Quality
Waterjet Newsletter – 08/06/2008
Advantage of Hydrodemolition
on the Bond Strength of Concrete Overlay In the repair work of concrete
bridge decks, pneumatic and hydraulic breakers are the conventional tools for
surface preparation. However these tools tend to cause damage to the surrounding
healthy concrete and steel reinforcement. Hydrodemolition
has emerged as a newer and more effective method. Yun
et al.* conducted an experimental study to demonstrate the advantage of hydrodemolition on the bond strength of VES-LMC overlay. VES-LMC is short for Very-Early
Strength Latex-Modified Concrete. It has been widely used as an overlay
material for concrete bridge deck repair because of its short curing time,
high durability, and high bond strength. In this experimental study, VES-LMC
was used as the overlay material. The concrete for the base slab was made
with ordinary Portland cement and a maximum aggregate size of 25 mm, with target
strength of 39 MPa. The bond strength of the
VES-LMC overlay was evaluated for these three surface conditions of the base
slabs: (1) treated with a spin jet; (2) treated with a pneumatic breaker; (3)
untreated.
It was found that the tensile bond
strength is the highest when the base slab was treated with the spin jet
(1.72 MPa). It was 28 percent higher than that of the
untreated surface (1.34 MPa) and 51 percent higher
than that of the breaker-treated surface (1.12 MPa). Based on visual inspection, it was
found that, in the case of the untreated surface, the dominate failure mode
is interface failure. But in the case of the breaker-treated surface, the
dominate failure mode is substrate failure, indicating substrate damage from
the breaking energy. In the case of the jet-treated surface, there is no
single dominate failure mode. * Yun,
K.K., Kim, S.K., Choi, S.Y. and Choi,
P.G. (2006) Effect of hydrodemolition on the bond
strength of VES-LMC overlay, Proceedings of the 8th Pacific Rim
International Conference on Water Jet Technology, |
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