Acceptable SEWF Systems
Because of their reactivity, the stabilizing binders needed to be applied on site or mixed with EWF no longer than 1 h prior to placement on the ground surface. Accordingly, the technical issues considered were (a) cure/set time prior to surface use, (b) range of EWF moisture and temperature conditions acceptable for use, (c) emission of fumes or odors, workable exotherms, and toxic or other chemical release concerns related to the binder/EWF mixture, and (d) any post-installation deleterious effects of SEWF on users.
Any viable field system must meet two primary user needs: impact safety and accessibility. The Americans With Disabilities Act (ADA 1990) states that accessible surfaces shall be stable, firm, and slip-resistant. Each viable SEWF system must also be non-toxic to users. In addition, the SEWF system should be porous, to allow water to drain from both the upper bonded surface and the lower unbonded interior of the mats. This is critical in reducing the biodeterioration potential of the wood fiber and in maintaining the cushioning behavior of EWF during subfreezing temperatures.
Impact safety is quantifiable through the use of the consensus standard ASTM F1292 (ASTM 1999a). Preliminary portable impact tests provided an indication of the cushioning performance of the stabilizing binder. The ADA criteria for accessible surfaces have not been defined adequately within the ADA accessibility guidelines for quantitative measurement on any specific surface. Currently, the only objective method suitable for assessing the firmness and stability of a playground surfacing system is the rotational penetrometer, a portable measurement device that simulates a wheelchair caster negotiating the test surface. For our study, two cooperators (Zeager Bros. Inc., Middletown, Pennsylvania; Beneficial Designs, Inc., Minden, Nevada) provided the apparatus for the portable impact test and the rotational penetrometer, as well as training in their use.
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