Protecting Pavement or Concrete Materials Against the Effects of the Destructive Action of Freezing and Thawing of Water and or Brine Solutions

1. Field of Invention

This invention relates to compositions and methods of reducing the breakup or spalling which occurs when a pavement is covered with either water or de-icing solutions produced from the action of a de-icing compound and then subjected to the destructive action of the freezing and thawing of these liquids--particularly when removal of snow or ice from pavement is sought.

2. Prior Art

The Operator, Snow Fighter's Handbook for the Utah State Department of Highways, gives the following description of a method for maintaining bare highways during snowfall: "Begin salt application when the ground is BARELY WHITE and it is wet enough to hold the salt on the roadbed. It is really important that the salt is applied at this time because you are doing more than just applying salt--you are forming a brine cushion to `float` the snow layer on. This brine has two purposes: 1--It melts snow from the pavement up so that snow and ice don't stick to it, and 2--It `greases` the snow layer so that the snow plows can push it off the road more completely than without it.

"On Type I service you apply straight salt at the rate of 0.25 cubic yards per 2 lane mile or salt-abrasive (1-1 salt-sand) mixture at 0.50 cubic yards per 2 lane mile. Let the salt sit (sic) one hour to develop a brine. Reapply every 6 hours during the storm when the storm lasts that long. Plow the road continuously every one and a half-hours--bare pavement maintenance."

If one quarter cubic yard of salt is estimated to weigh 450 pounds, if it is assumed that when the ground is "barely white" that there is 1/4inch of snow and if it is assumed that ten inches of snow is equivalent to one inch of water, the most concentrated brine that would be formed under the described highway practice would be about 2.7 percent by weight sodium chloride. This is also equivalent to 0.00355 pounds of salt per 0.1299 pounds of water per square foot of surface or 0.032 pounds of salt (1/18 cup or 0.45 volumetric ounces) per square yard.

In the February 1973 issue of "Consumer Reports" is found the following directions for keeping the snow off of a sidewalk: "The temperature is within a couple of degrees of freezing, wet snow is falling and the forecast is for a total accumulation of 2 inches: Spread rock salt or calcium chloride at about one cup per square yard to melt the snow as it falls or, shovel."

The Portland Cement Association published in 1968 the "Concrete Information" pamphlet titled "Effect of Various Substances on Concrete and Protective Treatments, Where Required." This pamphlet is a recognized source of information on the known affects that many chemicals have on concrete. With the exception of protective coatings, no mention is made in this pamphlet of any chemical which would protect concrete against the deleterious effects which either freezing and thawing or any chemical may have on concrete. In this pamphlet, the following is said of sodium and calcium chloride: "Frequently used as a de-icer for concrete pavements. If the concrete contains insufficient entrained air or has not been air dried for at least 30 days after completion of curing, repeated application may cause surface scaling."

Under the heading of Miscellaneous and of De-icers, the following statement is made: "Chlorides (calcium and sodium), urea and ethyl alcohol cause scaling of nonair-entrained concrete."

The following protective coatings are listed as treatments to prevent or reduce the damage to concrete from de-icers: "50% solution of boiled linseed oil in kerosene, soybean oil, modified castor oil, sand filled epoxy or coal-tar epoxy."

Volume 323 of the Highway Research Board Bulletin lists a test in which 2.4 pounds of de-icing salt was applied per square yard. (This is 75 times the recommended rate for highways.) In this test after 75 freeze-thaw cycles on air-entrained concrete that contained six percent entrained air, the calcium chloride had produced 41/2 times as much spalling as water and sodium chloride had produced 61/2 times as much spalling.

De-icing salts and de-icing solutions, when used to melt snow or ice on a concrete surface, causes the ice or snow to change to the liquid state and to form brine solutions which may vary from about zero percent brine to a saturated brine solution. Part of this solution is absorbed into the concrete, and as the air temperature falls below the freezing temperature of the solution, it freezes in the concrete. As the solution freezes, it expands and creates a stress in the concrete. Any part of the concrete that is stressed beyond its yield point breaks off from the main concrete mass. This destructive action is a force of nature and cannot be eliminated, but this invention modifies this process such that it become substantially less destructive.

It is thus the object of this invention to provide a method and a composition to significantly reduce the breaking up or spalling of concrete. More particularly, it is the object of this invention to reduce the spalling of pavement materials by the addition of polyethylene oxide to any materials which may be applied to the pavement just prior to a thawing and freezing cycle. The most obvious way to apply the polyethylene oxide, such that it is present during the freezing process, is in a snow and ice melting or a de-icing compound.

The types of pavement which have been found to be subject to spalling or break up from a freezing action are portland cement concrete and bituminous concrete. It has been found that by adding polyethylene oxide in such a way that it will be present in the solutions which are in contact with the concrete when the freezing action occurs, the spalling or concrete break up which ordinarily occurs, is significantly reduced.

One purpose of this invention is to treat a de-icing reagent with polyethylene oxide in order to produce a de-icing compound which, while melting the snow or ice, will also reduce the amount of freezing damage that such a compound produces on the sidewalks and roads each year. The polyethylene oxide may also be independently placed directly on the concrete, where the concrete is in contact with or contains water or water solutions which are subject to a freezing and thawing action.

One of the great problems of maintaining concrete, especially concrete walkways, roads and highways, is the rate at which the concrete breaks up. The cost of repairing and replacing these surfaces is millions of dollars each year. It is recognized, in the concrete industry that the use of de-icing salts is a major factor in accelerating the rate at which these pavements break up.

While considerable research has been done in an attempt to protect concrete from the destructive affects of the expansion of water or brine solutions as they freeze in concrete, most of this work has been done in the fields of developing protective coatings to prevent the absorption of the water into the concrete or in making an air entrained concrete which cushions the stress placed on the concrete by the freezing water. Little if any work has been done to find compounds which can be added to water or to de-icing salts to make them less destructive. This invention is thus unique in providing a chemical composition, polyethylene oxide, and a method which substantially reduces freezing and thawing damage to concrete.

It was found that polyethylene oxide has the property of reducing the amount of breakup which occurs when water or a water and a salt solution become absorbed into concrete and then are subjected to freezing and thawing cycles. This is illustrated by Examples 1, 2, 3 and 4.

In Example 1, the freezing damage produced by a distilled water solution, containing 1 percent polyethylene oxide, Polyox WSR 301, was compared with the freezing damage produced by palin distilled water. It was found that the addition of the polyethylene oxide prevented all of the spalling produced by the distilled water alone.

In Example 2, the freezing damage produced by a distilled water solution containing 2.5 percent sodium chloride and 800 ppm of Polyox WSR 301 was compared with the freezing damage produced by 2.5 percent sodium chloride in distilled water. The addition of the 800 ppm of the polyethylene oxide prevented 94 percent of the damage produced by a plain 2.5 percent sodium chloride solution.

Example 3 shows the freezing damage produced by a distilled water solution containing 3.3 percent of a high test calcium chloride, 94 percent to 96 percent anhydrous calcium chloride, plus 800 ppm of Polyox WSR 301 as compared with a plain 3.3 percent high test calcium chloride solution in distilled water. The addition of 800 ppm of the polyethylene oxide prevented 84 percent of the damage produced by a plain 3.3 percent calcium chloride solution.

About 81 percent of the damage produced by a plain 4.5 percent urea solution was saved by adding 800 ppm of Polyox WSR 301 to a comparable 4.5 percent urea solution. This is shown in Example 4.

Example 5 shows the freezing damage to concrete produced by various solutions of calcium chloride and salt, salt and calcium chloride, urea and calcium chloride or of calcium chloride, salt and urea as compared with the same solutions to which was added 800 ppm of Polyox WSR 301. In each comparable pair of solutions, the addition of the polyethylene oxide reduced the freezing damage to the concrete.

Example 6 shows that increasing concentrations of polyethylene oxide reduces the freezing damage to concrete at all levels of salt concentration tested. This includes 2.5 percent, 6.5 percent, 12.5 percent and 18.5 percent sodium chloride solutions. When combined with the data from Example 1, where 1 percent polyethylene oxide saved 100 percent of the freezing damage from plain distilled water and with Examples 7, 8, 9 where 1 percent polyethylene oxide saved 97 percent, 100 percent and 91 percent of the freezing damage produced by solutions containing 6.25 percent, 16 percent and 10 percent of sodium chloride, calcium chloride and urea respectively, it becomes apparent that the higher the concentration of the polyethylene oxide used the greater the protection there is against freezing damage to concrete.

Examples 10, 11, and 12 show that 100 ppm of polyethylene oxide in 1 percent solutions of sodium chloride, calcium chloride and urea reduced the freezing damage to concrete by 32 percent, 82 percent and 64 percent respectively.

Examples 13, 14, and 15 show that even 50 ppm of polyethylene oxide in 1 percent solutions of sodium chloride, calcium chloride and urea reduced the freezing damage to concrete by 38 percent, 59 percent and 41 percent respectively.

From these examples, it becomes apparent that polyethylene oxide protects concrete against freezing damage at low concentrations and that increasing concentrations give increasing protection. Stated in another manner, the protection against freezing damage is a function of the polyethylene oxide concentration. Example 6 shows that this is a continuous function at all salt concentrations. Examples 1, 7, 8 and 9 show that 91 percent to 100 percent protection is given at a polyethylene oxide concentration of 1 percent. Examples 2, 3 and 4 show that 81 percent to 100 percent protection is given at a polyethylene oxide concentration of 0.08 percent. Examples 10, 11 and 12 show that 32 percent to 82 percent protection is given at a polyethylene oxide concentration of 0.01 percent, and Examples 13, 14 and 15 show that 38 percent to 59 percent protection is given at a polyethylene oxide concentration of 0.005 percent. Averaging these values, the following protection is shown at the indicated concentration of polyethylene oxide:

Since the protection is zero at a concentration of zero percent polyethylene oxide and since the curve is continuous and since at the lower concentrations the curve approaches that of a straight line, the expected average protection would be about 46 .times. 0.001%/0.005%=9% at a polyethylene oxide concentration of 0.001 percent or 10 ppm.

There appears to be no upper limit to the concentration which would give protection except for the practical limits. The practical limits are imposed from the fact that (1) polyethylene oxide is relatively expensive and it would be impractical to use high concentrations; (2) a maximum of protection is achieved at about one percent concentration with an optimum of protection at about 0.08 percent; (3) the higher molecular weight polyethylene oxides are quite viscous and, at concentrations above about two percent, they become difficult to handle. In the same way, the lower molecular weight polyethylene oxides become difficult to handle at concentrations about about five percent.

The amount of de-icing compound to be used is determined by the need for thawing capacity. One desirable application of a de-icing compound is to produce a de-icing compound solution on the surface of a pavement during a snow storm. Such a solution prevents snow from sticking to the pavement and facilitates the removal of the snow leaving a bare pavement. This is done by applying a small amount of de-icing compound to the pavement when the snow is about 1/4 inch or 1/2 to 1 centimeter deep. Since most snow storms, in the U.S., occur at about the freezing temperature, it is necessary to apply only that amount of de-icing compound that will lower the freezing temperature about 2.degree. to 3.degree. F. or 1.degree. to 2.degree. C. When the snow is 1/4 inch deep, if it is considered that 10 inches of snow are equal to one inch of water, it would take about 1/2 ounce per square yard, or about 17 grams per square meter, of a sodium chloride type of de-icing compound to lower the freezing temperature of water by 2.degree. to 3.degree. F. To do this same job with a high test calcium chloride type of de-icing compound, it would take about 3/4 of an ounce per square yard, or 25 grams per square meter, and with a urea type of de-icing compound, it would take about 1 and 1/4 ounces per square yard, or 42 grams per square meter.

A frequent need of a de-icing compound is to remove ice from a pavement. This need can exist when the air temperature is about freezing or when the air temperature is down to -50.degree. F. or -45.degree. C. If possible, the best time to try to remove the ice is when the temperatures have moderated as it takes much less de-icing compound to do the job and the rate at which the ice melts is much faster. A frequent recommendation for using snow and ice melters to remove ice is to use about one cup of the snow and ice melter per square yard. A cup of salt weights about 0.63 pounds, or 284 grams. A cup of calcium chloride weights about 0.54 pounds, or 245 grams. A cup of urea weighs about 0.40 pounds or 180 grams. One square yard of ice which is 1/4 inch deep weights about 10.73 pounds, or 4870 grams. The brine that would thus be made by dissolving 1/4 inch of ice with a cup of de-icing compound would have the following concentrations:

Salt type = 284/(4870 + 284) = 5.5% Sodium chloride solution

Calcium Chloride = 245/(4870 + 245) = 4.8% Calcium chloride

Urea type = 180/(4870 + 180) = 3.6% Urea solution

The brine that would be produced by dissolving 1/4 inch of ice with two cups of a calcium chloride or a urea type of de-icing compound is as follows:

Calcium chloride = 490/(4870 + 490) = 9.1% Calcium chloride

Urea type = 360/(4870 + 360) = 6.9% Urea solution

The brines that would be produced by dissolving 1/4 inch of ice with three and four cups of a urea type of de-icing compound are as follows:

3 cups urea = 540/(4870 + 540) = 10.0% Urea solution

4 cups urea = 720/(4870 + 720) = 12.9% Urea solution

Referring these precentage brines to the freezing points of sodium chloride, calcium chloride and urea, the following table shows the freezing points of the above brines:

It would thus take between two and three cups of a high test calcium chloride to melt as much ice as 1 cup of sodium chloride. It would take between two and three cups of urea to melt as much ice as 1 cup of calcium chloride and to melt as much ice as 1 cup of sodium chloride does it would take between 3 and 4 cups of urea.

High test calcium chloride has two advantages as a snow and ice melting compound, i.e., an exothermic heat of solution and a low eutectic temperature. Both of these advantages are of the greatest use when the ice has to be melted at cold temperatures. At the higher temperatures that is, above about 20.degree. F or -6.6.degree. C, the amount of calcium chloride needed to melt the ice is relatively small and the heat of solution of the calcium chloride supplies only a small fraction of the heat of fusion needed to melt the ice. At the lower temperatures, the amount of calcium chloride needed to melt the ice becomes substantial and the heat produced from the calcium chloride going into solution becomes substantial. At the extreme example, the eutectic temperature of calcium chloride is -59.5.degree. F or -50.8.degree. C and the eutectic concentration of the calcium chloride is 31.5 percent anhydrous calcium chloride, or 33.2 percent of a high test calcium chloride. At this concentration, it would thus take 33.2 grams of pellet calcium chloride to melt 68.5 grams of ice, or 48.5 grams of high test calcium chloride to melt 100 grams of ice. The heat of fusion to melt 100 grams of ice is 7814 calories. The exothermic heat of solution for 48.5 grams of high test calcium chloride is as follows: 141 cal./gram .times. 48.5 grams = 6839 calories. In other words, at this extreme temperature, -59.5.degree. F, and concentration of calcium chloride, 31.5 percent, the heat of solution of the calcium chloride would supply 6839 cal./7814 cal. = 87.5 percent of the heat needed to melt the ice.

Urea has an advantage as a de-icing compound in the fact that it contains no chlorides and will not produce chloride toxicity in plants but, on the contrary, contains nitrogen and will stimulate plant growth. It would thus be advantageous to use a urea-type de-icing compound on products in areas where the de-icing solutions will drain onto any growing plants.

An added advantage of urea is the fact that it does not promote the corrosion of steel in concrete like the chlorides do. It would be an advantage to use urea on porches, overpasses, airport runways, and other places which contain reinforcing steel in the concrete.

Example 6 shows that sodium chloride produces the greatest amount of freezing damage at about 12.5 percent and as the salt increases or decreases from that concentration, the freezing damage decreases. This was true at zero ppm of polyethylene oxide and at concentrations of 800 and 1600 ppm of polyethylene oxide. Since the eutectic concentration is the highest concentration of a de-icing salt that will be produced as a de-icing solution freezes, the eutectic concentrations of these salt solutions, 23.1 percent anhydrous sodium chloride, 31.5 percent anhydrous calcium chloride, and 32.5 percent anhydrous urea, would be the highest concentrations for which freeze damage needs to be protected.

Example 1 shows that polyethylene oxide is effective in reducing the damage to concrete in the absence of any de-icing salts. Example 6 shows that as the concentration of sodium chloride increases the percent spalling increases up to a maximum of about 12.5 percent sodium chloride. This would indicate that, up to this point, as the solutions freeze in the concrete the stress placed on the concrete increases as the de-icing salt concentration increases. Since increasing concentrations of polyethylene oxide give increasing protections, one would expect that a certain minimum ratio of polyethylene oxide to salt might be needed. Examples 13 and 21 show the results of some tests which were run at low ratios of polyethylene oxide to calcium chloride. It can be seen that the protection given by a ratio of 1/300 is less than that given by a ratio of 1/200, that the protection given by a ratio of 1/200 is less than that given by a ratio of 1/120. As the ratio is reduced toward zero, the protection given drops to zero.

It is possible to form polyethylene oxide molecules of various sizes. An attempt was made to determine the effectiveness of each of the molecules available in reducing the freezing damage to concrete. Tests were made in which the molecules varied in molecular weight from 100,000 to 6,000,000. The tests were run in solutions of sodium chloride, calcium chloride and urea. The results of the tests are shown in Examples 16, 17, 18, 19 and 20.

All molecular weights, of the polyethylene oxides tested, were found to be effective in reducing the freezing damage to concrete. The polyethylene oxides with the larger molecular weights appear to be more effective but Polyox WSRN 750, with a molecular weight of only 300,000, was shown to be surprisingly effective. In each of the three tests, the Polyox WSRN 750 was more effective than the larger molecules WSR 205 and WSR 1105 with molecular weights of 600,000 and 900,000 respectively. In Examples 19 and 20, tests were run of polyethylene oxide compounds which had molecular weights from 100,000 to 400,000. These tests showed that while these compounds are probably not as effective in reducing the freezing damage to concrete they still produce a substantial reduction in the freezing damage.

The test work indicates that this snow and ice melting system will reduce the breakup of any surfaces which will break up under a freezing and thawing condition. Most of the work included in this application, was done on portland cement concrete. Some tests were also run on bituminous cement concrete. The results produced on the bituminous concrete are reported in Example 22. They show that polyethylene oxide reduces the damage which is produced in bituminous concrete by freezing.

The following factors affect the performance of concrete: water to cement ratio, cement content, cement type, air entrainment, workability, thorough mixing, proper placing and consolidation, curing time, temperature and humidity. In order to eliminate, as much as possible, the variables that occur in the concrete, all comparative freeze thaw tests were made on the same batches of concrete in the same freeze thaw machine at the same time. The concrete test pieces were all poured from the same batch. Except for Examples 6, 21 and 22, all batches were poured into 3 .times. 3 .times. 16 inch molds and were placed on a common platform and the platform was vibrated for 15 seconds in order to achieve equal consolidation. The test pieces were then cured in a 72.degree. F and a 100 percent relative humidity curing room. After curing in this atmosphere, they were then allowed to finish their cure at room temperature and room humidity. The portland cement concrete was made from batches which contained the equivalent of 500 pounds of cement and 300 pounds of water per cubic yard. The aggregate was 40 percent sand and 60 percent gravel.

In Example 6, the concrete was poured into 2 .times. 2 .times. 2 inch molds and then treated as described above for the 3 .times. 3 .times. 16 inch molds. In Example 21, the text pieces were made from the same batch of concrete and then tamped into small plastic cylinders. They were left in the plastic cylinders for seven days and then air dried for seven days.

In Example 22, the bituminous concrete samples were prepared by the Marshall Method. All comparative freeze thaw tests were made on samples which were mixed for two minutes at 270.degree. to 295.degree. F in a Blakesley Mixer. The compaction was made in a Marshall Compactor at 270.degree. to 280.degree. F and each set of samples, on which comparative freeze thaw tests were run, received the same number of blows.

When the polyethylene oxide is to be used with a de-icing salt or a de-icing compound, it is, in many but not necessarily in all instances, an advantage to mix the polyethylene oxide with the de-icing compound prior to the application. This is relatively easy to accomplish in a dry state as the powdery characteristics of the polyethylene oxide allows it to cling to the particles of de-icing compound. This is particularly true for urea.

If it is found that a dry mix allows too much segregation of the two materials, an excellent product can be produced by adding one or more de-icing compounds to a mixer and, while the mixer is in operation, adding the polyethylene oxide followed by .2 percent to 25 percent of either a water and urea solution or of plain water. This order of mixing works well for materials such as calcium chloride which hydrate readily as it bonds the polyethylene oxide to the surface of the de-icing compound. For such materials as sodium chloride, which do not hydrate readily, the order of mixing is to add water or a water and urea solution to the de-icing compound and allow the surfaces of the de-icing compound to be thoroughly wetted before adding the polyethylene oxide. The mixing operation should be continued until the polyethylene oxide is distributed over the surface of the de-icing compound.

Example of a method for making a batch of a de-icing mixture which contains Pellet (94 percent to 96 percent anhydrous calcium chloride) Calcium Chloride: Polyox WSR 301 as the source of polyethylene oxide and urea as a source of nitrogen as a plant growth stimulant.

The batch which was made, contained ten pounds, dry weight. The mixture was designed to contain 1.5 percent polyethylene oxide and 1.0 percent nitrogen from urea. The following percentages and weights were used:

The mixing procedure was as follows: 4368.2 grams of calcium chloride and 68 grams of Polyox WSR 301 were weighed into a mixing container. After thoroughly mixing the calcium chloride and the Polyox, a 50 percent solution of urea in water was sprayed onto this mixture and the mixing process was continued until the water-urea solution was thoroughly dispersed over the surface of the calcium chloride pellets and at the same time bonding the Polyox to the calcium chloride to produce a dry, free flowing product.

Example of a method of making a batch of a de-icing mixture which contains sodium chloride crystals, Polyox WSRN 750 as the source of polyethylene oxide and urea as a source of nitrogen as a plant growth stimulant.

The batch which was made, contained ten pounds, dry weight. The mixture was designed to contain 2.5 percent polyethylene oxide and 1.0 percent nitrogen from urea. The following percentages and weights were used:

The mixing procedure was as follows: 4372.7 grams of sodium chloride and 49.9 grams of urea prills were weighed into a mixing container. After thoroughly mixing the sodium chloride and the urea, the Polyox WSRN 750 was spred over the mixture and the mixing process was continued until the Polyox was thoroughly dispersed over the surface of the salt and the urea to produce a dry, free flowing product.

Example of a method of making a batch of a de-icing mixture which contains urea as the de-icing compound that will not produce chloride toxcicity in plants nor will it corrode reinforcing steel in concrete, plus Polyox WSRN 3000 as the source of polyethylene oxide. The following percentages and weights were used:

The mixing procedure was as follows: 4458.9 grams of urea prills were weighed into a mixing container and the Polyox was slowly added to the urea while blending the two products. The mixing process was continued until the Polyox was thoroughly dispersed over the surface of the urea to produce a dry, free-flowing product.

Example of a method for making a batch of a de-icing mixture which contains Flake Calcium Chloride (77 percent to 80 percent anhydrous calcium chloride) and Polyox WSRN 750 as the source of the polyethylene oxide with water as the agent to bond the polyethylene oxide to the calcium chloride.

The batch which was made, contained ten pounds. The mixture was designed to contain 1.2 percent polyethylene oxide. The following percentages and weights were used:

The mixing procedure was as follows: 4436.2 grams of flake calcium chloride and 54.4 grams of Polyox WSRN 750 were weighed into a mixing container. After thoroughly mixing the calcium chloride and the Polyox, the water was sprayed onto the mixture and the mixing process was continued until the water had been thoroughly dispersed over the surface of the calcium chloride and at the same time bonding the Polyox to the calcium chloride to produce a dry, free-flowing product.

Example of a method for making a solution which contains Polyox WSR N-750 as the source of polyethylene oxide and water as the solvent.

The batch which was made contained ten pounds. The solution was designed to contain 5.0 percent polyethylene oxide. The following percentages and weights were used:

The mixing procedure was as follows: 4309 grams of water were added to a mixing vessel. The speed of a 3-Blade Paddle Stirrer was turned up to about 700 rpm to produce a large vortex in the water. The Polyox was slowly added to the water. After the Polyox had been completely added to the water, the speed of the stirrer was turned down to about 300 rpm until sufficient viscosity had been developed in the solution to hold the undissolved particles in suspension, after which the stirrer was turned down to 60 rpm and the stirring process was continued until the Polyox was completely in solution.

Example of a method for making a de-icing solution which contains sodium chloride, as the de-icing reagent, Polyox WSR N-3000, as the source of polyethylene oxide and water as the solvent.

The batch which was made contained ten pounds. The mixture was designed to contain 0.7 percent polyethylene oxide. The following percentages and weights were used.

The mixing procedure was as follows: 3325 grams of water were added to a mixing vessel. While stirring, 1179 grams of salt were added. After the salt was in solution, the mixture was speeded up to produce a vortex in the solution and the Polyox was slowly added into the vortex to produce a dispersion of Polyox in the salt solution.

Example of a method for making a de-icing solution which contains calcium chloride as the de-icing reagent, Polyox WSR 301 as the source of polyethylene oxide and water as the solvent.

The batch which was made contained ten pounds. The solution was designed to contain 0.5 percent polyethylene oxide. The following percentages and weights were used:

The mixing procedure was as follows: 2926 grams of water were added to a mixing vessel. While stirring, 1588 grams of calcium chloride were added. After the calcium chloride was in solution, the mixer was speeded up to produce a vortex in the solution and the Polyox was slowly added into the vortex to produce a solution of Polyox in the calcium chloride solution.

Example of a method for making a de-icing solution which contains urea as the de-icing reagent, Polyox WSR N-750 as the source of polyethylene oxide and water as the solvent.

The batch which was made contained 10 pounds. The solution was designed to contain 0.9 percent polyethylene oxide. The following percentages and weights were used:

The mixing procedure was as follows: 2227 grams of water were added to a mixing vessel. While stirring, 2268 grams of urea were added. After the urea was in solution, the mixer was speeded up to produce a vortex in the solution and the Polyox was slowly added into the vortex to produce a dispersion of Polyox in the urea solution.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.