EFFECTS OF RETARDING ADMIXTURES ON PLASTIC SHRINKAGE OF PORTLAND CEMENT PASTE

This paper describes the effects of water reducing and retarding admixtures, ASTM Type D, on plastic shrinkage of portland cement paste under different controlled relative humidities. Three types of commercial admixtures were used each representing a different common chemical classification of such retarders. Concentration of each retarder was that which gave fifty percent retardation of a 0.50 water cement ratio mortar by penetration resistance. The length change measurements were made on thin cement paste sections floating on mercury. A magnetic proximeter was used to measure the length changes. The results of this work indicate that plastic shrinkages, when using retarding admixtures, are higher compared with the plastic shrinkage of plain paste. The higher shrinkage is due to the increased time in the plastic stage of paste and possible changes in paste microstructure evidenced by bleeding characteristics with some retarders. The appearance of plastic shrinkage cracks occurred during the transition from a higher measured rate of shrinkage to a subsequent lower one. Evidence indicates that plastic shrinkage is influenced by the rate of evaporation, hydration and microstructure of the paste.

• Supplemental Notes:
  • This study was conducted in cooperation with the U.S. Department of Transportation, Federal Highway Administration. Research Study tilted "Effects of Retarders on Volume Changes, Portland Cement Concrete".
• Corporate Authors:

  Purdue University/Indiana Department of Transportation JHRP

  Purdue University, School of Civil Engineering
  West Lafayette, IN  United States  47907-1284
• Authors:
  • Gowda, H
• Publication Date: 1973-8

Media Info

• Pagination: 96 p.

Subject/Index Terms

• TRT Terms: Admixtures; Nonmetals; Pastes; Portland cement concrete; Retarders (Chemistry); Shrinkage
• Subject Areas: Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00264019
• Record Type: Publication
• Source Agency: Federal Highway Administration
• Report/Paper Numbers: JHRP-20-73 Intrm Rpt.
• Contract Numbers: HPR-1(11) Part II
• Files: TRIS, USDOT
• Created Date: Dec 31 1974 12:00AM