This paper provides dynamic increase factors (DIF) in compression for two different High Performance Concretes (HPC), 100 MPa and 160 MPa, respectively. In the experimental investigation 2 different Split Hopkinson Pressure Bars are used in order to test over a wide range of strain rates, 100 sec 1 to 700 sec -1 . The results are compared with the CEB Model Code and the Spilt Hopkinson Pressure Bar technique is briefly described. tion takes a bilinear relation between DIF and log(e ) with a change in slope at strain-rate of 30 s. (Malvar and Ross, 1998) 2 SPLIT HOPKINSON PRESSURE BAR 2.1 How the SHPB works The principle of a SHPB device is shown in Figure 2. The axial compression impact is caused by the striker bar impinging the incident bar. When this occurs, an incident stress pulse is developed. The pulse propagates along the incident bar to the interface between the bar and the specimen. At this point, the pulse is both reflected and transmitted. The reflected wave propagates back along the incident bar and the transmitted wave attenuates in the specimen and into the transmitter bar. Both the incident and the reflected waves are measured by a strain gauge mounted on the surface at mid-length of the incident bar. Similarly, the transmitted wave is measured by a strain gauge on the surface at mid-length of the transmitter bar. (Li and Meng, 2003) Figure 3. Interfaces between pressure bars and specimen. The circular specimens are placed between the two long horizontally aligned pressure bars which serve as the medium for the propagation of elastic pulses as well as for measuring the stress-time history. Figure 3 and Figure 4. Figure 4. Strain gauge measured wave initiated strains in the SHPB setup. Interfaces at location a and b. Incident, reflected and transmitted, respectively. 2.2 How to read the data A typical output from a SHPB test is shown in Figure 5. Figure 5. Output from SHPB test. All three waves, ei(t), er (t) and et(t), are measured at the gauge locations, situated at some distance away from the interface. Therefore, an appropriate timeshifting procedure must be undertaken to transfer the strain histories from the gauge locations to the interfaces Figure 6. Figure 6. Time-shifted output from SHPB test. To calculate the specimen stress and the dynamic increase factor, Hooke’s law is used to determine the stress of the pressure bars from the measured strain values. Based on (Linholm and Bunshah, 1971) summery of SHPB technique following strain rate, strain and stress history with respect to time, can be calculated, respectively, as [ ] 0 ( ) ( ) ( ) ( ) i r t c t t t t L e e e e = − − (3)