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bare steel in concrete

Don_'s picture

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Concrete must be able to adhere itself to the steel in order for the steel to achieve it's full effectiveness. Paint or even rust can cause the concrete to not get quite as good a grip on the steel. This can be quite significant in slabs and footers. In anchor bolts this may not be anywhere as critical, but it will still effect the bond with the concrete somewhat.

(post #171189, reply #2 of 4)

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The problem with paint is that the water and heat present when the concrete cures can cause microscopic condensation between the layer of paint and the steel. This breaks the bond between the paint and steel thus breaking the bond between the concrete(thru the paint that it is in direct contact with) and the steel. Don.t confuse the epoxy used to coat steel, used in high strength structural applications, such as bridges, with paint. This is a process designed to inhibit rust formed durring the pouring stages from later causing structural weaknesses. If this is for a home don't worry just use bare steel and don't paint any anchors, lintels or other embeded steel.

(post #171189, reply #1 of 4)

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Concrete must be able to adhere itself to the steel in order for the steel to achieve it's full effectiveness. Paint or even rust can cause the concrete to not get quite as good a grip on the steel. This can be quite significant in slabs and footers. In anchor bolts this may not be anywhere as critical, but it will still effect the bond with the concrete somewhat.

(post #171189, reply #3 of 4)

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Sometimes in blueprints and specs, I find a reference to not
painting portions of steel that get imbedded in concrete. What
is the deal? What would be the harm in paintng an anchor or
something and then placing it in say a poured wall?

(post #171189, reply #4 of 4)

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Thank you for your help.

Bear