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Posted: Thu May 24, 2012 10:33 pm
by London Stone Paving
What if it works, are they then going to ask every customer to acid wash the flags?
How big a batch of this paving have they got?
Posted: Fri May 25, 2012 7:18 am
by local patios and driveway
This particular patio is tiny, maybe 10m sq. badly laid by some local bodger. Ive recommended replacing the lot and they do seem keen enough to sort it but want to try every avenue first
Posted: Fri May 25, 2012 8:12 am
by debyat
The supplier has agreed to replace the flags that have holes, but not prepared to replace the ones that have got the browning and look like stones coming through.
Posted: Fri May 25, 2012 8:35 am
by Brucieboy
debyat - all though I can't be 100% certain from the two photo's you've provided, the mottling effect looks like a phenomenom know as "aggregate transparency". It's caused by one or combination of number of factors including water absorption of the coarse aggregate, vibration method, mix design etc. Other than aethestics, it's not a real problem and may well reduce/weather with time. However, the exposed black particles look like the coarse aggregate showing through where the cement matrix covering them has delaminated. That is a problem in terms of durability and aethetics and probably why your supplier, quite fairly, has agreed to replace them.
Do not acid wash the slabs. All you'll do is remove the cement from the surface and cause an even bigger problem. When applied, the acid (hydrochloric) will cause the surface to fizz and dissolve the cement leaving the particles of sand. The cement dissolves because it contains about 65% lime.
Posted: Fri May 25, 2012 10:26 am
by local patios and driveway
Bruce im going to pass that info forward too. Thanks mate
Posted: Fri May 25, 2012 11:50 am
by debyat
Thanks Bruce really appreciate this