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This paper conducts a theoretical research into bond–slip relationship between ribbed steel bars and concrete. According to whether the concrete is cracked or not, the ascending part of the bond–slip curve is divided into two sections which are calculated by two different mechanical models. Based on the wedging action mechanism, the slip is introduced as displacement boundary conditions into the model, which is the main innovation of this study. The boundary conditions of the model are changed by the changing slip, so the bond stress values corresponding to all levels of slip are obtained. According to the rebar geometrical parameters specified in National Standard GB1499‐2007, the spacing of the adjacent ribs is fitted as a linear function of the rebar diameter. Then characteristic slip with the rib spacing as the main parameter is adopted in this study. Also, a negative exponential function is proposed for the descending part of the bond–slip curve. Specially, parameters of slipping path are therefore suggested for engineering applications. Comparison between calculated values and test results shows that the theoretical model can reasonably predict the local bonding problems with different steel bar diameters and concrete strength grades. [ABSTRACT FROM AUTHOR]

This study explored the potential of using biomass bamboo aggregates (BAs) developed from bamboo to replace natural aggregates (NAs) in concrete. The use of BAs not only solves the problems of environmental damage and energy depletion caused by NA mining but also improves the toughness of concrete. To address the weak adhesion between bamboo and cement, a method for modifying the surface of the BA with an epoxy mortar coating was proposed. Experimental works have examined the workability, physical, and mechanical properties of bamboo aggregate concrete (BAC) at various BA replacement rates (r =0%∼45%) and modification methods (unmodified, epoxy mortar-modified). The results indicated that BAC with r ≥35% exhibited good workability. As r increased, the water absorption rate increased, and the density decreased. Compared with normal aggregate concrete (NAC), BAC exhibited extended cracking and failure processes, suggesting that it has a postcracking deformation capacity. For BAC, the increase in the early strength growth was slower, but the increase in the strength later was faster, especially with higher BA contents. Despite larger r had negative effects on the mechanical properties, BAC with r ≥35% still met the strength criteria for non-load-bearing and secondary structures. Additionally, BAC exhibited a more pronounced size effect than NAC, but this effect diminished as the BA content reached 25%. Finally, equations for the 28-day strength and size effects of BAC specimens with varying r values were proposed. • Sustainable bamboo aggregates (BAs) were proposed for use in concrete. • Workability, physical and mechanical properties of bamboo aggregate concrete were studied. • Influences of BA replacement levels, curing ages and sizes were examined. • A 28-day strength fitting equation and a size effect formula were proposed. [ABSTRACT FROM AUTHOR]