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No mention of epoxy coatings for steel rebar? Look for green-coated rebar as you pass highway construction sites.
by dmckeon 5y ago
No mention of epoxy coatings for steel rebar? Look for green-coated rebar as you pass highway construction sites.
- quickthrowman 5y agoThere’s also hot-dip galvanized and stainless steel rebar.
- rsync 5y ago... with stainless being a much better (but much more expensive) choice. HD Galvanized is a coating whereas stainless steel is a different material - it is stainless all the way through ...
- sgtnoodle 5y agoIt's a coating, but my understanding is that it basically creates a battery that keeps the nearby iron from deteriorating. Small gaps in the coating therefore don't really matter as long as there is still some zinc nearby.
- frosted-flakes 5y agoLike zinc anodes on a boat?
- sgtnoodle 5y agoYep, I believe that's the same mode of operation. The definition of galvanic is, "relating to or involving electric currents produced by chemical action."
- redis_mlc 5y ago> stainless steel is a different material First time in my life that somebody said that about stainless steel. "On HN, our job is being pedantic."
- ddkto 5y agoEpoxy coating is falling out of favour, as it has two downsides: 1) is has a weaker bond to the concrete, so you need longer bars to transfer the force, and 2) if it gets damaged (scratched or cut), the corrosion will concentrate at that location, and you are more likely to end up with a fully rusted-through bar, as opposed to a small amount of corrosion spread over the whole bar. Reinforced concrete is much like clothing: a stitch in time saves nine. With regular cleaning and maintenance, it can last much longer than if you just let it deteriorate.
- chairmanwow1 5y agoFor some reason I stumbled across a wild YouTube channel by a guy named Tyler Ley that is “crazy for concrete”. If I remember correctly he’s a civil engineering professor and has a lot of fascinating videos about concrete. In particular one about epoxy coated rebar that gives interesting notes about why it has its problems: https://youtu.be/xVDy84rR5Z8 https://youtu.be/xVDy84rR5Z8 I had a great couple of days learning all about the complexities of concrete through his videos.
- Xamayon 5y agoThat certainly helps, but in some cases such as when the rebar is under tension the epoxy coating can result in unexpected failure if there is any damage to it. The small areas lacking coating are corroded more aggressively, resulting in deep pitting which can weaken the bar to the point of failure.
- brohee 5y agoIt's pretty dependent on skilled people using it, every ding must be properly repainted before the concrete is poured, so extra care must be taken transporting and laying it. https://www.ijser.org/researchpaper/Epoxy-Coated-Versus-Galvanized-Reinforcing-Steel-on-Bridge-Decks.pdf https://www.ijser.org/researchpaper/Epoxy-Coated-Versus-Galv... has a lot more, but clearly not a panacea...