Materials selection for concrete overlays : the final report Page: 69
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typical concrete pavement mixture design for ARS specimens was used and is provided in
Appendix B-2.
Calculation for ARS can be referred to ASTM C1399. The specification instructs to
calculate the average residual strength (ARS) for each beam to the nearest 2 psi using the loads
determined at reloading curve deflections of 0.020, 0.030, 0.040, and 0.050 in. as follows:
ARS = ((PA + PB + Pc + PD)/4) * k (4.1)
where:
k = L/bd2, in-2
ARS = average residual strength, psi,
PA+PB+Pc+PD = sum of recorded loads at specified deflections, lbf,
L = span length, in,
b = average width of beam, in., and
d = average depth of beam, in.
Finally, the mean ARS for each set of beams is calculated to the nearest 0.05 MPa [5 psi].
4.4.6 Bond Strength
Bond strength is one of the most important performance criteria for bonded overlays,
such as BCOs and ultra-thin or thin whitetoppings. For unbonded type overlays, bond strength is
not a performance criterion.
Seventeen 3-ft. by 3-ft. by 3-in. concrete overlays were placed in a period of three days.
A series of days with similar high and low temperatures, wind speed, and humidity was selected
in the effort to reduce any relative performance differences due to changes in the environmental
conditions. Also, each day, slabs were placed within a period of one and one-half hours to avoid
any large temperature shifts.
Bond strength of the 3-in. concrete overlays was measured in accordance with ASTM
C1583, and 2-in. diameter cores were tested in tension at 3, 7, and 28 days. A Dyna pull-off
tester from Humboldt was used to measure the bond strength. It was made certain that each core
was drilled at least 3.5 in. deep, well past the 3-in. depth of the interface for these concrete
overlays. After the tops of the cored surfaces were cleaned off and dried, a thin layer of 3000-psi
epoxy was applied, and the aluminum caps were then glued to the tops of the cores. After
sufficient time had passed for the epoxy to cure, the pull-off test was performed to measure bond
strength.69
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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/m1/89/: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.