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

Abstract and project information last updated: 1 March 2011. Project updates are dated below.

A young man stands in front of a steel cabinet structure that contains pink insulation.

Credit: Peng Li

Research assistant Lin Li collects sample installation on modulus as part of a research project that investigated base course materials used in Alaska’s roads. The team observed changes in the stiffness of materials, changes in soil-water characteristics under freeze-thaw cycles, and the influence of different percentages of fines and moisture on material properties.

AUTC
Project
Number
107045
Principal
Investigator
Juanyu (Jenny) Liu (UAF)
jliu6@alaska.edu
Funding
Agency

US Department of Transportation (RITA)

Alaska Department of Transportation & Public Facilities

Project
Budget
150000
Start
Date
3 August 2007
Estimated
End Date
31 March 2010

Abstract

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.