Portland cement

That entirely depends on local hunmidity.

I had a bag I got this summer for some odd jobs. Left outside in the old landrover.

The outside and top had caked, but inside it was still powdery. It set Ok when I had to put in two half bricks to tidy up some decorative brickwork.

If you seal it against moisture,. it lasts forever. If it gets rained on, its a solid lump the next day ;-)

If its still powdery, its OK.

Hah! yes sorry forgot to mention the bag has been kept inside with a relatively good warmish condition.

Just checked, it has gone a bit hard on top.

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From my experience if it's still powdery (like new cement) then it works fine. ..but I maybe wouldnt' use it on something critical if it's a mix of powder and clumps.

But powder and clumps is fine for rough concrete, especially if you have a mixer and mill it a bit with dry aggregate

Always a bit less than the time to your next job.

Colin Bignell