scorpionleather wrote:
I'm a newbie to pouring larger quantities of concrete/mortar/cement. I
have a batch I'll need to mix of 3 100 lb bags white portland
cement and 5 100 lb bags of tiny pebbles. What is the smallest size
mixer I can rent that will do this batch all at once? The local
rental has 6 cu ft and 9 cu ft tow-behind mixers. How much water
should I add initially? I am afraid of accidentally adding too much
water or if I'm too cautious and add it too slowly maybe it would
take away a bit from my troweling working time. How long to leave it
spinning round the mixer?

I have no idea how long your mixture will take to cure, but it's sure gonna
solidify long before you can trowel a 900+ pounds of cement.