Impact of Fines Content on Resilient Modulus Reduction of Base Courses During Thawing

AUTC project number: 107045

PI(s):

Juanyu (Jenny) Liu (UAF)

Funding:

US Department of Transportation (RITA); Alaska Department of Transportation & Public Facilities

  • Start Date: Aug 3, 2007
  • End Date: Mar 31, 2010

Project Summary

When spring comes to cold regions, the active layer (the top few feet of soil that freezes and thaws seasonally) thaws quickly, while deeper soil remains frozen. The active layer becomes saturated with water from snowmelt that collects atop the frozen layer. In these circumstances, roads across Alaska almost float on a soft foundation. Too often, poorly supported pavement buckles and sags under the weight of heavy tractor trailers and other vehicles, and it remains deformed once the soils drain and re-stabilize. One way to reduce this damage is to control the amount of fines (essentially rock dust) in a pavement mixture. This project investigated base course materials commonly used in Alaska's roads. Liu's team observed changes in the stiffness of the materials, as well as how their soil-water characteristics change under freeze-thaw cycles, and how different percentages of fines and moisture influence material properties. Field tests in Alaska's three DOT&PF regions and subsequent lab research have been completed. Data from this study will be used to produce better pavement designs, particularly in some rural areas, where project engineers might be forced to use locally available material with high fines content.