Fresh and hardened properties of 3D printing mortar modified by halloysite nanotube

This study presents the impacts of different dosages of halloysite nanotube (HNT) on the characteristics of 3D printing mortar (3DPM). The fresh behavior of 3DPM alongside with its hardened performance and microstructural characteristics were evaluated. Results indicated that HNT accelerates the setting time of 3DPM. 3% of HNT (HNT3) increased the yield stress and thixotropy of 3DPM by around 537 and 248%, respectively. The improvement in green strength (265%) and shape stability (69%) of 3%-HNT-modified 3DPM samples was observed. HNT3 also enhanced the flexural (45%), compressive (39%), and interlayer-bond (19%) strengths. Furthermore, durability-related characteristics results demonstrated that HNT3 can reduce sorptivity and gas porosity by approximately 42 and 55%, respectively, while it increases its electrical resistivity by about 48%. Outcomes obtained from microstructural analysis confirmed the denser microstructure of HNT-modified 3DPM. Therefore, HNT can be introduced as a promising candidate to improve both fresh and hardened characteristics of 3DPM.