Concrete discoloration patches

[haynewp]

I have been given the attached and was told that after polishing, the slab showed scattered white patches. This is the second time on a trial polished area this has happened. Could this be due to bringing fines up close to the top during hard troweling that have been exposed from the polishing? Thoughts?

 

[haynewp]

Picture of it.

 

[Agent666]

Really hard to tell as picture/movie doesn't really show detail, do you have something with a closer view of what your concerned about? I can make out some white specks for example and that's about all.

I'd hazard a guess its more likely some different coloured stones in the aggregate.

If you provide a close up photo folks might be able provide more info.

 

[haynewp]

I already asked for a clear close up instead of the video and that’s the best I’ve gotten so far.

 

[dik]

How was it cured?

Dik

 

[haynewp]

I will check.

 

[BridgeSmith]

Can't really see much from the picture and video, but I'll throw in my 2 cents worth. The only detrimental things I know of that show up as white patches in concrete are efflorescence and alkali-silica reaction (ASR), from using aggregate that reacts with the cement. Both reactions are accelerated by the presence of water. The concrete I've seen affected by ASR has white lines, rather than patches, but ours was exposed to weather, not polished, so it's a still a possibility, I suppose.