Analysis and Estimation of Service Life of Corrosion Prevention Materials Using Diffusion, Resistivity and Accelerated Curing for New Bridge Structures - Volume 1: Corrosion Prevention Materials (Monitoring and Forensic Examination).

摘要

This investigation compiles the results describing the performance of: (1) reinforced concrete specimens cast with 0.37 water to cementitious (w/cm) and binary blends of high performance concrete; the specimens have been exposed to seawater wet/dry weekly cycles for over 18 years; (2) diffusivity and resistivity of concrete after 5 years at the Key Royale Bridge (from cores); (3) high corrosion-resistant alloys (316, 304, 2304, and other alloys) cast in 0.5 water to cement ratio (w/c) concrete exposed outdoors to wet/dry cycles with 15% NaCl solution exposed for seven to ten years; (4) accelerated transport method to investigate corrosion initiation and propagation of duplex stainless steel embedded in concrete (2101 and 2304); (5) effect of mill scale on corrosion initiation of corrosion-resistant alloys embedded in mortar and exposed to simulated pore solution with incremental chloride additions; (6) follow-up of elongation (concrete prisms) due to alkali silica reaction (ASR) and the resistivity (cylinders) of concrete with 19% Fly Ash (FA), high alkalinity, seven different coarse aggregates, and, in some cases, Li additions; (7) chloride threshold as a function of elevation of carbon-steel-reinforced mortar piles simulating partially immersed concrete substructures. A number of specimens were terminated for forensic analysis. Resistivity, diffusivity (obtained from chloride profiles), and LPR were some of the tests used to assess the performance of the above-described materials. In the case of the concrete prism of the ASR investigation, selected specimens were terminated for petrographic examination of lapped surfaces and thin sections. It was found that FL2 coarse aggregate and both coarse aggregate granites might be prone to ASR for situations in which the pH of the concrete is increased. Further evidence was found that concrete with 50% FA has low apparent diffusion coefficiennt, but the chloride threshold is lowered compared to only ordinary Portland cement (OPC) concrete (as a result of lower pH in the pore solution). This caused corrosion to initiate on more rebars on specimens with 50% FA than on specimens with OPC only. Stainless steel 316 and 304 rebars, when properly pickled in the as received condition, show no sign of corrosion. However, 316 and 304 rebars that were wire brushed before embedding them in concrete, initiated corrosion after several years of exposure. From tests on reinforced mortar specimens, duplex stainless steels investigated appear to have a chloride threshold similar to that of 304.