Laboratory assessment of flexible thin-film membranes as a passive barrier to radon gas diffusion

This paper presents the experimental results of utilizing a flexible thin-film membrane as a passivebarrier to radon gas diffusion. Nine commercially available membranes of various compositions andthicknesses were evaluated as retardant to radon gas diffusion. The radon gas concentration ratiosacross the thin-film membranes alone and in combination with an adjacent concrete sample (effectivediffusion coefficient) were measured in a laboratory system with state-of-the-art instrumentation. An8.89 cm diameter, 10.2 cm thick concrete sample of standard composition (w/c = 0.5 and cement:sand: gravel = 1:2:4) was used to simulate a basement and slab-on-grade foundation typical ofWisconsin. The radon gas transport characteristics of this concrete sample (porosity, permeability anddiffusion) are documented.The experimentation has identified two superior flexible thin-film membranes that may be employedas effective barriers to radon gas diffusion. These include: Polyethylene Naphthalate (7.62x10-5 m)and Polyethylene Terephthalate Glycol, PETG (7.62x10-5 and 1.27x10-4 m) which had averagediffusion coefficients, D of 4.10 x 10-14 m2 s-1 and 1.66 x 10-14 m2 s-1, respectively. Measurements ofthe effective membrane/concrete diffusion coefficient yielded a further average reduction in D of 98%for the Polyethylene Naphthalate and 96% for the PETG. Details of the experimental set-ups andprocedures are described. The results of this investigation have shown that the application of aneffective thin-film membrane adjacent to an intact concrete slab can significantly reduce the diffusionof radon gas entry. Therefore, the employment of a flexible thin-film membrane should be consideredas a viable radon reduction technology method for residential new construction