, Professor Emeritus, Civil, Environmental and Geo-Engineering
Road salt--and particularly sodium chloride--is used for de-icing roadways during winter months in cold climates but can have a negative impact on the environment. This report describes research that investigated the use of permeable pavements that are not treated with road salt as an alternative to impermeable pavement surfaces that are treated with road salt. Various methods were used to quantify the snow and ice cover on impermeable and permeable pavements under near-identical but various environmental conditions. It must be noted, however, that impermeable pavements (including the ones in this study) are typically managed with road salt while permeable pavements are not. However, the following conclusions can be drawn from previous research and data collected during this project: 1) permeable pavements and the porous subbase beneath them function as thermal insulators, preventing heat transfer from the surface to below and vice versa; 2) permeable pavements that are clogged due to sediment accumulation or collapsed pores provide no benefit compared to impermeable pavement; 3) more sites with impermeable pavement had more friction than sites with permeable pavement; 4) more sites with impermeable pavement had less snow and/or ice cover than sites with permeable pavements; and 5) more sites with impermeable pavement had pooled water than sites with permeable pavements. This demonstrates the primary winter benefit of permeable pavements: meltwater can infiltrate through permeable pavements and prevent refreezing. Refreezing of meltwater on impermeable pavements creates dangerously slippery conditions which can be avoided with functional permeable pavements.