Elevated Temperatures of Portland Cement Mixtures Related to Surface Removal


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Title: Elevated Temperatures of Portland Cement Mixtures Related to Surface Removal

Author(s): R. H. Heiskell, R. H. Black, R. J. Crew, and H. Lee

Publication: Journal Proceedings

Volume: 54

Issue: 1

Appears on pages(s): 591-603

Keywords: no keywords

Date: 1/1/1958

The effect of heat on the surface removal of concrete was studied by con-ducting brush tests on samples which had been subjected to prolonged high temperatures in an oven or in direct contact with an oxypropane flame. Other methods of heat treating surface layers of concrete were investigated by direct application of an oxyaluminum torch on the surface and by the exothermic chemical reactions of pyrotechnic compositions placed directly on the surface. Tests showed that an oven temperature of 1100 F is required to decompose portland cement compounds sufficiently to reduce the resistance of concrete surfaces to abrasive removal methods. The temperatures produced at the surface of concrete by an oxypropane burner varied, depending on the rate of traverse of the flame, from 200 to 800 F. Spalling of concrete surfaces can be accomplished by prolonged flame treatment with an oxypropane or oxy-acetylene burner. Flame treating with a moving oxypropane burner gave a temperature of 120-600 F at 1/64 in. below the surface. No spalling was observed when an oxyaluminum flame passed over the surface at a speed of 10 ft per min; however, prolonged heating resulted in a rather violent spalling reaction.