Definition and Measurement of Flexural Toughness Parameters for Fiber Reinforced Concrete

Current and past approaches to assessing and defining the flexural toughness of fiber reinforced concrete are reviewed, and the difficulties associated with them are discussed. Refinements needed to ensure correct analysis and interpretation of load-deflection relationships in evaluation of flexural toughness are identified. A new system of defining toughness is proposed. It comprises a series of indices based on material behavior up to specified multiples of the first-crack deflection. This system is shown to be superior to the one currently advocated by The American Concrete Institute Committee 544 based on material behavior up to a deflection of 1.9 mm (0.075 in.). It is recommended as the basis for a standard test method to evaluate toughness, and appropriate provisions for inclusion in the standard are identified.