specimens. These test results show that both shortterm strength and stiffness of epoxy repaired beams reduce rapidly at uniform temperatures exceeding about 250 °F (121 °C). Under fire conditions, the strength reduction is primarily influenced by the presence or lack of fire protection coatings and the thermal gradient. Analytical techniques are presented for strength analysis of epoxy repaired beams under a variety of temperature and fire exposures.