Freeze-Thaw Model

Overview

Freeze-thaw occurs when air temperature drops low enough to freeze water (32°F/0°C), then increases enough for it to thaw again. Freeze-thaw usually occur most frequently in the wintertime, although it has the potential to occurs at any time of year. Freeze-thaw is the process by which porous materials such as concrete, brick and stone are damaged when liquid water freezes and the ice expands inside them the inside them, causing microscopic damage. With repeated events the damage accumulates. Non-porous materials such as steel are not affected. An environment that is very cold, may not have suffered from freeze-thaw very much if buildings and their materials stay below freezing for most of the winter. But with global warming, some areas may spend more time cycling above zero during the day, and below zero at night. Typical studies on material failure due to freeze-thaw look at the number of freeze-thaw cycles until the material fails. Figure 8: Average number of freeze-thaw days across North America.

Baseline Hazard Data

A freeze-thaw cycle is any day where there is an occurrence of daily Minimum Temperature (Tmin) less than 0 °C and a daily Maximum Temperature (Tmax) greater than or equal to 0°C. This data can be extracted from any local weather station that meets the duration and quality requirements for the freeze-thaw to occur, in countries that have seasonal temperatures that drop below freezing.

Climate Change Projections

Climate projections are used to establish a baseline number of freeze-thaw days and then used to project how these days will change over time. A range of CMIP5 and CMIP6 datasets with and without downscaling are available which are used to project the change in the annual number of eligible freeze-thaw days using Tmin and Tmax variables.