Iowa has been using low slump concrete for repair and resurfacing of deteriorated bridge decks on a routine basis since the mid 1960's. More than 150 bridges ,have been resurfaced by this method with good results. A study was initiated in 1973 to evaluate 15 bridges resurfaced with low slump concrete, and one bridge resurfaced with latex modified concrete. The evaluation includes an assessment of concrete physical properties, chloride penetration rates, concrete consolidation, and riding qualities of the finished bridge deck. Results indicate that the overall properties of these two types of concrete are quite similar and have resulted in a contractor option concerning which system shall be used on bridge deck repair/ resurfacing projects.

Experiences of the state of Iowa in developing and refining the process of resurfacing concrete pavements with portland cement concrete.

At head of title: National Cooperative Highway Research Program.

Chloride-ions penetrating into bridge decks and corroding the steel have been a major problem. As the steel corrodes it exerts stresses on the surrounding concrete. When the stresses exceed the strength of the concrete, cracks or delaminations occur. This, of course, causes deterioration and spalling of bridge deck surfaces. Both the Latex and Iowa Method were used to repair bridge decks for this project. The concrete was removed down to the steel and replaced with approximately 1 1/2 inches of low slump or latex modified concrete. The removal of unsound concrete below the top layer of steel was sometimes necessary. The objective of this project was to determine if the bridge overlays would provide a cost effective method of rehabilitation. To do this, unsound and delaminated concrete was removed and replaced by an overlay of low slump or latex modified concrete.

At head of title: National Cooperative Highway Research Program.

The Iowa Method for bridge deck overlays has been very successful in Iowa since its adoption in the 1970s. This method involves removal of deteriorated portions of a bridge deck followed by placement of a layer of dense (Type O) Portland Cement Concrete (PCC). The challenge encountered with this type of bridge deck overlay is that the PCC must be mixed on-site, brought to the placement area and placed with specialized equipment. This adds considerably to the cost and limits contractor selection. A previous study (TR-427) showed that a dense PCC with high-range water reducers could successfully be used for bridge deck overlays using conventional equipment and methods. This current study evaluated the use of high performance PCC in place of a dense PCC for work on county bridges. High performance PCC uses fly ash and slag to replace some of the cement in the mix. This results in a workable PCC mix that cures to form a very low permeability overlay.

This synthesis will be of interest to research, specifications, materials, design, and construction engineers; contract and specification administrators; agency project managers and staff; and concrete bridge deck construction contractors. This synthesis describes the state of the practice with respect to the development and present status of waterproofing membranes for concrete bridge decks. This report of the Transportation Research Board describes the use of waterproofing systems applied to new bridge decks and the rehabilitation of deteriorated concrete bridge decks. In addition, this synthesis describes current practice with regard to methods for assessing the effectiveness of membranes, criteria for use, installation practices, and factors that affect the performance of waterproofing systems in new construction and rehabilitation. Suggestions for future research are also included.