CMA – Calcium Magnesium Acetate
CMA is granulated calcium magnesium acetate, a patented chemical formulation from dolomitic lime and acetic acid. It was first identified as a low corrosion, environmental alternative to road salt by the U.S. Federal Highway Administration in the late 1970′s. It was then tested and commercially developed. Today, CMA is used worldwide to answer environmental concerns and solve problems associated with corrosion and concrete spalling.
CMA is generally used in a solid form and spread on the surface like other deicers. Although CMA is effective to the same temperatures as salt, CMA has many unique performance characteristics. Therefore, first-time users should review product application guidelines closely. For answers to frequently asked questions regarding CMA, please see the information sheet.
CMA is also used in liquid form, generally for anti-icing roads and bridges. Here, the fluid is applied prior to a storm event to prevent snow and ice from bonding to the surface. Liquid CMA is typically formulated in the field from dry CMA.
Please see for a brief summary of CMA’s benefits, application information, and product specifications.
CMA offers these advantages:
- Low Corrosion – About as corrosive as tap water
- Safe for Concrete – No more damage than from water
- Excellent Inhibitor – Reduces chloride corrosion
- Safe for the Environment – Low toxicity and biodegradable
- Residual Effect – Requires fewer applications
- Multi-Purpose – Use straight, with salt, with sand, or as a liquid
|Typical CMA customers are concerned with concrete spalling, corrosion or environmental issues. They include transportation agencies, military installations, universities, property management firms, and commercial facilities. They require the performance of a solid deicer without the risk of negative environmental impact or infrastructure damage generally associated with chlorides and urea. For these reasons, CMA is often specified by design engineers for use on bridge decks, parking garages and sidewalks, and by operation managers to solve environmental problems such as ground water contamination, soil compaction and vegetation burn.|
CMA Material Specifications
Calcium Magnesium Acetate (CMA) (3:7 Ca to Mg molar ratio)
Hydrated CMA 96% minimum
Inert Material 4% maximum
SHAPE: Hard, spherical pellet
BULK DENSITY: 40 lb/ft3 to 44 lb/ft3 (0.65 g/cm3 to 0.79 g/cm3)
RESIDUAL BASE: Maximum 0.4 meg base/gm pH 8 to 10 in a 10% solution
pH: 8 to 10 in a 10% solution
PACKAGING: 25 kg (55 lb.) poly bags; 1000 kg (1 metric ton – 2205 lbs.) Super Sacks, bulk
Minimum orders: 40 – 25 kg bags, 1 Super Sack, 21 metric tons (46,305 lbs.) bulk
CMA application rates vary according to climate and maintenance practices. CMA is applied at rates similar to road salt, but heavier in the first application and lighter as the storm continues. Typical application rates:
250 to 400 pounds per lane mile
5 to 15 pounds per thousand square feet
20 to 40 grams per square meter
CMA Customer Application Rates
Rate lb/ln mi
Daily Traffic (vehicles/day)
|MI DOT||Zilwaukee Bridge||300||24||45000|
|MA DPW||ROUTE 25||300||24||20000|
The bulk density of CMA is about 40 pounds/cubic foot compared to 70 pounds/cubic foot for salt. Since CMA is lighter, applications based on weight will appear to have 75% more pellets on the road surface compared to an equivalent application of salt.
CMA has been used successfully since 1986 by snow fighters worldwide. It is effective over a similar temperature range as road salt: performance decreases below 20 degrees F (-7 degrees C). Effectiveness is generally enhanced by traffic, sunlight, and warmer temperatures. Because CMA is acetate-based instead of chloride-based, it has unique performance characteristics. Over the years many techniques have been tested and adopted to increase its efficiency.
CMA Works Differently
When mixed with snow, CMA interferes with the ability of snow particles to adhere to each other or to the surface. It does not create a flowing brine like salt, but keeps the snow lighter and drier improving traction. Applied early in the storm, CMA prevents the formation of snow pack and the bonding of ice to the pavement surface, so snow and ice can be removed more easily by plow, broom or shovel.
CMA Has Residual Action
Because CMA does not produce a running brine, it does not move off the surface like other deicers. Therefore, fewer applications are needed during a storm and from storm to storm. Experience has shown that surfaces treated with CMA often exhibit anti-icing properties during subsequent periods of freezing moisture.
CMA Is Applied “Bottom Up”
Early application is the key to effective performance of all deicers, including CMA. At the beginning of a snow event, a heavier application of CMA may be appropriate depending on local conditions. Snow plows and the action of traffic will remove the snow – leaving a residual layer of CMA. Application rates may be decreased as the storm continues.
CMA exhibits very low corrosion rates on metals found in bridges, roadways, parking garages, and other steel and concrete systems. Commonly described as being about as corrosive as tap water, CMA is often used as the corrosion standard by which other deicers are judged. Years of real-world use coupled with laboratory tests throughout the 1980′s and 1990′s sponsored by the U.S. FHWA, U.K Department of Transport, and other independent institutions have concluded: CMA is a proven low corrosion deicer.
A switch to CMA on chloride-contaminated concrete structures may extend their useful life. Tests by the Denmark Ministry of Transport with steel rebar in chloride-contaminated concrete showed that when samples were treated with CMA solutions, corrosion rates were reduced. Later tests by BP Chemicals concluded: “CMA is non-corrosive towards steel reinforcement in concrete and can arrest incipient corrosion induced by prior use of rock salt deicers.”
The FHWA evaluated the corrosion effects of various “inhibited” deicers with the following results:
A number of laboratory tests suggest that CMA may be an effective corrosion inhibitor when combined with salt. Although tests were different in type and duration of exposure, all indicated that as little as 20% CMA in a CMA/salt blend resulted in a 70% to 80% reduction in corrosion. As expected, the best corrosion protection results from the use of pure CMA.
Many engineers specify CMA because it does not chemically attack concrete nor does it increase spalling caused by the freeze-thaw cycling of water. A U.K. Department of Transport study concludes: “With the exception of CMA, all of the deicing chemicals tested resulted in a greater deterioration of the concrete than water alone…CMA was the only chemical on weak structural concrete which satisfied the criterion for scaling damage.”
Testing by Michigan DOT confirmed that CMA dramatically reduced spalling in both air-entrained and non air-entrained concrete compared to salt alone. Blending small amounts of CMA (minimum 20% by weight) with sodium chloride resulted in a reduction in salt-induced concrete scaling.
When sodium chloride is used as a deicer, it can result in roads becoming salt licking stations for wild animals, particularly deer. CMA has been used in deer management areas of Scandinavia to prevent road accidents. In Finland, CMA mixed with sand at rates of 18-24 pounds per ton (15-20 kilograms per cubic meter) kept sand from freezing. Additionally this CMA rate was sufficient to deter reindeer from roadways. CMA has the aroma of vinegar, which does not appeal to animals.
CMA Comes In Various Forms
CMA is provided in bulk, 1 metric ton (2205 lb) supersacks, or 25 kg (55 lb) bags. CMA should be used at temperatures above 20°F (-7°C). CMA should be stored indoors or in weather-proof containers. Covering bulk CMA is advised in high humidity areas. When properly stored, CMA will remain effective for years.
A 25% CMA solution can be prepared by mixing CMA at a rate of 3 lb/gal (0.38 kg/l) of potable water. At higher concentrations some CMA may not dissolve. At 25% concentration, CMA has a gel point of 8°F (-13°C), a eutectic point of 4°F (-16°C), and specific gravity of 1.14.
Environment and Toxicology
CMA research conducted in a variety of academic and private laboratories indicates that negative environmental and toxicological impacts are highly unlikely from its use as a deicer. Of the information collected it can be said that:
- Concentrations used to deice roads have little to no toxic effects on grass, trees or roadside vegetation;
- Has little to no toxic effects on aquatic species, including vertebrates and invertebrates;
- Does not mobilize pre-existing heavy metals;
- Does not increase algae, periphyton or phytoplankton biomass;
- Is unlikely to cause problems in treatment plants receiving CMA in storm water runoff;
- Is unlikely to have significant negative impacts on dissolved oxygen in receiving water;
- Has low acute mammalian toxicity with effects similar or less severe than those of sodium chloride.
- BIODEGRADABILITYThe chemical oxygen demand (COD) of CMA was determined using EPA Method 410.1:COD = 0.75 g O2/gThe biological oxygen demand (BOD) of CMA was determined using EPA approved dilution methods (Hach). The 20-day incubation BOD value at 10°C is reasonably similar to the COD value suggesting that biological oxidation progresses to the endpoint in 20 days.BOD20 @ 2°C = 0.40BOD20 @ 10°C = 0.67
- AQUATIC TOXICITYEPA method 600/4-85-013 was used for measuring the acute toxicity of CMA to freshwater and marine organisms. No mortality was observed at any test level. Based on these study results CMA can be considered to be relatively harmless under generally recognized criteria for accessing acute aquatic toxicity.
Environmental Impact CMA Versus Road Salt
|Soils||Biodegradable in soil.
No adverse effect on soil compaction and strength.
Increases soil permeability
|Sodium may accumulate in soil
Breaks down soil structure, increases erosion.
Causes soil compaction which decreases permeability.
|Vegetation||Little or no adverse effect.
May stimulate roadside plant growth.
Acetate ion is the most abundant organic acid metabolite found in nature.
|Osmotic stress and soil compaction harm root systems.
Spray causes foilage dehydration damage.
Many plant species are salt sensitive.
|Groundwater||Poor mobility in soil, unlikely to reach groundwater.
Ca, Mg increases water hardness.
|Mobile Na and Cl ions readily reach groundwater.
Increases Na and Cl concentrations in well water along with alkalinity and hardness.
|Surface Water||Potential for oxygen depletion through biological oxygen demand(BOD) at concentration greater than 100 ppm in closed systems.
Decomposes in 5 days at 20°C, 10 days at 10°C, 100 days at 2°C.
Will not stimulate algae growth.
|Causes density stratification in ponds and lakes which can prevent reoxygenation.
Increases runoff of heavy metals and nutrients through increased erosion.
|Aquatic Life||Less toxic to trout than salt.
Minimal effect on trout eggs up to 5 times expected maximum runoff concentration of 1000 ppm.
No effect on food chain (zooplankton, daphnia, bluegill, and fathead minnows) up to up to 1000 ppm.
|Monovalent Na, Cl ions stress osmotic balance.
Toxic levels: Na 500 ppm stickleback, Cl 400 ppm trout.
|Human/Mammalian||Mild skin and eye irritant.
Acute oral LD50 in rats greater than 5000 mg/kg.
|Sodium linked to heart disease, hypertension. Cl causes unpleasant taste in drinking water. Mild skin and eye irritant.
Acute Oral LD50 in rats approximately 3000 mg/kg.
Slightly toxic. Contributes to winter road kills of wildlife.
|Water Treatment Plants||No significant increase in BOD or impact on bacterial activity.||No significant impact at expected concentrations.|
|Air Pollution||Can reduce sand use and resulting particulate emissions.||Can reduce sand use and resulting particulate emissions.|