Black indian limestone - Milky appearance on surface

[Matt444uk]

Hi, I have had a patio laid with black indian limestone slabs. Due to the weather it was laid in two stages, about 3 weeks apart (end of May, then mid-June). It was pointed with Rompox Easy after reading good reports on pavingexpert. After this, I sealed it with Geofix Stone Protector. The whole patio was sealed at the same time. Now a few weeks on, the first section has a a milky appearance on the surface (presumably efflorescence?), but the secon section is absolutely fine. All the slabs were from the same batch. Does anyone know if it is efflorescence or not and why it is only effecting the first part to be laid (literally to the slab). I have a good photo, but can't work out how to post it!. Thanks in advance for any help.

[DNgroundworks]

Maybe the first batch of paving was laid on a wetter mix and what you are seeing is efflorescence? The next batch being laid on a drier mix?

[Matt444uk]

Thanks for the comment. I must admit I wasnt really paying attention to the mix, other than I thought both were a bit dry (but then I'm no expert, I just pay the bills). I had two front steps done in the second stage and these were on wet mixes and are fine, but maybe there's something in what you say.

[Pablo]

You may find the second batch will turn the same colour in the next few weeks. If it is Effo then you're screwed the sealant will stop it from dispersing and hold it where it is and will take several years to weather off. I've never seen effo on limestone it 's such a dense stone that it absorbs virtually nothing. Geofix is renowned for making substandard products which is possibly the only other explanation for what happened.

[GB_Groundworks]

white spotting sounds more like trapped moisture by sealing it when moist, as pablo says geofix is not a professional choice.

[lutonlagerlout]

TBH some romex products are going wrong on me now too
I wont go into it in detail but i wont be using anything but sand and cement from now on i.e. easipoint
LLL

[London Stone Paving]

The only time I have experienced effo on black limestone is right around the edges where it has been pointed, probarbly caused by a really wet/cementy pointing mix.

The problem could have been caused by the romex or the sealant. Black limestone and anything chemical do not mix well.

There is no real solution apart from wait and see. We've had a few issues this year with black limestone we have supplied to customers. All the problems have risen by inexperience (not of installation techniques but inexperience of the use of chemicals wether used in cleaning or sealing the stone).

The problem comes up over and over again and I think I'm going to post some very clear and visible information on our website about the need to consult us before using any kind of chemical with black limestone. Obviously its not going to help you now Matt but it might be worth letting your supplier know about the problems you have faced if it will help some other unfortunate person in the future

[Matt444uk]

Thanks for your help. Thinking about the chemicals, the sealant was the same throughout, all applied by me to the letter of the instructions. The Romex product, was applied by the contractor, and while he did a great job, the Romex was supplied in two goes, the first in metal tins, the rest in plastic tubs. I asked the supplier and was told it was just a change of formulation & packaging. Interestingly, while the colour match is OK the problem area is where the first lot was applied. I don't suppose I will get much luck going back to Romex?