Eexperimental study of interface behaviour of geopolymer concrete

Flexural strengthening of reinforced concrete (RC) elements by incorporating additional layers of concrete is a widely employed technique for enhancing structural capacity. Typically, during design, the strengthened element is treated as monolithic to simplify calculations. However, this assumption often overlooks the significance of interface slip, a critical factor influencing the level of damage sustained by the strengthened element. The extent of interface slip depends on the bond strength and the surface preparation techniques used. Addressing this gap, this study undertook an experimental investigation to assess the bond strength of geopolymer concrete using manual roughening with a chisel and hammer, as well as sandblasting, in combination with epoxy-based and cement-based bonding agents. The bond strength was evaluated through slant shear and pull-off tests. Results showed that geopolymer concrete with 100% slag achieved the highest shear bond strength of 27.5 MPa in slant shear and 1.8 MPa in pull-off tests, representing an improvement of up to 25-35% compared to Portland cement concrete under similar interface conditions. Manual roughening combined with an acrylic bonding agent resulted in a 40-50% higher bond strength compared to sandblasting and epoxy bonding combinations. The findings of these tests underscore the potential of geopolymer concrete as a viable repair material for structures, owing to its commendable bond strength performance. These results contribute valuable insights into optimizing strengthening techniques for enhanced structural integrity and longevity.