white spots on concrete driveway

[PSUengineer1]

Please see attached pic. The driveway has not yet been sealed. No depressions detected at white spots. The driveway was poured less than one year ago in either October or November in a Northeast climate. Even if de-icing salts were applied over the short period of time since it was first poured, would it cause this damage? Were de-icing salts possibly used too early? Could the white spots be a form of efflorescence? what are the white spots a result of?
Thanks

 

[oldestguy]

Can you dig at the spots to see if there is weakness? The only thing I think might be the cause would be chert as the aggregate, but that is highly unlikely. Generally chert content is kept very low.

 

[PSUengineer1]

@ oldestguy,
thank you for your reply. I attempted to dig at the white spots, no weakness in the concrete detected from top side.

 

[TehMightyEngineer]

Hmmm, I haven't seen anything like that and can't find anything matching that in the literature I have on hand. Found this topic online: [URL unfurl="true"]http://www.diychatroom.com/f105/white-spots-newly-poured-driveway-189134/[/url] Reading that they seem to think it's caused by the aggregate either not having sufficient moisture during the pour or because the aggregate wasn't pushed lower enough during the finishing. However, theirs showed up right after the pour, not sure why yours would take so long to appear.

Do the spots disappear when the concrete is wet or do they stand out more? Do the white spots leave a dust on your finger when you rub it?

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com

 

[Wallache]

It might be curing compound, but that stuff usually wears off after a few months.

 

[PSUengineer1]

@ all:
Clarification: The concrete was poured in either October or November of 2014. thanks.

 

[hawkaz]

When did the spots first show up?

 

[JG2828]

If you pressure wash it, does it all turn "white"? Wondering if those spots are actually just clean concrete.

http://arninglawns.com/wp-content/uploads/2012/10/20121011_135957.jpg

 

[PSUengineer1]

@hawkaz: the spots first showed up around December 2014. Thank you.

 

[Allen78]

What kind of trees are near the driveway?

 

[Allen78]

Are you sure it was not sealed after the pour? The splatter spots look like rain drops.

 

[oldestguy]

Just viewed my front walk, some 20 years old. There are lighter, but not white,spots corresponding to where I think coarser aggregate is present. There has been misty rain going on all day and walk is slightly wet. The dry areas in shaded from mist are just plain gray. I attribute this to the varying degrees of moisture absorption, with aggregates not being very absorbent. Your aggregate may be petty hard stuff that does not absorb much moisture. The darker tone of the sandy zones is sort of the natural color change most materials get when more moisture is present I think. Does not appear to be of concern. By the way, why would you apply a seal anyway? In the north areas most concrete drives are air entrained concrete that resists salt very well.

 

[PSUengineer1]

@Allen78,
The driveway has never been sealed.

 

[Ron]

Rain or sprinkler on curing compound that was in process of drying.

 

[Guastavino]

I'm thinking what Ron said too.