Aircrete Blocks - Spares With Cracks
Posted 04 February 2016 - 02:42 PM
I've got a pile of spare blocks left over from the extension I built last year, which I had planned to use on the garage this year, they are stacked on block paving, on their sides, piled about 15-20 high. Just brought the bin in, which lives next to the pile, and noticed that, not the bottom one, but the two directly above that, has about 5 hairline cracks in them (you can see them as parts are damper than other), vertical (in the sense that they are laid on their side). They have roofing felt over the top of them, but i wouldn't say they are bone dry all of the time.
Any ideas what might have caused this, and are they any good for use?
Hoping we haven't had a bad batch, some of the other blocks had vertical (when stood up properly) fissures (not really cracks) in them, we had one or two of them which got used in the build, not had any problems with them, and i don't think they are cracks as such, but any idea what could be going on? They were in from day 1, still a few with the same markings in on the pile.
Posted 04 February 2016 - 04:39 PM
Water can fairly easily soak into these blocks and as they aren't that good in terms of tensile strength if it then freezes it could well expand and crack the blocks. It doesn't need to whole block to freeze, either, just a thin layer of ice on the outside will be enough to hold water in the block. Water has a maximum volume at around 4 deg C, so can expand inside as it cools and if the outer surface has frozen you could get an internal pressure build up that might be the cause.
Posted 04 February 2016 - 04:49 PM
I spoke to the block manufacturer about this too, and they said something I wasn't expecting.
Apparently, the blocks are designed to be used and stacked in 1 way only, and if the blocks are laid on their side, they have only about 15-35% of their compressive strength as tensile strength. Now I thought tensile strength was more things being pulled apart, like tearing a piece of paper? When I first got these blocks they were stacked on their sides (which seemed the most sensible way of stacking them for stability) for around 23days in total.
How are the blocks on the outer leaf going to be faring? They are painted with breathable masonry paint, but other than that are open to the elements, and the extension is currently unheated bar the bit which escapes from the house. Hoping having them like they are isn't going to be causing them any damage? According to the blurb, these blocks are meant to be immune from the freeze/thaw cycle? And also closed cell.
Posted 04 February 2016 - 04:54 PM
Posted 04 February 2016 - 04:58 PM
Posted 04 February 2016 - 05:02 PM
Makes a lot of sense. Pretty hard to keep things dead clean, and it's logical that the blocks aren't anywhere near as strong with a side load.
Posted 04 February 2016 - 05:04 PM
Posted 04 February 2016 - 05:06 PM
Posted 04 February 2016 - 05:12 PM
Another possible cause is the blocks where still green when they where delivered so hadn't fully hardened up.
I used them on my build and I thought they where much stronger than an ordinary block. Took a few more bangs with the hammer and bolster to break them.
Posted 04 February 2016 - 05:47 PM
Posted 04 February 2016 - 06:06 PM
I'm guessing the weight in cabinet kept to a minimum, and also thought about injecting plasterboard adhesive in the gap between board and wall? Or maybe some decorative wooden posts under the cabinets on top of worktop to give extra support?
Posted 04 February 2016 - 06:09 PM
Posted 04 February 2016 - 06:35 PM
Posted 04 February 2016 - 06:48 PM
Are you using anything specific?
(I'm sure it's covered in thread here as well)
Edited by daiking, 04 February 2016 - 06:51 PM.
Posted 04 February 2016 - 08:24 PM
I found in the past if you use the wrong fixing you can lose confidence, but use the right fixing and its as good as anything else
Edited by MikeGraham, 04 February 2016 - 08:25 PM.
Posted 05 February 2016 - 11:33 AM
Posted 05 February 2016 - 03:16 PM
Posted 05 February 2016 - 04:30 PM
Posted 05 February 2016 - 04:42 PM
Posted 05 February 2016 - 05:20 PM
Without a doubt the best way. Dot'n'dab really should be outlawed, as anyone who's pointed a thermal imager at a dot'n'dab wall will probably confirm.