Cargill WinterPave Solves Snow Problems
BY Sandy Lender
MoDOT and NB West Contracting solve weather-related safety issues on a problem section of pavement using Cargill’s WinterPave additive.
Route B in Jefferson County, Missouri, features a curving hill that once offered motorists a challenge in winter. Ice and snow made the steep grade treacherous during storms. To lessen danger for drivers, Missouri Department of Transportation (MoDOT) officers looked into an additive from Cargill for the maintenance of the 1,200-foot section. MoDOT Senior Materials Inspector, SL District, Mitch Huskey explained the situation.
“Essentially, it was a dangerous part of the road. It was a steep grade, which made it a good candidate to try the material. The pavement was two years old and the original treatment had some issues, primarily because it was such a steep grade. We had to fix it anyway; we plugged the WinterPave® product into that repair.”
MoDOT has a standing, on-call maintenance contract with N.B. West Contracting of Sullivan, Missouri, so Huskey worked with N.B. West’s Steve Jackson and Joe Schroer to put a plan in place. N.B. West crews milled approximately 2 inches deep from the shoved and raveling pavement on the problem roadway. Then they placed the entirety of the WinterPave mixture on a hill section with numerous curves approximately 1,400 feet in length and two lanes wide, in one lift. Remaining repairs were made with a standard BP-2 mix.
“The way we did the repairs wasn’t like it would be on a normal project out for bid,” Huskey said. “For this, we could write a work order, and work out getting the product.”
Jackson sat down with AsphaltPro at the 2019 National Asphalt Pavement Association (NAPA) annual meeting to discuss the project’s success. “MoDOT procured the WinterPave additive and stored it in 2,000-pound bags in a salt shed until we could pave the project in June.”
The timing might sound odd at first because the additive is named WinterPave, but let’s take a look at the pieces here. The granular additive replaces a percentage of fine aggregate in the mix to influence the final pavement’s performance during winter conditions. Roger Wilson, district manager for Cargill Salt—Road Safety, stated: “In general, WinterPave replaces 5 percent of the aggregate by weight, typically the sand or fine gradation material.”
Huskey explained that it took a little over a year to get the funding worked out to purchase the product. Then it took a couple months to get all 21 totes arranged because that much material wasn’t stored in the United States at the time. They had it shipped over from Italy and stored it until paving season. Wilson explained: “WinterPave is currently manufactured in Europe and shipped to the U.S. East Coast. We are working towards having the ability to manufacture it here in the United States. Current delivery time is approximately 8-10 weeks after receipt of order.”
“N.B. West is a good contractor and we’ve had the opportunity to work with those guys through the standing contract,” Huskey said. “That made it vey easy to get the material and have them work up the mix design. We delivered the sacks of material out to their plant.”
Schroer is the construction materials engineer for N.B. West, and he explained the process for getting the JMF and plant ready to go.
“The JMF was developed by us for a mixture using all virgin material,” Schroer began. “The MoDOT BP-2 was developed by 35-blow Marshall method with natural sand, of which a portion was substituted with WinterPave. There were no problems developing the design.
The mixture was produced at 290 degrees F with no modifications. There were no noticeable changes in operation or mixing. It was noticed that compacted specimens had an oily feeling, such as felt when contacting calcium chloride.”
Jackson shared that the team used the tines of a fork lift to hold the totes over the RAS bin, which metered the material into the mix at a target rate of 5 percent of total weight.
“Bags were raised over the bin with a fork lift,” Schroer confirmed, “then the bottom was cut open to empty the contents into the bin. It was easy to maintain the rate after calibration of the bin. Charlie Hayes was the project manager; Rob Neier was the plant operator. Except for the addition of the WinterPave, it was business as usual on both ends of the project. There was no mention of the mix behaving any differently than normal mixtures.”
“They did a great job getting their plant ready,” Huskey said. “The guys from Cargill came in and gave us some additional insight for putting the material through the plant, instead of it being trial and error.”
“For batch plants, WinterPave is shipped in 44-pound low-melt bags that are added after the aggregate is dried and just before the hot liquids are added,” Wilson explained. “For continuous drum plants, WinterPave is currently shipped in 2,200-pound bulk bags, and added using the RAP/RAS bin.” He explained these bins are typically monitored to allow a good control of the amount of material being added to the mix. “We discussed with the NB West folks at the end of the project the possibility of using a mineral feed system to introduce WinterPave into the production stream. There are other means that we are planning to investigate further as well.”
Since the 2018 summer paving, Huskey has seen a few weather events put the section to the test.
“In 2018, we had cold temperatures, but no snow. Basically, I just monitored the road. This winter, the building that takes care of the area has monitored it. What we’re seeing so far is that the snow and ice is not bonding to the pavement. We’ve had two really good storms.
The temperatures were cold in this second round. The product itself…people have to understand it’s not a hot plate. There will be snow on the pavement, but it keeps the snow and ice from bonding. It doesn’t thaw the road, but we have an easier time plowing. Our crews plow along and then when we get to that chunk, it cleans right off, real easy.”
Huskey shared that the agency wouldn’t pave a long stretch of miles with the product, due to its price point, but he also said it’s something he values for targeted areas. “It’s good for use on an intersection, a hill, curves, targeted areas” where weather-related safety issues plague an agency.
“Problem areas (busy intersections/elevations/sharp turns) where winter snowpack and/or black ice is an ongoing safety issue would be ideal target areas to incorporate this product,” Wilson shared. “WinterPave is also appropriate to help address similar winter safety issues in parking lots and asphalt walkways.”