喷射3D打印磷酸镁水泥与混凝土界面粘结性能研究

Bonding Behavior of Spray-Based 3D Printing Magnesium Phosphate Cement and Concrete

本文结合喷射3D打印全角度智能建造与磷酸镁水泥(MPC)快硬早强、高粘结性能,研究喷射3D打印MPC与混凝土界面粘结性能。通过掺加偏高岭土(MK)和粉煤灰(FA)调控MPC凝结时间、流变和力学性能,研发可喷射3D打印MPC,分析喷射3D打印MPC与混凝土界面粘结强度和微观结构变化规律。结果表明:MK通过降低MPC水化放热速率可明显提高MPC凝结时间,FA可缩短MPC初凝与终凝时间差,进而提高喷射3D打印MPC稳定性;MPC抗折强度随MK掺量先增大后降低,FA可进一步提高MPC抗折强度;随MK掺量增加,MPC静态屈服应力逐渐提高,FA对MPC屈服应力作用不明显,但可显著降低MPC塑性粘度,当掺加30%MK和15%FA时,可保证MPC良好可喷射3D打印建造性和泵送性;喷射3D打印通过高速喷射挤压作用,提高MPC与混凝土界面以及MPC层间粘结强度,使喷射3D打印MPC层间及其与混凝土微观界面粘结密实。

In this paper,combining the all-angle intelligent construction of spray-based 3D printing and magnesium phosphate cement(MPC)with fast hardening,high early strength and excellent bonding performance,the bonding behavior of the spray-based 3D printing MPC and concrete was studied.By adding metakaolin(MK)and fly ash(FA)to adjust the setting time,rheological properties and mechanical properties of the MPC,a spray-based 3D printing MPC was developed,and the change rule of the bond strength and microstructure of the interface between the spray-based 3D printing MPC and concrete was investigated.The results show that MK significantly prolongs the setting time of MPC by reducing the hydration heat release rate of MPC,and FA shortens the difference between initial setting time and final setting time of MPC,thus improving the stability of spray-based 3D printing MPC.The flexural strength of MPC increases first and then decreases with the addition of MK.FA further improves the flexural strength of MPC.With the increase of MK content,the static yield stress of MPC gradually increases.The effect of FA on the yield stress of MPC is not obvious,but the plastic viscosity of MPC significantly reduces.When adding 30%MK and 15%FA,the construction and pumping performance of MPC can be ensured.Through high-speed spray extrusion,the spray-based 3D printing improves the bond strength between MPC and concrete,which make the micro interface between MPC and concrete compact.