The Brew Cabin

Posted: **Wed Dec 14, 2005 3:21 pm**

We supply solvent and water based road marking paint to the U.K. and export market, but we seem to have a unique problem with regards to playgrounds and sports areas.
Occasionally on these surfaces (conventional roads and parking lots excluded - no problem here) once paint has been applied, cracking of the asphalt occurs at the edges of the markings. This can happen from about a month to 6 months after the paint has been applied.
It appears that the paint 'shrinks' and pulls the asphalt causing it to crack.
What I want to know, is why does it only happen on playgrounds and sports areas?
The only explanation I can come up with are things like: poor quality asphalt, laid too thin, poor quality substrate, not compacted correctly.
If anyone has an idea why this is happening I would appreciate a reply

Thanks
Howard

Posted: **Wed Dec 14, 2005 9:47 pm**

Without further info, I'd hazard a guess that it's a problem with the binder used in the macadam.

Do you know whether these affected areas are hand-laid or machine-laid bitmac?

Posted: **Thu Dec 15, 2005 7:11 pm**

This is only an educated guess...I'm with Tony that there's not really enough information to make a solid answer. One important question, by the way -- is there a difference in the cracking depending on whether solvent-based or water-based paints are used?

Here in the Colonies, the base asphalt for playgrounds, sport courts, and parking lots is usually the same or a similar formulation.

I would hazard a guess, then, that the problem lies in the finish coatings given.

Driveways and parking lots are expected to expand and contract as part of the normal freeze-thaw cycle. A harder grade of asphalt is also used to minimise the softening (and resulting glop on your tyres and shoes) that comes from having a black surface baking in the heat of a summer sun. Because the mechanical shear from tyres is far greater than you'd at first realise, the maintenance coatings are also usually made from the harder grades.

Playgrounds and sport courts, however, usually are coated with a coating (under the paint) that has a higher rubber (or latex) content in it, to provide some resiliency underfoot. While heat-softening still must be avoided, foot traffic is simply not as destructive as vehicular traffic, and more resiliency may well be a tradeoff with a lower shear resistance.

Don't know that it's a help, but it might give you a path to follow...

TarmacLady

Posted: **Fri Dec 16, 2005 3:13 pm**

seen the problem before,where the coating supplier blamed the blacktop contractor and vice versa. on asphalt with pre coated chippings rolled in it shouldnt happen,only other solution is to wait a few weeks until the bitumen has "set"/oxidised more and is thus stronger than freshly laid.

will be doubtful if it is a problem with the asphalt

The Brew Cabin

Solvent/waterbased paint on asphalt