Ultra-high ductile cementitious composite (UHDCC)

a new type of fiber reinforced concrete

exhibits ultra-high ductility and strain hardening ability during stretching. In this study

pull tests were conducted on 45 specimens whose ribbed steel bars were all anchored in UHDCC. The influences of anchorage length

pouring method

protective layer thickness

90-degree hook

and other parameters on the bonding performance were investigated

and a theoretical basis for the bonding strength of the force-bearing members using UHDCC was provided. Results show that all the specimens did not split due to the restraint of the fiber in the UHDCC. The pouring method of UHDCC had significant impact on the bonding strength

and the bonding strength of the specimen poured vertically was greater than that of the specimen poured horizontally. As the anchorage length of the specimen increased from 4d to 6d

the bonding strength tended to increase due to the strain hardening of UHDCC. When the anchorage length was longer than 6d

the anchorage length of the central anchoring specimen (with a thicker protective layer) had little effect on the bonding strength. However

the bonding strength of the eccentric anchoring specimen (whose restraint of UHDCC to the ribbed steel bar decreased due to the thinner protective layer) decreased with the anchorage length increased. A 90-degree hook with the length of 4d was added at the end of the steel bar when the length of the straight anchor section was 4d

and the ultimate bearing capacity was increased by 67%. However

when the length of the straight anchor section increased

the effect of the 90-degree hook on the ultimate bearing capacity began to decrease. When the absolute anchorage lengths were the same

the bearing capacity of the specimens without hooks was greater than that of the specimens with hooks. For the specimen whose steel bar had a 90-degree hook

the anchorage length must be guaranteed. Based on the test results

the bond-slip mechanism between ribbed steel bar and UHDCC was analyzed

and the equation of bonding strength between UHDCC and ribbed steel bar without 90-degree hook was given.