A stretch of gravel road was eating away at the Big Stone County (Minn.) Highway Department’s budget. As the annual bill for re-graveling and blading approached $8,000 per mile, Engineer Nick Anderson took action.
With heavy agricultural traffic causing deep ruts and extreme rough conditions, the 4.5-mile stretch of County Highway 35 struggled to meet state safety design standards. “We had to blade the section two to three times a week just to keep washboard areas at bay and keep loose gravel and soft subgrade areas from getting too dangerous for car traffic,” he says.
Because of these issues, the county scheduled the segment to be graded in 2004 and paved in 2005. The original 9-ton-per-axle design included a 2-foot sub-cut with granular backfill, followed by 10 inches of Minnesota Class 5 base material and 6.5 inches of bituminous pavement.
To help ensure the reconstruction’s success, Anderson took the advice of a nearby engineer and added base stabilizer to the project specs. Patented and distributed by Team Laboratory Chemical Corp. Inc.
of Detroit Lakes, Minn., Base One
is a safe and environmentally friendly liquid designed to increase the performance, strength, and stability of aggregate base material. It can be used in new construction, reconstruction, chip seal application, full-depth reclamation, and gravel surface treatment.
“The engineer in Wilkin County had been using it under all of his new pavements, so I thought I should try it,” says Anderson. “He was adamant about its performance.”
Anderson had experience with stabilizers. “When I worked for North Dakota, we did some lime base stabilization,” he says. “But it was a lot more expensive and labor intensive.”
To apply Base One, the construction crew first used a blade to windrow the top three inches of aggregate. Then a water truck treated the remaining material before the windrow was pulled back across the road in 1-inch lifts. The water truck treated each windrowed lift, and two rubber-tire rollers compacted the treated areas continually for each lift. The final graded surface received another application, and the final grade was compacted with the rubber-tire rollers again.
The entire process took two-and-a-half days; total cost to purchase and apply the chemical was less than $5,600 per mile.
“It firmed up the road grade nicely and was holding all the gravel in place,” says Anderson. “It totally eliminated the need to re-gravel anywhere on the section, and we only had to blade it one or two times per month at most — a big improvement over two or three times a week.”
Credit: Team Laboratory Chemical Corp.
The construction crew applied the Base One stabilizer with a water truck after a blade windrowed the top three inches of aggregate.
Budget constraints pushed paving the 4.5-mile stretch from 2005 to 2008. Because the stabilizer continued to perform well, the department adjusted its specs to include only 5.5 inches of bituminous pavement instead of 6.5 inches as originally planned and saved $40,000 per mile. “We were able to make that decision because all indicators showed that the soft areas were every bit as hard as the rest of the road grade,” says Anderson.
Two years later, the department hired an independent firm to conduct falling weight deflectometer tests every one-tenth of a mile in each driving lane. The results ranged from 12.5 to 23.7 tons with an average strength of 14.1 tons. “We built a 14.1-ton road using a 9-ton design and liquid stabilizer,” he says.
The pavement has endured four Minnesota winters (average January temperature is 1 degree F) without cracking, which is unusual. “Normally, a road will release with at least a couple cracks per mile by year two,” says Anderson. “But the grade seems to be so well consolidated and hard that there’s only minimal seasonal expansion and contraction of the road bed. There aren’t any cracks at all going into its fifth winter.”
The department now includes Base One in specs for all new pavement, but doesn’t use the product to minimize gravel loss. With gravel available at $2 per yard, re-graveling is inexpensive.
Although the cost savings are not as great for Big Stone County, Anderson sees how the stabilizer could benefit his colleagues. “It keeps the gravel in place so you don’t need to regravel nearly as much,” he says. “One neighboring county engineer hasn’t had to re-gravel about 20 miles of treated road for seven years.”
One of the first communities to try Base One, Big Stone County’s experiment has paid off. “It did everything they said it would.”
—Goodell (firstname.lastname@example.org) is a public relations specialist for The Promersberger Co. (http://www.promersberger.com) in Fargo, N.D.