Materials selection for concrete overlays : the final report Page: 57
xviii, 192 p. : col. ill. ; 28 cm.View a full description of this report.
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Chapter 4. Laboratory Investigation
This chapter reports on the activities and results of the laboratory investigation of
relationships between portland cement concrete overlays (herein referred to as concrete overlays)
and the critical physical properties of typical overlay mixture constituents. The investigation
methods were based on the information and data gathered from literature reviews and from
forensic reports and condition surveys on existing Texas overlays. The main objective of this
investigation was to determine from a selected group of constituent concrete overlay materials
and in what proportions yielded the best performance. It is anticipated that this information will
then be used to produce longer lasting concrete overlays for Texas highways.
4.1 Introduction
From the information gathered from literature reviews and condition surveys, candidate
materials for concrete overlays were identified and characterized. A factorial matrix was
constructed to study the interaction between the materials. A number of tests was performed and
analyzed to determine performance limits that can be used to specify which materials are to be
used in concrete overlays and at what levels.
4.2 Selection of Candidate Materials
Potential materials that may be suitable for concrete overlay constructions were identified
from the literature review and conditions surveys.
4.2.1 Cement
A typical Type I/II portland cement that meets ASTM C150 -11 "Standard Specification
for Portland Cement" was obtained from Texas Industries, Inc. (TXI) in Bridgeport, Texas. This
cement had a Blaine fineness of 375 m2/kg. The Na2Oeq and SO3 content are 0.41 and 2.7%,
respectively. The cement had the following Bogue composition: C3S = 63.2%, C2S = 10.7, C3A
= 6.6% and C4AF = 9.4%. The single drop test yielded a w/f= 0.580 and a packing density of
0.634. Unless concrete overlay is expedited or prone to sulfate attack, Type I/II is typically
adequate for concrete overlay purpose because this type of cement develops less heat of
hydration avoiding many problems associated with high temperature development during
hydration.
4.2.2 Coarse Aggregate (CA)
A locally available dolomitic crushed limestone that conformed to the requirements
found in Item 421 and 360 in TxDOT specification was selected [63]. The maximum nominal
size of the CA was 1 in. which is a commonly used size for 3 in. or thicker concrete overlays.
4.2.3 Fine Aggregate (FA)
Since there was no specific requirement for the selection of fine aggregate found in the
literature review, locally available Colorado River (siliceous) sand that meets TxDOT Standard
Specifications Items 421 and 360 was selected.57
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Kim, Dong H.; Fowler, David W.; Ferron, Raissa P.; Trevino, Manuel M. & Whitney, David P. Materials selection for concrete overlays : the final report, report, July 2012; Austin, Texas. (https://texashistory.unt.edu/ark:/67531/metapth303706/m1/77/: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.