Sharring experiences in urban infrastructure delivery.

Unusual Cracking of Crosswalk Pavers

By: Tom Davis Category: Paving, Recent Posts

And u2012-11-21 07.39.39.jpgnusual cracking has been observed in the concrete unit pavers either side of the crown of concrete streets. The crosswalks have been in service for 10-15 years and there are others installed at the same relative time that do not show similar cracking. The pavers are installed in recesses in a reinforced concrete street cross-section and placed on a 1″ deep sand bed with sand swept and vibrated in after placement to lock them in place.

As you see in the photos the cracks are appearing largely in the lane either side of the crown. The cracks are either side of the center and run across in the narrow direction.

Given that the cracks are occurring in distinct locations and not across the entire crosswalk one would assume the failures are not due to defects in the pavers.  The failures are most likely due to changes in the sand supporting layer. As the majority of the cracks are near the crown one could conclude that the sand is migrating to the edge of the pavement that is slightly downhill.  For that to happen the sand in the lower areas –near the curbs– would have to migrate out.

As noted in other posts at this site sand is often seen above the bricks in the area next to the gutter when water stands there after a rain. The crosswalks where the cracks are occurring do not show signs of such puddling and migrating sand at the gutter.

Why are the cracks occurring? I do not have a definitive answer and offer the above thoughts for your consideration. Based on this issue and others I believe a sand stabilizer or a material that reduces the tendency of the sand granules to not migrate would be worth serious consideration.

A valid point could also be made that the center lanes have the most traffic and failures due to repeat loadings would appear there first.


Leave a Reply