For the saturated concrete surface condition without the application
the primer resin (Fig. 7a), the specimen treated with wirebrushing
(WB-S-NP) resulted in a pull off strength of 1.1 MPa,
where the other specimen treated with sand–water blasting (SBS-
NP) resulted in 0.6 MPa. Failure strength of the sprayed FRP layer
on saturated concrete surface treated by both sand–water blasting
and wire-brushing was lower than failure strength of concrete.
Thus, it was concluded that higher moisture content in interface
zone can significantly reduce the bond strength of layer on substrate
in the both cases sand–water blasting and wire-brushing
treatment. In the case of the saturated surface condition, pull-off
bond strength of 3.0 MPa was observed with the primer coated
specimen treated with the sand–water blasting (SB-S-P) and pulloff
bond strength of 2.3 MPa was measured with the primer coated
specimen treated with the wire brushing (WB-S-P) (Fig. 7b). Regard
to the saturated concrete surface condition with the application
of the primer, the failure strength was much higher than that
without the application of a primer coating. It was seen from the
result that the influence of the use of primer resin was significant
on pull-off bond strength for saturated concrete substrate.
Although primer resin can increase failure strength of the sprayed
FRP composite on saturated concrete surface treated by both sand–
water blasting and wire-brushing, it was not sufficient to guarantee