3D printing lightweight mortars with cork to improve thermal efficiency in buildings

Abstract

3D printing lightweight aggregate concrete potentially allows building components with reduced thickness and lighter structures. However, the effect of lightweight additives in 3D printing compositions, particularly the use of cork, in the fresh and hardened properties of 3DP is still unknown. This study demonstrates that adding increasing amounts of cork (0%, 25%, 50%, 75%, and 100%) in place of fine sand enhances the insulation of printable mortars. Cork mortars positively reduced the required yield stress at the bottom layer in the fresh state due to lighter bulk densities. Attaining lower hardened densities (1363.0 - 1791.5 Kg/m3), printed mortars with high amounts of cork (50, 67, and 100%) showed fair values of thermal conductivity ranging between 0.40 and 0.96W/mk, for a value of 1.42W/mk of the reference. Cork composites presented sufficient mechanical strength, with a compressive strength between 21.1MPa at 100% cork and 51.1MPa at 17% cork compared to 58.3MPa of reference mortar. Printing did not considerably affect strength development or thermal conductivity in printed mortars. The latest showed isotropic behavior in all test directions, while mild anisotropy was found for compressive and tensile strength. Micro and macrostructure analysis revealed that printing reduces macropores in the sample's core relative to the compaction of lightweight aggregate mortars. When applied on a large scale, these composites can bring printed constructions closer to meeting thermal comfort standards with reduced self-weight.