USE OF ACCELERATORS IN HIGHWAY CONCRETE

A REVIEW IS PRESENTED OF THE USE OF ACCELERATORS IN CONCRETE WHEN DECREASED SETTING TIME OR INCREASED RATE OF STRENGTH DEVELOPMENT IS DESIRED. AN ACCELERATING ADMIXTURE IS DEFINED AS A MATERIAL THAT IS USED FOR THE PURPOSE OF ACCELERATING THE SETTING AND STRENGTH DEVELOPMENT OF CONCRETE. THESE ADMIXTURES ARE USEFUL, PARTICULARLY IN COLD WEATHER, FOR MODIFYING THE PROPERTIES OF PORTLAND CEMENT TO: (1) EXPEDITE THE START OF FINISHING OPERATIONS AND, WHEN NECESSARY, THE APPLICATION OF INSULATION, (2) REDUCE THE PERIOD OF TIME REQUIRED FOR PROPER CURING, ESPECIALLY IN THE LATE FALL PAVING WHERE EARLY APPLICATION OF DE-ICING SALTS MAY BE EXPECTED, AND (3) PERMIT EARLIER LOADING OR OPENING OF PAVEMENTS AND STRUCTURES TO TRAFFIC. THE BENEFITS OF AN ACCELERATOR ARE THE RESULT OF A HIGHER RATE OF HYDRATION OF THE PORTLAND CEMENT WHICH REDUCES THE INITIAL SETTING TIME OF CONCRETE, RELEASES THE HEAT OF HYDRATION MORE RAPIDLY, AND INCREASES THE INITIAL RATE OF DEVELOPMENT OF COMPRESSIVE AND FLEXURAL STRENGTHS. THE BEST KNOWN AND MOST WIDELY-USED ACCELERATOR IS CALCIUM CHLORIDE. USUAL RECOMMENDATIONS LIMIT THE DOSAGE OF CALCIUM CHLORIDE TO A MAXIMUM OF 2 POUNDS TYPE 1 PER BAG OF PORTLAND CEMENT. CALCIUM CHLORIDE MAY BE USED WITH ALL TYPES OF PORTLAND CEMENT AT THE RATE OF 1 TO 2 PERCENT CALCIUM CHLORIDE BY WEIGHT OF CEMENT, WHETHER ADDED AS THE SALT OR AS A PROPRIETARY COMPOUND. CONCENTRATED CALCIUM CHLORIDE SOLUTIONS ARE NOT COMPATIBLE WITH SOME AIR- ENTRAINING ADMIXTURES. THE CALCIUM CHLORIDE AND OTHER ADMIXTURES THEREFORE, SHOULD BE ADDED TO CONCRETE SEPERATELY. A RECENT POLL OF STATE HIGHWAY DEPARTMENTS REVEALED THAT ABOUT 1/10 OF THEM USE ACCELERATORS FREQUENTLY, ABOUT 1/2 USE THEM ON OCCASION, AND ABOUT 1/3 NEVER USE THEM. EXTENT OF USE ON STRUCTURES AND PAVEMENTS IS ABOUT THE SAME.

  • Supplemental Notes:
    • No 6, pp 1-8
  • Publication Date: 1965-7

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Filing Info

  • Accession Number: 00213704
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 3 1970 12:00AM