In article , The Natural
Philosopher writes


Its fine. You are just impatient.

If it didn't turn to rock, its OK. I just used a half bag I had leftover
from last year, and it went off allright in a coule of days, once I had
sieved the rock hard lumps out of it and used a bit more than usueal for
luck...

This is not true, cement powder loses its reactivity and you will end up
with a weak matrix, not critical as far as a post mix is concerned but
could be critical elsewhere. Cement is at its most reactive just after
its manufactured and gets slower and weaker from then on. Just because
it has set doesn't mean its strong.

Oh by teh way, there is not size dependent cire time for concrete. Its
only depebndeint on temperature. generally it sets overnight in summer,
and about 2 nights in winter, to the level it feels 'hard' and takes on
full strength over a couple of weeks.

You obviously don't work with structural concrete or even slabs that
need to have achieved a certain strength before loading. Concrete has
initial set (surface hard) and final set (hard all the way through), you
are right to say that these can be dependant on temp but you can achieve
a false surface set if you have severe drying conditions. The rate of
strength gain of concrete is a well understood area and are usually
measured at 1, 3, 7, and 28 day intervals.


It takes time to DRY OUT though...


--
David