Effects of Long Term Moisture Storage on Concrete Test Samples

Concrete flexural strength is the primary thickness design input for rigid airport pavement. Therefore it is necessary to have an accurate estimate of pavement strength not only at the time of construction but also at the time of pavement testing. Researchers have three alternatives for estimating concrete strength at the time of testing, test cast samples which have been cured in the laboratory, test cast samples cured in the field, or cut samples from the pavement immediately after traffic testing. At the National Airport Pavement Test Facility (NAPTF) during Construction Cycle 6 (CC6), all three test sampling methods were used with varying results for concrete strength depending on the curing method. Three different concrete mix designs were used on the project. All mixes were straight cement, with no supplementary cementitious materials (SCMs). MRS1 was a “low” strength mix with a design flexural strength of 500 psi. MRS2 was a “medium” strength mix with a design flexural strength of 750 psi. MRS3 was a “high” strength mix with a design flexural strength of 1000 psi. The MRS1 concrete mix was made with gravel and sand aggregates. The MRS2 and MRS3 concrete mixes were made with dolomite and sand aggregates. The main difference between MRS2 and MRS3 mixes was the amount of cement. Laboratory tests were performed around the time of pavement testing which was approximately two years after construction. Samples from MRS2 and MRS3 stored in the moisture curing room for two years had a lower average flexural strength than tests performed at 28 days. The flexural strengths of field samples from MRS1, MRS2 and MRS3 mixes were higher than at 28 days. Sawed beams from MRS1, MRS2 and MRS3 had flexural strength approximately the same as those beams tested at 28 days. Petrographic analysis indicated that MRS2 and MRS3 concrete samples left in the curing room had Alkali-Silica Reaction (ASR) damage and secondary ettringite formation in ASR induced cracks. The conclusion is that prolonged storage of concrete samples in curing rooms is not recommended since tests made after this time do not reflect the condition of the pavement which has cured in a much drier environment. Field cured samples or saw cut sample are more likely to give a good estimation of concrete strength at the time of testing.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Photos; References; Tables;
  • Pagination: 15p
  • Monograph Title: 2014 FAA Worldwide Airport Technology Transfer Conference Proceedings: Innovations in Airport Safety and Pavement Technology

Subject/Index Terms

Filing Info

  • Accession Number: 01538139
  • Record Type: Publication
  • Report/Paper Numbers: P10091
  • Files: TRIS, ATRI, USDOT
  • Created Date: Sep 9 2014 6:34AM