REVIBRATION OF RETARDED CONCRETE FOR CONTINUOUS BRIDGE DECKS

SURVEYS OF EXISTING STRUCTURES INDICATE THAT TRANSVERSE CRACKS IN BRIDGE DECK CONCRETE ARE OF SIGNIFICANCE WITH RESPECT TO BRIDGE DECK DETERIORATION AFTER EXPOSURE TO FREEZING AND THAWING AND DEICING AGENTS. TRANSVERSE CRACKS MAY BE FORMED OR INITIATED ALREADY IN THE FRESH CONCRETE, AND MAY BE CAUSED BY CHANGES IN DEFLECTION AND ROTATIONS OVER SUPPORTS DURING CONSTRUCTION, OWING TO THE DEAD WEIGHT OF THE CONCRETE. AN ADDITIONAL CAUSE OF CRACKING OF CONCRETE CAN BE THE RESTRAINT OF SUBSIDENCE DUE TO BLEEDING OF THE FRESH CONCRETE AFFORDED BY THE TOP REINFORCING STEEL. LABORATORY STUDIES WERE CONDUCTED TO INVESTIGATE THE EFFECTIVENESS OF REVIBRATION OF CONCRETE IN REPAIRING CRACKS SEVERAL HOURS AFTER IT WAS PLACED. IN ADDITION, THE EFFECT OF REVIBRATION ON CONCRETE DURABILITY WAS INVESTIGATED, AND FIELD EXPERIMENTS WERE CONDUCTED TO VERIFY THE RESULTS FROM THE LABORATORY TESTS AND TO INVESTIGATE THE FEASIBILITY OF REVIBRATION IN BRIDGE DECK CONSTRUCTION. THE LABORATORY TESTS SHOWED THAT SURFACE REVIBRATION WITH A VIBRATING SCREED IS AN EFFECTIVE METHOD TO CLOSE FLEXURAL CRACKS ON THE CONCRETE SURFACE AS WELL AS SUBSIDENCE CRACKS AT THE LEVEL OF THE TOP REINFORCEMENT AND INTERNAL CRACKS THAT DO NOT PENETRATE TO THE CONCRETE SURFACE. SURFACE REVIBRATION IS EFFECTIVE TO A DEPTH OF AT LEAST 4 IN. FROM THE CONCRETE SURFACE. REVIBRATION COULD BE CONDUCTED SUCCESSFULLY IN THE LABORATORY AS LONG AS THE PENETRATION RESISTANCE OF THE CONCRETE ACCORDING TO ASTM C 403-68 DID NOT EXCEED A VALUE OF 60 PSI. MOST CONCRETES WILL REACH THIS VALUE APPROXIMATELY 30--60 MINUTES PRIOR TO INITIAL SET (DEFINED AS THE TIME AT WHICH PENETRATION RESISTANCE REACHES 500 PSI.) IF PROPERLY CONDUCTED, SURFACE REVIBRATION RESULTS IN A SMOOTH CONCRETE SURFACE SO THAT NO ADDITIONAL FINISHING AFTER SURFACE REVIBRATION, EXCEPT BELTING AND BROOMING, IS REQUIRED. COMPRESSIVE STRENGTH AND ABRASION RESISTANCE OF CONCRETE WERE LITTLE AFFECTED BY REVIBRATION. HOWEVER, AFTER SURFACE REVIBRATION A SLIGHT INCREASE OF THE SPACING FACTOR OF AIR VOIDS CLOSE TO THE CONCRETE SURFACE WAS OBSERVED. ACCELERATED FREEZING AND THAWING TESTS ON CONCRETE SURFACES EXPOSED TO DEICING CHEMICALS SHOWED NO SIGNIFICANT DIFFERENCE IN SURFACE SCALING OF REVIBRATED AND NON- REVIBRATED CONCRETE. HOWEVER, IT IS LIKELY (ALTHOUGH NOT PROVEN IN LABORATORY EXPERIMENTS) THAT SURFACE REVIBRATION WILL IMPROVE THE RESISTANCE OF CONCRETE AGAINST SURFACE SPALLING. PORTIONS OF THREE BRIDGE DECKS WERE REVIBRATED APPROXIMATELY 2HOURS AFTER THE CONCRETE WAS PLACED. IT WAS SHOWN THAT THE ENTIRE WIDTH OF A BRIDGE DECK CAN BE REVIBRATED WITH A VIBRATING SCREED IN A CONTINUOUS OPERATION. THE SCREED SHOULD BE DESIGNED IN SUCH A WAY THAT ITS PROFILE CAN BE ADJUSTED TO MATCH THE PROFILE OF THE DECK PRIOR TO REVIBRATION. IN ADDITION, PROVISIONS SHOULD BE MADE THAT DURING REVIBRATION THE SCREED DOES NOT FLOAT FREELY ON THE CONCRETE SURFACE. UNDER THESE CONDITIONS SURFACE REVIBRATION OF BRIDGE DECKS CAN BE CONDUCTED SUCCESSFULLY AND NO EXTENSIVE FINISHING AFTER REVIBRATION IS REQUIRED. /AUTHOR/

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  • Supplemental Notes:
    • Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved. 67 PP, FIGS, PHOTS, TABS, 26 REF, 7 APP
  • Authors:
    • Hilsdorf, H K
    • Lott, J L
  • Publication Date: 1970

Media Info

  • Media Type: Digital/other
  • Serial:
    • NCHRP Report
    • Issue Number: 106
    • Publisher: Transportation Research Board
    • ISSN: 0077-5614
  • Publication flags:

    Open Access (libre)

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Filing Info

  • Accession Number: 00215372
  • Record Type: Publication
  • Files: TRIS, ATRI
  • Created Date: Jun 22 1971 12:00AM