02-20-2014, 01:33 PM
quote:
Originally posted by Mtviewdude
General rule of thumb, you can add 1-2 gallons per cubic yard to increase the slump without it being too much of an issue. If I had to choose between 1-2 gallons -vs- poor slump, I would add the water, any more I would reject the batch.
However if you are curious, from the studies I have read.
Adding ~2.5 gallons per cubic yard reduces the strength ~25%
Adding ~5.0 gallons per cubic yard reduces the strength ~50%
Adding ~7.5 gallons per cubic yard reduces the strength ~75%
Hawaii concrete mixes (due to their aggregates) tend to be stronger then specified. On the 4k psi mix we ordered the cylinders were breaking at ~5.2k.
Usually on the batch form it will specify "max add water".
Nice... I didn't see that. It's been about 15 years since I worked out here (Kona side) professionally speaking. I recently ordered a minimum 3 yard (as I recall) 4k batch from the Pahoa yard. I used it for my cesspool lid. The lid is 12" thick but I had no problems screeding the top off after vibrating it. I would have needed additional water but could have added it topside if was after a smoother finish. It's nice to hear they are mixing above the cited test. Over hydrating out here has obviously been accounted for to some reasonable degree.