In this investigation, the influence of the mixture consistency and the size of imperfections (created deliberately) behind reinforcing bars on the bond strength of the bars was studied using shotcrete "pull-out" specimens sprayed with the dry-mix process.
Bond strength of GFRP bars in conventional concrete depends on bar diameter, surface condition (sand coated, ribbed, helically wrapped or braided), embedment length, bar mechanical properties and environmental conditions.
The test results showed that, in the case of the concentrically loaded specimens, the uniaxial strength was greater than the design strength ( P_{o} = 0.85f^{prime}_{c} A_{c} + f_{ys} A_{s} + f_{yl} A_{l} ) (A c, A s, A l = area of concrete, steel, or longitudinal bars, and f yl = yield strength of longitudinal bars) due to the confinement effect.
Bond strengths of HM bars were consistently lower than their LM counterparts for both ECC and NC irrespective of embedded length and bar diameter as evident from the mean ratio of bond strength of HM bar to LM bar of 0.87.
The bond strength between BFRP bars and concrete is similar to the bond strength of steel bars and concrete and shows good bond performance.
Previous studies also reported that the bond strength of GFRP bars embedded in NC decreased with the increase of the bar diameter (Hossain et al. 2014; Hao et al. 2009).
The characteristic yield strength of steel bars was 360 MPa and the mean yield strength of the steel bars was f y = 382 MPa (obtained from direct tension tests on three specimens).
Based on analysis of test results of all four phases of the AUB research program, design recommendations insignificant effect of steel galvanizing on bond strength of hooked bars anchored in normal are provided concerning the anchorage length of galvanized reinforcing bars in normal and high strength concrete structures.
Bond strength of HM bars are comparatively lower than there LM counter parts for both ECC and NC irrespective of embedded length and bar diameter.
"We didn't exactly highlight its location," he said of the box, "and it would also have taken someone a few times to gauge the likely strength of the bars.
