AI-generated representative image showing interlocking concrete pavers with melting snow and water around the joints, illustrating winter performance research on permeable pavements. Credits – Gemini
The findings were published in the journal Water in 2021. Seven winters of temperature data from Madison, Wisconsin, helped researchers examine how permeable pavements respond to cold weather. The US Geological Survey studied three types of permeable pavement: interlocking concrete pavers, pervious concrete and porous asphalt. The pavers had fewer days below freezing, higher temperatures during snowmelt, slower freezing and faster thawing than the other two surfaces.
In summer 2014, researchers established three test plots at a research site in Madison, Wisconsin, next to an overflow parking area. Each plot covered about 500 square feet, or 46.5 square metres, and had an aggregate base about 21 inches, or 53 centimetres, deep beneath the pavement. What the temperature data showed The main comparison covered 303 winter days with simultaneous readings from all three pavement types. The daily average air temperature was below freezing on 182 of those days. During those days, temperatures in the top, middle and bottom layers beneath the pavers remained above freezing on 42%, 68% and 81% of days, respectively. The corresponding figures were 20%, 38% and 74% for pervious concrete, and 25%, 45% and 74% for porous asphalt. The gaps between the pavers occupy about 10% of the surface, while pores in pervious concrete and porous asphalt extend across their surfaces. Researchers identified 137 melt days from meteorological records. Temperature data were available for 103 of those days for the pavers, 47 for pervious concrete and 89 for porous asphalt. On days with available data, the daily maximum temperature across all measured depths stayed above freezing on 96% of paver observations, 93% of porous asphalt observations and 83% of pervious concrete observations.
The plots represented interlocking concrete pavers, pervious concrete and porous asphalt. An impermeable liner and concrete walls separated the plots from the surrounding ground and from one another. The adjacent conventional parking area was not one of the three pavement types in the temperature comparison. These percentages are rounded summaries of the study data. The researchers suggested that differences in construction may help explain the results. The researchers proposed that the arrangement of the pavers, the movement of air and water through the gaps and aggregate base, and the thermal mass of the concrete blocks may affect heat transfer. These are possible explanations offered by the authors, rather than mechanisms independently established by the experiment. The darker, porous asphalt surface may also absorb more sunlight, helping explain why it stayed warmer near the surface than the previous concrete. These temperature differences matter during snowmelt. When the layers below a pavement remain above freezing, meltwater is more likely to infiltrate instead of pooling on the surface and refreezing. There are some boundaries to remember. The study was at a single site in one city, the plots were small, and nobody drove on them, so the findings reflect temperature behaviour rather than how well each surface handles traffic. The work was funded by various donors, including a foundation for teaching and research on interlocking concrete pavements, as well as Wisconsin agencies, the City of Madison and the USGS. The authors say the funders played no role in the findings. The findings suggest that all three permeable surfaces can retain temperature conditions that allow water to infiltrate during winter melt events, with interlocking pavers performing best in the temperature comparisons.
