Bonding Performance of Toothed Interfaces in 3D Printed Alkali-Activated Concrete (2026-01)¶

Alkali-activated materials, with their high utilization efficiency of industrial solid waste and low-carbon emission characteristics, have emerged as an important sustainable alternative to conventional concrete. Their integration with 3D printing technology demonstrates significant potential in the fields of construction industrialization and green building. However, the layer-by-layer nature of 3D printing tends to form weak interlayer interfaces, and the rapid hardening characteristics of alkali-activated concrete further exacerbate the risk of interfacial bonding failure. In this research, a toothed interface structure was introduced, and a rotatable printhead compatible with a square-shaped extrusion nozzle was developed to systematically investigate the effects of extrusion angle and tooth geometry on interfacial bonding performance. The pore structure of the printed components was analysed. Results show that a larger extrusion angle combined with a moderate tooth angle (22.5°) significantly enhances interfacial mechanical strength. Although an excessively large tooth angle increases porosity, the toothed interface effectively modifies the geometric configuration of medium-sized pores, alleviates local stress concentration, and guides crack propagation along a more tortuous path. As the extrusion angle increases and the tooth angle decreases, the failure modes shift from interfacial debonding to mixed failure and vertical cracking. Mechanical analysis reveals a logarithmic relationship between compressive strength and total porosity, while splitting and shear strengths are linearly correlated with interfacial porosity.