Concrete Surface Defect - Reinforce Pattern Shows on Surface
Concrete Surface Defect - Reinforce Pattern Shows on Surface
(OP)
We have a project in which the reinforcing pattern is showing in the surface of the concrete after it has set (photo attached). The clear cover over the reinforcing is 2 inches. Does anyone have any idea why this is occurring and how to prevent it?





RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
This can be prevented by using a lower water-cement ratio and controlling the slump of the mix. Over-vibration is also a common cause.
Check the actual cover on the rebar.
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
What is the slump after Super-P addition?
Why are you adding plasticizer at site? What brand?
How is it being added?
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
Q: What size is your coarse aggregate?
A: ASTM C33, No. 57 (from 1" to No.4).
Q: What is the slump after Super-P addition?
A: Slump not taken after the addition of Super-P. Half the maximum recommended dose is being used.
Q: Why are you adding plasticizer at site?
A: Monitor slump prior to the addition of Super P.
Q: What brand?
A: DARACEM 55 by Grace.
Q: How is it being added?
A: Measured in a calibrated container and then added to the drum and thoroughly mixed.
Q: Is there cracking along the bars?
A: No.
Q: Slab thickness?
A: 20 inches.
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
thread507-293677: Concrete Slab Reinforcement Rippling
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
I doubt those are the reasons. You could use much larger aggregate in a 20" slab, and 4" slump is pretty standard stuff. I would look more to the plasticizer...not sure why it was required.
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
Dik
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
Greg
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
Overvibration or vibration of the rebar mat and too high slump of concrete are the main reasons.
Consider dropping the plasticizer and use the coarse and fine aggregates from the same source.
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface
My opinion....temperature. Particularly of the steel before placement, but also of the mix. We generally use 1 1/2" aggregate in a slab of this thickness to reduce heat.
RE: Concrete Surface Defect - Reinforce Pattern Shows on Surface