Toughness measurements of high-strength concrete reinforced with steel fibers

Results from an experimental and numerical study of high-strength concrete (f;The research objectives were to study the fracture behavior of high-strength concrete beams reinforced with steel fibers in terms of toughness parameters based on the ASTM C1018-92, the Japan standard JSCE-SF4 and fracture mechanics theory. The importance of making accurate deflection measurements and the effect of the method of measuring the displacement on the toughness and other flexural characteristics was considered. The experimental program consisted of testing eighty notched and unnotched beams. The primary variables of the research were the fiber type, fiber volume percentages, and testing procedure. A theoretical model is proposed to evaluate the fracture behavior of the concrete tested using the R-curve approach. Carpinteri's model is used to assess the failure of the material and Jenq and Shah's two-parameter model is also used to study the fracture behavior of the material.;This investigation showed that the calculated toughness indices vary with the testing procedure, particularly with the method used to measure the deflections. The CMOD-controlled tests generate more consistent toughness indices than ASTM C1018. The JSCE flexural toughness is sensitive to fiber type and fiber percentage. The R-curve is a comprehensive way of describing the fracture behavior and appears to be a better indicator of the effectiveness of fibers than the ASTM C-1018 toughness indices.