Title:
Flexural Fatigue Performance of Steel Fiber Reinforced Concrete--Influence of Fiber Content, Aspect Ratio, and Type
Author(s):
Colin D. Johnston and Robert W. Zemp
Publication:
Materials Journal
Volume:
88
Issue:
4
Appears on pages(s):
374-383
Keywords:
fatigue (materials); fatigue tests; fiber reinforced concretes; flexural tests; metal fibers; reinforcing steels; Materials Research
DOI:
10.14359/1875
Date:
7/1/1991
Abstract:
The performance of steel fiber reinforced concrete under flexural fatigue loading is examined in terms of fiber content (0.5 to 1.5 percent by volume), fiber aspect ratio (47 to 100), and fiber type (four types). Data from 194 fatigue tests and 135 complementary static loading tests are presented both as S-N relationships with the maximum stress expressed as a percentage of the strength under static loading, and as relationships between actual stress and number of loading cycles. The S-N relationships depend primarily on fiber content and aspect ratio. Fiber type is secondary in importance. The 100,000-cycle endurance limits are 84 and 89 percent of the first-crack strength under static loading for the better combinations of fiber type and amount (characterized by at least 1.0 percent volume of fibers of an aspect ratio of 70 or greater). The corresponding limits drop to 75 to 80 percent for the less effective combinations characterized by fiber amounts of 1.0 percent or less and aspect ratios of 47 to 54. The relationships between actual stress and number of cycles depend primarily on fiber content. Aspect ratio and type are secondary in importance, especially when differences in water-cement ratio and water-cement ratio plus fly ash are taken into account. The best performance, a 100,000-cycle endurance limit of 6.9 MPa, is obtained with 1.5 percent by volume of 75 aspect ratio cold-drawn wire fibers in concrete with a w/c + f of 0.49. For 0.5 percent of the same fibers, the 100,000-cycle limit is only 5.2 MPa, despite a lower w/c + f of 0.39.