Materials selection for concrete overlays : the final report Page: 58
xviii, 192 p. : col. ill. ; 28 cm.View a full description of this report.
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4.2.4 Fly Ash
Class F fly ash "Legs" was selected to determine the effects of its integration in concrete
mixtures. Compared to Class C fly ash, Class F fly ash typically generates less heat of hydration.
Use of fly ash can improve workability, fiber distribution, and reduce shrinkage. The properties
of "Legs" are provided in section 4.3.1.
4.2.5 Reinforcements
Due to their recent increased usage in concrete overlays applications around the country,
several fibers suggested by TxDOT were selected for use in this study. Types of fibers included
four macro synthetic types, one micro synthetic type, and one steel fiber type. Fibers were also
blended to determine the combined effects in shrinkage control.
In addition to fibers, No. 4 reinforcement bars and No. 6 wire mesh were used for a
customized restrained shrinkage experiment. Usage of reinforcement bars is the traditional way
of controlling shrinkage cracks in concrete pavement construction. However, the installation of
reinforcement bars is a time consuming and labor intensive process. Wire mesh has frequently
been used as an alternative method to control shrinkage cracks in the field.
4.2.6 Admixtures
Admixtures vary for every project. Since the focus of the research was not to study
admixtures and their effects, only a water reducing agent, WRDA 82 (manufactured by Grace),
was used.
4.2.7 Bonding Agents
In bonded concrete overlays or whitetoppings (under normal placement conditions), the
performance is shown to as good or better, if no bonding agent is utilized, as long as the surface
has adequate texture and is clean and dry (but brought to SSD just before the overlay placement)
and free of dust, white (contaminated) water, and other debris. Therefore, no bonding agents
were utilized in this research.
4.3 Characterization of Candidate Materials
In order to establish the properties and practicality of using the candidate materials, a
series of laboratory tests has been performed. Candidate materials have been characterized,
passed through a screening process, and used in making concrete specimens, which are tested for
performance limits.
4.3.1 Materials Properties
The following are properties of materials selected for the research:
* Cement: Type I/II from TXI in Bridgeport.
o Specific Gravity = 3.15.
* Fly ash: Class F "Legs (name of the plant)."
a Chemical and physical properties given in Table 4.1.58
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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/m1/78/: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.