Evaluating The Effects Of Combined Freezing AndThawing And Flexural Fatigue Loading Cycles OnThe Fracture Properties Of FRC

Abstract

In cold climate regions, the life span of concrete structures can be significantly reduced if the mechanical properties of critical components of a structure are affected by the deterioration caused by simultaneous fatigue loading and freezing and thawing cycles. This makes the residual mechanical properties of the constitutive concrete material an important design consideration, after years of exposure in such a climate. The objective of the research program was to evaluate the residual mechanical properties of plain and Fiber Reinforced Concrete (FRC) (hooked-end steel, corrugated steel, and polyolefin fibers) exposed to several combinations of freezing and thawing cycles and flexural fatigue loading cycles. The residual mechanical properties (flexural strength, flexural stiffness, and flexural toughness) and the flexural fatigue resistance of the conditioned plain and FRC specimens were compared to the properties of unconditioned companion specimens to quantify the level of damage caused by each conditioning combination and to determine whether the addition of fibers could reduce the level of damage caused by conditioning. In general, the results indicated that the flexural strength, stiffness, and toughness of plain concrete and both steel and polyolefin fiber reinforced concrete, after exposure to a combination of 300 freezing and thawing cycles followed by 2 million cycles of flexural fatigue loading, 10-40% or 10-45% of the 90-day flexural strength, is greater than or approximately equal to the lowest residual flexural strength, stiffness, and toughness of specimens exposed to 300 freezing and thawing cycles or 2 million flexural fatigue loading cycles (between the same stress range). Interestingly, for all specimens, the residual flexural strength, after flexural fatigue loading at a stress range between 10-45% of the 90-day flexural strength value, was higher than specimens exposed to a stress range between 10-40% of the 90-day flexural strength. The applications of freezing and thawing cycles on all specimens (plain concrete and FRC) prior to flexural fatigue loading cycles resulted in higher flexural fatigue endurance limit than unconditioned specimens. D. P. Forgeron & J.-F. Trottier High Performance Structures and Materials II, C.A. Brebbia & W.P. De Wilde (Editors) © 2004 WIT Press, www.witpress.com, ISBN 1-85312-717-5