white powdery stain on concrete pavers

[Pulpo]

I have some concrete pavers that have a white powdery stain around or towards the edges.

The concrete pavers are coloured and about 500mm square and 50mm deep.

Some areas of the paving are worse than others but as much as 70% of the pavers are effected.

It was laid about 6 months ago, with a plastic membrane then paving sand on top.

The white powdery stain can be removed very easily by rubbing with the foot but.

If the stain is not removed it etches the colour oxide from the pavers.

Is it a salt stain?

Is it from the paving sand and or concrete pavers?

I would normally use crusher dust [dolomite] but was strongly advise to use the paving sand.

Any suggestions to rectify the problem.

Many thanks

Pulpo

[mic-d]

It will be salts from the concrete pavers. Sand is inert and insoluble and there's not likely to be much else mixed in with it. Since you have a plastic membrane down too, that really only leaves the pavers themselves. Its called efflorescence and will continue until the pavers are weathered and the salts are leached away(which might be a long time given that you have an impermeable membrane below the pavers) You can buy cleaners for it or use HCl, but they are likely to add to the salt problems in themselves. After you clean them you can use a penetrating sealer on them that will stop further staining. Have a look at this:
http://www.factsfacts.com/MyHomeRepair/efflorescence.htm

Cheers
Michael

[Trav]

It will be salts from the concrete pavers. Sand is inert and insoluble and there's not likely to be much else mixed in with it. Since you have a plastic membrane down too, that really only leaves the pavers themselves. Its called efflorescence and will continue until the pavers are weathered and the salts are leached away(which might be a long time given that you have an impermeable membrane below the pavers) You can buy cleaners for it or use HCl, but they are likely to add to the salt problems in themselves. After you clean them you can use a penetrating sealer on them that will stop further staining. Have a look at this:
http://www.factsfacts.com/MyHomeRepair/efflorescence.htm

Cheers
Michael


Dammit. I was going to be so helpful on this thread, but I couldn't think of anything else to add. Not a thing. Nada. Zilch.

Good response mic-d. :D

Trav

[MarkV]

Pardon my ignorance but why would you put a plastic membrane under pavers:confused:

[mic-d]

I suppose its a way of suppressing weeds, but they'll still seed in cracks/joints unless you've used cement gap filler/grout...

Cheers
Michael

[Pulpo]

Thanks for reply.

Heres hoping the mositure from the concrete pavers dissipates soon.

The placing of the plastic membrane is a long story.

It certainly stops the weeds but not neccessary as the crack between the pavers has cement sand for filling.

The weeds dont seem to come up from the bottom anyway rather they grow in the cracks between pavers.

I have done a bit of paving and never used the plastic before and unlikely to use it again.

Cheers

Pulpo