Materials selection for concrete overlays : the final report Page: 3
xviii, 192 p. : col. ill. ; 28 cm.View a full description of this report.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
Chapter 2. Literature Review
2.1 Introduction
This chapter presents a comprehensive literature review about the current state of
knowledge on the material selection, mixture design/proportioning, and construction for concrete
overlays. The task involved gathering information on concrete overlays applications by the
Texas Department of Transportation (TxDOT) as well as other states, with special emphasis
focused on gathering information about the constituent materials, mixture design/proportioning,
and recommended construction methods. The research team also reviewed performance and
characteristics of fibers used in concrete overlays.
2.2 Overview of Concrete Overlays
The main purpose of constructing concrete overlays is to optimize/extend the use of the
remaining life of the existing pavement by placing an additional layer of concrete above it. By
choosing the concrete overlay option, it is possible to expedite construction, reduce cost, increase
structural integrity, improve riding quality, and protect structure against deleterious
environmental effects.
Concrete overlays are categorized into two types: bonded concrete overlay and unbonded
concrete overlay. In bonded concrete overlays, there are ultra-thin and thin whitetoppings and
bonded concrete overlays (BCOs). These concrete overlays require bonding between the
concrete overlay and the existing pavement. Unbonded concrete overlays include conventional
whitetopping, and unbonded concrete overlay (UBCOs). Whitetoppings can be bonded or
unbonded depending on their thickness. One other type, partially bonded concrete overlays, is
not discussed in this report since it is not used for highway applications in Texas.
2.2.1 Whitetopping
The term "whitetopping" indicates a concrete overlay that is used to resurface an existing
asphalt pavement. Whitetoppings are subcategorized by the thickness and the bond conditions.
Purposes and Uses
The purposes of whitetopping are to rehabilitate deteriorating asphalt pavements, to
increase load capacity and improve ride quality. Since whitetoppings do not develop typical
distresses that are found in asphalt pavements, it is a good alternative to placing an asphalt
overlay. Whitetoppings are classified as the following:
* Ultra-thin whitetopping (UTW): This overlay typically consists of a 2-to 4-in.-thick
concrete and is used when the existing pavement is considered to be in fair or better
condition with minor surface distresses (shoving, rutting, alligator cracking, etc.
The overlay relies on existing pavement to carry much of the load, and good bond
will promote monolithic behavior. Monolithic behavior reduces flexural stresses in
the overly, which can lead to early cracking and failure. UTWs are generally used
in light traffic applications.
* Thin whitetopping (TWT): TWT is identical to UTW, but the overlay is thicker
(typically around 5 to 8 in.) and is used when the existing pavement is considered to
Upcoming Pages
Here’s what’s next.
Search Inside
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
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/m1/23/: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.