Degradation of the bond performance between composite limestone powder concrete and steel bars under a sulfate freeze–thaw environment

Abstract

An experimental investigation was conducted to explore the degradation of the bond performance between five types of composite limestone powder concretes and steel bars under a sulfate freeze–thaw environment. The failure model, ultimate bond strength, peak slip and bond–slip curve were researched. Three types of anchorage lengths were adopted in the investigation. The results indicated that limestone powder and fly ash reduced the ultimate bond strength and increased the peak slip of split failure. Slag increased the ultimate bond strength and reduced the peak slip. The bond performance between the composite limestone powder concrete and steel bars decreased with increasing anchorage length. Limestone powder exacerbated the degradation of the bonding performance of concrete under freeze–thaw cycles, while slag slowed the reduction in ultimate bond strength and corresponded with lower peak slip and more brittle failure. The constitutive relationship between the conventional environment τ (s, d/L) and the sulfate freeze–thaw environment τ (s, fts) was established, and the correction factor for the critical anchorage length of the sulfate freeze–thaw environment was derived. Thus, the influences of limestone powder, fly ash and slag on the critical anchorage lengths were analysed.