The Brew Cabin

A contractor completed a paving block job for my drive. Paving block colour is brindle. As they laid them some of the blocks appeared to me to be off colour. That is reds turning greyish. I asked them about this and they said it was just salt deposits and would wash off when raining. We had a couple of rainy days, but off colouring is still there. What could be the reason for this ? Could it be corrected ? Any help would be appreciated.

Is this discolouration like a milky deposit on the surface?

There are two common 'deposits' on new concrete block paving that can make the colour look wishy-washy.

The first is soap oil residue. This is not seen all that often, but is more prevalent during the summer. Soap Oil is the vernacular for Mould Release Agent and it's used to line the moulds used in the manufacture of the blocks to prevent the concrete 'sticking', so that, when they are pressed out from the moulds, the blocks are perfect and intact. Soap Oil is water soluble and will disappear after a few showers of rain, that's why I say it's more commonly seen during the summer, when we can go for, oh..., hours without any rain! ;)

The second common agent of discolouration is efflorescence and this is a natural phenomenon with all high-quality concrete products. It comes about because of the ongoing reaction between the lime in the cement, the rest of the aggregates, atmospheric humidity and the air itself. It can look like a white power or dust on the surface of the paving, often more pronounced at the edges. Again, it's a temporary non-critical phenomenon and should disappear in under 6 months.



If it's like that shown above, it will eventually vanish. If it's not, then you need to speak with the contractor and get them to write into their guarantee that, if this phenomenon is still visible in, say, next April, then they'll replace the affected blocks as part of their defects liability.

I have recently seen a contract with severe dark staining over 70% of Pavers ,could this be Oil soap residue as mentioned.

Dark staining? That's unlikely to be a soap oil, which is often a white or milky looking deposit, but not as limey/powedery as efflorescence,. Do you have a picture or the name of the block type, Tony?