# concrete slump



## gpop (May 14, 2018)

Pouring a pad 15 x 28 one foot thick using 4000 psi concrete over rebar. Pad has conduits and stands already installed.

Mixer driver will ask what type of slump i require then add water. Is it better to have a runny mix on a pad or a stiffer mix as the duct back i did i had it runny and it looked great until it cured then the top looked like the water evaporated and it left a stony surface (it was a duct bank so it wasn't a big deal, It may have also been over vibrated).

Any tips?


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## backstay (Feb 3, 2011)

Less water makes better concrete. I’m lucky, my cousin is a retired concrete finisher and does small jobs for me.


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## MikeFL (Apr 16, 2016)

Tell him a 4" slump. That's very well within spec and does a nice job while not being too hard to work with. 
More water harms the mix. 
Add plasticizer if you need it to flow better. 
Use a vibrator to make sure you surround the reinforcement well.


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## Jlarson (Jun 28, 2009)

I usually tell em 4, knowing sometimes we'll get more like a 5.


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