Utilization of waste materials in a novel mortar-polymer laminar composite to be applied in construction 3D-printing

3D printing of cementitious materials is gaining attention in the construction industry. However, convenient methods are needed for integrating reinforcement into 3D-printed concrete. This paper demonstrates the mechanical enhancement offered by a novel form of mortar-polymer laminar composite. The polymer reinforcement is itself extrusion 3D-printed as lattice-like sheets, which are interlaced with mortar layers in a manufacturing process that is compatible with rapid and robotic construction. Displacement-controlled compression tests were carried out on three different composites. One of these was made with normal mortar, while two had added waste material components: biochar or fly ash. Polymer reinforcement increased the overall ductility of all composites that were cured in air-dry condition-the relevant condition for material printed on-site. These ductility improvements were seen even though the addition of the polymer decreased the overall peak compressive stress in all but one case. When mortars contained either biochar or fly ash, incorporating plastic reinforcement provided similar ductility to reinforced mortar without these waste materials. On the other hand, introducing biochar to unreinforced mortar reduced its ductility appreciably. The demonstrated composites may therefore enable increased use of waste materials in cement mixtures for building construction.