The Durability of Concrete Containing High Levels of Fly Ash

This thesis presents data from a laboratory study on the effect of curing on the carbonation and permeability of high-volume fly ash concrete (HVFAC). Concrete mixtures were produced at a range of water-to-cementing-materials ratios (W/CM = 0.34, 0.40 and 0.50) and fly ash replacement levels (0%, 30%, 40% and 50%) using fly ashes of different compositions (Type F, CI and CH). Concrete specimens were moist-cured for various periods (1 to 28 days) prior to exposure to one of the following conditions: (i) accelerated carbonation (approximately 1% CO2 by volume), (ii) indoor (23°C and 50% RH), or (iii) outdoors (sheltered from direct precipitation). A limited number of specimens were treated with different curing compounds after stripping the molds at 1 day and these specimens were subjected to the same exposure conditions. In addition to monitoring changes in compressive strength, the depth of carbonation was determined periodically by spraying freshly fractured surfaces with phenolphthalein indicator, and the “permeability” was measured indirectly by determining electrical conductivity (as per ASTM C 1202). The data indicate that HVFAC carbonates at a significantly faster rate than plain portland cement concrete at the same W/CM. The rate of carbonation increases with the level of fly ash and differences become particularly marked as the degree of moist curing is reduced or the W/CM is increased. The increased sensitivity of HVFAC can be offset by (i) specifying lower W/CM, (ii) extending the period of moist curing, or (iii) increasing the depth of cover when such concretes are used. The results are discussed in the context of code requirements for reinforced concrete structures.

• Record URL:
  http://www.cement.org/bookstore/profile.asp?itemid=SN2989
• Corporate Authors:

  Portland Cement Association

  5420 Old Orchard Road
  Skokie, IL  United States  60077
• Authors:
  • Burden, D
• Publication Date: 2006

Language

• English

Media Info

• Media Type: Web
• Features: Glossary; References; Tables;
• Pagination: 110p

Subject/Index Terms

• TRT Terms: Carbonation; Compressive strength; Concrete; Concrete curing; Curing agents; Durability; Electrical conductivity; Fly ash; Permeability; Portland cement concrete; Water cement ratio
• Uncontrolled Terms: High volume fly ash concrete; Indoor; Moist curing; Outdoor exposure
• Subject Areas: Highways; Materials; I32: Concrete;

Filing Info

• Accession Number: 01041376
• Record Type: Publication
• Report/Paper Numbers: PCA R&D Serial No. 2989
• Files: TRIS
• Created Date: Jan 30 2007 1:29PM