Mechanical properties of cast half-grouted sleeve splice with rebar bonding defects

This paper describes an experimental study on the mechanical properties of cast half-grouted sleeve splice with rebar bonding defects, i.e. strip off ribs or mortar coatings of connecting rebar, which may lead to inadequate cohesiveness between the rebar and grout. A total of 12 groups of specimens were tested to study the effects of bonding defects on the bearing capacity, failure modes, and strain distribution of the grouted sleeve splice. The strip off rib length-to-embedded length ratios (0.3, 0.5, and 1), the proportion of mortar coating surface area along the embedded length (0.5 and 1), and the rebar diameter (12 mm and 20 mm) were investigated. The test results show that the failure modes of the specimens can be divided into rebar tensile failure and rebar bond slip failure. The load-displacement responses of the specimens occurring due to rebar failure were similar. Moreover, the bond strength between the rebar and grout decreased significantly, while the strip off rib length increased. When the strip off rib length coefficient reached 100%, compared with a specimen with no defects, the average tensile capacity of the sleeves splice of 12 mm and 20 mm diameter rebars were decreased by 26.5% and 58.3%, respectively. The mortar coating had no significant effect on the connection performance of the specimens. To evaluate the performance of the specimens, based on the experimental data, simple ratios comprising the yield, strength, ductility and capacity ratios were discussed and proposed.