July 9 - July 15, 2012
What are the most effective procedures for protecting steel and adjacent concrete together?
William slama of International Paint/Ceilcote Products on
July 9, 2012:
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It is first assumed that appropriate coating or lining systems have been selected for the specific application for each substrate and that the surface prep for each is correct. In many cases, one system may be suitable for both substrates. Basically, there is only one major consideration - differential movement! First, from the engineering standpoint, all practical means should be employed to minimize differential movement betewwn the two substrates. That could include protruding "pins," welded rebar, or special bonding agents. Correct treatment notwithstanding, it is reasonable to expect at least minor movement between the two caused by temperture changes as well as variable loading. Simple unreinforced coatings have essentially no capability to withstand the movement between the two substrates, so consequential cracking can be expected. When a reinforeced system will be applied, some limited (5-20 mils) movement can be tolerated. That can be enhanced by applying a band of flexible material under the reinforced lining straddling the substrate connection. That is sometimes referred to a "bridge joint" or a "hinge joint " if it is in a corner. Even those have limited movement capabilities, probably 30-50 mils,even more for a "hinge joint." Where more movement must be tolerated, a groove must be constructed between the two and a classical "expansion joint" should be applied after bringing the coating or lining system(s) down into each side of the joint.
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