About this Study

Background

In our previous work (Phase I Final Report: Interagency Agreement 00-CO-11111124-154, 2002 by Laufenberg et al 2001), basic processing techniques to produce wood-resin composite playground surfaces with improved accessibility for users of wheelchairs and walkers were developed. There was also a need to retain adequate impact-energy absorption performance attributes to preclude some head and limb injuries to playground users. The composite systems developed consisted of a combination of a resin and engineered wood fiber (EWF) in the top surface layer with just EWF below. That work identified designs using compatible resin (e.g. latex, silicone and polyurethane) binders and various species and textures of engineered wood fiber (EWF). It included laboratory testing of energy absorption and surface firmness on trial surfaces in plywood boxes 0.5 m x 0.5 m (18” x 18”) at a uniform depth of 0.3 m (12”). Seven systems were identified as having reasonable performance and thence recommended for Phase II outdoor field evaluations.

Present Study

Phase II research focused on outdoor evaluation of the binder/fiber options identified as minimally acceptable and promising in our Phase I evaluations. The Phase II work studied field durability and looked at changes in performance by quantifying the impact and accessibility of these novel surfaces after field exposure. This series included seven surface treatments, and a control surface, installed in a series of outdoor test beds in Madison WI to gather field experience on long-term performance and durability. The binders evaluated were a) synthetic latex emulsion, b) a low molecular weight silicone and c) foaming and non-foaming resilient polyurethanes. Systems were evaluated over a 6-month period.

Acceptable Surfacing System Requirements

Stabilizing binders needed to be applied on-site or mixed with the EWF no longer than an hour prior to placement on the ground surface. Practical considerations evaluated were a) cure/set time prior to surface use, b)range of EWF moisture and temperature conditions acceptable for use, and c) emissions of fumes or odors, workable exotherms, and toxic or other chemical release/concerns from the binder/EWF mixture needed to be minimal.

The development guidelines require that the system provide impact safety and good accessibility. The Americans with Disabilities Act (ADA, 1990) states that accessible surfaces shall be stable, firm, and slip-resistant. These three criteria have not been defined adequately for measurement on any specific surface. Therefore, we’re required to make this evaluation subjectively. In addition, each Resin-EWF system should allow water to drain from both the bonded surface and unbonded interior of the mat system. This is critical in reducing the biodeterioration potential of the wood fiber and in maintaining cushioning behavior of EWF during sub-freezing temperatures.

Impact safety is quantifiable via the ASTM F1292 and F355. Preliminary tests using a portable impact test provided an indication of stabilizing binder cushioning performance and a small-scale test meant to simulate a wheelchair (ASTM F1951 rotational penetrometer test) was used to assess accessibility potential. Two cooperators (Zeager Bros. Inc. and Beneficial Designs Inc.) provided these portable test apparatuses and training in their use.

The desired resin/EWF system needs to provide impact safety and appropriate accessibility over a number of seasons. It must retain the performance characteristics of impact-energy absorption and surface resiliency. We need to evaluate the ability of the mat to drain water from its bonded surface and unbonded interior to reduce biodeterioration and maintain cushioning behavior during freezing temperatures. Impact and accessibility of these novel surfaces were measured after a six (6) month field exposure from April-October 2002 in Madison WI. Subsequent 12-month exposure performance testing of each Phase II EWF surface will be evaluated in the Spring of 2003 and reported in a later report.