The Effects of Air Content, Water-Cement Ratio, and Aggregate Type on the Flexural Fatigue Strength of Plain Concrete
F. Wayne Klcriber and Dcrh-Yinn lee
Appears on pages(s):
aggregates; air entrainment;
'(materials); fatigue tests; fine aggrega
plain concrete; water-cement ratio.
tes; fati ue
Rigid pavement design procedures currently in use con-sider only the modulus of rupture strength of concrete in deter-mining the fatigue life of concrete highway pavements. The effects of entrained air, water-cement ratio, and aggregate type are considered only to the extent they affect the modulus of rup-ture of the concrete. The purpose of this study was to determine the effects of air content, water-cement ratio, and aggregate types on the flexural fatigue strength of plain concrete and to develop fatigue curves that incorporate these effects and thus could be used for design. Fifteen series of concrete were investigated in this study. The variables consisted of air content, water-cement ratio, coarse aggregate type and fine aggregate type. Over 350 beams were sub-jected to flexural one-third point fatigue loading in which the bottom fiber stress varied from essentially zero to a predeter-mined maximum stress. Of the variables investigated, air content and coarse aggregate type were determined to have the greatest effect on flexural fatigue strength. Water-cement ratio also affects the fatigue strength but to a lesser degree. Fatigue strength of concrete was not significantly influenced by the type of fine aggregate used.