Fatigue Characteristics of High Performance Fiber-reinforced Concrete

摘要

This paper provides a summary of a study of fatigue behavior undertaken as part of SHRP project C-205 on the fresh and gardened properties of high early strength fiber-reinforced concrete (HESFRC). HESFRC was defined as achieving a minimum target compressive strength of 5 ksi (35 MPa) in 24 h. Several properties of HESFRC were investigated: for the fresh mixture, the air content, inverted slump test, temperature, and unit weight; for the hardened composite, the compressive, bending, and tensile properties. Optimum mixtures that satisfied the minimum compressive strength criterion, and showed excellent values of modulus of rupture, toughness indices in bending, and split tensile behavior, were selected for fatigue testing. In this paper a description is given of key results of the fatigue bending test only. The experimental program included a total of 24 fiber-reinforced control specimens tested under static flexural loading, and the remaining 14 specimens were tested under fatigue loading. Two mixes containing 2 vol% of hooked steel fibers were selected. For each mix, three different target load ranges were applied: 10-70%, 10-80%, and 10-90% of the ultimate flexural capacity, as obtained from the corresponding control static test with fibers. A typical relation between maximum fatigue stress and number of cycles to failure was derived, suggesting a fatigue endurance limit of the order of 65% even if specimens are in a cracked state.