United States Department of Transportation
i
Microsilica modified concrete for bridge deck overlays : final report.
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1997-01-01
[PDF-1.19 MB]
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Abstract:This report summarizes the performance of microsilica concrete (MC) overlays on seven distressed portland cement concrete bridge decks at three sites in Oregon. This report emphasizes the overlays' condition after four years of use.
After four or five years, there was cracking on all seven overlays and delamination on five overlays. On the two overlays without delaminations, the cracking had not increased during the second year of use. On the five overlays with delaminations, the number and length of the cracks and the number and size of the delaminations increased during the third and/or fourth year of use.
Despite the cracking, all of the overlays had no excessive surface wear or rutting, spalling around the crack edges, potholes, or popouts. All of the overlays had good tire-to-pavement friction numbers.
The only maintenance was the sealing of cracks on one overlay with methacrylate and sand at a cost of $4,000.
The overlays met two of their three design objectives after three or four years' use. They were still adding strength to the deck and providing a smooth and durable wearing surface. However, as they were cracked, it is surmised that they are no longer sealing the underlying deck from the intrusion of chlorides.
The Oregon Department of Transportation is continuing to specify MC as an overlay material. Experience with the material and revision of the MC specifications has reduced construction problems, and consequently, improved the quality of subsequent MC overlays.
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