COMPARISON OF PROPERTIES OF FRESH AN HARDENED CONCRETE IN BRIDGE DECKS

A STUDY WAS MADE ON SEVENTEEN BRIDGE DECKS CONSTRUCTED IN 1963 UNDER REGULAR CONTRUCTION PROCEDURES. THE PURPOSE WAS: (1) TO COMPARE IMPORTANT PROPERTIES OF CONCRETE AS FRESHLY PLACED IN RANDOMLY SELECTED BRIDGE DECKS WITH THOSE AFTER HARDENING OF THE CONCRETE; (2) TO DETECT THE INFLUNECE, IF ANY, OF DIFFERENT SCREEDING METHODS; AND (3) TO RELATE THE PERFORMANCE OF THE DECKS TO THE OBSERVED PROPERTIES OF THE FRESH AND HARDENED CONCRETE. DESCRIPTIONS OF THE STRUCTURES, PROCEDURES, AND MATERIALS ARE GIVEN. IT IS EMPHASIZED THAT THE CONSTRUCTION TOOK PLACE DURING A TRANSITION TO SPECIFICATIONS AND PROCEDURES DESIGNED TO ELIMINATE PROBLEMS THAT WERE BECOMING RECOGNIZED IN DECK CONSTRUCTION. FROM TESTS ON FRESHLY MIXED AND HARDENED CONCRETE SAMPLES AND OBSERVATION OF THE PERFORMANCE DURING SEVEN YEARS THE FOLLOWING CONCLUSIONS ARE DRAWN: (1) WHEN VIEWED AGAINST THE PERFECTION DESIRED BY THE ENGINEER, THE PERFORMANCE OF THESE DECKS HAS BEEN DISAPPOINTING OR BORDERLINE. WHEN VIEWED AGAINST THE PERFORMANCE THAT WOULD BE EXPECTED FROM CONCRETE WITH THE PROPERTIES OBSERVED, THE PERFORMANCE HAS BEEN BETTER THAN MIGHT BE EXPECTED. (2) THE PERFORMANCE OF THE 17 STRUCTURES IN THIS STUDY CLOSELY PARALLELS THE PERFORMANCE OF A LARGE SAMPLE OF BRIDGES INCLUDED AS A PART OF A NATIONWIDE STUDY OF BRIDGE DECK PERFORMANCE. (3) THE PRIMARY CAUSE OF VARIABLE OR BORDERLINE PERFORMANCE OF CONCRETE IN BRIDGE DECKS IS VARIABLE OR BORDERLINE FRESH CONCRETE. (4) EVEN WITH THE USE OF ELABORATE MECHANICAL EQUIPMENT DILIGENT ATTENTION MUST BE GIVEN TO THE DETAILS OF ACCEPTED PRACTICES OF GOOD CONCRETING SUCH AS MAINTENANCE OF LOW WATER CEMENT RATIOS, ADEQUATE AIR CONTENTS, AND PROMPT AND THOROUGH CURING. (5) THE AGREEMENT OF PROPERTIES SUCH AS UNIT WEIGHT AND AIR CONTENT MEASURED IN BOTH THE FRESHLY MIXED AND HARDENED CONCRETE IS ACCEPTABLE FOR ENGINEERING PURPOSES. (6) NO INFLUENCE OF THE SCREEDING METHOD ON THE PROPERTIES OF THE CONCRETE IN PLACE WAS FOUND. (7) TRAFFIC VOLUMES AND DESIGN FEATURES SEEM TO HAVE HAD LITTLE INFLUENCE IN THE ADVERSE PERFORMANCE OF THE SEVENTEEN BRIDGES. (8) THE ONLY THREE BRIDGES THAT ARE FREE FROM SCALING ARE THE ONLY THREE BRIDGES THAT CONTAINED AN ADEQUATE ENTRAINED AIR VOIDS SYSTEM. (9) FOR THE CLASS OF MIXTURES USED IN THESE DECKS, A MINIMUM AIR CONTENT OF 5 PERCENT WAS FOUND TO BE NECESSARY IN ORDER TO PROVIDE A VOID SPACING FACTOR OF 0.0055", WHILE AIR CONTENTS OF 4 PERCENT PROVIDED SPACING FACTORS BELOW 0.0075". (10) THE THE IMPORTANCE OF THE EARLY APPLICATION OF CURING WAS REFLECTED IN THE SCALING OF SEVERAL DECKS OF APPARENTLY SATISFACOTRY CONCRETE TO WHICH CURING WAS APPLIED VERY LATE. (11) UNCERTAINTY EXISTS AS TO THE EXACT PROPORTIONS OF THE COMPONENTS, ESPECIALLY WATER, IN THE CONCRETE IN THESE BRIDGE DECKS. (12) THE INFLUENCES OF WATER-REDUCING ADMIXTURES ON RETARDING THE SETTING AND REDUCING THE WATER REQUIREMENT WERE APPARENT IN THE SAMPLES FROM THIS PROJECT, AS WAS THE ACCELERATING EFFECT OF HIGH INITIAL MIXTURE TEMPERTATURE. (13) THE DATA FROM THREE SPANS SUGGEST THAT THE CRACKING COMMON TO THEM MIGHT BE EXPLAINABLE FROM HIGH SAND EQUIVALENTS OF THE FINE AGGREGATES USED. (14) POPOUTS WERE CONFINED TO STRUCTURES USING AGGREGATES KNOWN TO BE SUSCEPTIBLE TO THIS TYPE OF DEFECT. /AUTHOR/

  • Record URL:
  • Supplemental Notes:
    • VHRC 70-R56
  • Corporate Authors:

    Virginia Highway Research Council

    Charlottesville, VA  United States 
  • Authors:
    • Newlon, H H
  • Publication Date: 1971-6

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 65 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00214139
  • Record Type: Publication
  • Files: NTL, TRIS
  • Created Date: Jul 17 1972 12:00AM