Effects of cycling fatigue on chloride permeability of plain concrete.

摘要

The dissertation describes an empirical study of the effects of high amplitude (stress ratio) cyclic flexural loading and resulting localized cracking on chloride permeability of plain concrete. Third point flexural loading was applied to notched beams at one cycle/second, using a closed-loop control system governed by the measured deformation at the notch mouth (CMOD). The work addresses two types of fatigue: conventional constant load per cycle and a new technique with constant deformation per cycle. Both mechanical compliance (CMOD/Load), (the inverse of stiffness), and chloride permeability (K cl) using "Rapid" test (ASTM C1202-94) were monitored with progressive levels of deformation. The measured Kcl is a composite measurement through the 3.75" dia, 2" thick cores recovered from beam sections bracketing the distressed area. Comparisons are made between the distressed Kcl and that measured on cores of "intact" concrete obtained at the non-loaded sections of the same beams. A relationship between chloride permeability and compliance is indicated, showing that the fatigue-induced cracking affects both mechanical and diffusive behavior.