Center for Applied Research
and Technology Development:
Economic Geology Group
Historical Use of Taconite Byproducts
as Construction Aggregate Materials in Minnesota: A Progress Report
by Julie
A. Oreskovich and
Marsha M. Patelke
Report of Investigation
NRRI-RI-2006-02
October, 2006
Download a copy of this report RI200602.pdf
INTRODUCTION
Coarse taconite tailings and crushed taconite rock (Mesabi Hard
Rock™) have been a staple of the road construction industry
on Minnesota’s Mesabi Iron Range for over four
decades. Comparable to trap rock in quality, taconite
aggregates have proven to be strong and durable when used as subgrade
and base material and in bituminous pavements. The superior hardness
and durability of these materials make them a viable candidate for
exporting to the Twin Cities metro and out-state areas and to
surrounding states as stand alone aggregate or for blending with local
aggregates to produce more competent pavements. Documenting how and
where taconite byproducts have been used in Minnesota, along with
related test and longevity data, will provide the potential end user a
basis for selecting these materials over another aggregate source.
OVERVIEW
Highway projects in northeastern
Minnesota commonly utilize taconite byproducts (Mesabi Hard
Rock™) as construction aggregates. Many segments of Trunk
Highway (TH) 53-US from the Cotton area to north of the city of
Virginia, Minnesota, are paved or overlain with bituminous mixes
containing taconite byproducts, as is TH 61-MN heading from Duluth up
the North Shore of Lake Superior to Silver Bay and TH 169-US from
Virginia to Chisholm. These, along with other Minnesota state highways
in the region, may also lie on a base of coarse taconite tailings or
incorporate taconite tailings as filter rock in edge drains. In Mesabi
Range cities such as Virginia, taconite byproducts are used in nearly
every city street for drainage, fill, subgrade, base, bituminous
non-wear and wear courses, and bituminous overlays.
In large metropolitan areas of the upper
Midwest, i.e., Minneapolis, St. Paul, Chicago, etc., increased
consumption and projected shortages of aggregates and / or competent
aggregates have generated an interest in exporting taconite byproducts
(Mesabi Hard Rock™) for use as construction aggregates. To
prove the quality and value of Mesabi Hard Rock™, it is
important to document how taconite byproducts have been used in
Minnesota’s roads over the past forty plus years, and
demonstrate how well they have withstood the test of time.
From the Minnesota Department of
Transportation (Mn/DOT) to the highway departments of St. Louis, Lake,
and Itasca counties to the Public Works departments of local
municipalities such as Virginia, Hibbing, and Grand Rapids, taconite
byproduct usage in road construction has been widespread and well
documented. Archived and current records contain project data that
include byproduct type, application, location, and test results.
Pulling this historical data together into database format gives the
potential user the means for evaluating the viability of using taconite
byproducts in comparable projects.
Identification of existing roadways and
structures that incorporated taconite byproducts into their composition
provides the opportunity for conducting field observations and locating
historical source material from which to draw test cores. Evaluation of
such cores will determine how these materials behave over time, as some
structures have been in place for over forty years. Relating
structural performance to physical test data, as collected from
archived records, will enable prediction of future performance, and
yield a historical base on which to proffer these materials as suitable
aggregate materials for out-state and out of state areas.
Download a copy of this report RI200602.pdf