Effect of Concrete Removal Equipment and Methods on the Condition of Deck Concrete Left in Place

About the report:

This report describes the evaluation of the condition of concrete samples taken from sections of a five-span bridge in which the concrete in the parapet and deck along the exterior beam was removed using six different methods. Deck and parapet concrete was removed with 30-lb (14-kg) hammers, 90-lb (41-kg) hammers, a 750 ft-lb (104 m-kg) hoe ram, and a Universal Processor 50 concrete crusher. Parapet concrete was also removed with a hoe ram and a concrete crusher. A seventh test section served as an undisturbed control. Four tests of concrete samples taken adjacent to the exterior beams and approximately 4 ft (1.2 m) from the beams did not indicate that the concrete was damaged by any of the removal methods. The tests involved (1) determining the compressive strength of cores, (2) determining the tensile bond pullout strength of transverse bars in cores, (3) determining the permeability to chloride ion of cores, and (4) microscopically examining specimens to determine if the bond between the concrete and the reinforcing bar was damaged. Compared to the use of the 30-lb hammer, the use of the hoe ram and crusher to remove the deck and parapet concrete provided a reduction in time of 94 percent and a reduction in cost of 59 and 58 percent, respectively. In view of the much higher efficiency and lower cost associated with highly mechanized techniques of concrete removal, the Virginia Department of Transportation should employ the use of alternatives to the 30-lb hammer more frequently.

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