This project overlayed three existing bridges on SR 5 in Skagit and Whatcom Counties with microsilica modified concrete. The bridges involved were 5/725 Alger Road Undercrossing; 5/803 Samish Inn Undercrossing; and 5/807 South Bellingham Undercrossing. The minimum overlay thickness was 1-1/2 in. Superplasticizer was added to the mix. The concrete was mixed in a conventional batch plant, with the technical representative from the microsilica supplier providing assistance. The microsilica modified concrete overlay was finished and cured as prescribed by WSDOT's specification for LMC overlays. The finished decks exhibited an abnormal number of shrinkage cracks, which had to be sealed. Problems with excessive slump are believed to be the cause of this cracking.
Washington (State). Dept. of Transportation.
Bridge decks, Cement additives, Concrete, Cracking, Overlays (Pavements), Repairing, Shrinkage, Silica fume, Slump test, Superplasticizers, Thickness.