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Thursday, 20 September 2007 |
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Page 20 of 21
Concrete
Pitting And Spalling
Small chips in the surface of the concrete can occur at the end of obstacles that attract small aerial maneuvers such as rails, manual pads, and ramps. The skater is exiting the obstacle and the board doesn’t move as expected, sometimes landing directly on its side. The axles of the skateboard deliver a sharp impact to the concrete surface and can produce miniscule pits. Over time the pits accumulate and are felt as a slight roughness under the board. Pitting does not present significant safety or maintenance concerns in a concrete context, but small divots in composite or wood surfaces can allow moisture to permeate the layers of the surface material and create problems.
Rust can bleed through small cracks. While not a problem for skaters, it can be unattractive.
During concrete finishing, trowels and floats are used to draw moisture to the surface of the wet concrete and push the pebbly aggregate downward. When this process is overdone it can weaken the surface strength of the concrete so that the cement becomes brittle and flaky. This will usually present itself shortly after construction is complete and appear as patches of roughness where the concrete seems to have been chipped away. Called spalling, these patches can present safety concerns in high-traffic areas, but only in the most severe cases. However, spalling is the result of poor craftsmanship and is not appropriate for cosmetic and safety reasons. Spalling should be repaired at the contractor’s expense by chipping out the section and patching with fresh concrete.
Cracks And Chipping
It is inevitable that cracks will occur in concrete skateparks. The slabs and structures settle over time, cracks appear, moisture penetrates the cracks and widens them. Most cracks present no safety concerns unless they present a variation of height over 1/8th of an inch. Cracks with no height variance should be carefully monitored if they are more than 1/16th of an inch wide.
Cracks on vertical or steep surfaces will sometimes “bleed” rust from the rebar inside. Though this can be a disaster in the cosmetic sense, rust stains do not present diminished riding qualities.
Dents between coping blocks is called "knuckling" and should be repaired.
The leading edge of structures that have no protection, like formed concrete, may become chipped over time as the impact from skateboard axles can weaken it. With repeated use and over many months, the edge will reveal exposed aggregate within the cement and slowly become less appealing to the skaters. Patching the edge may provide a very short-term fix to a problem that took months to occur. It is much better to cut away the whole worn area and replace it with a new patch of concrete.
Granite provides much more resistance to this kind of use. Cutting out the worn section and replacing it with granite may provide many more years of use while introducing a new, premium surface to the venerable skatepark.
Precast Concrete
A trend in modular or prefabricated skateparks is emerging. Some companies are opting for concrete surfaces rather than the wood substrate and wood or composite surfaces. These pre-cast structures are new to the world of skateparks and not much is currently known about their durability or longterm issues. However, when built-in-place concrete is simply not an option, pre-cast is appearing to be an adequate solution for communities looking to build a low-maintenance prefabricated facility.
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Last Updated ( Sunday, 10 February 2008 )
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