Oh that delicious chocolate bar with the light and airy honeycomb centre…Although I never liked it at all I have a lasting memory of my Grandmother syphoning boxes of the stuff from the working men’s club for me to ‘enjoy’.
Fast forward to today and the airy honeycomb centre is reserved for cast concrete walls and contractors scratching their heads for a solution. I’m writing this blog because recently there has been a spate of Honeycombing problems that have been compounded by carrying out knee jerk reaction repairs. In panic mode swathes of decent concrete surfaces have been lost in refacing walls and columns. Blowholes obliterated, joint and board lines lost and surface flatness and tone compromised! In effect the concrete has been lost to a bag and a half of full cream fairing coats.
However…Honeycombing might look and taste awful but it’s no big deal to fix so in the wise words of the Cadbury’s Caramel Bunny: “take it easy.”
Honeycombing occurs due to lack of compaction. I've often seen, heard and read that honeycombing is attributed to poor workmanship as lack of compaction seems to be equated with not bothering to compact, consolidate or vibrate the mix adequately. I won't go off on one but this is one dimensional thinking as equally the case could be that there is congested reinforcement that does not easily allow for full compaction for example. Anyway that's up for further discussion which hopefully will happen. Back to the repair category...
Honeycombing sits closely with construction damage as a category of repair.
By definition, if it is hard to compact concrete it is usually in a hard to reach place (with a poker vibrator or similar). Hence, honeycombing will naturally tend to occur at the extremity of a pour... at the base, corner, edge or some form of junction point (knockout for example). Honeycombing may look like a disaster but is forgiving as a repair mostly because of it's positioning. Plea...
A focus of our work is concerned with Architectural concrete repair to fair faced concrete. For me this image is fascinating. Not just because I've never seen grout loss quite so honestly displayed before but also because this image clearly illustrates cause and effect.
The base of the column (steel shuttering) had a tiny band of hydration staining (dark line) and some very minor honeycombing (voids around larger aggregates). On the floor, in almost a mirror image was the grout that was lost, lying in place. Call me boring but THIS is my Friday night out.