International Concrete Abstracts Portal

Repair and maintenance of aging bridge decks and parking decks has become increasingly important due to concrete and steel deterioration from exposure to deicing salts, acid rain, and other hostile elements. Rapid curing thin polymer concrete overlay offers a cost-effective option in protecting and extending the service life of the deck. The paper discusses the performance, physical properties and application techniques using a flexible epoxy polymer overlay. The low modulus epoxy binder is designed to achieve a balance between toughness and flexibility. With the use of gap graded aggregates, the flexible epoxy binder system provides low permeability, enhanced skid resistance while accommodating thermal and mechanical stresses. The outstanding performance and service life of flexible epoxy overlays has been documented in the SHRP study in 1991. The importance of proper surface preparation and quality control during application is critical to the success and durability of the overlay.

Methyl-methacrylate (MMA) based polymer concretes have been used for thin overlays, patching repairs, and bearing pad applications since the late 1970’s. These polymer concretes are moisture and wear resistive and have been used to protect embedded reinforcing steel from corrosion attack. This paper reports on the condition of a post-tensioned parking garage that was repaired in 1983 using a thin mma polymer concrete overlay. An earlier paper reported on the garage condition, repair methods and materials (1). Comments will be made on the overlay wear, cracking, bonding to the substrate, continued corrosion of embedded reinforcing steel, and surface delaminations after 13 years of service. Comparisons of conditions in 1981 and 1995 are also made. Comments on the success of the application with respect to structural integrity and material durability are made at the end of the paper.

The performance of polymer concrete bridge deck overlays ranging in age from 6 to 19 years is presented. The performance is based on tests for tensile bond strength, permeability to chloride ion, thickness and skid number. The physical and mechanical properties of the concretes used, the types of uses, the application methods, and the economics, are also described. It is shown that multiple-layer epoxy, multiple-layer epoxy urethane, and premixed polyester styrene polymer concrete overlays can provide skid resistance and protection against intrusion by chloride ions for 20 years or more and are an economical technique for extending the life of concrete decks reinforced with black steel, particularly when overlays must be constructed during off-peak traffic periods to minimize inconvenience to motorists. Also, multiple-layer polyester overlays have a life of ten years.

The San Francisco Oakland Bay Bridge was designed for six lanes of automobiles on a lightweight concrete upper deck. Two lanes of truck traffic with a third switch lane supported on a conventional concrete slab shared the lower deck space with two commuter rail tracks. Instead of using paint to delineate the lanes on the upper deck, ceramic tile embedded into a concrete mortar wear coat acted as a lane striping. This eliminated the paint re-striping maintenance operation. It was expected that the bridge could operate that way for a long time when it was opened to traffic with much fanfare, automobile caravans and political speeches on November 12, 1936. The bridge carried approximately 25,000 vehicles per day during its first year. In 1957, the commuter rail line ceased to operate. Traffic volume had increased to nearly 100,000 vehicles per day while 25% of the capacity of the bridge was not beiig utilized. In 1958 the reconstruction of the Bay Bridge began. The rails were removed, precast lightweight concrete panels were added, the approaches to the two decks were modified and the upper deck was strengthened to accommodate the new truck loading. In 1963, trffic capacity was increased by converting the facility into five unidirectional mixed vehicle and truck traffic lanes on each deck. To do so required removing or covering the embedded ceramic tile lane boundaries. Removal would be tedious and patching the resulting holes expensive. The alternative of covering them with a thin surfacing was easier and, in addition, protected the concrete deck which was beginning to show some transverse cracking and chloride intrusion. A coal-tar epoxy binder with quartz beach sand broadcasted over the sprayed-on binder was applied yielding a total thickness of approximately 5 mm. The lower deck was resurfaced in 1964 utilizing the same system. The coal-tar epoxy held up

Sulfur concrete (SC) has been used successfully as an overlay to protect hydraulic concrete from attack in highly corrosive environments The SC dealt with in this paper is based on Canadian technology which uses a sulfur cement composed principally of thermodynamically stable, microcrystalline sulfur. Methods for the production and placement of this SC are discussed, together with several case histories of its use as an overlay on hydraulic concrete. Field experience has shown SC to be a durable, cost-effective overlay with many of the attractive physical characteristics of polymer concretes, such as high resistance to corrosion and abrasion, impermeability and high physical strength.. Being a hot mix, produced in a modified asphalt plant, it must be placed as an overlay in a thickness of at least 3 in.(7.5 cm) unless the substrate has been warmed. SC overlays can be placed with vibrating screeds and with slightly modified asphalt and concrete paving machines