By Laura Fay, Marc Valenti and Bret Hodne, Contributing Authors
When working with deicers, whether liquid or solid, agencies commonly use chlorides as the base material. Sodium chloride (rock salt) or salt brine (rock salt suspended in water), magnesium chloride and calcium chloride each work well when used in the right conditions.
For example, straight salt brine or rock salt work best on roads down to about 20 F (pavement temperature), while calcium and magnesium chloride will work effectively at pavement temperatures down to approximately 10 F.
But what if you want to add some calcium chloride to your salt brine to make it more effective at colder temperatures? Or you want to add calcium chloride and an organic (also known as a carbohydrate) to improve performance? Or, if you are prewetting your rock salt with magnesium chloride and want to know if this will help it work at colder temperatures?
It is important to know how to test for this and what tests should be considered.
Why You Should Test Deicers
There are many reasons to test deicers, and these typically fall into two categories – performance and impacts.
Evaluating the performance of deicing products can include determining the coldest effective working temperature, measuring how much snow and ice can be melted and determining if there are other performance benefits. For example, if it stays on the road longer or allows for easier post-storm clean up.
It is important to note that all deicing products will have some type of impact, whether to vehicles and infrastructure in the form of corrosion or to the environment. Impacts to consider include corrosion, toxicity and various elemental concentrations.
Every agency weighs performance and impact differently; it’s typically based on level of service expectations, environmental considerations and or budgetary constraints.
Testing Deicers
Testing deicers is something you can do at your shop (or shed/garage). Samples also can be sent to a lab; it really depends on what kind of results you want.
For example, you can fill a jar with your own blended liquid deicer and set it outside and see if it freezes, or you can apply the blended product down on the pavement in your maintenance yard to see how well it works. These tests will give you some idea of how the product will perform.
However, if you want hard numbers, you can send the products off to a lab for testing. In some instances, this may be required to ensure the product meets specification or is non-toxic, and in other instances, it may be to help you maximize performance.
Testing for Temperature Performance
To determine if you will see improved performance or if a deicer can work at colder temperatures, a tried-and-true test is Eutectic temperature.
The eutectic temperature is the coldest temperature when the brine remains a liquid, essentially the freezing point of the product. For salt brine this is minus 6 F, for magnesium chloride this is minus 29 F and for calcium chloride this is minus 60 F.
Therefore, it stands to reason that if you blend 90% salt brine with 10% calcium chloride you will likely measure a colder eutectic temperature for the blend.
Remember that you will only use straight salt brine down to 20 F, but with the new eutectic temperature data for your 90:10 (Salt Brine: Organic) blend, you may feel more confident applying the blend down in the 10 F range.
Ice melting capacity, ice penetration and ice undercutting are laboratory tests that have been used to assess deicer performance.
These test methods can produce highly variable results that are difficult to repeat. The results from these tests can give you an idea of relative product performance, such as how much ice salt brine melts versus a 90:10 blend of salt brine with calcium chloride at 15 F.
The Rocker Test, a newer ice melting capacity test method, offers more repeatable results for liquid deicers, but not yet for solid deicers.
Testing for Residual Performance
A great way to test longevity of a deicer on the roadway or residual is to go out each day after application and take pictures. If you see the lines from application, it is apparent that some of the product is still on the road surface.
Another example of this is side-by-side testing of products on roads. You can see when more snow and ice was removed from the lane treated with one product than the other.
Testing for Impacts
When considering testing deicers for impacts there are three main focus areas: corrosion, toxicity and elemental analysis. Again, if you are working with a vendor, you can request these results. If they are unable to provide them, the product is not well characterized, or you want to test a blend of your own, then you can send a sample off to a laboratory.
Corrosion testing to characterize deicers typically uses mild steel. It compares the deicers corrosion rate (weight loss over time) to that of pure water and 3% sodium chloride solution.
A good reference here is the Clear Roads Qualified Products List (QPL), which provides corrosion scores for various deicing products. A passing corrosion score on the QPL is 70% less corrosive than the 3% sodium chloride solution.
Look for reduced corrosion rates in products that have corrosion inhibitors or organics.
Toxicity testing of deicers may or may not be required but is recommended to ensure the deicer passes federal, state and or local standards. Note that state and local standards vary across the country and may be more or less stringent than each other and federal standards.
Toxicity testing typically includes testing for aquatic toxicity to various species and testing for biological oxygen demand (BOD) or chemical oxygen demand (COD). Many non-chloride deicers, for example acetates and formates (commonly used at airports), organics, and other deicer additives can have environmental impacts that are not seen in chloride-based deicers.
Elemental analysis also will help ensure that the deicer passes federal, state and local standards. Common things to test for include the phosphorus group, nitrogen group, heavy metals, arsenic and cyanide.
Additional suggested elements to test for can be found in the Clear Roads QPL guidance document.
If you are purchasing a solid or liquid deicer or additive from a vendor, they should be able to provide you with the test results from an independent laboratory to enable you to make an informed decision about use.
However, keep in mind that some deicers or additives used in blends may not be engineered or well characterized. In this instance, additional testing may be needed. If it is a new product to you, take the time and money to independently test it.
So, should you test deicers? That is up to you unless it is required. You can do the testing on your own or you can send it out to a lab. Make the choice that is right for you, your agency and the information that needs to be obtained. RB
Laura Fay is a senior research scientist at Montana State University’s Western Transportation Institute. Marc Valenti is the manager of operations in Lexington, Mass., and Bret Hodne is the public works director in Buckeye, Ariz.
