Comparative Evaluation of Flexural Fatigue Behavior of High-Volume Fly Ash and Plain Concrete


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Title: Comparative Evaluation of Flexural Fatigue Behavior of High-Volume Fly Ash and Plain Concrete

Author(s): V. Ramakrishnan, V.M. Malhotra, and W.S. Langley

Publication: Special Publication

Volume: 229


Appears on pages(s): 351-368

Keywords: compressive strength; concrete; endurance limit; fatigue life; fatigue stress; flexural fatigue; flexural strength; fly ash; modulus of rupture

Date: 9/1/2005

Research on structural concrete incorporating high volumes of low-calcium (ASTM Class F) fly ash has been in progress at CANMET since 1985. In this type of concrete, the cement content is kept at about 150 kg/m3. The w/cm materials ratio is of the order of 0.30, and fly ash varies from 54 to 58 percent of the total cementitious material. A large dosage of a superplasticizer is used to achieve high workability. This paper presents the results of an investigation conducted to determine the flexural fatigue strength and the endurance limit (for four million cycles) for high-volume fly ash concrete and its corresponding plain concrete (control concrete). A total of 40 prisms, 20 prisms 75 x 100 x 400 mm in each concrete, were tested in flexural fatigue at a frequency of loading of 20 cycles per second (HZ). The prisms which survived four million cycles of fatigue loading were tested in static flexure (modulus of rupture). The high-volume fly ash concrete has slightly higher (7%) endurance limit than the plain control concrete. There was an increase (15 to 30 percent) in the static flexural strength (modulus of rupture) for both high-volume fly ash and plain concretes when the prisms had been previously subjected to four million cycles of fatigue stress that was lower than its fatigue strength.