A novel experimental technique to determine the spalling strength of concretes

A polymeric buffer bar is employed to replace the conventional metallic transmission bar in a split Hopkinson pressure bar to determine the spalling strength of a long concrete rod that is placed between the metallic incident bar and the polymer buffer bar. Since the polymer bar material has a lower mechanical impedance than the concrete specimen, spalling can be produced in the concrete rod after the compressive wave in the concrete specimen is reflected back as a tension wave at the concrete/buffer bar interface. The spalling in the concrete is detected by examining the profile of the transmitted pulse in the buffer bar. Even though the profile of the transmitted pulse recorded by the strain gages on the buffer bar may vary due to wave dispersion in such a viscoelastic buffer bar, a 3-D finite element analysis indicates that the wave dispersion correction is not necessary when the transmitted pulse is used to determine the spalling strength of the concrete specimen. The spalling strength is determined by using the records from the strain gages on the buffer bar on the basis of classic 1-D theory of characteristics.