Radon Penetration of Concrete Slab Cracks, Joints, Pipe Penetrations, and Sealants

Abstract

Radon movement through 12 test slabs with different cracks, pipe penetrations, cold joints, masonry blocks, sealants, and tensile stresses characterized the importance of these anomalous structural domains. Diffusive and advective radon transport were measured with steady-state air pressure differences controlled throughout the deltaP = 0 to 60 Pa range. Diffusion coefficients (deltaP = 0) initially averaged 6.5 x 10(-8) m2 s(-1) among nine slabs with only 8% standard deviation, but increased due to drying by 0.16% per day over a 2-y period to an average of 2.0 x 10(-7) m2 s(-1). An asphalt coating reduced diffusion sixfold but an acrylic surface sealant had no effect. Diffusion was 42 times higher in solid masonry blocks than in concrete and was not affected by small cracks. Advective transport (deltaP < or = 60 Pa) was negligible for the slabs (10(-16) m2 permeability), pipe penetrations, and caulked gaps, but was significant for cracks, disturbed pipe penetrations, cold joints, masonry blocks, and concrete under tensile stress. Crack areas calculated to be as small as 10(-7) m2 significantly increased radon advection. Algebraic expressions predict air velocity and effective crack width from enhanced radon transport and air pressures. Masonry blocks, open cracks, and slab cold joints enhance radon penetration but stressed slabs, undisturbed pipe penetrations, and sealed cracks may not.

Estimating the oxygenated zone beneath building foundations for petroleum vapor intrusion assessment

“…However, U.S. EPA [6] suggests that diffusive transport through permeable concrete slabs can also enhance the oxygen availability in the subsurface and reports values for the effective diffusion coefficient for oxygen through permeable concrete slabs in the range of 1.08 to 15.6 cm 2 /h. Although these effective diffusion coefficients of concrete are significantly lower than the ones typical of soils [32–34], the net flux of oxygen through the slab might be significant if the building size is large enough to make the diffusive oxygen flux from open ground surface beyond foundation edge, negligible towards the middle of the subslab zone. Furthermore, wind or changes in barometric pressure may also periodically facilitate oxygen transport into the subsurface beneath the building foundation [35–37].…”

Indoor air pollution and the contribution of biosensors

“…This inert radioactive gas arises directly from the decay of radium-226 contained in various minerals (36). Thus, the structural defects in floors and walls, drains and piping, electrical connections and cellars with earth floors may be the main sources of radon within a building (37). The half-life of radon decay is 3.82 days, which creates a series of short-lived radioisotopes known as progeny or radon daughters(e.g., electrically charged Po-218 and Po-214) (38).…”

Analysis of Indoor Radon Concentration Levels and Influencing Factors in Kunshan

“…Although there are several factors that influence the release of radon from rocks and soils into the air, such as radium content, porosity, humidity, air pressure and temperature, radon in ambient air comes mainly from the ground (7.6 x 1019 Bq/a, 77.7% of all radon sources in ambient air), plants and groundwater (1 x 1019 Bq/a, 10.2%), and the rest from the nuclear industry, the phosphorus industry, construction, and the combustion of coal and natural gas. There are two main sources of indoor radon, one is when radon penetrates from the soil into the building directly, and the other is emitted from the building materials, both of which will pollute the indoor air [2]. Radon has been identified as one of the leading causes of adverse health problems in occupants due to its accumulation in indoor environments.…”