INSULATION OF PAVEMENT SUBGRADE

THE INSTALLATION AND PERFORMANCE ARE DESCRIBED OF POLYSTYRENE INSULATION BOARDS IN THE SUBGRADE OF A ROADBED AREA SUBJECT TO FROST-HEAVING. A DOUBLE LAYER OF 1 1/2 INCH THICK 8 X 2 FOOT SHEETS WAS PLACED 18 IN. BELOW GRADE; SINCE THE SUBGRADE SOIL CONSISTED OF FINE SAND NO GRANULAR CUSHION WAS NECESSARY. BOARDS OF 1 AND 2 IN. THICKNESSES WERE USED TO PROVIDE A 48-FOOT TRANSITION AT EACH END OF THE INSTALLATION. FIVE THERMOCOUPLES WERE INSTALLED, ONE DIRECTLY ABOVE AND ONE BELOW THE BOARDS, AND THE OTHERS AT 3, 5, AND 7 FEET BELOW THE TOP OF THE ROADWAY. AFTER THE GRADE WAS RESTORED, THE OLD SURFACING (2 1/2 IN. COLD-MIX BITUMINOUS BASE WITH CHIP SEAL) WAS PULVERIZED AND PLACED ON THE GRADE. THE AREA WAS THEN PRIMED WITH AN MC-250 BITUMEN AND COVERED WITH A 2 INCH BLADE-LAID BITUMINOUS COLD MIX. THE TOTAL COST WAS APPROXIMATELY $7900; A PARTIAL BREAKDOWN OF THE COSTS ARE GIVEN. ELEVATION CHECKS MADE DURING MID-WINTER REVEALED NO EVIDENCE OF FROST-HEAVING IN THE INSULATED AREAS, ALTHOUGH SMALL HEAVES DID DEVELOP JUST OFF THE LOW END OF EACH AREA INDICATING DESIRABILITY OF LONGER TRANSITIONS OF INSULATION IN DIRECTION OF WATER MOVEMENT. SIMULTANEOUS READINGS OF TEMPERATURE DIFFERENTIALS OF THERMOCOUPLES LOCATED DIRECTLY ABOVE AND BELOW THE INSULATION RANGED UP TO 48 DEGREES; THE LOWEST TEMPERATURE ABOVE THE BOARD WAS NINE DEGREES BELOW ZERO, AND THE LOWEST DIRECTLY BELOW WAS 32 DEGREES F. THE HIGHEST READINGS WERE 81 AND 57 DEGREES F RESPECTIVELY. OBSERVATION OF THE INSTALLATIONS THROUGH TWO YEARS INDICATED THAT POLYSTYRENE INSULATION EFFECTIVELY ELIMINATES FROST-HEAVING. ALSO IF THE INSTALLATION CAN BE DONE DURING ORIGINAL CONSTRUCTION, COSTS WOULD BE CONSIDERABLY REDUCED.

  • Supplemental Notes:
    • 7 Pp, 1 Tab
  • Corporate Authors:

    North Dakota State Highway Department

    State Highway Building, Capitol Grounds
    Bismarck, ND  USA  58505
  • Authors:
    • Bibow, R
    • Haykel, A L
  • Publication Date: 1969-11

Subject/Index Terms

Filing Info

  • Accession Number: 00237819
  • Record Type: Publication
  • Files: TRIS, STATEDOT
  • Created Date: Apr 13 1970 12:00AM