LONG-TERM ENGINEERING PROPERTIES OF RECYCLED PLASTIC LUMBER USED IN PIER CONSTRUCTION

Plastic lumber manufactured using post consumer waste plastic has been proposed as an acceptable material for use in the construction of doc ks, piers and bulkheads and is touted to outlast conventional wood pro ducts due to its strength, durability and resistance to rot. This stud y examines the long-term engineering properties of plastic lumber manu factured using post consumer waste plastic (TRIMAX, Ronkonkoma, NY). P lastic lumber profiles were used in the decking of a pier built in Wes t Meadow Creek, Old Field, NY during December 1995. Samples of plastic lumber were removed from the deck of the pier periodically over a two -year period and returned to the laboratory for testing. Results of en gineering tests showed the in-plane compression modulus (260 +/- 30 MP a), dimensional stability and the Shore D surface hardness (60 +/- 2) of plastic lumber removed from the pier remained similar to or greater than their pre-placement values. In contrast, significant changes in the modulus of elasticity of plastic lumber were measured with prolong ed weathering. The modulus of elasticity of plastic lumber initially d ecreased from 1370 Pa to 750 Pa following 12 months weathering, a decr ease equal to 45% of its pre-placement value and then increased during the second year to close to its initial value. The high variability i n the modulus of elasticity should restrict the use of plastic lumber profiles to non-load bearing structural applications. (C) 1998 Elsevie r Science B.V. All rights reserved.