Author : Frederick Williamson
Publisher : Unknown
Page : 0 pages
File Size : 54,8 Mb
Release : 1964
Category : Air-entrained concrete
ISBN : OCLC:1426858792
A Study of Concrete Freeze-thaw Durability and Air Void Parameters by Frederick Williamson Pdf
As a result of the knowledge that concrete freeze-thaw durability depends on the number, size, and spacing of air voids throughout the mass, rather than on the total volume of entrained air voids, study of the air void system of hardened concrete has become concentrated on the determination of significant air void parameters. This thesis presents the results of an investigation to determine relationships between freeze-thaw durability and air void parameters of hardened concrete. Specifically, the objective of this study was to establish the pattern of the relationships between concrete durability and both the void spacing factor and the specific surface of the voids. Eighteen concrete mixes, representing six air contents up to approximately nine per cent by volume, and three common cement contents, were prepared and tested during this program. Air void parameters of the hardened concrete, as determined by the lineal traverse method of microscopic examination (A.S.T.M. C 457 - 60T), were measured and related to freeze-thaw durability data obtained from tests performed in accordance with A.S.T.M. procedure C 290 - 57T. Compressive strength data were also obtained for all concrete mixes prepared. Compressive strength test results verified the well-known relationships involving strength, age, cement content, air content, and water-cement ratio. The most significant test results available from this investigation are those relating concrete freeze-thaw durability and air void parameters. It was found that air entrainment up to approximately six per cent air by volume improved the concrete freeze-thaw durability, by decreasing the air void size and spacing, and increasing the specific surface of the voids. At air contents greater than approximately six per cent, further air entrainment did not significantly improve the freeze-thaw durability. Freeze-thaw durability was found to be practically independent of both cement content and water-cement ratio, for air contents above approximately two per cent. Protection of concrete from freeze-thaw deterioration is thus more effectively realized by air entrainment, than by variations in cement content and/or water-cement ratio. Observed data showed that relationships between concrete durability and both specific surface and spacing factor are non-linear. A rapid increase in durability with decreasing void spacing indicates a critical void spacing factor of approximately 0.005 inch, for conditions of these tests.