A novel additive mortar leveraging internal curing for enhancing interlayer bonding of cementitious composite for 3D printing

•Additive cementitious mortar incorporating cellulose fibers was proposed for enhancing interlayer bonding of 3DCP.•A simple cross-over test was adopted to measure the interface bonding of 3DP concrete;•Achievement of interlayer tensile bond strength exceeding 1.91 MPa for a print time interval of 60 min.•Cellulose fiber retains water for internal curing, aids hydration and mechanical anchorage and helps reduce shrinkage.