Properties of Mass Concrete Containing Fly Ash at High Temperatures

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Title: Properties of Mass Concrete Containing Fly Ash at High Temperatures

Author(s): K. W. Nasser and H. M. Marzouk

Publication: Journal Proceedings

Volume: 76

Issue: 4

Appears on pages(s): 537-550

Keywords: compressive strength; C,S; fly ash; high temperature tests; hydrothermaI reactions;mass concrete; modulus of elasticity; stress-strain relationships; tobermorite.

Date: 4/1/1979

Abstract:
This investigation is a study of the effect of high temperature on the structural properties of mass concrete containing fly ash. Tests were performed on cylinders exposed for periods of over 6 months to temperatures of 70 to 450 F (21.4 to 323 C). Preliminary results of the investigation show that temperatures have minor effect on both strength and elasticity up to 160 F (71 C); however, in the temperature range of 250 to 300 F (121 to 149 C) there was an increase i.n strength and in one case it was 52 percent while the modulus of elasticity remained constant. The increase in strength is attributed to the formation of tobermorite which is a product of the reaction of lime and fly ash at high pressure and temperatures. At 350 and 450 F (177 and 232C) both strength and elasticity were reduced by about 60 and 65 percent, respectively. The deterioration of the structural properties is attributed to the transformation of most of the tobermorite and tobermorite gel into crystallized alpha dicalcium silicates having poor binding qualities.