PRINCIPLES AND METHODS OF MANUFACTURE AND CONTROL FOR AIR-ENTRAINED CONCRETE /IN GERMAN/

CONCRETE WITH A HIGH CONTENT OF FINELY DISTRIBUTED ARTIFICIAL VOIDS IS RESISTANT TO FROST AND DE-ICING SALTS. ACCORDING TO THE THEORY OF CONCENTRATION GRADIENTS, IT IS ASSUMED THAT THE CHLORINE PENETRATING INTO THE CONCRETE SURFACE LOWERS THE FREEZING POINT SO THAT THE CAPILLARY WATER FREEZES FIRST IN AN INTERMEDIATE LAYER. IF FREEZING CONTINUES, THE FREEZING PRESSURE CANNOT ESCAPE AND IS ABSORBED BY THE ARTIFICIAL VOIDS. RESISTANCE TO FROST IS DETERMINED BY THE VOID SPACING FACTOR EXPRESSED BY AN INDEX REPRESENTING THE MAXIMUM DISTANCE THE FREEZING PRESSURE HAS TO TRAVEL TO REACH THE NEAREST VOID. THIS VOID SPACING FACTOR CAN ONLY BE DETERMINED FOR HARDENED CONCRETE. A DETAILED DESCRIPTION IS GIVEN OF THE MICROSCOPE FOR MEASURING THIS DISTANCE. IF THE LATTER IS INFERIOS TO 0,25 MM, CONCRETE IS RESISTANT TO FROST AND SALTS; IF IT EXCEEDS 0,40 MM, FROST DAMAGES CAN OCCUR. IN FRESH CONCRETE, THE VOIDS CONTENT IS MEASURED WITH A PRESSURE VESSEL USING THE METHOD OF EQUALIZATION OF PRESSURE. SPECIAL INSTRUCTION FOR THE TESTING, ACCEPTANCE AND SUPPLY OF AIR-ENTRAINING AGENTS FOR ROAD SURFACINGS, PUBLISHED BY THE AUSTRIAN ROAD RESEARCH INSTITUTE (RLP67) DEFINE THE INFLUENCE OF ADMIXTURES ON THE SETTING AND COMPRESSIVE STRENGTH OF CONCRETE AND THEIR AIR-ENTRAINING CAPACITY UNDER UNFAVORABLE CONDITIONS. THE NEED FOR CAREFUL IN-SITU CONTROL OF THE VOIDS CONTENT IS STRESSED IN ORDER TO PREVENT SALTS FROM DAMAGING SHORT SECTIONS OF ROAD. VISUAL CONTROLS CAN BE EASILY CARRIED OUT AND FURTHER PRESSURE VESSEL TESTS CONDUCTED. IT IS POSSIBLE TO SEE AIR-ENTRAINING AGENTS IN HARDENED CONCRETE WITH A SMALL PORTABLE MICROSCOPE. MACROGRAPHS REPRESENTING THE SURFACE STRUCTURE CAN BE USED TO DETERMINE VOID SPACING. /LCPC(A)/RRL/

  • Supplemental Notes:
    • Vol 1, pp 67-80, 3 FIG, 2 TAB, 8 PHOT, 9 REF
  • Corporate Authors:

    European Cement Association /France

    ,    
  • Authors:
    • Blumel, O W
    • Springenschmid, R
  • Publication Date: 1969-7

Subject/Index Terms

Filing Info

  • Accession Number: 00215026
  • Record Type: Publication
  • Source Agency: Road Research Laboratory /UK
  • Files: TRIS
  • Created Date: May 16 1971 12:00AM