Forum: Block Paving
Topic: Inconsistent colours in charcoal block paving
started by: FBF

Posted by FBF on 25 July 2017,16:52
Does anyone have any advice please about inconsistent colours in my Marshalls charcoal standard block paving that was laid 2 months ago – all from the same batch?

My front patio has some blocks that look darker when wet, but lighter whilst drying and then match all the others once dry. Out the back I have block boarders around granite with a whole host of variable colours, which I'm not sure is just down to efflorescence.

Pics Here: < >

I chose charcoal blocks as I wanted to seal them to make them as dark as possible for contrast with the granite and to match my black window frames on the house. I experimented with Brett, Bradstone, Stonemarket and Marshalls and chose Marshalls standard blocks as they were the darkest, truest black without a brown tone. I spoke with Marshalls about my concerns over the colours whilst the blocks were being laid and sent them photos. This was their answer:

“The most likely explanation for this is a variation in levels of moisture retention in the blocks. All concrete products will to some degree absorb moisture due to the slightly porous nature of the concrete material itself.  Whilst this does not affect the physical performance of the units, variations in moisture content can create slight variations in the appearance of the paving units, as units which absorb more moisture tend to be darker in colour. In Marshalls’ experience the variation will become less noticeable over time as the natural build-up of surface detritus gradually reduces the porosity of the units and the concrete continues to hydrate. Also variation in moisture content does not generally affect the strength or durability of the paved area and typically the visual issue invariably lessens over time. Either way the requested weathering period of 6 months is still, we believe, the most appropriate course of action at this point; as both efflorescence and differences in moisture retention levels will, in the majority of incidences resolve of their own accord within this time frame.”

However, I’ve now had some folk suggest to me that if this was their garden they would be swapping out the blocks in the front patio, and insisting Marshalls came to investigate the back because sealing with a colour enhancing product will not make all the blocks look consistent in colour and they are so variable it is unlikely that they will blend after 6 months. Also, I don’t want them to blend because they are all faded. I chose these to remain black – hence wanting to seal them before that happens!

Any advice or experience of this very gratefully received. Thanks ;o)

Posted by Tony McC on 28 July 2017,13:19
You can't argue with the explanation given by Marshalls - it's pretty much what I would have said had they not beaten me to it, and they key fact is that variation in hue does not affect the performance of the blocks, nor their service life. It's purely aesthetic.

It could be argued that, had the blocks been more thoroughly randomised prior to laying, the variation might have been less noticeable....might have been!

However, what you are left with is an aesthetic issue and as such it's wholly subjective. What you see as unacceptable, other customers might not even notice. Now, had this been a high value, premium product sold on its visual attractiveness and aesthetic appeal, Marshalls might have judged that it wasn't quite as lovely as they'd like it to be, and offer you a swap, but what we are talking about here is cheap-as-chips concrete block paving, on which they are lucky to break even, if truth be told, and it's a product sold more on its function and 'value-for-money' than aesthetic appeal, so you can't really expect more than what you've had....and explanation, and a totally valid explanation at that!

Of course, if it bugs you that much, you can buy replacement blocks and swap them out, but, in a year or two, what you now see as variation will be practically undetectable. As the concrete continues to cure, and the dyes "mellow" with exposure to UV light, those variations will dissipate and all will begin to look pretty much uniform.

If you wanted strong, stable and vibrant colours, then CBPs were probably not the best choice.

Posted by FBF on 29 July 2017,09:56
Is there a sealant that may help to uniform the colours as much as possible or am I best to leave them to weather and seal next year?
Posted by ResiblockBoss on 31 July 2017,11:36
If you wish to see what the paving will look like after it has been sealed (assuming you use a quality PU based product) – simply run the hose over the surface.

Posted by Tony McC on 01 Aug. 2017,11:05
I'd leave them until next year, and then see if that very nice ResibockBoss will send you a sample of his rather good sealant. :D
Posted by FBF on 01 Aug. 2017,13:12
Hi Tony, Hi ResiblockBoss,

Thanks for your replies. Sorry - I should have said in my first post that I actually had some samples of Resiblock back in March and tested it on all the makes of blocks I had prior to choosing the Marshalls. In fact, I had so many block and paving samples here so I could see what they looked like when wet, dry and drying that my back garden looked like a stone merchant at one point! Anyway - the Resiblock tests gave great results, hence why I chose the Marshalls as it looked the blackest once sealed – even better than the Driveline50. So, after my research and experiments, my original intention was to seal my blocks with Resiblock Matt once the blocks had been down a while. However, The reason I posted here was because I had a number of companies visit to quote for professional cleaning and sealing and a few of them commented that the variation in my blocks was so great (see in particular the photo that shows one run of blocks wet, then drying then dry) that even with a sealant they would never all look uniform. I hadn’t heard of this before - hence my question here.

So - the idea of wetting the blocks to see what they would look like when sealed is actually one of the problems I have - particularly on the front patio, as it is when the blocks are wet or drying, that the anomalies show up the most! When they are dry they actually all look the same.

I rather agree with waiting till next year to seal now, so that is what I’ll do and if things haven’t improve ed then I guess I will take Marshall’s own advice and go back to them.

Just out of interest – I’ve just come across a product that is a pigmented block sealer - < > Does anyone have any experience of using this, it's effectiveness or longevity? Is this an option to consider if my blocks really don’t become more consistent next year?

Posted by R&A Pressure Washing on 01 Aug. 2017,17:31
Smartseal = shite
Resiblock Superior or Superior Matt is really all you should need. If they dry uniform then can't see what the problem is?? all surfaces IE stone, concrete, wood etc dry at different rates, but if once dry you have the look you are after, then what is the problem?

Posted by FBF on 01 Aug. 2017,19:14
Quote (R&A Pressure Washing @ 01 Aug. 2017,17:31)
... if once dry you have the look you are after, then what is the problem?

Hi Roger,

The problem is that whilst the front blocks look uniform when dry, they don't when they are wet, and the edges round the granite whilst looking more uniform when wet, look totally different when drying or dry - as shown in the pics! I want to seal these charcoal blocks to prevent them fading over the years and to make them as dark as possible all the time, so leaving them unsealed indefinitely in not an option.

As Resiblockboss said -  run a hose over the surface to see what they look like when sealed - so in other words, it would seem that the blocks in the front will still look inconsistent when sealed. Now what will happen out the back is another matter. Perhaps they will all go the same colour, but the risk is that I'll seal them and they won't hence why I was contemplating the pigmented sealant that would most certainly make them all look uniform, which would in turn set off the granite beautifully. It would also have the advantage of making the kerb corners the same colour as the blocks and kerb edges which - for some bizarre reason - never match one another despite being made to go together!

I'm aware that you are not a fan of Smartseal - does this apply to all their products, not just their Natural Stone Sealer? Do you mind if I ask why?!! They have a pretty large product range so it's hard to imagine that all their products are rubbish otherwise how would they stay in business!! I'm not trying to be argumentative, but I'd very much like to understand why you think this.

Is there another brand of pigmented block sealant you would recommend or would Resiblock be your only choice?

Posted by R&A Pressure Washing on 02 Aug. 2017,12:56
I feel I have no need to explain myself for the dislike of smart seal other then some sealers I have had to remove from block paving has been there stuff where they have failed.
Re the concrete pigment dye, this is usually used for PIC paving so again going to be an acrylic sealer used, which I am not a fan of. You can buy concrete dyes direct from a company called PIC's there in Yorkshire I think, they make some of smart seal's sealers, just branded up in there colours etc.

I can access the photos for some reason ??

Posted by Tony McC on 09 Aug. 2017,10:58
Maybe the simplest solution is to < replace > the 'sore thumb' blocks and then look to get the sealing done.
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