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Effect of induced vibration
When concrete repairs are carried out close to a source of vibration, for example on a bridge deck with traffic still running on an adjacent carriageway, there may be concerns that the vibrations may affect the concrete properties. It has been suggested that the strength development may be affected as well as the bond between the new concrete and old concrete and the bond with the reinforcement.
Various surveys have looked at the effects of traffic-induced vibrations on bridge repairs, considering partial-depth and full-depth repairs, bridge-deck overlays, bridge widening and deck replacements. The conclusions are that, under normal conditions, traffic-induced vibrations do not cause segregation, bond failure to existing concrete or reinforcement, poor strength development or cracking in the fresh concrete, provided that the concrete is well proportioned. Clearly it is desirable to maintain a smooth riding surface and a smooth transition at expansion joints to reduce the amplitude of traffic-induced vibrations. In addition it is necessary to avoid differential movements between the young and old concretes.
Further information is given in a paper by Ansell and Silfwerbrand.
Other references:A Ansell and J Sifwerbrand, The vibration resistance of young and early-age concrete, Structural Concrete (the Journal of the fib), Vol 4, No 3, September, 2003, pp 125-134.
