re: Someone in Lake Charles got a pretty sick looking patio built * Update from owner pg 13 *

Most concrete plants already put retarder in starting around May1st or earlier if it is unseasonably hot in April. Drivers don’t keep super plasticizer in their trucks and that would have been the only chemical that “might” have made that concrete placable at 4 hours. But even at that point, the load should only have a one time addition of water. Re-tempering old concrete just makes it gum up faster and accelerates the process of heat of hydration.

My guess is that the load was re-tempered several times while it sat baking and again before every time they filled the buggy. Just to make it wet enough to come out of the drum and down the chute. That situation causes the concrete to set up within a couple of minutes after it hits the ground. It’s basically unplacable at that point.

If the driver had super p with him (which is unlikely) the concrete would have been okay if placed within 2.5 hours. The driver would have had to have 15-18 ounces per 100 weight of cement in a yard to be effective. Each yard would have had approximately 500 lbs of cementicious . Straight Portland cement or a 85%/15% Portland/Fly Ash or Slag ratio. It would have taken almost 900 ounces to chemically treat the slump on a 12 yard load. But again drivers don’t carry a couple of 5 gallon buckets of super p because this type of practice by a finisher is rare and they are trained to inform the finisher of the risk involved in choosing to pour old and multiple re-tempered concrete.

Super P, if ordered to be in the mix, is added at the batch plant. It simply increases the slump from a standard 3”-5” up to an 8” slump without affecting the water/cement ratio of the mix design. It is an admixture that finishers pay extra for in order to have a much more easily placable mix.

The only time you will see drivers carrying super p is if they are on a project that is long term (2-5 years) like a WTP where loads are routinely tested and inspected at a checkpoint before getting released to the point of placement. If they test below the lower slump limit, the testing company will allow them to add super p and re-mix and then test again.

But you never have drivers toting super onto a tingly dink residential patio job.