Placement of Low-Slump Concrete: Final Report

About the report:

Low-slump concrete is being used on bridge decks mainly to prevent or minimize spalling and delaminations resulting from corrosion of the reinforcing steel. Other beneficial effects reported include high strength and durability. This study investigated the field conditions necessary to achieve dense, impervious, good quality low-slump concrete that would provide long-lasting bridge decks. The parameters considered were consolidation, texturing, bonding, freezing and thawing durability, and permeability. When placed under the conditions of this study, low-slump concrete retained a comparatively large number of coarse voids because of its stiff consistency. Specimens consolidated manually by rodding and vigorous tapping exhibited better consolidation than those compacted by mechanical vibrators. However, the permeability studies indicated that even though the low-slump concrete specimens contained more coarse voids than desired, they can provide a resistance to the penetration of chlorides comparable to that provided by ordinary bridge deck concretes of good quality. To provide a satisfactory bond between the low-slump overlay and the base concrete, the surface of the latter must be sandblasted and cleaned. Conventional metal tines did not provide the deep surface texture desired for the low-slump concrete, but proper texturing could be obtained with a metal roller.

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