SUMMARY
Indian standard Code-IS:456-2000 and Eurocode EC:02-2004 for the design of the concrete structure is limited to the concrete with compressive strength of 55 MPa and 90 MPa respectively. For defining the stress block parameters and for the design of concrete structures using Very high strength concrete (100 MPa to 150MPa); a well-defined stressstrain behavior becomes necessary, particularly the experimental values for the strain at peak stress and ultimate strain capacity. The presents study attempts to cater to these needs by experimentally evaluating the unconfined stressstrain behavior of nine cylindrical specimens with a compressive strength between 100 MPa to 150 MPa, in a servocontrolled (Strain-controlled) compression testing machine. The strain values recorded at peak stress for 100 MPa and 150 MPa concrete are approximately 3000 microstrains and 3500 microstrains respectively. Compared to normal and high-strength concrete, the rising limb of the curves for VHSC (Very high strength concrete) is much steeper and approaches a straight path, also the strain at peak stress and ultimate strain coincide, depicting a negligible post-peak strain hardening region. LVDT and compressometer gave different strains for the same load and specimen. This signifies the role of the gauge length ratio used in these strain measuring devices.