Development of Hydrophobic Mortar for 3D Printing

Abstract

This article aims to develop hydrophobic mortar for 3D printing. Calcium stearate was used to replace hydraulic cement at the rates of 10, 12.5 and 15% by weight of binder. In addition, micro polypropylene fiber with a 6 mm length was used in mixture at the rates of 0.2 and 0.4% by volume. The flowability of mortar was controlled between 180 – 190 mm by varying the water to binder ratio. Both fresh and hardened properties of mortar were investigated in terms of setting time, water absorption, compressive strength, contact angle, and printability of 3D mortar printing. The results showed that the setting time of mortar was increased, and the compressive strength was decreased with the increased of calcium stearate content. However, the use of micro polypropylene fiber could improve the compressive strength of mortar. Moreover, the contact angle was increased up to 142° and the water absorption of mortar was decreased by 91.0% when calcium stearate was presented in the mixture at 15%. The use of micro polypropylene fibers caused a slightly decreasing in the surface contact angle. For the 3D printability, calcium stearate gave hydrophobic and self-cleaning property on the printed sample surface. Additionally, the buildability of mortar for 3D printing was enhanced by incorporating 0.2% micro polypropylene fiber.