Materials selection for concrete overlays : the final report Page: 36
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These two sections were constructed with siliceous river gravel aggregate, and the original PCC
had a severe level of distress prior to the BCO construction. Also, those two sections were the
only ones that featured fibers for reinforcement. The number and aspect of the PCC patches
observed in these two sections are an indication that TxDOT had repaired these sections many
times in the past. These are the only sections that feature the combination of those three
characteristics: SRG, fiber reinforcement and severe PCCP distress prior to BCO placement.
It is interesting to note that there were other sections that had suffered severe distress
before the BCO was constructed (Sections 6, 7 and 9), and despite such condition, the survey
results shows that their performance was still excellent (only one spall in section 6, and no other
distress). The difference between these successful BCOs and the BCO sections in poor condition
is that the better performing ones did not use fibers as reinforcement. Survey photos are given in
Appendix A-3.
3.9 Houston - IH 610 South
On July 22, 2010, a field trip was conducted to inspect two more BCO sections in
Houston. Both of these BCO projects visited are on Interstate Highway 610, the urban section
known as the South Loop, which is a major freeway encircling downtown Houston. These
projects were deemed as some of the most important of the existing concrete overlays in the
state, because they correspond to some of the oldest rehabilitations of this type that are still in
service and performing well, and both of them involve experimental sections. One of them
corresponds to the first BCO project in Texas, which was constructed in 1983.
The project was an experimental BCO on a 1000-ft. CRCP segment. Built in July and
August of 1983, the BCO has delivered excellent performance over time, as previous condition
surveys have demonstrated. It consists of five 200-ft. test segments, with several combinations
of reinforcement (no reinforcement, welded wire fabric, and steel fibers) and BCO thicknesses (2
and 3 in.), all constructed on the four eastbound lanes, between Cullen Blvd. and Calais St. For
the BCO construction, the surface was prepared by cold milling and sandblasting. Portland
cement grout was used as a bonding agent for the vast majority of the section. The original
existing pavement, constructed in 1969, consisted of 8-in.-thick CRCP on top of a 6-in.-thick
cement treated subbase. Table 3.7 shows the experimental factorial for thickness and
reinforcement, the variables investigated in the experimental sections [43, 47].
Table 3.7: South Loop factorial for 1983 BCO experiment
Reinforcement Type
None Steel Mat Steel FibersOverlay 2 in. O 00
Thickness 3 in. OQA sounding survey conducted in 1990 on this section revealed some minimal
delamination of the overlay [5]. Condition surveys conducted in 1996 showed little distress on
the section and no major performance problems [48].
The other BCO project studied in this field trip is also on the southeast part of the IH-610
Loop. The approximate project limits are from just east of SH 288, to just west of Telephone
Rd., extending for about 4 miles; this overlay is placed on either side of the 1983 experimental
sections. This project started in 1989 and was completed in 1990. It consisted of a 4-in.-thick36
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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/m1/56/: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.