Experimental study on the bond performance between all-light shale ceramsite concrete and rebar

Abstract

Driven by the growing demand for lightweight materials in sustainable construction, the interfacial bonding mechanism between all-lightweight shale ceramsite concrete and rebar requires further investigation. Therefore, 57 central pullout tests were conducted to systematically evaluate the effects of concrete strength, rebar diameter, surface shapes, and yield strength on the bond behavior. The results revealed two failure modes, pullout and splitting failures, controlled by the ratio of concrete cover thickness to strength. Increased concrete strength significantly enhanced bond capacity, with ribbed rebars exhibiting 2.4 to 4.6 times higher bond strength than plain rebars, while yield strength exerted negligible influence. Rebar diameter exhibited contrasting effects, with larger diameters improving bond performance under pullout failure while smaller diameters performed better under splitting failure. The ascending branches of bond-slip curves exhibited decelerated growth rates with increased rebar diameter or concrete strength. Post-peak behavior diverged sharply with splitting failures causing abrupt stress reductions, while pullout failures exhibited gradual degradation due to concrete crushing and reduced mechanical interlock. Based on diffuse crack theory and thick-walled cylinder theory, the theoretical models for bond strength, peak slip and bond-slip relationships were developed, achieving a maximum prediction error of 16.22 % and mean squared error of 1.48 for peak slip. The proposed models demonstrated superior accuracy with 80 % experimental data alignment, outperforming existing prediction frameworks.