Articles

Grenzbruecke Basel—The First Swiss Exposed UHPC Overlay

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Abstract

This is an accepted article with a DOI pre-assigned that is not yet published.

Since 2004, over 300 UHPC overlay projects and over 12,000 m3 (15,700 yd3) of UHPC have been installed across Switzerland. However, it is common practice in Switzerland to finish the UHPC overlay with an asphalt layer as its final riding surface. Inspired form the successful rehabilitation of US bridge decks with an exposed UHPC overlay riding surface, a 4" to 7" (100 mm to 180 mm) UHPC layer was installed on the Grenzbruecke Basel in 2022. In total, over 1,200 yd3 (900 m3) of commercially available KIBAG Ahadur UHPC were installed over an area of 86,000 ft2 (8,000 m2). The thicker than usual 2" UHPC overlay layer was necessary to match the exiting elevation of the adjacent lanes. Significant overlay installation challenges occurred due to the vibrations and slope of the structure as was validated with a mock-up study under simulated field conditions. This resulted in paving the UHPC overlay in two lifts. Additional new innovative construction methods were incorporated including 1. Onsite mixing with two new mobile batch plants, 2. Utilizing KIBAG Ahadur UHPC with preblended steel fibers in the premix, 3. Hydroscarification of an UHPC overlay layer, 4. Curing without plastic sheeting, and 5. Grinding and grooving of the final riding surface. This presentation will discuss UHPC material properties, project details, vibration mock-up study, equipment selection, surface preparation, hydroscarification, construction methods, placement techniques, curing procedures, grinding & grooving, project challenges, and successes of the first exposed UHPC overlay project in Switzerland.

Keywords: bridges, project examples. applications

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