This study aims to investigate the impact of an expansive agent and carbon fibre in repair mortar (overlay) on the bond strength at different water-to-binder ratios (w/b). Measurements of the flexural and compressive strengths, drying shrinkage, and mercury intrusion porosimetry (MIP) were used to evaluate the properties of the overlays, and the compressive strength, drying shrinkage, and splitting tensile strength were adopted to evaluate the properties of substrate. The exposure surface after splitting a cube into two halves was used as repair surface of substrate. The bond strength was evaluated by a splitting tensile test, and backscattered electron images were acquired to observe micro-cracks of the repair bond. The experimental results indicated that the drying shrinkage of the repair mortar was reduced by the carbon fibre and expansive agent. The total porosity of the repair mortar was increased and the compressive strength was decreased by the expansive agent. Interface failure accompanied by partial substrate failure and repair mortar failure accounted for 85.7% of bond failures. The incorporation of the expansive agent and carbon fibre in the repair mortar resulted in growth rates of 25.18% and 33.56%, respectively, for the splitting tensile bond strength at w/b of 0.30. This enhancement decreased as the w/b decreased. The repair effectiveness improved as the compressive strength ratio (repair mortar/substrate concrete) increased with a certain range (no more than 1.45). Therefore, the expansive agent and carbon fibre have the potential to improve the bond strength when the strengths of the substrate and of the repair material are equivalent and the repair bond under splitting tensile stress.

这项研究旨在研究修补砂浆中的膨胀剂和碳纤维（覆盖层）对不同水胶比（w / b）下粘结强度的影响。测量挠曲强度和抗压强度，干燥收缩率和压汞法（MIP）来评估覆盖层的性能，并采用抗压强度，干燥收缩率和劈裂拉伸强度来评估基材的性能。将立方体分成两半后的曝光表面用作基材的修复表面。通过分裂拉伸试验评价粘结强度，并获得反向散射电子图像以观察修复粘结的微裂纹。实验结果表明，碳纤维和膨胀剂可降低修补砂浆的干缩率。膨胀剂可提高修补砂浆的总孔隙率，并降低其抗压强度。界面故障伴有部分基材故障和修补砂浆故障占粘结故障的85.7％。在w / b时的劈裂拉伸强度为0.30时，在修补砂浆中掺入膨胀剂和碳纤维的增长率分别为25.18％和33.56％。随着w / b的减少，这种增强作用降低了。随着抗压强度比（修补砂浆/基层混凝土）在一定范围内（不超过1.45）增加，修复效果得到改善。因此，