Reinforced concrete pipe cracks : acceptance criteria [revised July 29, 2011].

Final report; 07/01/2009-7/1/2011.PDFTech ReportBDK84 977-06Reinforced concreteConcreteCrackingCorrosionReinforcing steelPipeFloridaUniversity of South Florida. Dept. of Civil and Environmental EngineeringBusba, E.Sagues, A.Mullins, G.University of South Florida. Dept. of Civil and Environmental EngineeringFlorida. Dept. of TransportationNTL-HIGHWAY/ROAD TRANSPORTATION-MaterialsNTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and PerformanceUS Transportation CollectionInspection of recently placed reinforced concrete pipes often reveals cracks. Florida DOT was inneed of in-place crack acceptance criteria. This project was intended to determine the influential parametersresponsible for crack healing in in-place Reinforced Concrete Pipes (RCP), determine what maximum crackwidth was amenable to autogenous healing and sufficient to mitigate reinforcement corrosion, and formulateguideline models for pipe crack acceptance criteria during construction. A literature survey indicated areasonable expectation for autogenous healing to eventually occur for cracks narrower than about 0.020 inch.The prognosis was less favorable for wider cracks, and there was little assurance that autogenous healing wouldreliably take place for crack widths exceeding about 0.100 inch. Laboratory experiments did not producesignificant autogenous healing of 0.100-inch or 0.020-inch-wide cracks in reinforced concrete pipe specimensover an approximately 2-month-long period. Corrosion tests showed that significant reinforcement wire corrosioncould take place in a short time in reinforced concrete pipe with 0.100-inch-wide cracks, and that corrosiondamage was considerably slower when the cracks were 0.020 inch wide. Corrosion was aggravated by thepresence of moderate chloride ion contamination (500 ppm), but active steel corrosion occurred even without it.A predictive model for corrosion development in cracked reinforced concrete showed for 500 ppm chloride veryshort durability projections for the 0.100-inch-wide crack condition, and moderately strong to little limitation indurability for the 0.020-inch-wide crack cases. Acceptable crack width guideline models proposed for discussionincluded a restrictive alternative, with 0.020 inch width allowable only for environmental chloride no greater than500 ppm; a less restricted alternative allowing 0.020 inch up to 2000 ppm chloride; and a sliding option for up to2000 ppm chloride where pipe service life was progressively derated to zero for crack widths increasing from0.020 inch to 0.100 inch. In all models the acceptable width defaulted to 0.010 inch if the other conditions werenot met