Materials selection for concrete overlays : the final report Page: 27
xviii, 192 p. : col. ill. ; 28 cm.View a full description of this report.
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Chapter 3. Condition Surveys of Existing Concrete Overlays in
Texas
Forensic studies conducted on bonded concrete overlays (BCO) that had construction
problems in Texas were reviewed. Also, a number of sites were visited throughout Texas to
perform condition/evaluation surveys, as part of CTR Project 0-6590 Research Task 2, Condition
Survey and Evaluation of Existing Concrete Overlays in Texas. The research objectives in this
task entail the review of reports of construction and performance histories and making site visits
to existing concrete overlays in the state to evaluate their performance to date. Two researchers
performed the surveys and wrote the findings in this chapter.
3.1 Forensic Study of BCO on IH-10 El Paso [45]
This bonded concrete overlay experienced delaminations in several areas soon after the
construction. This report provides the causes of failure and recommendations for future
expedited concrete overlays. Delamination of the overlay was due mainly to inadequate paste
adhesion. The factors that led to delaminations include the following:
* Very low initial water content of the concrete mixture.
* Loss of available water to substrate absorption.
* High rate of evaporation.
* Withholding water from the mixture at batching.
The following recommendations were made based on the forensics report:
* Surface preparation: Shotblasted and/or hydro cleaned surface should be in SSD at
placement of the overlay and should be air blasted within an hour before placement.
* Evaporation rate: Placement only under acceptable environmental conditions
(typically evaporation rates of less than 0.2 lb/ft.2/hr).
* Opening to traffic: Must be at least 12 hours old and has attained a splitting tensile
strength of at least 500 psi.
* Timing of curing: Apply curing as soon as possible to prevent water loss due to
evaporation.
3.2 Forensic Study of BCO on IH-10 Fort Worth [46]
This project also experienced early delaminations after construction. After extensive
forensics work, the cause of the problem was found to be due to negligence in surface
preparation in construction and was not a design failure. Debris was found in core samples that
were extracted where the delaminations occurred. The conclusions regarding the cause of the
problems are listed below:
* Surface preparation and cleaning was done in a hurried way.27
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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/m1/47/: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.