Larfarge Tarmac’s Topmix Permeable pavement has been making headlines the past couple of weeks with what appears to be an unquenchable thirst for water.
And in the company’s product video (below), it does seem to take on huge amount of liquid, touted at 600 liters per minute per square meter. Do some conversion work and it’s roughly 15 gallons per minute per square foot. This is a drastic increase over what the National Ready Mixed Concrete Association states at perviouspavement.org as a typical rate of 5 gallons per minute per square foot for permeable/pervious concrete pavement.
But it’s important to note that Topmix Permeable allows water to flow through its mixture, the very nature of permeable/porous pavements, which have been around for some time, and doesn’t actually absorb liquid. This is well known by paving contractors, but is the perception left by some of the recent articles.
What’s also known is that this type of product isn’t meant for high-volume roadways. In other words, it’s not a panacea for dealing with potential standing water on highways and interstates.
However, the product is ideal for where the company recommends its use — low volume residential roads and parking lots, bike and pedestrian paths, driveways and even road shoulders. There are other limitations, such as areas with what the company describes as having “heavy silt loads”, such as recycling centers and areas with sawdust stockpiles. And of course there is the fact that the sub-base underneath must be applied accurately.