Effect of different surface preparation techniques on the bond behavior of normal and fiber-reinforced geopolymer concrete

Abstract

Fiber-reinforced geopolymer concrete offers a sustainable alternative to conventional concrete; however, its application to repair and strengthen existing concrete structures is inadequately understood. The effectiveness of repairing and strengthening system depends upon the bond characteristics of existing and overlay concrete. Therefore, the present study aims to assess the bond performance of normal (old) concrete and fiber-reinforced geopolymer (new) concrete (FRGC) using different bond tests such as split tensile, bi-surface shear, and slant shear tests. The performance of four interface preparation techniques has been compared: wire brushing, epoxy, carbon fiber reinforced polymer (CFRP), and glass fiber-reinforced polymer (GFRP). Moreover, the effect of various sizes of groove width on the bond characteristics of old and new concrete interfaces is also investigated. CFRP and GFRP, as surface preparation techniques over plain old concrete surfaces, showed the highest split tensile, bi-surface shear, and slant shear strength. Additionally, the interface prepared with grooves of 40 mm width and 10 mm depth with epoxy represented a 113.5% enhancement in slant shear strength compared to the ungrooved one because of the additional mechanical interlocking provided by the defined shape of the grooves. The composite prepared with FRGC as new concrete performed equivalently and even better in some cases than new normal concrete due to the increased interfacial adhesion and dense transition zone created by PVA fiber. Thus, FRGC, being sustainable, has the tendency to replace conventional concrete as an effective and efficient repairing and strengthening concrete. Finally, the obtained experimental results have been compared with the predicted interfacial shear capacity using different design code models, and amongst them, Eurocode 2 predictions are closest to the experimental results.