Open bag of cement, ok to use?

[23vc]

If I've got a half bag of cement open since 2 weeks ago, stored outside but with a bucket over it, and it's still powdery with the odd lump which I can chuck away, is it still ok to use?
It's for facework on my extension rather than something trivial

 

[JohnD]

A rule of thumb is that "if the cement is free from lumps that cannot easily be broken with the fingers" then you can use it.

Any hard lumps that don't break up during mixing means it is unsuitable.

You shouldn't really have left it outside. There might be a hard layer at the bottom, unless the bag is waterproof.

A new bag won't cost much.

 

[23vc]

Thanks I'll chuck it, only cos it's totally structural/visible

 

[John D v2.0]

Agreed with the other John, basically you wouldn't get 100% the full rated strength, but if you filter out any lumps or easily break them up it will be fine.
I store my spare cement in a plastic bin bag in the porch (as there is basically a greenhouse)
Unless you're making something where strength is critical (a bridge) where you need to controlling the curing carefully then the strength doesn't matter much.

 

[^woody^]

basically you wouldn't get 100% the full rated strength

If it's powder then, then the hydration process has not started and so it will give 100% strength.