Query sub standard flags??? - Spotting on flags

[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?

[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

[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.

[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.

[local patios and driveway]

Bruce im going to pass that info forward too. Thanks mate

[debyat]

Thanks Bruce really appreciate this