Mechanical Properties of 3D-Printed Carbon Fiber-Reinforced Cement Mortar

The 3D printing process is different from traditional construction methods of formwork casting due to the use of additive manufacturing. This study develops a suitable 3D-printed carbon fiber-reinforced cement mortar (CFRCM) considering the extrudability, fluidity, setting time, and buildability of the CFRCM. The difference in compressive strength and flexural strength between 3D-printed specimens and conventional cast specimens was investigated by varying the amount of carbon fiber added (carbon fiber to cement ratio, 2.5 vol.parts per thousand, 5 vol.parts per thousand, 7.5 vol.parts per thousand, and 10 vol.parts per thousand) and the curing times (7th day and 28th day). The results of the experiments indicate that the addition of 6 wt.% cement accelerators to the cementitious mortar allows for a controlled initial setting time of approximately half an hour. The fluidity of the CFRCM was controlled by adjusting the dosage of the superplasticizer. When the slump was in the range of 150 mm to 190 mm, the carbon fiber to cement ratio 2.5 vol.parts per thousand could be incorporated into the cementitious mortar, enabling the printing of hollow cylinders with a height of up to 750 mm. Comparing the 3D-printed specimens with the traditionally cast specimens, it was found that the addition of a carbon fiber to cement ratio of 7.5 vol.parts per thousand, and 10 vol.parts per thousand resulted in the optimal compressive strength and flexural strength, respectively.