Materials Performance

OCT 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

Issue link:

Contents of this Issue


Page 102 of 138

OCTOBER 2018 WWW.MATERIALSPERFORMANCE.COM 14 users, immediate measures will be taken, such as placing weight limits on the bridge or closing it if that is necessary, Lasa explains. Preventive maintenance activities, which include cyclical and condition- based activities, are a cost-effective means of extending the service life of highway bridges because they slow future deterioration and help to circum- vent expenses associated with extensive bridge rehabilitation or replace- ment. Cyclical maintenance activities, performed at predetermined intervals, are intended to preserve and delay the deterioration of bridge elements, while condition-based maintenance activities are performed on bridge com- ponents in response to known defects. Mitigating corrosion is a big part of bridge preservation efforts, adds Whitmore, who notes that corrosion is the number one reason why rein- forced concrete structures deteriorate. "If you can do things to defer or miti- gate corrosion—slow it down or arrest it entirely—then you can effectively and economically extend the service life of the structure compared to letting it get to a condition where you need to replace the entire structure or signifi- cant components of the structure." COMB AT T ING BRID GE CORR OSION As state DOTs aim for bridge service lives of 100 years or more, there are essentially two strategies for achieving this when designing a new bridge: design and materials that render the structure immune to its exposure con- dition, and design and materials that work to mitigate the effects of the exposure conditions on the structure. Whitmore notes that in many cases, immunity is the best solution for new structures when it is practical or possible because corrosion is eliminated as a deterioration mechanism rather than being deferred until later. Examples of immunity strategies include eliminating the use of salt on bridge decks and the use of noncorroding materials such as stainless steel (SS) and non- metallic glass fiber reinforced polymer (GFRP). If chlorides reach the rein- forcing bar (rebar), these materials won't corrode. Mitigation strategies include the use of better-quality concrete, thicker concrete cover over the rebar, better drainage so salty water is eliminated more quickly, and the use of coatings or membranes to protect the concrete. Each DOT, if they have corrosion problems, is working either in-house or through a consultant to review the situation, develop a plan for dealing with the corrosion, then implement some form of repair in the field that deals with the underlying corrosion problem. Most state DOTs use bridge inspec- tion data to ensure that an obvious problem is flagged so it can be addressed, Whitmore says. Some state DOTs will have a bridge preservation engineer, and in some cases a bridge preservation department. The FDOT maintains a corrosion group that consults with the eight FDOT districts on corrosion issues. "Corrosion is one of our biggest expenses during the service life of the structures, and most of our corrosion issues are due to the coastal marine environments," Lasa comments. "If a district thinks they may have a corrosion problem, they call the FDOT corrosion group and that group does a corrosion assessment, and reports on the condition of the structure and makes recommendations on how to proceed to control corrosion," he explains. The FDOT classifies the corrosivity of the environment where bridges will be located. The three classifications are slightly aggressive, moderately aggressive, and extremely aggressive. Based on the corrosion classification of the environment where the structure is going to sit, there are design guidelines developed by the FDOT that tell the designer what type of corro- sion prevention materials or techniques to use. "Each additional corrosion prevention material or technique adds cost to the bridge, so if we have a bridge that is located in a slightly aggressive

Articles in this issue

Links on this page

Archives of this issue

view archives of Materials Performance - OCT 2018