Effect of Moisture Content and Fiber on the High-Temperature Properties of Tunnel Second Lining Concrete

Abstract

The critical moisture content of concrete with different fibers and the quality loss of different moisture contents are analyzed by simulating the real heating curve of the building material in a fire, and a fire test on the concrete slab is conducted. Results show that (1) moisture content greatly influences the surface burst degree, number of cracks, time of water seepage, and quality loss of the specimen after a fire; (2) the critical moisture content of fireproof fiber concrete burst is higher than that of three other kinds of concrete (normal concrete, polyethylene fiber concrete, and polypropylene fiber concrete), and has the highest crack resistance; and (3) the observation of fire spalling and the burn crisp degree of the concrete slab with the same moisture content verified that the fireproof fiber has a better anti-burst effect. Testing the post-fire side face of concrete slabs and the regional rebound value show that rebound value losses are not the same because of different temperature distributions on the side faces of the concrete slabs. The loss of mechanical property of the concrete is related to the temperature field.