Bonding strength of steel rebars perpendicular to the hardened 3D-printed concrete layers

Passive rebars are inserted into interior hollow channels within a 3D-printed mortar geometry and then bonded with a wet joint of filling mortar, in order to test the bonding strength of the rebars within the mortar structure. Standardized test procedures are adapted for the test procedure. The test results revealed bonding strengths with shear stresses within an interval between 16.75 MPa and 18 MPa, dependent upon rebar diameter, and good early strength development of the bonding mortar of at least 14 MPa during the first week. No specimen failed because of debonding between the filling mortar and the 3D-printed cylinder, nor because of debonding of the cylinder and the concrete poured around its exterior.

Automated summary

This study tests the bonding strength of passive rebars within a 3D-printed mortar structure by inserting the rebars into interior hollow channels and bonding them with filling mortar. Test results show that the bonding strengths range from 16.75 MPa to 18 MPa, depending on the rebar diameter, and the bonding mortar exhibits good early strength development of at least 14 MPa during the first week. No specimen failed due to debonding between the filling mortar and the 3D-printed cylinder, or between the cylinder and the concrete poured around its exterior.