asphalt contractors receive complaints or lawsuits based on allegations of faulty asphalt or bituminous surface courses," says Maxine Williams president of BASE-SEAL International Inc., Houston, Texas. "In reality, the problem does not lie in a faulty bituminous surface or misapplication at all, but in the fact that the road base was not properly constructed or stabilized. As a result, the asphalt cracked, peeled, or separated from the road base, or severe undulation occurred due to base faults and deformation."
Such was the case in Walton County Florida, when Hurricane George slammed into the panhandle coast. On September 27, 1998, the Hurricane hit and made its way through the county, bringing 27 inches (686 mm) of rainfall in a 36 hour period. The flood waters washed out several roads and caused major damage to the county’s surface transportation infrastructure.
Says Nelson Miner, P.E., engineer with Walton County, "...Only those roads that we had stabilized utilizing our new reconstruction program [FDR including BASE-SEAL and Top Shield] are intact. Some shoulders and ditches eroded as much as 12 feet (3.7m) in some areas. We have a monumental reconstruction task ahead of us to recover from the storm."
of repeatedly having to repair and re-repair roadways … Brooks
Davis, assistant superintendent for District 3… discovered, a new
nonstandard soil admixture to be used for roadway full-depth
reclamation on flexible pavement sections, as well as for soil
stabilization of existing, unpaved mid–to low–volume county roads.
BASE-SEAL is an inorganic chemical additive with three main purposes:
to act as a surfactant; to keep the soil’s particles moist by
hydroscopic, or moisture absorbing, properties; and to act as a
polymeric catalyst. Moreover, the product promised to help build a
more flexible road base in order to increase durability and the life
expectancy of the pavement cross sections. By mixing the BASE-SEAL
product with water and then incorporating it into the existing
in-place soils, along with lime kiln dust, the BASE-SEAL provides a
stable foundation upon which hot mix asphalt can be placed with low
life cycle costs.
…Walton County officials approved the program and the reclamation / soil stabilization project began.
This procedure, according to Williams ensures a
uniform and consistent homogenous base course blend… Davis agrees:
"Once we get these products mixed into the soil, the rain doesn’t
have the same effect as it does on a traditional clay base. It
(BASE-SEAL) is the best thing we’ve seen in this area so
…[Phillip W. "Ace" Wise, C.E.T., Flexible Pavement Reconstruction Design and Base Course Soil Stabilization Consultant on this project,
stated:] the road can be traveled upon within an hour of the TOP-SHIELD application. And, because it is transparent and environmentally safe, TOP-SHIELD will not splash onto cars, adjacent roadways or driveways like tar and asphalt liquid...
[Wise further stated] "The average cost and time estimates show that Walton County can now construct almost 2.5 miles (4 km) of 20-year life roads for the same amount of money that a 1 mile (1.6 km) required prior to their new road rehabilitation program. Not only does this time factor make the traveling public happy, but the cost factor is equally pleasing."
… says Davis, "In some places, we had 30-plus inches (760 mm) of rain. The stabilized roads were virtually unharmed. Once this mixture ( BASE-SEAL and TOP-SHIED) was in place and cured, 3 feet (0.9 m) of water ran over it and didn’t wash any of it away."
Since September’s storm, Walton County has finished the base coarse and paved 10.9 more miles (17.5 km). "We’ve stabilized 8 miles (12.9 km) and have another 5 miles (8 km) that are ready to be paved," says Davis. "In the winter, the curing time can take a little longer, up to three to four weeks. But, soon it will be ready for the asphalt contractors to come and pave. We’ve had very good success with both the BASE-SEAL and the TOP-SHIELD."
The stabilization project was so well accepted, in fact, that the Federal Emergency Management Association (FEMA) stepped in to see how well BASE-SEAL International’s products performed after the flood. "FEMA has tentatively agreed to the extensive use of this roadway stabilization method as a mitigation option for the unpaved roads, including the shoulders and ditches," says Miner
"We intend to continue improving our roads utilizing this new method, which is very cost effective and saves significant construction time when compared to the conventional methods this county used in the past. Our Board of Commissioner’s goal is to continue to provide the very best roads and bridges possible and to have all our secondary roads stabilized with a pavement surface coarse installed when the next destructive hurricane comes to visit."
[ Since the writing of this article, Walton County, Florida, has built and paved 29 miles of county roads, utilizing the above method at a cost savings to tax payers of 50% over conventional methods, with no base failures.]