For each specimen, average, standard deviation and coefficient
of variation (in percent) were calculated based on the five pulloff
tests for each specimen as listed in Table 4. For the unsaturated
concrete surface condition test specimen without the use of primer
resin, the specimen treated with wire brushing (WB-US-NP) resulted
in a pull off bond strength of 4.8 MPa (average value), where
the other specimen treated with sand–water blasting (SB-US-NP)
resulted in 5.7 MPa (average value). Pull-off bond strength of
WB-US-NP and SB-US-NP specimens was higher than concrete failure
strength with range from 3.6 to 4.3 MPa from tensile splitting
test, as shown in Fig. 6a. The sand–water blasting treated specimen
(SB-US-P) resulted in a pull-off strength of 3.7 MPa with the application
of the primer coating, whereas the wire brushing surface
treated specimen (WB-US-P) resulted in a pull-off bond strength
of 4.6 MPa. With the application of prime resin on concrete surface,
it was also found that the pull-off bond strength of sprayed FRP
layer on concrete treated by wire-brushing is higher than concrete
failure strength, while that of coating on concrete treated by sand–
water blasting was within the range of concrete failure strengths
from 3.6 to 4.3 MPa, as seen in Fig. 6b. It was concluded from the
results that both sand–water blasting and wire-brushing treatment
methods were very effective to introduce the desired failure
strength due to good mechanical interlocking at interface between
the sprayed FRP layer and concrete surface.
(a)
For each specimen, average, standard deviation and coefficientof variation (in percent) were calculated based on the five pullofftests for each specimen as listed in Table 4. For the unsaturatedconcrete surface condition test specimen without the use of primerresin, the specimen treated with wire brushing (WB-US-NP) resultedin a pull off bond strength of 4.8 MPa (average value), wherethe other specimen treated with sand–water blasting (SB-US-NP)resulted in 5.7 MPa (average value). Pull-off bond strength ofWB-US-NP and SB-US-NP specimens was higher than concrete failurestrength with range from 3.6 to 4.3 MPa from tensile splittingtest, as shown in Fig. 6a. The sand–water blasting treated specimen(SB-US-P) resulted in a pull-off strength of 3.7 MPa with the applicationof the primer coating, whereas the wire brushing surfacetreated specimen (WB-US-P) resulted in a pull-off bond strengthof 4.6 MPa. With the application of prime resin on concrete surface,it was also found that the pull-off bond strength of sprayed FRPlayer on concrete treated by wire-brushing is higher than concretefailure strength, while that of coating on concrete treated by sand–water blasting was within the range of concrete failure strengthsfrom 3.6 to 4.3 MPa, as seen in Fig. 6b. It was concluded from theresults that both sand–water blasting and wire-brushing treatmentmethods were very effective to introduce the desired failurestrength due to good mechanical interlocking at interface between
the sprayed FRP layer and concrete surface.
(a)
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