Confined and unconfined compressive strength and deformation of concrete at high strain rates

Dispersion of an elastic wave propagating in the transmitter bar of the split Hopkinson pressure bars (SHPB) is studied with records from two surface strain gage stations. The characteristics of dispersion are demonstrated and discussed. Fourier series expansion and the Fast Fourier Transform were employed along with numerical results of the Pochhammer-Chree analysis of stress waves in an infinitely long cylinder to reconstruct pulses from the SHPB. The advantages of dispersion correction technique are demonstrated for concrete specimens tested in the SHPB.; Extensive studies of uniaxial unconfined dynamic impact tests of high strength concrete cylindrical specimens with a maximum aggregate size 12.7 mm (0.5 inch) were performed with a 75 mm (3 inches) diameter SHPB. Studies of the fracturing processes were carried out with detailed and abundant information acquired from the SHPB results, to which the dispersion correction technique was applied. Surface strain gages were mounted on some of the tested specimens. The recordings from these strain gages were studied in detail for the understanding of the failure processes. It was found that these gage records furnish valuable information in this study.; A new cementitious material system SIFCON (Slurry Infiltrated Concrete) was uniaxially impact tested with the SHPB. Its ductile response and damages were presented and investigated.; Passively confined dynamic impact experiments on plain concrete specimens were performed with steel and aluminum jackets and the SHPB. The specific requirements of the specimens employed in jacketed tests were achieved with metallic-mold casting. The confining pressures were obtained by mounting surface strain gages on the jackets. Permanent deformation and residual static strength were studied in the characterization of the behavior of plain concrete specimens under dynamic multiaxial loads.