Understanding Early-Age Shrinkage of High-Performance Concrete for Bridge Deck Applications

The paper discusses results and analyses from a series of early-age autogenous shrinkage measurements for several high performance concrete mixtures developed for bridge deck applications using fly ash and silica fume tests. These tests were performed under temperature-controlled conditions to investigate the influence of mixture proportions and binder composition on early-age shrinkage measurements. For bridge decks, it is desirable to minimize autogenous shrinkage. Because autogenous shrinkage is due to self-dessication, it cannot be mitigated with curing techniques. Rather it must be addressed during mix design. Excessively high autogenous shrinkage can lead to cracking that reduces the life span of bridge decks and negates the benefit of reduced permeability by providing a direct path for chlorides to reach reinforcing steel. Corrections for measured strains resulting from temperature effects are also discussed. The problem of autogenous shrinkage measurement at early ages is complicated by the nebulous definition of strains during the transition from a semi-liquid to a solid. It is hence necessary to complement autogenous shrinkage measurements with measurements of concrete setting times. The presence of free water within the concrete matrix (as indicated by setting times) greatly influences the thermal expansion of concrete. In order to accurately represent very early-age measurement of autogenous shrinkage, the thermal expansion of the concrete due to heat of hydration must be corrected for. A tri-linear model was used where the coefficient of thermal expansion varies from initial to final set. Results show that silica fume significantly increases autogenous shrinkage, and the fly ash reduces autogenous shrinkage slightly. Additionally, companion tests on chloride permeability show that silica fume causes the permeability to increase significantly. Ternary blends of cement, fly ash, and silica fume are shown to take advantage of the best features of both silica fume and fly ash, offering the durability improvement typical of silica fume, along with the early-age shrinkage-reducing effects of fly ash.

• Corporate Authors:

  Iowa State University, Ames

  2711 South Loop Drive
  Suite 4700
  Ames, IA  United States  50010-8664
• Authors:
  • Earney, T P
  • Gopalaratnam, V S
  • Luckenbill, G C
• Conference:
  • 2006 Transportation Scholars Conference
  • Location: Ames Iowa, United States
  • Date: 2006-11-15 to 2006-11-15
• Publication Date: 2006

Language

• English

Media Info

• Media Type: Print
• Features: Figures; References;
• Pagination: 11p
• Monograph Title: Compendium of Student Papers Presented at the Transportation Scholars Conference, Iowa State University, November 15, 2006

Subject/Index Terms

• TRT Terms: Admixtures; Binder content; Bridge decks; Cement; Chlorides; Concrete setting; Cracking; Durability; Fly ash; High performance concrete; Measurement; Mixtures; Pavement performance; Permeability; Reinforcing steel; Shrinkage; Silica fume; Temperature; Thermal expansion
• Uncontrolled Terms: Autogenous shrinkage; Chloride permeability; Early age; Setting time
• Subject Areas: Bridges and other structures; Design; Highways; Materials; I24: Design of Bridges and Retaining Walls; I32: Concrete;

Filing Info

• Accession Number: 01039117
• Record Type: Publication
• Files: TRIS
• Created Date: Jan 3 2007 8:48AM