WHY SLABS CURL. PART I: A LOOK AT THE CURLING MECHANISM AND THE EFFECT OF MOISTURE AND SHRINKAGE GRADIENTS ON THE AMOUNT OF CURLING

Most slabs on grade curl, but research to determine why slabs curl and how curling can be reduced has been too scattered to receive the attention it deserves or to contribute to a better understanding of the problem. This paper provides a summary of this previous research and what it may mean to designers and contractors. The cited research findings indicate that: (1) curling is the result of nonuniform drying that establishes the moisture gradient, the resulting stress distribution and applied curling moment, and thus the amount of curl; (2) the drying takes place in the top few inches regardless of the slab thickness or external environment; (3) for a given moisture gradient, different concreting materials can cause different shrinkage gradients within a slab, with the differences likely to be greater near the bottom of the slab; (4) a wet subbase increases the shrinkage gradient and the applied curling moment; (5) whether concrete curls more when placed directly on a vapor retarder or on a granular subbase depends on the moisture content of the subbase; (6) relative humidity of the drying environment can change the shrinkage gradient, with slabs exposed to a lower relative humidity curling sooner than slabs exposed to higher relative humidity; and (7) the same concrete may exhibit different amounts of curl due to factors related to different final environments such as temperature and relative humidity at the surface.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/oclc/4163061
• Corporate Authors:

  American Concrete Institute (ACI)

  38800 Country Club Drive
  Farmington Hills, MI  United States  48331
• Authors:
  • Suprenant, B A
• Publication Date: 2002-3

Language

• English

Media Info

• Features: Figures; Photos; References;
• Pagination: p. 56-61
• Serial:
  • Concrete International
  • Volume: 24
  • Issue Number: 3
  • Publisher: American Concrete Institute (ACI)
  • ISSN: 0162-4075

Subject/Index Terms

• TRT Terms: Concrete; Concrete hardening; Curling; Deformation curve; Humidity; Literature reviews; Moisture barriers; Moisture content; Setting (Concrete); Shrinkage; Slab on grade; Slabs; Subbase (Pavements); Temperature; Thickness
• Uncontrolled Terms: Drying (Concrete); Moisture gradient
• Subject Areas: Highways; Materials; I32: Concrete;

Filing Info

• Accession Number: 00921719
• Record Type: Publication
• Files: TRIS
• Created Date: Mar 22 2002 12:00AM