The search for an effective substitute for the deicing agent sodium chloride has led to the development of calcium magnesium acetate (CMA). However, CMA is not commercially available. A project for the production of CMA using resources in Maine was carried out at the Maine Department of Transportation. After the product was made, other physical and chemical tests were also performed. The results indicated that CMA can be made in Maine from an apparent abundant source of high magnesium limestone and acetic acid (cider vinegar). A 10 percent solution of acetic acid with 10 min of agitation with the magnesium limestone coarse aggregate provides the best production of CMA for this grade. A commercial production of CMA should consider the constant reflux method with constant monitoring of the pH. Evaporation of the solution by solar energy is not effective because of the large amount of rainfall in Maine, Bituminous concrete batch plants have waste heat, which might be able to aid in this evaporation need. The field trial of CMA as a deicing agent demonstrated both advantages and disadvantages. A major concern is its dustiness. Outdoor uncovered storage of CMA is not practical. The corrosion effect of CMA solution toward metal or concrete needs further study.

The use of sodium chlorid (NaCl) as a deicing aqent on highways has been under scrutiny for some time. The chief concern is environmenta1 compatibility. Sodium chloride is corrosive in nature and it affects the water-absorbing capability of soil (! _, 1l. Many research agencies have been searching for an effective substitute for sodium chloride. In March 1980, Dunn and Schenk (3) of Bjorkste Research Lab, Inc., published their findings on their study for a salt substitute. Their pl:'aject was sponso· red by FHWA. The results indicated that calcium magnesium acetate (CMA) was a promising alternative for NaCl. This new deicing agent would react at about the same melting rate as NaCl in the tempel:'atul:'e range of common activity, but CMA also had the advantage of being a corrosion inhibitor. The run-off from melting action would be beneficial to most soils, and thel:'e is an insignificant effect to water supplies. Realizing tbe potential of CMA use and the knowledge that CMA is not produced commercially, FHWA initiated a pooled fund project for CMA in May 1981 to find an efficient manufacturing process and to establish an evaluation procedure for the product. Ultimately a production contract was awarded to SRI International, and an environmental study contract was awarded to the California Department of Transportation. Both research programs began in October 1981, and many interim reports have been published since then. The work undertaken at SRI International has been to produce acetic acid by usinq Clostridium Thermoaceticum to ferment biomass-derived sugars. The acetic acid was then combined with dolomitic lime to produce CMA.