Concrete wall spalling - causes? 1

[Kom3]

Hi, I have concrete that is spalling from a wall in an industrial yard. I don't know what caused it. There appears to be no leak from the roof or impact. I am left guessing it is just spalling due to moisture from the environment getting in over time and causing the rebar to rust and concrete to spall. The building pre-dates world war II so it is old. I will tell them to patch it and apply fresh coat of paint to the building. Thoughts if there might be more to this? Picture attached.

 

[Ingenuity]

Depending on the clear cover, given the age of the structure I would test for carbonation with phenolphthalein indicator solution on a ‘fresh’ fractured concrete piece.

 

[lexpatrie]

You need to judge for yourself the criticality of that rebar, otherwise, it never had chamfer so it made it's own chamfer plus a bonus, could be freeze thaw as well if northern and some vestige suggests water concentration (a former solidly frozen downspout)? Looks unlikely in this scenario, but there's a window above?

 

[TRAK.Structural]

As part of the repair I would specify a corrosion inhibitor to be applied and a bonding agent.

 

[Tomfh]

Looks like rebar corrosion within the carbonation zone—pretty standard example based on this image. Tap along the edge to check for any other loose sections.

It’s worth checking carbonation depth and rebar depth in a few spots too, to see if it’s just a localised issue due to reduced cover, or part of a bigger problem.

See here a chunk from a beam corner with similar issues. In this example many bars were within the 15mm carbonated zone, with extensive corrosion evident as a result.

 

[LittleWheels]

As others have identified, very likely to be carbonation, particularly given the age of the building. The problem is only going to get worse over time as more reinforcement will get affected as the carbonated zone deepens.

Be careful about incipient anode effect with localised concrete patch repairs.

 

[rabuilt]

@Tomfh nailed it.

The thing I thought worth adding is a potential cause. There is a significant tension force center over the opening. Secondly, is water getting into the wall during the freeze-and-thaw cycle? As the freezing water occurs, an additional tension force could be applied, which could lead to spawning. Water could have caused the rust... if the rust gets to where it delaminates, this could add tension stress, thereby cracking the blocks or leading to the spalling.

 

[Mark_J]

My guess is the elevation is facing South and in an area of freeze/thaw commonly occurring during the winter (i.e. 20^ at night, 40^ day) during winter months. Water is collecting directly under the lintel and it is popping out the concrete to the rebar.