Construction of buildings is traditionally a manual process. Recent advances in additive “3D” manufacturing technology promise to reduce the cost of construction substantially, by autonomously printing sequential layers of a structure from the bottom up. However, current attempts to 3D print structures using Ordinary Portland Cement (OPC) are limited by the medium. OPC reacts over hours and days with water to harden. Thus, print speed is limited with OPC: too fast and wet cement will collapse under its own weight, too slow and the layers will not adhere well to each other. Mixed OPC slurry pumped through the gantry must be used before it hardens in the conduits. These systems mostly utilize 3-axis gantry designs, in large part to support the weight of the conduits and wet cement being supplied to the print head. The structure size is then limited by the size of the gantry which defines the area of the print bed, as well as the maximum height of the structure. Many potential construction sites have limited access that may not support the delivery of large gantry systems.
Alternative cement chemistries utilizing two slurries that do not react until combined already exist commercially, albeit not yet very competitively with OPC. One example of such a chemistry is a basic magnesia (MgO) slurry (Part B) and a mild acid phosphate (e.g., KH2PO4) slurry (Part A) which can react to form a hard cement in minutes. These slurries may also contain other fillers to control for viscosity and add strength or reduce the cost of the material. Such chemistries, due to their exothermic nature and fast cure may not always work well when poured in bulk form (i.e., traditional OPC construction methods), but lend themselves well to 3D printing methods. Although seemingly unrelated to one not having the benefit of this disclosure, various polymer epoxy systems wherein a “PART B” hardening agent is mixed with a “PART A” resin would also lend themselves to a methodology which eliminates the limitations of gantry systems. While bulk polymers have not historically been used in construction, the methodology claimed herein may promote the adoption of polymer materials as a part or whole in building scale structures.