The Use of Nontraditional Stabilizers for Construction of Airports in Alaska

Abstract

The cost of constructing unsurfaced gravel airports in rural Alaska can easily
reach between $30 and $40 million due to the lack of gravel. The lower Kuskokwim and
Yukon River delta soils consist entirely of fine silts and sands. Consequently, any gravel
required must be imported at a cost of $300 to $600 per cubic yard ($392 to $785 per cubic
meter). In an effort to reduce these costs, the Alaska University Transportation Center, in
partnership with the Alaska Department of Transportation and Public Facilities developed the
use of two part chemical stabilizers to stabilize local marginal materials. Several stabilizing
products were incorporated in silt and sand in an effort to find the optimal and most costeffective
stabilizer. These products included geofiber, chemical stabilizers, and curing agents.
Laboratory work included California Bearing Ratio and unconfined compressive strength
tests on Horseshoe Lake sand, Fairbanks silt, and other standard sands. Test results revealed
that sand-geofiber mixtures should contain an optimum amount of fines (silt) to mobilize the
mix strength effectively. It was also found that the inclusion of an optimum geofiber content
in Fairbanks silt (0.2% geofiber by weight) and in Horseshoe Lake sand (0.5% geofiber by
weight) maximizes their bearing capacity. Using chemical stabilizers in conjunction with
curing additives, bearing capacity was also enhanced as evidenced by unconfined
compressive strengths of 1,100 psi (7.6 MPa) achieved for the sands and 600 psi (4.1 MPa)
for the silts. This research showed that strength and bearing capacity enhancement of Alaskan
marginal soils at airfield construction sites is feasible and cost-effective through the use of
nontraditional stabilizers. Future research will evaluate the durability and freeze-thaw
susceptibility of these optimized soil-stabilizer mixes.