Journal Published Online: 01 December 1994
Volume 16, Issue 2

Crack Counts in Air-Entrained and Non-Air-Entrained Concrete Subjected to Accelerated and Fog-Room Curing



Concrete cured by the accelerated steam method, at atmospheric pressure, sometimes shows a reduced rate of strength gain at later ages. This loss of potential strength has been attributed to a number of factors, including microcracking caused by differential stress within the material. This may result from differences in the thermal expansion coefficients of the solid phases themselves and from the greater differences between the coefficients of solids and water. Because entrained air voids help to protect concrete from damage by frostaction by providing void spaces that reduce the build-up of hydraulic pressure caused by migrating water, we postulated that entrained air may similarly benefit concrete subjected to accelerated steam curing. The loss of potential strength in the steam-cured specimens was assumed to result from an increase in internal microcracking.

Specimens of air-entrained and non-air-entrained concrete were made and subjected to fog-room curing and to accelerated steam curing. However, crack-counts made at ages of 1 day and 28 days under an optical microscope were similar in both air-entrained and non-air-entrained concrete. At 28 days, crack-counts were higher in the fogcured concrete than in the steam-cured concrete whether air-entrained or not. Consequently, the data did not support the suggestions that entrained air would reduce internal stresses and resulting microcracking. Also, regardless of air-entrainment, it was found that crack counts were highest in samples that had gained strength most rapidly.

Author Information

Gillott, JE
The University of Calgary, Calgary, Alberta, Canada
Czarnecki, B
The University of Calgary, Calgary, Alberta, Canada
Pages: 5
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Stock #: CCA10288J
ISSN: 0149-6123
DOI: 10.1520/CCA10288J