United States Department of Transportation
i
Task 6 : material thermal input for Iowa materials.
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2008-02-01
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[PDF-4.59 MB]
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Alternative Title:Material thermal input for Iowa materials : task 6;Material Thermal Inputs of Iowa Materials for MEPDG;
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Edition:Final report.
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Abstract:The present research project was designed to determine thermal properties, such as coefficient of thermal expansion
(CTE) and thermal conductivity, of Iowa concrete pavement materials. These properties are required as input values by
the Mechanistic-Empirical Pavement Design Guide (MEPDG).
In this project, a literature review was conducted to determine the factors that affect thermal properties of concrete and the
existing prediction equations for CTE and thermal conductivity of concrete. CTE tests were performed on various lab and
field samples of portland cement concrete (PCC) at the Iowa Department of Transportation and Iowa State University. The
variations due to the test procedure, the equipment used, and the consistency of field batch materials were evaluated.
The test results showed that the CTE variations due to test procedure and batch consistency were less than 5%, and the
variation due to the different equipment was less than 15%. Concrete CTE values were significantly affected by different
types of coarse aggregate. The CTE values of Iowa concrete made with limestone+graval, quartzite, dolomite,
limestone+dolomite, and limestone were 7.27, 6.86, 6.68, 5.83, and 5.69 microstrain/oF (13.08, 12.35, 12.03, 10.50, and
10.25 microstrain/oC), respectively, which were all higher than the default value of 5.50 microstrain/oF in the MEPDG
program. The thermal conductivity of a typical Iowa PCC mix and an asphalt cement concrete (ACC) mix (both with
limestone as coarse aggregate) were tested at Concrete Technology Laboratory in Skokie, Illinois. The thermal
conductivity was 0.77 Btu/hr•ft•oF (1.33 W/m•K) for PCC and 1.21 Btu/hr•ft•oF (2.09 W/m•K) for ACC, which are
different from the default values (1.25 Btu/hr•ft•oF or 2.16 W/m•K for PCC and 0.67 Btu/hr•ft•oF or 1.16 W/m•K for
ACC) in the MEPDG program. The investigations onto the CTE of ACC and the effects of concrete materials (such as
cementitious material and aggregate types) and mix proportions on concrete thermal conductivity are recommended to be
considered in future studies.
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