INFLUENCE OF PUMPING ON CHARACTERISTICS OF AIR-VOID SYSTEM OF HIGH-PERFORMANCE CONCRETE

The results of an experimental study in which a high-performance air-entrained concrete mixture (water-cement ratio = 0.29; 28-day average compressive strength of 75 MPa) was pumped at the job site horizontally and vertically are presented. Concrete specimens were taken before and after pumping. The specimens were subjected to the ASTM C 457 microscopical determination of the characteristics of the air-void system. The size distribution of the air voids was also recorded using a computer-assisted image analysis system. The study results indicate that pumping can reduce the total air content and increase the air-void spacing factor. It was observed that the loss of air is mainly due to a very significant decrease of the number of small air voids (<100 microm in diameter); the number of larger voids is very little modified. This suggests that the frost durability may be more detrimentally affected than it first appears, when only the air content and the spacing factor are considered. It was also found that the loss of small air voids is more important for vertical pumping than for horizontal pumping, probably because the pumping pressure involved is higher. A mechanism is proposed to explain the observed effect of pumping on the characteristics of the air-void system.

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 30-36
  • Monograph Title: Concrete and concrete pavement construction
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00711777
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 19 2001 12:00AM