Transportation Research Record 860 sured during concrete placement and initial curing; bridge-deck cores were ana· lyzed for cracks and signs of bonding problems in the reinforcing steel and tested for strength and soundness. Laboratory beams were constructed and tested to simulate a transverse strip of a deck slab. Periodic deflections and vi· brations were applied from time of casting to one day. No deterioration that could be attributed to traffic during construction and curing of the decks was found in existing decks. The study of the cores showed no difference in cracking in cores taken from disturbed areas of the deck from that in cores taken from undisturbed areas. There was evidence of creation of a void in the new concrete around certain rebar dowels bent at right angles in a horizontal plane on emerging from the old concrete. This situation was found only in cores taken at the joint between old and new concrete, and only one bridge of all that were studied had this bent-dowel detail. The study shows that no detrimental effects should be expected in deck concrete supported by steel and prestressed concrete beams spanning up to about 100 ft when the decks are widened or reconstructed under normal traffic.

Bridge-deck concrete that is placed adjacent to moving traffic undergoes considerable disturbance from vibrations and deflections caused by the traffic. A study made to determine the effects of that disturbance is reported here. concrete, in a fluid state when placed, rapidly becomes plastic and then solid within a period of 2 or 3 h after mixing. Disturbances at very early ages could cause changes in its physical character that would influence its behavior in service. Puddling of the fluid material causes segregation, which causes problems in durability and reduced strength. If the reinforcing steel moves about in the plastic concrete, it could wallow out a void, depending on the relative movement and the plasticity of the concrete. such areas reduce or destroy bond, and they can cause durability problems if invaded by water. The early-age sol id concrete (that only a few hours old) has little strength and little capacity for strain. It is easily cracked when the strain becomes great.