Why Is the Concrete Sloughing Off?

[Dibbons]

We have reinforced concrete columns supporting the garage structure. One of them is shedding the outer top coat of smooth concrete and underneath the top layer, the base layer is all powdery. The other columns don't show any such symptoms for the moment. Should I be concerned? Thank you.

The following two photos show the column in question. The the last photo is the column that still looks OK. construction was completed between 5 and 10 years ago.

 

[Hey-O]

It's the skim coating they put on the column to give it the smooth even look. Water may have wicked up and got under it and popped it loose. The column should be fine, from what I can see.

 

[#41]

I'm not familiar with that type of construction, but it looks to be a mortar top coat failure that is flaking off. This would not be a structural issue - it just looks bad. Why - Poor mortar mix? Bad preparation causing lack of adhesion, high salt exposure?

 

[coronet68mx]

Humidity, salt, wet environment, everything #41 said, you live in la paz, I grew up in a beach in the Pacific Ocean, my grandma owns an hotel in the beach and that happen a lot in the coast, you're gonna be fine, reinforced concrete needs more than that to have structural damage.

 

[Hey-O]

Most concrete these days use limestone instead of hard river rock. Limestone is softer and sucks up water which turns the outside of the rock from smooth and hard , instead it becomes a little pasty. When it dries again it turns to dust and or powder. This powder causes the skim coat to lose it's adhesion and it separates and falls off. An easy fix and should match up fine in color if done by someone who deals with this all the time.