DM 35 (Cal/Mag)

The hygroscopic nature of calcium and magnesium chlorides gives DM 35 its ability to draw and retain moisture from its surroundings.  On gravel roads this means that the fine particles in the road material will bind together better and help hold coarser components in place.  The resulting absence of dust indicates that road surface materials are being held in place and are not airborne or being thrown to the roadside.  While proper road construction and maintenance is essential to achieve maximum benefit, the use of DM 35 contributes significantly to air environmental quality (dust reduction), reduced aggregate costs (holds materials in place) and a firmer and safer compact road surface (less dust and reduced pot-holing).  Indirectly DM 35 also benefits in reduced requirements for additional gravel and grading and the cost and time involved to provide such. 

The following graph is from a study conducted by the University of Windsor "Properties of Mixed Calcium and Magnesium-Chloride Brines for Dust Control and Road Stabilization" April 10, 2012, Keith Taylor, PhD, Wei Feng, M.Eng 

The study compared the weight change of the mixed concentrated calcium-magnesium brine (DM 35*) to 30% magnesium chloride and 35% calcium chloride under climate controlled conditions.

At a relative humidity of 70% (common in Ontario in the summer) and using a temperature of 25 degrees C, all three solutions absorbed moisture yielding 34% additional weight or more with DM 35* actually showing the greatest uptake in weight (moisture) of more than 37%.

It should be noted that magnesium chloride is commonly used at strengths between 28 and 30% by weight in Ontario.

Included in the conclusion to this study (which was performed using several variations of relative humidity and temperature) was the following:  "According to the hygroscopicity and recovery tests conducted here, the concentrated brine (DM 35*) has shown a very close water uptake ability, recovery and stability as commercial calcium chloride and magnesium chloride under summer conditions..."

*Dustmaster 35 name added to identify the concentrated brine tested.