EFFECT OF SOME ADMIXTURES ON EARLY SHRINKAGE AND OTHER PROPERTIES OF PROLONGED-MIXED CONCRETE SUBJECTED TO HIGH EVAPORATION

THE EFFECT OF DIFFERENT ADMIXTURES ON THE EARLY SHRINKAGE CHARACTERISTICS, AND ON PLASTIC SHRINKAGE CRACK FORMATION (BOTH SURFACE AND INTERNAL) IN CONCRETES MIXED FOR ONE HOUR AT 30C AND SUBJECTED TO 5 HOURS OF HEAVY EVAPORATION IMMEDIATELY AFTER CASTING, WAS STUDIED. PROPERTIES OF HARDENED CONCRETE, SUCH AS STRENGTH AND DRYING SHRINKAGE, OF EVAPORATION AND CONTROL (COVERED) SPECIMENS WERE ALSO STUDIED. THE ADMIXTURES TESTED INCLUDED WATER-REDUCING/SET RETARDING, WATER-REDUCING AND AIR-ENTRAINING AGENTS IN DIFFERENT AMOUNTS AND COMBINATIONS. TESTS SHOWED THAT THE EARLY SHRINKAGE CAUSES A DENSER MATRIX, BUT WHEN IT IS ACCOMPANIED BY INTERNAL TENSILE STRESSES (DUE TO RESTRAINING EFFECTS) EXCEEDING THE TENSILE STRENGTH CRACKS DEVELOP. AS ADMIXTURES AFFECT BOTH SHRINKAGE AND STRENGTH, THEY HAVE A SIGNIFICANT EFFECT ON THE DEGREE OF CRACKING. IT WAS ALSO CONFIRMED THAT THE LATTER SHOULD PREFEREABLY BE EVALUATED BY ANALYZING THE INTERNAL CRACKS, NOT THE SURFACE ONES. UNDER THE TEST CONDITIONS REPORTED, SET-RETARDED CONCRETE MIXES SHOWED THE HIGHEST EARLY SHRINKAGE AND SEVERE INTERNAL CRACKING. THE REFERENCE MIXES AND WATER-REDUCED MIXES SHOWED INTERMEDIATE VALUES. THE ONE-HOUR REFERENCE MIX SHOWED HIGHER SHRINKAGE AND HEAVIER CRACKING THAN ITS 5 MIN. COUNTERPART. THE COMPRESSIVE STRENGTH OF SEVERELY CRACKED EVAPORATION SPECIMENS WAS ONLY SLIGHTLY LOWER THAN THAT OF (UNCRACKED) CONTROL SPECIMENS, WHEREAS THEIR DRYING SHRINKAGE WAS MUCH LOWER. /CRIC/FESR/RRL/A/

• Supplemental Notes:
  • pp 319-350, 5 FIGS, 6 TABS, 77 PHOTS, 9 REFS
• Authors:
  • Jaegermann, C H
  • Ravina, D
• Conference:
  • Intl Symp Admix Mortar & Concr /Belg/
• Publication Date: 1967

Subject/Index Terms

• TRT Terms: Admixtures; Air entraining agents; Concrete; Cracking; Drying rate; Mix design; Physical properties; Plasticizers; Polymer concrete; Retarders (Chemistry); Shrinkage; Water reducing agents
• Uncontrolled Terms: Concrete cracking; Concrete properties
• Old TRIS Terms: Shrinkage cracks
• Subject Areas: Highways; Materials;

Filing Info

• Accession Number: 00212952
• Record Type: Publication
• Source Agency: Road Research Laboratory /UK
• Files: TRIS
• Created Date: May 4 1970 12:00AM