I mixed a wheelbarrow load of concrete (sand, cement, water) this morning, but before I could use most of it, I got called away and didn't get back until this evening, like 7-8 hours later. By now the concrete is half set - very stiff and dry and has to be almost scraped out so it can't really be used.
But I find if I add a little water and mix, it's back to the same consistency as when I first mixed it this morning. This saves a bit of work and cement / sand.
My question is, is it any good at this stage (being used for laying patio slabs) or I should I just dump it and mix a new batch?