Permeable interlocking concrete pavements (PICP) allow stormwater to infiltrate directly through aggregate-filled joints. Best practices for the winter operation of PICP is poorly understood. Unlike conventional impervious pavements, melted snow and ice infiltrates directly through the PICP joints to underlying aggregate layers, underdrains or native soils.
The University of Toronto conducted this study at a PICP test pad, constructed in 2017, located at the Toronto and Region Conservation Authority’s (TRCA) Kortright Centre for Conservation in Vaughan, Ontario. The test pad included four 2 m by 2 m (6.6 ft by 6.6 ft) PICP cells constructed with a generic grey paver arranged in a herringbone pattern and one 2 m by 2 m (6.6 ft by 6.6 ft) asphalt control cell. A perforated pipe drained the PICP cells. The asphalt cell was drained via a catch basin. Concrete curbs between cells prevent the inter-mixing of flows.
De-icing practices were tested over two winter seasons in 2018 and 2019. Two PICP cells received road salt at medium 0.049 kg/m2 (10 lb/1000 ft2) and low 0.024 kg/m2 (5 lb/1000 ft2) application rates and two cells received road salt pre-wetted with beet juice also at medium and low application rates. The asphalt control cell received road salt at a medium application rate. Surface friction, surface temperature and water quality were measured.
The results of this study indicate that the PICP provides equivalent or higher levels of safety compared with asphalt when treated with de-icing products at medium or low application rates. Re-freezing of melted snow and ice after sunset was observed on the asphalt surface creating black ice but not on the PICP cells. Consequently, compared to asphalt pavements, PICP surfaces will require use of less deicers and will have lower risk of slips and falls for pedestrians and lower risk of skidding for vehicles throughout the winter. Key findings of this research to be detailed in the presentation include the following: