How Weather Conditions Affect Salt Performance?
Canadian winters bring their own set of challenges. Property managers, snow removal contractors and municipalities work very hard to maintain the roads ice- and snow-free. For many decades, rock salt has been a common choice for deicing due to its affordability and availability. You have to know that rock salt doesn’t work the same in every condition. Its effectiveness depends on factors like temperature, wind, sunlight, humidity or rain. In this article, we will explore how weather conditions affect salt performance in detail. Let’s get started!
The Science of Deicing: How Salt Works
It’s important to know how salt melts ice to understand how weather impacts salt. Salt does not melt ice directly; it is activated with the help of moisture. When salt gets into contact with moisture, it forms brine that has the ability to reduce the freezing point of water. This process is called freezing point depression. As brine formation is a physical and chemical process, its formation and effectiveness highly depend on the weather conditions.
Factors that Affect Salt Performance
Air Temperature vs Pavement Temperature
Temperature plays a major role in how the salt works. In terms of snow removal, temperature will be of two types. Air temperature and pavement temperature. The heat-holding capacity of the air will be different from that of asphalt and concrete. This means the pavement’s temperature will be different from what the weather forecast shows.
- Warmer Pavement: After a sunny day, the pavement can still hold the heat even after the temperature drops after sunset.
- Colder Pavement: After several days of cold weather, the pavement temperature can remain frozen even when the surrounding temperature rises.
Salt working depends on the surface it touches. So, pavement temperature is considered more important than the air temperature.
The Impact of Temperature on Salt Melting Capacity
Rock salt works well at higher winter temperatures. As the temperature increases, the salt melting capacity slows down and takes a longer time to create brine. This shows that rock salt becomes less effective in extreme cold temperatures.
The Critical Threshold: -9°C to -12°C (15°F to 10°F)
Rock salt reduces the freezing point of water to as low as -21°C (-6°F) in ideal conditions. It works best in temperatures between -9°C to -12°C (15°F to 10°F). Below this point, salt loses its effectiveness. So, most contractors use additives in standard rock salt to improve its effectiveness.
Solution for Extreme Colder Temperatures
When temperatures drop, it’s better to use additives to improve the effectiveness of the standard rock salt:
- Pre-wetted / Treated Salt: Mixing regular rock salt with calcium chloride or magnesium chloride speeds up the brine formation process.
- Calcium Chloride: It releases heat when it’s dissolved and helps the ice to quickly melt and remain effective even in extreme cold temperatures to -32°C (-25°F).
- Magnesium Chloride: Works well in temperatures as low as -20°C (-5°F), making it a great choice for extreme weather. It is an eco-friendly option compared to most deicers.
Humidity and Moisture Content
As we already discussed, salt needs water to form brine. So, humidity in the air and moisture on the surface are important for the salt to start melting snow and ice.
High Humidity and Deliquescence
Some deicers can absorb water from the environment and create brine on their own. Calcium chloride and magnesium chloride are main examples, as they draw moisture from the air and immediately start their melting process. Whereas standard rock salt is less hygroscopic. In cold and dry weather, the salt can remain the same and doesn’t form brine. It takes longer to work until the moisture from the atmosphere activates it.
Low Humidity and Dry Snow
If the conditions are extremely dry or during snowstorms, rock salt cannot start brine formation. During such conditions, applying prewetted salt or brine is important so that it reduces the bounce of the salt and speeds up the activation of the salt.
Wind and Drift Factors
Most of us forget wind as one of the factors in winter weather management. The salt application will be affected by wind in two major ways. They are scatter/bounce and drift accumulation.
Salt Scatter and Bounce
When salt is spread on the dry pavement, the wind and vehicles passing by can sweep up to 30 to 50% of the salt. So, most of the salt will end up in gutters, plants or nearby water resources. This can cause material wastage and result in uneven coverage. So, when salting on a dry pavement, it’s better to use prewetted salt to improve adhesion and reduce bounce and scattering of the salt.
Blowing Snow and Ground Blizzards
At times of severe temperatures, the rise of high winds can carry powdery snow across the roads and become dangerous. During these conditions, using wet salt can make it stick to the ground and build up more. During these events, it’s better to use snow plows or materials like sand to improve traction until the wind dies down.
Precipitation Types and Rate of Accumulation
The precipitation type will let us know when and how to apply salt.
- Light to Moderate Snow: When it is light or moderate snowfall, pre-wetted salt application can prevent the snow from sticking to the surface of the road. Due to this, the snow will form as a loose slush, making it easier to plow.
- Heavy, Wet Snow: There will be high water content in heavy and wet snow. If salt is applied on the deep, wet snow without plowing it, the water can immediately turn salt into brine that makes it less effective at melting ice. This melted snow will refreeze into an even harder layer. For best results, it’s better to plow the snow and apply salt on the surface.
- Freezing Rain and Sleet: Freezing rain can cause various challenges. It can cause a dangerous layer of ice on roads and sidewalks. Due to rain, the existing salt can be washed away and also weaken the new salt applications. During such conditions, it’s better to opt for a coarse-grade rock salt. Due to the large granule size, the traction will be improved and creates a protective layer of brine.
Solar Radiation
Solar radiation is considered a natural booster for deicing materials.
Radiant Heating
Dark asphalt absorbs heat from the sunlight even when the air temperature is below freezing. As we discussed above, sunlight warms the pavement, and its temperature will be different from the air temperature. This extra temperature greatly helps with brine formation, making it melt ice and snow faster and clear the surfaces more than on cloudy or overcast days.
Nighttime and Cloud Cover
Cloud cover will block the solar radiation, and nighttime operations do not have thermal input. So, the salt performance directly depends on the chemical reaction and the traffic movement. So, when you are working during the night or on cloudy days, it’s important to adjust the application rates accordingly or make use of the treated salts to improve the results.
Traffic Density and Mechanical Action
Traffic directly doesn’t indicate the weather condition. Still, it plays a major role in how well the salt works in different weather.
Traffic can affect deicing in two ways. Namely:
- Mechanical Friction: Tires move on the spread salt, which makes it smaller and increases the surface area. Due to this, the amount of salt exposed to moisture will be increased, which thereby increases the brine creation.
- Thermal Transfer: The tire friction and heat of the engine can transfer slight thermal energy to the surface of the road, which thereby increases the pavement temperature.
Partner with Canada Salt Group Ltd for Reliable Winter Solutions
The weather during Canadian winters can be unpredictable, changing rapidly. So, having the right deicing products ready is important for maintaining safety and accessibility regardless of the severity of the weather. At Canada Salt Group Ltd, we deal with high-quality bulk road salt and salt solutions tailored according to your requirements that perform well in any winter extremes. Contact us today for a free quote!
