Materials selection for concrete overlays : the final report Page: 29
xviii, 192 p. : col. ill. ; 28 cm.View a full description of this report.
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* Two to three years after BCO placement, no significant debonding seemed to have
occurred.
* The (steel) fiber reinforced sections proved to be far superior in their ability to
control longitudinal and transverse cracking.
* After almost two years of BCO service virtually none of the cracks showed
evidence of spalling.
* The five test sections on South Lop 610 have been monitored for approximately
two years at the time of the report. During this period, satisfactory performance has
been noted on most of the pavement response variables. However, the long-term
performance still needs to be established.
A sounding survey conducted in 1990 on this section revealed some minimal
delamination of the overlay [5]. Condition surveys conducted in 1996 showed few distresses on
the section and no major performance problems [48]. The success of this first experience led
TxDOT to implement a second BCO project.
3.4 Evaluation Study of Second BCO in Texas
The second BCO was implemented on the north side of IH-610 in Houston. The section
of interest consisted of a 3.5-mile stretch on the northwest part of the loop, between East T.C.
Jester Blvd. and IH-45. Originally built in the late 1950s, the 8-in. slab of CRCP on a 6-in.-thick
cement stabilized subbase was overlaid with a 4-in.-thick BCO in 1986 [30]. This overlay
project experimented with several variables, including reinforcement, coarse aggregates, bonding
agents and existing pavement conditions (various levels of distress).
Within the project limits, ten test subsections were identified, with lengths ranging from
400 to 600 ft., each including different combinations of the aforementioned variables. During
and after construction, some delamination took place between the BCO and the original
pavement. It was found that most the delaminations occurred within the first 24 hours after
placement, due to the presence of adverse environmental conditions during overlay placement,
i.e., high evaporation rates and high daily temperature differentials, and the delaminations always
occurred at a joint, crack or edge. The following lists the findings from the evaluation report [47]:
* Bonded concrete overlays significantly reduce the pavement deflection. The
deflection reduction magnitudes indicate the slab performed monolithically. The
section of CRC with siliceous river gravel reduced deflection the most as expected
due to its higher modulus of elasticity.
* The existing pavement conditions did not affect the overlay pavement performance
as long as most of the existing distresses were repaired before the overlay was
placed.
* Overall, there was a significant decrease in the amount of all types of distress. The
section of CRCP with limestone had the least number of transverse cracks, and the
siliceous river gravel and fiber reinforced sections were second and third,
respectively. Spalling and punch outs did not exist on any of the test sections.29
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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/m1/49/: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.