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Posted: Sat Jul 16, 2011 5:11 pm
by London Stone Paving
Wouldn't mind putting this question to the board.
We've got a client who's buying 400m2 of our Jura Limestone for a job at Wentworth. He is concerned about efforessence leaching through. We've been selling this product for about 4 years now and I have never had 1 complaint about leaching on this product. Even so, the contractor does not want to take the risk and does not mind the cost of taking precautions. Am I right in telling him that an SBR bond bridge will provide adequate protection from leaching?
Cheers
Steve
Posted: Tue Jul 19, 2011 9:16 am
by Tony McC
It would definitely minimise the risk of eff leaching, but it's never wise to guarantee 100% certainty.
Limestone can 'play up' in out damp climate, although the Jura is generally very stable. For me, I'd be more concerned about the use of overly rich cementitious bedding/jointing. There's too much use of 3:1 mortars for bedding when, certainly for car-free areas, 6:1 or 8:1 would be more than adequate.
I note that more and more suppliers are now pushing the use of silver sand with white cement for the paler natural stones.
Posted: Tue Jul 19, 2011 2:58 pm
by London Stone Paving
Thats very good advice Tony, thanks. I've got to say I always used to opt for a 4:1 mix and I never had problems with leaching or loose flags.
Your spot on about the Jura being stable and as I said in the initial post I have never had any issues with leaching on the Jura Limestone, client is just very eager to cover his back in this case.
suppliers are advocating the use of white cements and silver sand. Peronally I think that if you need to use white cement etc on a natural stone product to avoid leaching then the product is too soft and probarbly not suitable anyway.
The Indians are really pushing the rainbow and teakwood sawn sandstone at the moment and people are buying it because its cheap. What people dont realise is that its cheap because its soft and very easy to cut. Because its easily cut everyman and his dog can cut the stuff in India which creates competition and drives the prices down.
Posted: Tue Jul 19, 2011 9:11 pm
by jonnyboyentire
Cant blame your client about covering his back on 400m2 !
I worried about this greatly when I laid 260m2 of black limestone in Sunningdale. The cement my supplier stocks is Dragon Alfa and it's apparently known to reduce leaching. Mastercrete etc apparently can show through.