slate driveway

[dock]

i have a slate cobble stone driveway, it is unsealed. some of the stones have started to rust on the surface. what can i use to clean off the rust?
and then should i use a zylene based concrete sealer to keep it from rusting again?

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[GraniteGirl]

Just a few questions:

What is the substrate?
How old is the installation?
What kind of slate (Indian, Chinese, Brazilian, American?)


Oh - and what do we call you? :D

[dock]

The driveway is laid on sand, it is chinese grey slate.
we just installed it a few weeks ago and from washing it has started to rust.

[Stonehenge]

Whats up Dock ?

Some forms of slate contain inherent elemental iron oxide which becomes futher oxidized when a higher exposure to water and chemicals occurs.

The rusting phenomena is likely to persist in your natural stone installation,
it may be just the nature of things.


Michael of Stonehenge

[GraniteGirl]

What Michael said.

There is no way a sealer will prevent your stone from rusting. The iron is inherent in the material, and even if you do seal the top, moisture will still penetrate from the substrate, causing the iron to rust.

Being that the stone is from China, I am doubtful as to wether it is a fully metamorphosed slate, too. Does the stone slough off mud when it gets wet?

[dgunnels]

Just curious. Don't where 'dock' lives but are slate driveways common? Doesn't seem like a good application to me. I know there are slate roof tile but wouldn't a slate drive fail quickly from the pressure/weight/traffic?

[dock]

We live in BC Canada, and no, slate driveways are not popular here, in fact we had never seen one before. (but we can say that about alot of the details we did in our house). We did a slate roof, and some slate stone on walls and decided to match driveway. The slate on driveway is very thick and heavy, and is laid on a sand bed, it should not crack, however may need to be releveled at some point. We havent had a good rain yet since install, the rusting was from cleaning sand off with presure washer. Ive noticed a small amount of rust on the wall stone as well, i guess it may just be nature of stone and we may just have to accept that?

Thanks for input
Dock

[dock]

Adriana, im not sure what you mean by slough off mud, sorry.
The driveway isnt finished being installed yet, and there is still sand on it from install (sweeping sand in between stones). When sprayed, mud and sand removes well doesnt stick?
does that help with your question?

[jvcstone]

Dock, what GG was refering to is that some material, especially material comming out of asia, is not a true geological slate, but rather a poorly,( or sometimes not even) metamorphosed shale--- the sedimentary rock that slate is formed from. There have been reports of the poor quality material turning into mud in wet applications which is the natural thing for shale to do since it is only dried mud anyway, but totally inappropriate behavior for real slate. Your driveway pavers are most likely going to be just fine if they have the compressive strength to handle traffic. you'll just have to adjust to the rust spots. :shrug:
JVC