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Is this something I really need to worry about? I need to lay a couple of courses below what will be a new doorway and realised my 2 bags of cement are dated 2010. They both seem ok so does this stuff really go off?
It does go off and 10 years might be pushing it a bit but it is a low stress application. I did my patio with out of date cement years ago and it has been fine. If you aren't in a huge rush I'd maybe mix up a bit, leave it a week or two then go at it with a hammer.
The sell-by date is more to do with elf'n-safety than the cement actually 'going off'. Cement has reducing agents added to reduce the risk of contact dermatities, but these reducing agents deteriorate with time, see
Make sure you use the appropriate PPE when using any cemetitious product.
Cement seems to absorb water and the powder sets into lumps over time, although my experience of mastercrete is that it does this much more slowly than cement used to. I reckon if powder still I'd use it in a low stress application, might mix it a little stronger just in case. I'm no brickie though, just diyer.
Thanks for the responses guys. I still have 2 unopened bags (and the bags are sealed plastic) so I'm going to go ahead and use them as it's such a low stress situation.. It's only about 16 bricks in total and I should have completed the job when I built the original wall.
I did make a sample yesterday and it appears ok but that is only overnight!
That shelf life expiry link was very interesting - I never realised it was related to preventing dermatitis.
If it's still powdery, I'd use it. If it has lumps in it, take them out, don't attempt to crush them and use them.
At least one of the bags is still powder and thats all I need 🙂