Stress Wave Propagation and Spalling in a Steel Reinforced Concrete Cylindrical Bar

By using the <i<φ</i<74 mm Hopkinson pressure bar, experiments were conducted to study stress wave propagations in a cylindrical steel reinforced concrete bar and the subsequent spalling of the bar. Strain gage were used to measure the stress wave propagations in the specimen, and a high-speed camera was used to record the spall fracture of the specimen. The experimental results show that under the lower loading speeds, elastic stress wave in the reinforced concrete specimen appears without observable dispersion and attenuation. At higher loading speeds, the reinforced concrete fractured due to reflected tensile stress pulse (spalling). The spall strength of the specimen is estimated to be about 7 MPa. In addition, the cracks on the concrete surface close and open repeatedly under the tension and compression of the reflected stress waves.