Title: Predicting Freeze-Thaw Durability of Concrete-A New Approach

Author(s): Emmanuel K. Attiogbe

Publication: Materials Journal

Volume: 93

Issue: 5

Appears on pages(s): 457-464

Keywords: air-entrained concrete; air voids; air-void system; concrete durability; freeze-thaw durability; frost resistance; mean spacing; protected paste volume; spacing factor.

DOI: 10.14359/9850

Date: 9/1/1996

Abstract:
The calculated air-void spacing factors used in assessing the probable perfor mance of concrete under repeated cycles of freezing and thawing do not re-flect the random distribution of air voids in real concrete. This is certainly part of the reasonfor the lack of a consistent correlation between the standard spacing factor and freeze-thaw durability. Because of the lack of a consistent correlation, excellent concrete mixes stand the chance of being rejected when the standard spacing factor is used to assess the potential durability. The recently developed mean spacing model for air voids is used with data obtained from ASTM C 666 to establish a new procedure for predicting the freeze-thaw durability of concrete. The values of mean spacings and volume fraction of cement paste in the zone of protection of air voids F provide the basis for the prediction. A plot of s against F yields three distinct zones of durability: a zone of probable durable concrete, an intermediate zone of uncertain durability, and a zone of probable nondurable concrete. The air-void spacing limit to insure a durable concrete is found to be more stringent the smaller the value of F. The spacing limit is higher the lower the water cementitious materials ratio, implying that a constant spacing limit cannot provide a consistent basis for assessing the durability of all grades of concrete.