Predicting Spacing Factor In Hardened Concrete

For Portland cement concrete subjected to freezing and thawing, a large number of closely spaced small air bubbles provide short flow distance to relieve excess pore pressure buildup and prevent damage. Thus, a good air void system containing small, closely spaced bubbles is necessary to improve durability of concrete pavement in regions experiencing numerous freeze thaw cycles. In practice, many transportation agencies specify a minimum volumetric air content to ensure a spacing factor less than 0.2 mm (0.008 in.). Spacing factor in hardened concrete can be obtained directly by ASTM C457, but the method is time consuming and unsuitable for construction quality assurance. The KT-86/AASHTO TP 118 Super Air Meter (SAM) test method and apparatus was developed to predict the ASTM C457 spacing factor by testing fresh concrete within 10 minutes. Results from this test include total air content and SAM number, where the latter is correlated with ASTM C457 spacing factor. In this research, a number of low-slump paving mixtures were evaluated since this type of concrete is most susceptible to frost damage. This study statistically evaluated the predictive capability of this test method along with a model based on SAM number and the volumetric ratio of air to cementitious paste, to ascertain presence of good air void structure in fresh concrete for concrete pavements. The ratio of volumetric air to cementitious paste appears to be the most important factor for predicting spacing factor.


  • English

Media Info

  • Media Type: Web
  • Features: Figures; References; Tables;
  • Pagination: 13p

Subject/Index Terms

Filing Info

  • Accession Number: 01764355
  • Record Type: Publication
  • Report/Paper Numbers: TRBAM-21-03914
  • Files: TRIS, TRB, ATRI
  • Created Date: Dec 23 2020 11:27AM