Undispersed Agglomerates and Strength of Microsilica Concrete

The American Society for Testing and Materials C 1240 requires wet-sieved microsilica to pass the #325 sieve with no more than 10% retained, and advises that care be exercised “to avoid retaining agglomerations of extremely fine material.” The Ohio Department of Transportation (ODOT) has found that densified microsilica samples submitted sometimes do not meet this specification, apparently because wet-sieving is not capable of breaking the agglomerations. In this study, the possible repercussions of densification into larger particle sizes on the mechanical and other engineering properties of microsilica concrete are examined. Results of microsilica tests conducted suggest that C 1240 is not an appropriate test for assessing the suitability of microsilica for use in concrete. Tests conducted on concrete specimens indicate that those made with undensified microsilica show higher flexural and compressive strengths than concrete made with densified microsilica and microsilica abused by prolonged exposure to moisture, for both natural and crushed aggregate. The strengths of undensified microsilica concrete were followed by that of densified and abused microsilica concretes in decreasing order. Trends observed in almost all mixes with respect to increase in strength with age, microsilica type, aggregate type and specimen size were as expected. The strength increased with age and the strength increase was more rapid in the initial ages than during later ages. Both large and small cylinders attained compressive strengths of more than 5000 psi after 28 days of curing. Therefore, densified microsilica concrete can be used in the construction of pavements and bridges by ODOT.

Language

  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References; Tables;
  • Pagination: 23p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01043883
  • Record Type: Publication
  • Report/Paper Numbers: 07-2174
  • Files: TRIS, TRB
  • Created Date: Feb 8 2007 6:51PM