|ASTM Specifies Plastic Lumber for Exterior Decking
Due to the hardy recycled-plastic content of plastic lumber which
repels water and insects, its use in traditional wood applications
is growing. In July, ASTM released D 6662, Standard Specification for Polyolefin-Based Plastic Lumber Decking
Boards. The brainchild of engineers, manufacturers, and recyclers
in Committee D20 on Plastics, the specification was developed to bring uniform
quality requirements to polyolefin-based plastic lumber products
used as exterior residential decking.
The specification details a procedure to calculate recommended
span lengths for spacing of support joists. This procedure was
developed using experimental data from a typical unreinforced
plastic lumber made predominantly from recycled high-density polyethylene.
The methodology to develop span lengths for other types and compositions
of plastic lumber is detailed in an appendix of D 6662.
D 6662 defines plastic lumber as a manufactured product of more
than 50 weight percent resin generally rectangular in cross-section
and typically supplied in sizes corresponding to traditional lumber
board and dimensional lumber sizes. It may be filled or unfilled
and composed of single or commingled resins.
Plastic lumber materials are inherently rot- and insect-resistant
and dont require chemical treatments or coatings to have or maintain
this resistance, said Richard G. Lampo, a materials scientist
in the Materials and Structures Branch at the U.S. Army Corps
of Engineers Laboratory, Champaign, Ill. This translates into
very low maintenance needs for the life of the material which
can be especially beneficial to the user as the overall life-expectancy
of plastic lumber can be several times that of traditional wood
materials in outdoor applications. These plastic lumber products,
made predominantly from recycled plastics, also help divert significant
amounts of waste plastics otherwise destined to landfilland that
amount will increase as the market continues to grow.
The development of the latest standard for plastic lumber decking
boards is noteworthy since it will not only make it easier for
users to specify plastic lumber decking, he concluded, but it
also further paves the way for the development of standard designs
and material specifications to construct all-plastic lumber structuresfor
example, the plastic lumber boardwalk and observation deck constructed
at Fort Belvoir, Va., where structural-grade plastic lumber was
used for the underlying support structure and railing system.
Lampo chaired a group of approximately 50 members of Section D20.
20.01, Manufactured Recycled Plastic Lumber and Shapes, who have
developed a total of eight standards for plastic lumber since
1997 (including D 6662):
D 6108, Standard Test Method for Compressive Properties of Plastic Lumber
D 6109, Standard Test Method for Flexural Properties of Unreinforced
and Reinforced Plastic Lumber;
D 6111, Standard Test Method for Bulk Density and Specific Gravity of
Plastic Lumber and Shapes by Displacement;
D 6112, Standard Test Method for Compressive and Flexural Creep and
Creep Rupture of Plastic Lumber and Shapes;
D 6117, Standard Test Method for Mechanical Fasteners in Plastic Lumber
D 6341, Standard Test Method for Determination of the Linear Coefficient
of Thermal Expansion of Plastic Lumber and Plastic Lumber Shapes
Between -30&Mac251;F and 140&Mac251;F (-34°C and 60&Mac251;C); and
D 6435, Standard Test Method for Shear of Plastic Lumber and Shapes.
Additional standards under development by Section D20.20.01 include
a new specification for plastic lumber materials for bending member
applications, such as joists and beams, and a standard practice
for plastic lumber deck design and construction.
For further technical information, contact Richard G. Lampo, Materials and Structures Branch, Facilities Division, U.S. Army
Engineer Research and Development CenterConstruction Engineering
Research Laboratory, Champaign, Ill. (phone: 217/373-6765). Committee
D20 meets Nov. 4-7 in Dallas, Texas. For meeting or membership
details, contact Kathie Morgan, director, ASTM Technical Committee Operations (phone: 610/832-9721).
To learn more about plastic lumber, consult the Web site of the Plastic Lumber Trade Association. //
Copyright 2001, ASTM