Sharring experiences in urban infrastructure delivery.

Pavers and the Importance of Sand

By: Tom Davis Category: Amenities, Recent Posts, Sidewalk Features

Note sand washing to surface and spalding of corners.Concrete unit pavers are getting a bad reputation in some circles as they have not provided a care-free pavement. But, there is no such thing as care-free pavement. Some just need more care than others and that is the case with concrete unit pavers–particularly in high traffic situations in a wet environment. Ironically loose sand is what holds them together.

The paver itself is a high strength, dense block of solid concrete that can take a lot of abuse provided it is securely in place. By securely in place they mean supported evenly on the bottom and locked in place on the sides. For the pavers to be “locked-in-place” the very small gapNote sand on surface and empty gaps. Spalding of pavers is clearly evident. between the pavers must be filled tightly with sand. At the initial placement, and later during major repairs, the sand must be vibrated into place with a light-weight vibrating plate compactor. The sand granules wedge into the rough surface of the paver and with their sharp edges jammed together they create a structure that is hard to take apart–or work apart.  Ask anyone who has tried to get one of the pavers out of a correctly made surface. Usually you chip a corner or edge and give up, break it and find a replacement.  [Know this will happen to you so keep “attic stock” i.e. an extra pallet or two left over from your installation.]

CIMG3888.JPGThe key to a long-life pavement is first the support from the sand bed below and the sand in the gap between the pavers. [This article assumes you have a concrete slab below the sand bed designed to support the loads transferred to it by the pavers.] If either support is reduced then the sand migrates out of the small space between pavers and then from underneath. Any concrete will crack when unevenly supported or loads applied putting part of it into tension rather than compression. One end of the paver usually settles pressing the top edge against its neighbor,  loads are applied unevenly and the edge spalls or the paver cracks in to two pieces. The spalled wedge-shape piece works its way out and more sand moves into the space accelerating the unraveling of the paver structure. Standing water over uneven, broken pavers.

There is a new polymer additive being used to help the sand granules “stick” together better. Such products appear to allow for less frequent re-sanding and repairs but they do not allow you to avoid the inevitable maintenance.

The second key to a long-life paver surface is no standing water. Other articles at this blog address that issue.

For want of a little clean sharp sand the great looking paver surfacing will be lost. The analogy is that if you do not check the oil in your high priced luxury car and the car fails was it due to bad design or bad construction?


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