Bond characteristics between high early strength engineered cementitious composites and substrates

An experimental study was undertaken to assess the bond characteristics of High Early Strength Engineered Cementitious Composites ? HES-ECC combining very high early strength, high ductility and low early age shrinkage. To do this, composites with different water to cementitious materials and slag to Portland cement ratios were produced. With the purpose of enhancing composite properties in terms of ductility and early age shrinkage characteristics, pre-soaked lightweight aggregates (LWA) were incorporated in some of the HES-ECC mixtures. In addition to HES-ECCs, a mixture of repair material (REPM) which is commercially available and extensively used for fast and durable repair of infrastructures was produced to compare the bonding performance. For the evaluation of bond characteristics on specified days, slant shear and tensile pull-off tests were performed. Along with the basic mechanical properties of proposed materials, influence of compressive strength and differential shrinkage on individual bond strength results was also discussed. Finally, comparison has been made between the results obtained from slant shear and tensile pull-off tests. The experimental results indicate that the influence of compressive strength and differential shrinkage on bond strength results varies significantly depending on the preferred test type. Furthermore, the usage of HES-ECC mixtures significantly improves the bond characteristics of a repair assembly in comparison to REPM. Enhanced bond performance of HES-ECC mixtures over REPMs can more visibly be seen in the case of direct pull-off tests. Keywords: High-Early-Strength-Engineered Cementitious Composites (HES-ECC); Bond strength; Slant shear test; Direct pull-off test; Mechanical properties.