So what kind of blowholes are affecting our visual concrete? Big ones, medium ones and small ones? Yes those ones but there’s something else…
In our quest for an ever growing understanding of potential issues with visual concrete, like learning a language, the more you know the more there is to know.
We’ve come across another type of blowhole that we call ‘Milky Way Blowholes’… trillions of tiny minute pinpricks of air that make the concrete appear slight ‘browner’ in tone. In essence swathes of Milky Way Blowholes look fine, especially at 3m or so. There’s no point in touching them at all.
But what if within the galaxy of visual concrete these Milky Way Blowholes are punctuated by numerous ‘normal’ blowholes? A wormhole is opened and swallows you up for the following reasons:
Milky Way blowholes make the surface less dense with increased porosity. Whilst filling punctuated blowholes surrounded by dense concrete is not necessarily an issue, filling large blowholes surrounded by the Milky Way really is!
What happens is that essentially it is impossible to just fill the hole. Repair mortar also fills the surrounding pinpricks returning that area to fully dense smooth concrete. The resulting finish is a blotchy patchwork of repaired splodges, clearly worse than the blowholes themselves. Even if the repair is perfectly colour matched, the pinpricks will still absorb light and the repair will bounce light back, resulting in a lighter perceived tone.
There are only three options in this case:
To leave it all alone
To very skilfully repair in a shape that flows horizontally like the bands of concrete itself, or
To carry out a holistic repair to the whole surface filling 90% of the porous surface.
This is what we came across on our last post finishing project in Lancaster. Just when you think you’ve devised a fool proof methodology, concrete comes along and forces you to rethink your strategy. We chose the last option by the way.