As well as the use of re-used composite in the form of strips, the use of shredded material also was investigated. Shredded composites yields flakes that are also oblong in shape (see photo below) and can therefore act as a reinforcement in the same way as strips. The advantage of shredding is that it is a more economical process than sawing the old composite into strips. On the other hand, as can be seen from Figure 2, the strength that can be achieved in a new products is on a lower level than with the use of strips.
Re-use for retaining walls in canals
There are a great number of canals in The Netherlands. The manifold canals originate from the fact that large parts of the land were reclaimed from the sea and canals were needed for transportation but also to remove drainage water. To maintain the integrity of the shore of a canal, generally a camp sheet is installed that acts as a retaining wall. Camp sheeting can be manufactured in different ways and using different materials, depending on the depth of the water at the shore side, the height of the soil-wall to be retained and the type of soil (sand, clay, peat). Camp sheeting is in permanent contact with water, both at the canal side and at the soil side. Therefore the materials must be long term water resistant. Both steel and tropical hard wood camp sheeting are degraded at the water surface within 20 years and have to be replaced. The photo right shows a degraded steel camp sheeting (Photo by/courtesy of BiinC).
Medium size camp sheeting is generally constructed as so-called sheet-piling: interlocking profiles of tropical hard wood which are vertically installed into the soil using a vibrating hammer block. Tropical hard wood profiles used for camp
Photo by/courtesy of BiinC
sheeting have a typical length of 3 to 6 metres of which the retaining height of the soil is typically one third of its length, the other part being forced into the ground. The profiles have a cross-section with a typical thickness of 40 to 60 mm and an effective width of 200 to 400 mm and are fitted with a tongue- and-groove detailing to interlock with the neighbouring profiles. Although tropical hard wood has a relatively high durability in wet conditions the life-time under these conditions is limited to 20 years maximum. Moreover, it is undesirable to use tropical hard wood because of the strain it puts on the rain forests. Therefore it was investigated whether these tropical hard wood profiles can be replaced by composite profiles made from re- used EoL thermoset composites.
It is the expectation that the new composite camp sheeting made with EoL thermoset composite will be extremely durable since the service life of composite products in wet conditions is reported to be 60 to 100 years [5]. Moreover, the new composite profiles can be engineered for a high mechanical strength, using the reinforcing elements of the EoL composite in combination with virgin material. Paradoxically, two drawbacks of the re-use of EoL composite principle work to the advantage in the design of these new camp sheeting. The first drawback is the relatively heavy weight of the new composite, the second is the limitation to flat designs like profiles and panels because of the relatively large and oblong elements.
The Report • September 2017 • Issue 81 | 55
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