Is My Concrete Too Wet?
Hello Rusty,
Thanks for all of your advice up to this point. But I just layed a couple small slabs and the first one went actually fairly well. The second one I layed was larger (5 x 5) and the finish didnt go as easy as the first. I had a ton of water on the top of the slab when I floated. I would push it off an more would come. So the result was still decent, but the water would actually expose the aggregate in some areas and other areas looked very sandy. I had the homeowner tell me (he had some experience) that the concrete was mixed to wet…..? I mixed 2 80lb. bags with approximately 2.5 gallons of water. This is acutally what the mixer recommended also. The homeowner also thought that the premixed bags should have had larger aggregate and that could be the problem. The aggregate in the bags was all pea gravel size. Anyway I thought I would ask the pro himself to see what you think. Your video shows insane amount of slurry to work with and I havent experienced anything near this yet. Also, do you think I need to be concerned about this slab for the future. Again, your advice is extremely appreciated.
Chad S….
Here is the Multitorial Chad is referring to: Groovy Concrete
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Hi Chad, Thanks for letting me help. Any time your concrete has a lot of water rising to the surface during floating, it is too wet.
Several things affect the moisture content in the mix:
Porosity of the sand and aggregate
Clay quantities in the sand
Moisture in the substrate
Then there are environmental factors:
Direct verses indirect sun light
Wind
Humidity
Obviously: rain
You also mention the amount of “cream” you see in my videos; mixing time will affect the amount of cream (what we call “butter”) you workup during the floating process. Air and a frothy mixing time can help with getting good cream to the surface – this makes mechanical mixing advantageous.
But… also… the texture, size and clay quantity of the aggregate and sand (also cement to aggregate ratio) affects the amount of workable cement cream that comes to the surface.
Obviously if you are using premix concrete, you are at the mercy of your premix bagging company and there is only so much you can do. I mention in Groovy Concrete ( http://www.monumentmasonry.com/multitorials/tconcrete.htm ) that you can bring a few bags of pure Portland cement to the job with you and ad a shovel or two per bag to help increase the cement to sand ratio which will most of the time, bring up more cream in the floating process.
I hope this helps. Good Luck!
Gratefully Yours,
Rusty