Abstract

This report is not wholly a culmination of a planned or programmed research project. It is a historical account of damage sustained by both new and old concrete bridge-decks -- through freeze-thaw, salt action, etc, -- and of some expedient repairs which have been effected. The problem of durability in concrete bridge-decks has become increasingly critical during the past ten years or so and is now a major concern to highway engineers throughout the northern tier of states. While there is not yet a concerted agreement in regard to the cause of the trouble, relief is being sought through improved construction practices, air-entrainment, and protective coatings of various kinds. Similarly, relief from perpetual maintenance or complete replacement of existing bridge decks is being sought through improved methods for making repairs.

The performance of individual slabs in a deck is sometimes markedly different from that of a nearby slab; and, even within a particular slab, only one corner or one end may be affected. This signifies poor concreting practices. The concrete sustaining damage was undoubtedly over-watered, over-worked, de-aired, and segregated. The proper placement of deck concrete is perhaps the more serious aspect of the problem than the repair, because improper placement automatically incurs a premature maintenance liability. Of course, as the need for repairs arises in due time, reliable methods of repair should be employed. It is in this latter respect that the repair experiences recorded in this report are expected to be the most fruitful.

None of the damaged decks which have been observed thus far has shown any evidence of overloading by traffic (adjudged by the absence of any checker-board crack-pattern on the underneath side of the deck); the trouble seems to be attributable almost entirely to weathering; and the weathering invariably seeks out and attacks the poorest concrete often revealing the mistakes made by the workmen and their attempts to hide them.

Improper drainage of the deck and gutter can be one of the contributing factors to damage. Even slabs and gutters sometimes have "bird-baths" in them. Cinders, sand, road-debris, and snow sometimes impound water and prevent drying. Such areas are exposed to water and moisture beyond their normal time and damage is often associated with these conditions.

Report Date

2-1-1963

Report Number

No. 200

Digital Object Identifier

http://dx.doi.org/10.13023/KTC.RR.1963.200

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