INVESTIGATION AND APPRAISAL OF THE PERFORMANCE OF CEMENT TREATED BASES AS USED IN COMPOSITE PAVEMENTS IN CALIFORNIA

ONE HUNDRED SEVENTY-FIVE CLASS A AND CLASS B CEMENT TREATED BASE B (CTB) PROJECTS BUILT BETWEEN 1950 AND 1962 WERE EVALUATED. SIXTY-FOUR PERCENT ARE GIVING EXCELLENT SERVICE, SEVENTEEN PERCENT WERE RATED GOOD, EIGHT PERCENT FAIR AND ELEVEN PERCENT REQUIRED EXTENSIVE MAINTENANCE EARLY IN THEIR DESIGN LIVES. THE MAIN CAUSES OF FAILURE APPEARED TO BE: INSUFFICIENT CEMENT CONTENT, POOR MIXING OF CEMENT, EXCESSIVE TRIMMING OF THE COMPACTED CTB, INSUFFICIENT CTB THICKNESS, INADEQUATE CTB COMPACTION OR DEFICIENCIES IN THE AC SURFACING THICKNESS OR QUALITY. A SIGNIFICANT IMPROVEMENT IN THE PERFORMANCE OF CTB COMPOSITE PAVEMENTS WAS CAUSED BY: (1) EXTENDING THE CTB AT LEAST ONE FOOT INTO THE SHOULDER, (2) PLANT MIXING THE CTB, (3) BUILDING THE PROJECT IN A TEMPERATE CLIMATE, (4) INCREASING THE THICKNESS OF THE AC SURFACING, (5) LIMITING THE COMPACTED THICKNESS OF ANY ONE LAYER OF CTB TO 0.50 FOOT, (6) USING TYPE II CEMENT RATHER THAN TYPE I, (7) USING A MINIMUM CTB THICKNESS OF 0.50 FOOT, AND (8) PROVIDING A MINIMUM IN SITU CTB COMPRESSIVE STRENGTH OF 500 PSI. FIELD SAMPLING OBSERVATIONS SHOWED THERE WAS GENERALLY VERY LITTLE BOND BETWEEN LAYERS OF CTB BUT THE AC WAS NEARLY ALWAYS WELL BONDED TO THE TOP OF THE CTB. EXCESSIVE TRIMMING OF A COMPACTED CTB WAS SHOWN TO CAUSE DISINTEGRATION OF A THIN LAYER AT THE TOP OF THE CTB WHICH SUBSEQUENTLY CAUSED EXTENSIVE PUMPING AND CRACKING OF THE AC SURFACING. /AUTHOR/

  • Supplemental Notes:
    • Hpr-pr-1 (6), STATE-D-2-6
  • Corporate Authors:

    California Division of Highways

    Bridge Department
    Sacramento, CA  USA  05914

    Bureau of Public Roads /US

    400 7th Street, SW
    Washington, DC  USA  20590
  • Authors:
    • Zube
    • Gates
    • Shirley
    • Munday
  • Publication Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 00230669
  • Record Type: Publication
  • Source Agency: Bureau of Public Roads /US
  • Files: TRIS
  • Created Date: Aug 15 2004 2:20AM