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In December 1995, New York put recycled plastic lumber made from discarded milk jugs, water bottles and detergent containers to use in a pier at West Meadow Creek, Old Field. However, the modulus of elasticity fell after 12 months before recovering towards its initial level during the second year. The reported in-plane compression modulus was 260 ± 30 MPa, while the Shore D surface hardness was 60 ± 2. Its reported value decreased from 1,370 Pa to 750 Pa after 12 months of weathering, according to the researchers’ abstract. The authors described this as a decrease equal to 45% of its pre-installation value.
In their abstract, Breslin and his co-authors reported that the in-plane compression modulus, dimensional stability and Shore D surface hardness of the plastic lumber removed from the pier remained similar to or greater than their values before installation.
Titled ‘ Long-term engineering properties of recycled plastic lumber used in pier construction ’, its dimensional stability, compression modulus and Shore D surface hardness remained similar to or greater than their original values, according to the study published in ResearchGate. The researchers said this variability limited the material’s suitability to non-load-bearing structural applications. Two years of monitoring examined how the material’s engineering properties held up in the marine environment. The results showed that not every measured property deteriorated during the monitoring period. These findings provided evidence that several important characteristics of the recycled material were retained during its use on the pier. However, the results need to be distinguished from the material’s performance in bending, which was assessed through its modulus of elasticity. The researchers found significant changes in that property during prolonged weathering. Consequently, the study did not establish that every engineering property remained unchanged, but it documented stability in three of the measured characteristics. The modulus of elasticity showed a different pattern from the other measured properties. During the second year, the modulus of elasticity increased again to a value close to its initial level.
The structure measured 1.2 metres by 9.1 metres and was partially constructed using the recycled material. The research examined plastic lumber profiles incorporated into the decking of a fixed pier at the West Meadow Conservation Centre in Old Field. The researchers tested samples before installation and collected further samples from the completed pier for laboratory examination during the monitoring period. The study investigated dimensional stability, Shore D surface hardness, in-plane compression modulus and modulus of elasticity. These measurements allowed the researchers to compare the material’s engineering properties before and after exposure to outdoor marine conditions. The pier was not heavily trafficked during the monitoring period. Passenger boat trips were most frequent between May and October, at four to six trips per week, while their frequency fell to fewer than one trip per week during autumn and winter.