cement going off

[chas2008]

I know cement can go off by getting damp into it and setting hard, it also has a shelf life, once its well passed this date does its chemical properties decrease ?
i ask because i recently laid some coping stones and the mortar mix, which i know i got right , is almost acting like there is not enough cement in it ie, dry crumbling sand!!
and guess what ?..i used some old blue circle cement i found in the garage i assumed as it hadnt set hard it was still usuable, was i wrong in thinking this ?

[buildersmate]

Yes, I've unwisely done the same thing with the same result. Never again.

[chas2008]

cheers for that, the answer i wanted...although a bag of cement is only a couple of pounds it seemed silly buying a whole bag just for a couple of coping stones, lesson learnt and the other unopenend bag needs to be launched ..