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Norman Hyett / Brynglas tunnels on the M4 / CC BY-SA 2.0

Removing calcium carbonate salts from motorway underpass

We recently received a call from The Highways Agency seeking help with removing slippery calcium carbonate deposits that had formed on the surface of the road, in the Newport tunnel on the M4.  


The salts were seeping though and dripping down from the stone roof of the tunnel, forming hard, carbonate deposits on the roof and the ground below - in exactly the way that stalactites and stalagmites form in a cave. Anyone who has touched a one of these intriguing formations will know that they are as smooth as ice, so you can easily imagine how potentially dangerous this could be for drivers passing through the tunnel.


Calcium carbonate is notoriously hard to remove and we couldn’t take any risks of leaving traces of the contaminant on the asphalt surface. A specially formulated chemical can be used to remove the hard, carbonated deposits, however the Highways agency preferred our suggestion of media blasting, seeing it as a more environmentally friendly option.  


To minimise inconvenience to the public, work was carried out at night, when the road was closed for routine maintenance. Our team managed to completely remove the salts using powdered glass and completed the job within the prescribed time frame.

The highways agency were delighted with the outcome and we were praised for the quality of our work as well as the efficiency of our operations.

For more information about removing calcium carbonate from any exterior surface contact Max or Andy Morris on 0333 234 1445 or email your enquiry.

Image Attribution - Norman Hyett / Brynglas tunnels on the M4 / CC BY-SA 2.0


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