Methods for three-dimensional concrete printing (3DCP) of lightweight, reinforced, complex geometric concrete structures

Abstract

Methods of additive manufacturing a complex geometry cementitious structure (3D concrete printing) are provided for depositing a printable cementitious composition in a toolpath by passing it through a printhead of a robotic additive manufacturing device to deposit it onto a target. The depositing forms at least one layer of a printed wall that defines a shell structure with an open region. In certain aspects, the methods introduce a liquid rapid-setting concrete into at least a portion of the open region to reinforce the printed shell structure. After setting, the liquid rapid-setting concrete forms a solid within a hardened printed shell that together define a solid additively manufactured cementitious structure. In other aspects, the depositing includes forming at least one internal feature defining an open conduit configured to receive a reinforcement component. Together, the shell structure and the at least one internal feature define an additively manufactured cementitious structure.

Description

Attorney Docket No. 2115-008422-WO-POAMETHODS FOR THREE-DIMENSIONAL CONCRETE PRINTING (3DCP) OF LIGHTWEIGHT, REINFORCED, COMPLEX GEOMETRIC CONCRETE STRUCTURESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 691,039, filed on September 5, 2025. The entire disclosure of the above application is incorporated herein by reference.FIELD

[0002] The present disclosure relates to methods of additive manufacturing of a printable cementitious composition (three-dimensional concrete printing (3DCP)) to form additively manufactured cementitious structures that are lightweight, reinforced, and have complex geometric structures.BACKGROUND

[0003] This section provides background information related to the present disclosure which is not necessarily prior art.

[0004] Reinforced concrete (RC) enables the construction of essential long- span, large, multi-story infrastructure for urban densification and is thus vital for projected rapid urbanization. A significant concern arises from the inefficient utilization of concrete, which is the second most consumed substance worldwide. Creating structurally efficient forms that minimize material usage often necessitates the use of custom or bespoke formwork, which can incur high costs, sometimes exceeding 50% of the allocated budgets for the entire structure.

[0005] Additive manufacturing (AM) also commonly referred to as three-dimensional (3D) printing of cementitious materials, like concrete (concrete additive manufacturing or concrete three-dimensional printing - 3DP (3DCP)), can help to shape concrete without the need for formwork and has the potential to enable the creation of materially optimized structural parts. Additive manufacturing (AM) / three-dimensional (3D) printing is a process by which material is applied in an additive, layer-by-layer formation technique. Additive manufacturing can form structures having complex geometries and freeform shapes and is of particular interest in the construction industry.

[0006] However, for over two decades, 3DCP has focused on single-family homes with thick, unreinforced walls that use more concrete and cement than traditional formwork-basedAttorney Docket No. 2115-008422-WO-POA concrete structures. The utilized technology, often based on Contour Crafting, involves a computer numerical control (CNC) machine that prints concrete layer-by-layer along a planar path. This results in a permanent formwork filled with rebar and concrete. Yet, achieving materially optimized forms with planar 3DCP (P-3DCP) is challenging due to their inherent complex geometries such as sharp cantilevered branches and surfaces, that often require additional supports to prevent collapse during 3D printing. Including these supports in a component design can lead to material waste, where extra scaffolding was necessary during the 3D printing and was removed in post-processing steps.

[0007] Another approach to mitigate this complexity includes a complex topology- optimized form that is divided into smaller simple components to satisfy planar 3D printability. Additionally, each part was encased by sand to support the overhangs. Subsequently, the final structure was assembled by post-tensioning of its many parts; however, the structures suffered from imprecise segment interfaces, risking reduced structural integrity and inaccurate assembly alignment. It would be advantageous to develop approaches toward 3DCP that enable the efficient fabrication of lightweight or material-optimized structural building elements.SUMMARY

[0008] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0009] In certain aspects the present disclosure relates to a method of additive manufacturing a cementitious structure. In certain variations, the method may comprise depositing a printable cementitious composition in a toolpath by passing the printable cementitious composition through a printhead of a robotic additive manufacturing device to deposit the cementitious composition onto a target. In certain aspects, the target may be either a substrate or the cementitious composition in a hardened state that was previously deposited. The depositing forms at least one layer of a printed wall that defines an open region. The method may further comprise introducing a liquid rapid- setting concrete into at least a portion of the open region to reinforce the at least one printed wall. After setting, the liquid rapid-setting concrete forms a solid within the hardened printed wall that together define a solid additively manufactured cementitious structure.

[0010] In one aspect, the printed wall defines a shell structure that encloses at least a portion of the open region.

[0011] In one further aspect, the depositing further forms at least one internal feature defining an open conduit configured to receive a reinforcement component.Attorney Docket No. 2115-008422-WO-POA

[0012] In one further aspect, the method further comprises placing a reinforcement component into the at least one internal feature.

[0013] In one further aspect, the placing of the reinforcement material occurs prior to the introducing the liquid rapid- setting concrete into the open region.

[0014] In one further aspect, the rapid- setting concrete surrounds the reinforcement component in the open region.

[0015] In one aspect, the depositing and the introducing are repeated at least one time to form the solid additively manufactured cementitious structure.

[0016] In one aspect, the depositing occurs in an environment having a temperature of greater than or equal to about 29°C.

[0017] In one aspect, the solid additively manufactured cementitious structure is topology optimized.

[0018] In one further aspect, the solid additively manufactured cementitious structure comprises at least one branch or overhang region that is susceptible to collapse under self deadloading.

[0019] In one aspect, the toolpath is a geometrically informed non-planar (GINP) toolpath and the depositing further comprises employing a geometrically informed variable (GIV) material deposition method that (i) regulates a flow rate of material passing through the printhead during the depositing; (ii) regulates a speed of the print head; or (iii) both (i) and (ii).

[0020] In one aspect, the depositing comprises (i) regulating the flow rate of cementitious material passing through the printhead, wherein the depositing occurs at a first flow rate for a first duration and the method further comprises adjusting the flow rate of the cementitious material passing through the printhead to a second flow rate distinct from the first flow rate for a second duration.

[0021] In one aspect, the robotic additive manufacturing device is an automated three- dimensional printer at least partially controlled by a computer numerical control (CNC) system.

[0022] In one aspect, the at least one layer comprises a first layer and at least one additional layer and the method further comprises repeating the depositing of the printable cementitious composition in the non-planar toolpath over the first layer to form the at least one additional layer thereon.

[0023] In one aspect, the cementitious composition comprises ordinary Portland cement and water.

[0024] In one further aspect, the cementitious composition further comprises a reinforcement phase.Attorney Docket No. 2115-008422-WO-POA

[0025] In one aspect, the additively manufactured cementitious structure further comprises at least one reinforcement component. The at least one reinforcement component may be selected from the group consisting of: metal rebar, a reinforcement wire, a reinforcement cable, a tensioning mechanism, and combinations thereof.

[0026] In one aspect, the method occurs without using any scaffolding to form the solid additively manufactured cementitious structure, for example, during the depositing and the introducing the liquid rapid- setting concrete.

[0027] The present disclosure also contemplates a method of additive manufacturing a cementitious structure. The method may comprise depositing a printable cementitious composition in a toolpath by passing the printable cementitious composition through a printhead of a robotic additive manufacturing device to deposit the cementitious composition onto a target. In certain aspects, the target is either a substrate or the cementitious composition in a hardened state that was previously deposited. The depositing forms at least one layer of a printed wall that defines a shell structure with an open region and at least one internal feature within the open region defining an open conduit configured to receive a reinforcement component. Together the open region and the at least one internal feature define an additively manufactured cementitious structure.

[0028] In one aspect, the method further comprises placing a reinforcement component into the at least one internal feature after the depositing.

[0029] In one aspect, the depositing occurs for a first duration, the method further comprises placing a reinforcement component into the at least one internal feature after the first duration, and the method further comprises continuing the depositing after the placing.

[0030] In one aspect, the solid additively manufactured cementitious structure is topology optimized.

[0031] In one aspect, the additively manufactured cementitious structure further comprises at least one reinforcement component selected from the group consisting of: metal rebar, a reinforcement wire, a reinforcement cable, a tensioning mechanism, and combinations thereof.

[0032] In one aspect, the method occurs without using any scaffolding to form the additively manufactured cementitious structure, for example, during the depositing.

[0033] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.Attorney Docket No. 2115-008422-WO-POADRAWINGS

[0034] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0035] FIGS. 1A-1E show conventional planar additive manufacturing (e.g., 3D printing) of concrete with planar (P-3DCP). FIG. 1A shows a conventional OptiBridge™ 3D printed concrete structure with additional scaffolds. FIG. IB shows an XtreeE™ structure with extra scaffolding during the 3D printing process, while FIG. 1C shows the XtreeE™ column after scaffolding is removed. The OptiBridge™ and XtreeE™ projects requiring extra scaffolding surfaces during 3D printing to support extreme overhangs that are later removed. FIG. ID shows misalignment of segments that occurs when assembling multiple simplified parts of a Girder beam. FIG. IE shows an inherent staircase effect that occurs in conventional P-3DCP.

[0036] FIGS. 2A-2D. FIG. 2A shows a conventional planar 3DCP requiring external supports (yellow) for overhangs. FIG. 2B shows a non-planar printpath (NP-Path), slicing shapes along contours, but requiring 6-axis freedom to tilt the end effector of a robotic additive manufacturing device. FIG. 2C shows a method of generating varying layer heights in an NP-Path and remapping them to the possible domain of extruded concrete filament thickness. FIG. 2D shows an S-shape prototype showing variation of height across a layer.

[0037] FIGS. 3A-3F. FIG. 3 A shows topology optimization (TO) results for a given 6 loads and 3 supports of a complex structure. FIG. 3B shows translation an additively manufactured cementitious structure / stay-in-place concrete formwork (SP-formwork) to incorporate casting and a reinforcement component (rebar) according to certain aspects of the present disclosure. FIG. 3C shows post-rationalization to enable integration of discrete rebar. FIG. 3D shows a first prototype for forming a full 3DCP SP-formwork, where post-casting failed at the branched areas as a result of moment force. FIG. 3E shows a schematic of a branch with different angles with increasing susceptibility to collapse. FIG. 3F shows the 3D printed structure (3DCP) having a branch with a relatively lower angle from the schematic in FIG. 3E.

[0038] FIGS. 4A-4D show methods involving sequential rebar integration and casting of a quick- setting concrete in the openings of at least one wall of an additively manufactured cementitious structure / stay-in-place concrete formwork that prevents collapse of branches in accordance with certain aspects of the present disclosure. FIG. 4A shows a branch having an extreme overhang that may be susceptible to collapse. FIG. 4B shows a printed structure or formwork with openings defined therein that can receive both metal reinforcement components in the form of rebar and a rapid setting concrete that fills the openings and encases the metalAttorney Docket No. 2115-008422-WO-POA reinforcements. FIG. 4C shows the printed structure or formwork where both metal reinforcements (e.g., rebar) and a rapid setting concrete has filled openings and encased the metal reinforcements. FIG. 4D shows an additively manufactured structure that includes printed external shell structure or formwork having filled regions with both metal reinforcements (e.g., rebar) and a rapid setting concrete that fills the openings and encases the metal reinforcements.

[0039] FIGS. 5A-5D. FIG. 5A shows an initial casting after 15 layers of concrete printing having integrated conduit features for receiving reinforcement materials. FIG. 5B shows 10 cm height of cast fast-setting material for every 20 layers of NP-3DCP according to certain variations of the present disclosure. FIG. 5C shows deformation observed due to delay in sequential casting. FIG. 5D shows successful printing of the S-shaped part according to certain aspects of the present disclosure.

[0040] FIG. 6 illustrates various views of a 3D-printed stay-in-place formwork having integrated features or conduits for receiving a reinforcement component (labeled void A) along with open regions to be filled with cast fast-setting concrete (hatched area labeled void B). The design thus includes two separate cavities — one serving as a conduit for reinforcement integration and the other designated for casting fast- setting concrete, in accordance with certain aspects of the present disclosure.

[0041] FIGS. 7A-7C. FIG. 7A shows that heating the environment to 29.4°C during 3D printing of a concrete structure ensures stable 3DCP of at least 10 layers and at least 35 layers as shown in FIG. 7B. FIG. 7C shows room temperature (22°C) induced layer deformations in a 3D printed concrete structure occur after 10 layers.

[0042] FIG. 8 shows evolutions of plastic viscosity and static yield stress of 3DCP mortar and cast mortar at different ages.

[0043] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.DETAILED DESCRIPTION

[0044] Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific compositions, components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of theAttorney Docket No. 2115-008422-WO-POA disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0045] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, elements, compositions, steps, integers, operations, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Although the open-ended term “comprising,” is to be understood as a non-restrictive term used to describe and claim various embodiments set forth herein, in certain aspects, the term may alternatively be understood to instead be a more limiting and restrictive term, such as “consisting of’ or “consisting essentially of.” Thus, for any given embodiment reciting compositions, materials, components, elements, features, integers, operations, and / or process steps, the present disclosure also specifically includes embodiments consisting of, or consisting essentially of, such recited compositions, materials, components, elements, features, integers, operations, and / or process steps. In the case of “consisting of,” the alternative embodiment excludes any additional compositions, materials, components, elements, features, integers, operations, and / or process steps, while in the case of “consisting essentially of,” any additional compositions, materials, components, elements, features, integers, operations, and / or process steps that materially affect the basic and novel characteristics are excluded from such an embodiment, but any compositions, materials, components, elements, features, integers, operations, and / or process steps that do not materially affect the basic and novel characteristics can be included in the embodiment.

[0046] Any method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed, unless otherwise indicated.

[0047] When a component, element, or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other component, element, or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directlyAttorney Docket No. 2115-008422-WO-POA between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0048] Although the terms first, second, third, etc. may be used herein to describe various steps, elements, components, regions, layers and / or sections, these steps, elements, components, regions, layers and / or sections should not be limited by these terms, unless otherwise indicated. These terms may be only used to distinguish one step, element, component, region, layer or section from another step, element, component, region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first step, element, component, region, layer or section discussed below could be termed a second step, element, component, region, layer or section without departing from the teachings of the example embodiments.

[0049] Spatially or temporally relative terms, such as “before,” “after,” “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially or temporally relative terms may be intended to encompass different orientations of the device or system in use or operation in addition to the orientation depicted in the figures.

[0050] Throughout this disclosure, the numerical values represent approximate measures or limits to ranges to encompass minor deviations from the given values and embodiments having about the value mentioned as well as those having exactly the value mentioned. Other than in the working examples provided at the end of the detailed description, all numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. For example, “about” may comprise a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in certain aspects, optionally less than or equal to 0.1%.

[0051] In addition, disclosure of ranges includes disclosure of all values and further divided ranges within the entire range, including endpoints and sub-ranges given for the ranges.Attorney Docket No. 2115-008422-WO-POA

[0052] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0053] Efficient concrete design and construction methods are needed to meet growing demand for buildings and infrastructure, while minimizing environmental impact. While 3D printing can effectively produce small-scale, materially optimized parts, like car components, using planar toolpaths and additional supports, this approach is not efficient for larger construction and building elements, especially when using concrete or other cementitious materials. Given the larger scale and the speed required for constructing such structures, this approach leads to substantial material waste and increased fabrication time. Current techniques for 3D concrete printing use a planar toolpath, parallel to the ground or along a single plane, to guide the 3DCP tool head. These current techniques can limit the application of 3DCP to simple geometric shapes, such as orthogonal walls, because they encounter difficulty when printing overhangs, layer cantilevers, and filament section or angle variations. Further, the surface finishing and resolution are also often low.

[0054] Thus, the field of 3DCP has primarily focused on fabricating simple formal walls, with limited attention given to material reduction, enhancing structural efficiency, or the overall architecture of 3D-printed building elements. Structurally efficient forms entail complex geometries, such as extreme overhangs, ribbed geometries, and branching structures that cannot be readily fabricated by the current methods of planar-3DCP (P-3DCP), which restricts material deposition to horizontal layers. A fundamental challenge in fabricating complex geometries is ensuring their buildability during 3D printing without using wasteful support material for scaffolding overhangs. To address this, in certain aspects, the present disclosure contemplates methods of using a new non-planar (NP) method for robotic 3DCP that can vary the print-layer(s) orientation and height and further is not limited to printing in horizontal layers. In NP-printing, each new layer nearly perfectly sits on the previous one without “overhangs,” in contrast to planar printing, where new filaments have limited support and are subject to collapse if not externally supported.

[0055] By way of example, FIGS. 1A-1E show conventional methods of 3DCP. As can be seen, such current construction methods suffer from geometric limitations when printing overhangs, layer cantilevers, and low-quality surface finishing when using a traditional planar toolpath.

[0056] More specifically, as discussed above, one commonly employed 3DCP technology is based on Contour Crafting, involving a CNC machine that prints concrete layer-by-layer along a planar path. This results in a permanent formwork or shell structure filled with rebar andAttorney Docket No. 2115-008422-WO-POA concrete. Yet, achieving materially optimized forms with planar 3DCP (P-3DCP) is challenging due to their inherent complex geometries such as sharp cantilevered branches and surfaces, that often require additional supports to prevent collapse during 3D printing, for example, supports 20 as shown in the 3D printed structure 22 in FIG. IE. Further, as shown in FIGS. 1A-1C, an OptiBridge™ and XtreeE™ 3D printed structures 30, 40 are shown, which respectively require extra scaffolding surfaces (shown as scaffolding 32 in OptiBridge™ 3D printed structure 30 and scaffolding 42 in XtreeE™ 3D printed structures 40) during 3D printing to support extreme overhangs that are later removed. These supports thus lead to material waste, for example, as seen in FIG. 1C, where a post-processed XtreeE™ structure is shown, where extra scaffolding 42 necessary during the 3D printing (in FIG. IB) was removed in post-processing steps to leave open regions 44. Another approach to mitigate this complexity was presented in the optimal concrete girder project, where a complex topology-optimized form was divided into smaller simple components to satisfy planar 3D printability and additionally, each part was encased by sand to support the overhangs. However, as can be seen in FIG. ID, the final OptiBridge™ 3D printed 30 structure 30 was assembled by post-tensioning of its many parts with imprecise segment interfaces 34, risking reduced structural integrity and inaccurate assembly alignment.

[0057] Moreover, the commonly used planar toolpath approach in 3D concrete printing processes has proven to be a challenge, because it is not capable of handling the complex geometries produced through topology optimization (TO). Topology optimization is a technique that generates an efficient distribution of material based on performance criteria, such as strength or weight, for a given set of supports. Designs generated from TO often feature intricate shapes, such as branching and angular tubular forms, as well as a hierarchical arrangement of materials at varying scales (as shown in FIGS. 3A-3D that will be discussed further below). In FIG. IE, a portion of a topologically optimized form and the planar tool path method used in conventional 3DCP is shown, where a detailed view / close-up shows the “staircase effect” resulting from cantilevering of each layer. These cantilevering layers 24 of extruded filament (the “staircase effect”) limits the angle of tubular features and ultimately imposes geometric limitations. Therefore, such designs pose difficulties or are even impossible to fabricate using the typical 3D concrete printing methods that employ planar toolpaths. Further, the properties, especially rheology, of the printable cementitious composition pose further challenges to fabricating such complex structures.

[0058] The present disclosure contemplates methods that can achieve the manufacturing of lightweight structural building elements, without support material and excessive discretization. In certain aspects, methods are provided that couple automated or robotic additive manufacturingAttorney Docket No. 2115-008422-WO-POA(e.g., 3D printing) of a printable cementitious composition to form printed complex topology optimized geometry components / structures in combination with sequential casting of a rapid or fast setting, set-on-demand concrete. In certain aspects, the methods of the present disclosure provide an innovative non-planar tool-path and segmentation approach for the robotic 3D printing of topologically optimized concrete structures, which may also comprise sequential casting of a fast setting concrete in one or more open voids defined by the printed concrete structure(s).

[0059] In various aspects, the printable cementitious composition may be any of those known for additive manufacturing (e.g., 3D printing) that has a fresh state and a hardened state. In the fresh state, the cementitious composition is flowable and extrudable during the additive manufacturing / 3D printing process, so that it may be processed, pumped, and extruded at an aperture of a nozzle (e.g., on an end effector) during printing. However, in the hardened state, the composition desirably exhibits strain hardening behavior. In the hardened state, the cementitious composition further exhibits buildability and rapid hardening. In certain variations, the cementitious composition comprises a pozzolanic material, such as ordinary Portland cement, fly ash, and the like. The cementitious composition may further comprise an aggregate, such as a fine aggregate, or a reinforcement phase of a particle or fiber. The cementitious composition may comprise water. Other conventional ingredients may include high range water reducing agent (HRWRA), viscosity modifying agents, and other cementitious additives.

[0060] In certain aspects, material usage in concrete slabs is substantially reduced, for example, by up to about 60% to 75%, to help reduce the environmental impact of the concrete industry. Moreover, as will be described further herein, the structures formed by the present methods may further comprise introduction of a rapid-setting / fast-setting or quick-set cementitious material or concrete, such as Quikrete™ concrete products.

[0061] Thus, the present disclosure provides methods of additive manufacturing of a cementitious composition to form at least one wall or a shell of an additively manufactured cementitious structure that may be topology optimized, for example, defining complex structures that may have branching, bifurcations, and sharp angles, among other features. Thus, in certain aspects, the methods are directed to geometrically informed variables that are used to control the deposition process. In certain aspects, a method of additive manufacturing is contemplated that comprises depositing a printable cementitious composition in a non-planar toolpath by passing the printable cementitious composition through a printhead of a robotic additive manufacturing device to deposit the cementitious composition onto a target. The printhead is often part of an end effector of a robotic arm. The printing head / printhead typically comprises at least one aperture, for example, an aperture of a nozzle of a 3D printhead, where the printable cementitious compositionAttorney Docket No. 2115-008422-WO-POA passes and is deposited onto a target. Notably, the printhead / aperture may define different extruded shapes, such as round, rectangular, or irregular cross-sectional shapes in the deposited filament.

[0062] In the fresh state, the cementitious composition is flowable and extrudable. The cementitious composition may be deposited in a flowing continuous stream that is formed by a deposited ribbon or filament of the cementitious material. The cementitious composition also transforms into a hardened state, for example, exhibiting typical tensile strengths associated with cementitious compositions, such as greater than or equal to about 2.5 MPa and a compressive strength at 100 hours of greater than or equal to about 20 MPa. In certain variations, the target is a substrate or the target is the cementitious composition in a hardened state that was previously deposited via the additive manufacturing process. In this manner, a layer-by-layer deposition process can occur to form a bonded layered structure from the cementitious composition. In certain aspects, the deposited filaments or layers can optionally be aligned normal to the axis of loading. In this manner, the depositing forms at least one layer of an additively manufactured cementitious structure. In certain variations, the robotic additive manufacturing device is an automated three- dimensional printer, which may be disposed on a robotic arm, and may be at least partially controlled by a computer numerical control (CNC) system.

[0063] In certain variations, the present disclosure provides a computational model that incorporates nonplanar and variable material deposition based on the shape and geometric features of the topology-optimized parts. This allows for efficient use of material by placing it precisely where it is needed for structural purposes while eliminating unnecessary overbuilding with excessive amounts of materials. In certain aspects, the present technology first provides a geometrically informed non-planar toolpath method developed based on formed geometric features of the structure. A Geometrically Informed Non-Planar (GNIP) toolpath is a curved or spiral path for the printing head to follow rather than straight lines. Second, a geometrically informed variable (GIV) material deposition method is employed to regulate an amount of cementitious material dispensed or passed through the printing head during the printing process. Geometrically Informed Variable (GIV) Material Deposition refers to a technique regulating the amount of material being deposited along the toolpath based on the shape of the printed parts. The material flow rate can be adjusted by the material flow rate or speed of the robot.

[0064] As such, in certain aspects, the non-planar toolpath is a geometrically informed non-planar (GINP) toolpath. In other aspects, the methods of the present disclosure further comprise developing the geometrically informed non-planar (GINP) toolpath by analyzing formed geometric features, as described further below.Attorney Docket No. 2115-008422-WO-POA

[0065] Thus, the printing may involve a topology-informed non-planar printpath (NP- Path). A non-planar (Geometrically Informed Non-Planar (GNIP)) toolpath can be determined for any given geometry for three-dimensional concrete printing (3DCP). Such a model can also generate data for variable material flow rates along the toolpath. This variable material flow rate can then be calculated in relation to the maximum and minimum layer heights (LH). For example, a maximum layer height may be about 75% of a printhead nozzle diameter, while a minimum layer height may be about 25% printhead nozzle diameter.

[0066] Non-planar printpath (NP-Path) and variable material deposition for 3DCP of components having complex geometries is described herein. FIGS. 2A and 2B show NP-Path and variable material deposition can accurately follow intricate shapes of topology-optimized structures. For example, FIG. 2A shows conventional planar 3DCP that requires external supports or scaffolds 50 in overhangs 52. Each layer 54 has a first thickness or height Hi on a first side and a second thickness or height H2 on a second side, which are the same for the planar 3DCP process. In FIG. 2B, NP-Path shows slicing shapes along contours, but requires 6-axis freedom to tilt an end effector 56 of a robotic printing device. Each layer 58 has a first thickness or height Hi on a first side and a second thickness or height H2 on a second side, which differ from one another. NP-3DCP allows for adjustable orientations and layer heights to model complex 3D geometries precisely, as shown in FIGS. 2C and 2D, but necessitating the use of robotic arms with 6 degrees of freedom.

[0067] While robotic non-planar 3D printing in plastics has significantly enhanced scaffolding-free construction, surface quality, and mechanical integrity, research on NP-3DCP remains limited. Regardless of the method used to generate NP-Path, the layer heights must be adjusted to fit within the maximum and minimum height capacities of the 3DCP system. A computational model was developed that automatically adjusts the material deposition rate in accordance with the variation in height difference between two layers being 3D printed using a simple equation Eq. (1).H * W=F / V (1) where H = extruded material / filament height; W = extrudate material width; F = material flow rate based on pump speed; V = robot print speed. Varying material deposition rates across the NP- Path can be achieved through varying material flow rate (F) or robot print speed (V). The conducted tests suggest that varying V, while keeping the F constant, provides more control over the process and eliminates unstable material deposition that negatively impacts buildability. However, one challenge lies in accounting for the uneven deformation of deposited concrete filaments as a result of the weight of subsequent layers and shrinkage. Integrating these factorsAttorney Docket No. 2115-008422-WO-POA into the computational design of printpath is more complex in NP-3DCP due to the constantly changing geometry. However, enhanced data collection and real-time adaptation of the NP-Path can be used to address these issues.

[0068] In yet other aspects, the depositing further comprises employing a geometrically informed variable (GIV) material deposition method that (i) regulates a flow rate of material passing through the printhead during the depositing; (ii) regulates a speed of the print head; or (iii) both (i) and (ii). For example, where the depositing comprises (i) regulating the flow rate of cementitious material passing through the printhead, the depositing may occur at a first flow rate for a first duration and the method further comprises adjusting the flow rate of the cementitious material passing through the printhead to a second flow rate distinct from the first flow rate for a second duration. In this manner, a variable amount of material may be deposited in select regions of the target, for example, providing variable thickness of the deposited layer.

[0069] In certain variations, the methods involve employing both a geometrically informed non-planar (GINP) toolpath and employing a geometrically informed variable (GIV) material deposition method that (i) regulates a flow rate of material passing through the printhead during the depositing; (ii) regulates a speed of the print head; or (iii) both (i) and (ii).

[0070] Thus, the printing may involve a variable material deposition rate guided by the NP-Path for precise concrete deposition along the contours of complex shapes. Further, the methods of the present disclosure contemplate forming lightweight concrete structures and complex geometries in concrete by combining 3D Concrete Printing with the sequential casting of fast-setting concrete. More specifically, to prevent overhang failure during printing, in certain aspects, the methods include concurrent non-planar 3D concrete printing (NP-3DCP) of a printable cementitious material along with casting of a fast- setting cementitious material within one or more void regions defined by the printed cementitious material structure. While NP-Path addresses some issues, as discussed above, sharp tubular overhangs such as those from topology optimization may still collapse. These areas risk failure under their own weight without support or an immediate material setting. Thus, in accordance with certain aspects of the present disclosure, the cast fast-setting concrete introduced into the 3D printed shell structure takes its shape from the adjacent 3D-printed concrete shell or formwork and, at the same time, shores up the 3D-printed formwork because of its fast setting time.

[0071] Furthermore, in the areas where additional structural reinforcement is needed, such as structural ribs, one or more of the following may be employed. In one aspect, 3D printing of the non-planar stay-in-place formwork (SP-formwork) occurs, which defines at least one printed wall of a printed shell structure, followed by sequential integration of reinforcement componentsAttorney Docket No. 2115-008422-WO-POA(e.g., rebar integration, tensioning components like tensioning wire, tensioning cables) and sequential rapid-setting concrete casting. For example, the features for receiving a reinforcement component may be designed to receive a single metal rebar, carbon fiber flexible cables, or posttensioning wires or cables, such as metal wires and metal cables. In another aspect, the structure may include incorporating one or more features into the 3D printed structure capable of receiving a reinforcement, for example, a reinforcement conduit defined within one or more voids within the 3D printed structure. The reinforcement conduit that receives the reinforcement can be included as part of the Non-Planar SP-formwork design, which permits post-integration of tensile elements, such as tensile wire.

[0072] In certain aspects the present disclosure relates to methods of additive manufacturing comprising depositing a printable cementitious composition, which may be in a non-planar toolpath, by passing the printable cementitious composition through a printhead of a robotic additive manufacturing device to deposit the cementitious composition onto a target. The target may be either a substrate or the cementitious composition in a hardened state that was previously deposited. The depositing thus forms at least one layer (e.g., of a wall or shell) of an additively manufactured cementitious structure, which may be topology optimized. While Non- Planar 3D Concrete Printing (NP-3DCP) is used to achieve precise outlines in complex geometries, as will be appreciated by those of skill in the art, the present methods are not confined to non-planar 3D printing and complex geometries. The methods of the present disclosure may also be applied to planar 3D printing and non-cantilever forms. For example, such methods may involve 3D printing concrete mortar without any accelerator or with minimal accelerator. Typically, after a few layers of 3D printing with such concrete, the form collapses due to the deformation of each 3D-printed concrete filament. With the incorporation of sequential casting of fast-setting concrete, the cast concrete sets rapidly and provides support to the 3D-printed formwork, preventing collapse (it will also create a strong bond with the 3D printed form). Similarly, in this scenario, 3D printing of one or more void features, like conduits for reinforcement, can enable later integration of reinforcements after the structure is formed.

[0073] Thus, in various aspects, the method may further comprise casting a rapid or fast setting concrete within one or more open regions defined by the printed section or wall of the additively manufactured cementitious structure to enable fabrication of complex geometry shapes, for example, to fabricate parts with cantilevers and / or extreme overhangs. Notably, the passing of the printable cementitious composition and the casting of rapid-setting concrete may be conducted sequentially and / or multiple times to form the final additively manufactured structure, where at least a portion of the voids defined by the wall(s) are filled by the rapid-setting concrete. ThisAttorney Docket No. 2115-008422-WO-POA enables inclusion of sharp tubular overhangs and other structures that are often prone to collapse under their own dead load if there is no support or immediate setting of material. The cast liquid fast-setting concrete takes its shape from the wall of 3D-printed concrete formwork and, at the same time, shores up the 3D-printed formwork because of its fast setting time.

[0074] In certain aspects, the casting of fast-setting concrete occurs when the 3D-printed stay-in-place concrete formwork (e.g., at least one wall of the additively manufactured cementitious structure) is still moist and not set. This forms a stronger bond between the wet 3D- printed stay-in-place formwork and cast quick- setting concrete, so that the 3D-printed formwork will be structurally activated. This results in higher compression strength compared to the traditional 3DCP method where the stay-in-place formwork is 3D printed and is cast once the concrete is fully set.

[0075] In certain variations, a traditional reinforcement cage (e.g., made of a metal reinforcement material), that may be CNC bent, is inserted into the stay-in-place concrete formwork sequentially, as it is being 3D printed, following sequential casting with the rapid setting concrete in the void regions defined by the at least one wall of the additively manufactured cementitious structure / stay-in-place concrete formwork.

[0076] In other variations, the methods of the present disclosure may include 3D printing a feature, such as one or more reinforcement component conduits, as part of the stay-in-place formwork for reinforcement integration. For example, the one or more features configured to receive reinforcements may be disposed within the openings defined by the at least one wall of the additively manufactured cementitious structure / stay-in-place concrete formwork. This allows for later integration of reinforcement materials, like a single rebar, carbon fiber flexible cables, or post-tensioning cables, in the feature / conduit. The diameter of the conduit can be greater than or equal to about 4 mm and as large as desired.

[0077] As shown in FIG. 6, the methods of the present disclosure may entail creating two distinct cavities (labeled voids A or 62 and B or 64) within an additively manufactured cementitious structure 60. In this process, the issue of reinforcement may be bypassed. In a typical 3DCP method, the rebar must be integrated into the 3D-printed formwork before casting, posing a challenge, especially when simultaneously addressing the potential collapse of the 3D-printed formwork. As shown in the designs in FIG. 6, the printed cementitious composition (3DCP) defines at least one wall 66 of the additively manufactured cementitious structure / stay-in-place concrete formwork 60. The 3DCP further defines at least three distinct B voids 64 that are conduit features for receiving reinforcements 68. The A voids 62 defined within the wall structures 66 and around the B voids 64 may be at least partially filled with a rapid setting concrete composition 70.Attorney Docket No. 2115-008422-WO-POACasting of the rapid-setting concrete composition 70 may occur intermittently during the printing process of layers 72 to form the at least one wall / shell 66 of the additively manufactured cementitious structure / stay-in-place concrete formwork 60. Further, reinforcements 68 may be optionally placed intermittently during the printing process in the integrated printed features / conduits 64 for receiving wires / reinforcements 68.

[0078] In certain aspects, the at least one layer of the additively manufactured cementitious structure comprises a first layer and at least one additional layer and the method further comprises repeating the depositing of the printable cementitious composition in the non- planar toolpath over the first layer to form the at least one additional layer thereon.

[0079] In certain aspects, the cementitious composition comprises ordinary Portland cement and water. In certain aspects, the cementitious composition further comprises a reinforcement phase.

[0080] In certain aspects, the additively manufactured cementitious structure further comprises at least one reinforcement component, such as one or more selected from the group consisting of: metal rebar, a reinforcement wire, a reinforcement cable, a tensioning mechanism, and combinations thereof.

[0081] One variation of the present methods were tested with a 1:1 scale prototyping of a topologically optimized reinforced structural wall. Another variation was examined through a series of S-shaped specimens representing complex rib scenarios in a materially optimized form. Using normal- setting printable concrete to create SP-formwork, these methods were evaluated to assess a worst-case scenario. Unlike two components (2K) 3DCP, where an accelerator is mixed with the concrete at the end-effector to reduce the setting time of the 3D printed formwork, one component (IK) 3DCP uses a standard concrete mix that sets more slowly, significantly increasing the risk of collapse after several layers. As will be discussed herein, using such methods for forming structures with complex geometries can highlight the challenges to be addressed in order to efficiently 3DCP lightweight structural elements.

[0082] A full-scale load-bearing structure 80 or “Branch Wall,” measuring 1.2 meters in width and 2 meters in height, was designed using computational topology optimization (TO) techniques, as shown in FIGS. 3A-3F. It features an intricate arrangement of branches or ribs 82 with a maximum overhang of 30 degrees and thin membrane sections 84 between these ribs 82. The ribs 82 are aligned at the paths of internal forces given specific six loading points 86, and three supports 88, and act as structural load-bearing areas as shown in the model in FIG. 3A. They are adapted / translated into a non-planar stay-in-place formwork (SP-formwork) system designed to have features formed in internal voids 90 of the printed structure 80 that accommodate rebarAttorney Docket No. 2115-008422-WO-POA92 surrounded by cast concrete of 25 to 35 mm, as shown in FIG. 3B, to accommodate for minimum concrete needed around rebar 92. To optimize the integration of rebar 92 into the 3D printing process, the ribs 82 were simplified into more linear trajectories as shown in FIG. 3C, which helps in incorporating longitudinal rebar 92 more efficiently without the need to segment them into smaller pieces. A simple NP-Path that enables 3DCP along the contour of geometry was generated to direct the end effector of the robotic printing device for variable material deposition.

[0083] Two prototypes were fabricated based on this design, one that was intended for 3DCP the entire structure then integrating rebar and casting it, and one that would involve interrupted integration of rebar and sequential casting. FIG. 3E shows a schematic of a branch 82A with different angles with increasing susceptibility to collapse, as an angle increases. FIG. 3F shows the structure as 3D printed having a branch 82B with a lower angle than in FIG. 3E to avoid collapse. Branches with extreme overhangs (30 degrees), although not problematic during the printing process, were susceptible to collapse from their own weight once they reached a certain height from the bifurcation point (approximately 50 cm). This was because the bonding strength at the layers located at bifurcation was not strong enough to overcome the moment force as the height of the branch increased. The increased weight of the branch can lead to delamination of the interlayers over time, weakening structural integrity as shown in FIG. 3D.

[0084] To address this, a second prototype was successfully fabricated incorporating the casting of set-on-demand concrete (fast- setting) with sequential rebar reinforcement at every 50 cm. This is shown in FIGS. 4A-4D, where sequential rebar 102 integration and casting of a quicksetting concrete 104 in the openings 108 of the printed structure 100 prevents collapse of branches 106 that were collapsed in the earlier prototype. FIG. 4A shows a branch 106 having an extreme overhang that may be susceptible to collapse. In FIG. 4B, the printed structure 100 may have openings 108 defined therein that can receive both metal reinforcement components in the form of rebar 102 and the rapid setting concrete composition 104 that fills the openings 108 and encases the metal reinforcements 102 (shown after filling in FIG. 4C). This process may thus occur sequentially, where the printing with the cementitious material to define the printed structure / formwork 110 that is followed by introducing a reinforcement 102 and / or filling the openings within the printed structure with a rapid setting concrete 104. This may be followed by additional printing and reinforcement steps to form an overall complex structure 100, for example, as shown in FIG. 4D.

[0085] To expand methods for manufacturing complex geometries, NP-3DCP and sequential casting of quick-setting concrete can be conducted, while further 3D printing cavities for later post-tension element placement. To investigate the feasibility of this method, an S-shapedAttorney Docket No. 2115-008422-WO-POA structure 120 featuring internal reinforcement conduits 122 was designed. 50 non-planar layers 124 with heights ranging from 6.5 mm to 17.2 mm, guided the continuous adjustments of the toolhead 126 tilt angle from 0 to 40 degrees relative to the Z-axis, for example as shown in FIG. 5D. Investigations were conducted into how many layers 124 could be 3D printed before casting, as well as how high casting can be to eliminate deformation of 3DCP SP-formwork under hydrostatic pressure. For the printable material used, about 10 cm height (approximately 10 layers) of cast fast-setting material 128 is used for every 20 layers 124 of NP-3DCP, as shown in FIG. 5B. To allow the lower layers 124 to gain sufficient stiffness, 5 cm height of quick-setting concrete 128 was cast in the first 15 layers 124 as shown in FIG. 5A. In the areas where the layer 124 height and overhanging angle were at their maximum, any delay in sequential casting resulted in observed deformation as observed in FIG. 5C. Early tests identified two challenges: determining an optimal ambient temperature for increased buildability before casting and selecting an ideal concrete material rheology for 3DCP of SP-formwork and casting.

[0086] In various aspects, temperature control can increase buildability in 3D concrete printing. Higher temperatures of both the layer surfaces and the surrounding environment can significantly decrease the initial setting time of extruded concrete, helping in buildability. This approach can be used for 3DCP of complex geometry structures with a one-component (IK) system, which generally builds limited early strength. To determine optimal temperature requirements for achieving sufficient early strength, comparative tests at three different temperature settings were conducted: room temperature (22°C), and heated ambient temperature (29.4°C) on a similar shape with a planar path. Maintaining a heated ambient temperature of approximately 29.4°C, which resulted in layer surface temperatures between 23.9-25.6°C, proved effective for the continuous 3DCP of up to 35 layers 130 with variable layer heights in the Z-axis, as shown in FIGS. 7A-7B. Conversely, experiments conducted at room temperature (22°C) showcased layer deformations after 10 layers 130 reflected in the structure shown in FIG. 7C. Thus, in certain variations, the depositing of the printable cementitious material may occur in an environment having a temperature of greater than or equal to about 29°C.

[0087] In certain examples, two different mortars were prepared for 3DCP and casting due to different process-related rheological requirements. 3DCP mortar possesses a high yield stress for shape retention and buildability, whereas casting mortar possesses a low viscosity for excellent formwork-filling. The 3DCP mortar comprises ASTM Type I ordinary Portland cement (OPC) commercially available from Quikrete Holdings, Inc., Boral Micron3 fly ash, fine silica sand with particles sizes of 0.2 to 0.6 mm and superplasticizer were also incorporated into the admixture. The water-to-cement ratio, water-to-binder ratio and sand-to-binder ratio were set at 0.65, 0.33,Attorney Docket No. 2115-008422-WO-POA and 0.35, respectively. Additionally, 0.19 wt.% of superplasticizer, relative to the binder, is included. The casting mortar uses a fast-setting cement from Quikrete Holdings, Inc., characterized by an initial setting time of 10 minutes, with a w / c ratio of 0.14.

[0088] Rheological properties (z.e., plastic viscosity, dynamic viscosity ( / / ), and static yield stress (TS)) were measured using an ICAR Plus rheometer, equipped with a coaxial cylinder having an inner radius of 100 mm and a four-blade vane geometry with a radius of 63.5 mm and a height of 127 mm. The flow curve test protocol involved pre- shearing at 30 rpm for 20 s; followed by actual shearing at an initial speed of 30 rpm and final speed of 0.6 rpm, with data captured at 24 distinct points, each for 5 s. The stress growth test protocol involved pre-shearing at 30 rpm for 20 s; followed by a rest period of 2 minutes; and then continued at 30 rpm until peak stress was reached. The j and TS of 3DCP mortar were tested at ages of 15, 30, 45, and 60 minutes after mixing with water, and the j of casting mortar was tested at ages of 5, 10 and 15 mins. The intervals were selected according to the printing process (i.e., extrusion started 30 mins after mixing with water, which includes the mixing, resting and pumping, and took 30 minutes for printing) and the sequential casting process (i.e., casting started 5 mins after mixing with water) for one batch of the material.

[0089] FIG. 8 presents the results of rheological tests. In the case of 3DCP mortar, the j values were relatively constant below 20 Pa-s at 60 mins, whereas the TS values increased gradually from 277 Pa at 15 mins to 457 Pa at 60 mins. In the case of cast mortar (rapid- setting concrete), the j value increases sharply from 41.9 Pa-s at 5 mins to 190.4 Pa-s at 15 mins.

[0090] In various aspects, the present disclosure contemplates fabrication of additively manufactured / 3D printed cementitious structures having complex geometries inherent in materially optimized form, but without discretization and support material. Thus, the fabrication methods may be conducted in the absence of any scaffolding or other supports. The methods may comprise a hybrid of non-planar 3DCP and sequential casting of fast-setting concrete. To further avoid challenges such as collapse during 3DP of extreme overhangs, one or more of the following strategies may be used. By combining non-planar 3DCP with sequential casting of fast-setting concrete, branches up to 790 mm with 70-degree overhangs may be successfully printed. For example, the Branch Wall weighs 367 kg with load bearing capacity of 3,600 psi, achieving a 68% material reduction compared to traditional concrete walls, and a 76.4% reduction compared to standard 3DCP walls.

[0091] For example, simultaneous 3D concrete printing (3DCP) and sequential casting of fast-setting concrete can be used to fabricate parts with cantilevers and extreme overhangs. The sharp tubular overhangs are often prone to collapse under their own dead load if there is no supportAttorney Docket No. 2115-008422-WO-POA or immediate setting of material. However, the present methods contemplate use of casting of liquid fast- setting concrete into one or more openings defined within the 3D printed formwork, so that the fast- setting concrete takes its shape from the 3D-printed concrete formwork and, at the same time, internally strengthens the 3D-printed formwork because of its fast setting time.

[0092] In this method, the casting of fast- setting concrete can occur when the 3D-printed stay-in-place concrete formwork is still moist and not set. This results in formation of a stronger bond between the wet 3D-printed stay-in-place formwork and cast concrete, so that the 3D-printed formwork will be structurally activated, resulting in higher compression strength compared to the traditional 3DCP method where the stay-in-place formwork is 3D printed and is cast once the concrete is fully set.

[0093] In one variation, the method further contemplates 3D printing integrated features that can serve as a reinforcement conduit configured to receive a structures reinforcement, which forms part of the stay-in-place formwork for reinforcement integration. Thus, sequential placement of reinforcements, like metal rebar, may be employed. In the case of flexible reinforcement materials, like carbon fiber flexible cables or post-tensioning cables, integration with the conduit can occur at a later stage after the structure has been formed. For example, in certain aspects, the method may create two distinct internal cavities, one configured to receive a reinforcement material component and one configured to be at least partially filled with a fastsetting concrete.

[0094] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

Attorney Docket No. 2115-008422-WO-POACLAIMSWhat is claimed is:

1. A method of additive manufacturing a cementitious structure comprising: depositing a printable cementitious composition in a toolpath by passing the printable cementitious composition through a printhead of a robotic additive manufacturing device to deposit the cementitious composition onto a target, wherein the depositing forms at least one layer of a printed shell structure that defines an open region; and introducing a liquid rapid- setting concrete into at least a portion of the open region to reinforce the printed shell structure, wherein after setting, the liquid rapid- setting concrete forms a solid within a hardened printed shell structure that together define a solid additively manufactured cementitious structure.

2. The method of claim 1, wherein the printed shell structure encloses at least a portion of the open region.

3. The method of claim 2, wherein the depositing further forms at least one internal feature defining an open conduit configured to receive a reinforcement component.

4. The method of claim 3, further comprising placing a reinforcement component into the at least one internal feature.

5. The method of claim 4, wherein the placing of the reinforcement component occurs prior to the introducing of the liquid rapid-setting concrete into the open region.

6. The method of claim 5, where the rapid- setting concrete surrounds the reinforcement component in the open region.

7. The method of claim 1, wherein the depositing and the introducing are repeated at least one time to form the solid additively manufactured cementitious structure.

8. The method of claim 1, wherein the depositing occurs in an environment having a temperature of greater than or equal to about 29°C.

9. The method of claim 1, wherein the solid additively manufactured cementitious structure is topology optimized.

10. The method of claim 9, wherein the solid additively manufactured cementitious structure comprises at least one branch or overhang region that is susceptible to collapse under self dead-loading.

11. The method of claim 1, wherein the toolpath is a geometrically informed non- planar (GINP) toolpath and the depositing further comprises employing a geometrically informedAttorney Docket No. 2115-008422-WO-POA variable (GIV) material deposition method that (i) regulates a flow rate of material passing through the printhead during the depositing; (ii) regulates a speed of the printhead; or (iii) both (i) and (ii).

12. The method of claim 1, wherein the depositing comprises (i) regulating a flow rate of cementitious material passing through the printhead, wherein the depositing occurs at a first flow rate for a first duration and the method further comprises adjusting the flow rate of the cementitious material passing through the printhead to a second flow rate distinct from the first flow rate for a second duration.

13. The method of claim 1, wherein the robotic additive manufacturing device is an automated three-dimensional printer at least partially controlled by a computer numerical control (CNC) system.

14. The method of claim 1, wherein the at least one layer comprises a first layer and at least one additional layer and the method further comprises repeating the depositing of the printable cementitious composition in the toolpath over the first layer to form the at least one additional layer thereon.

15. The method of claim 1, wherein the cementitious composition comprises ordinary Portland cement and water.

16. The method of claim 15, wherein the cementitious composition further comprises a reinforcement phase.

17. The method of claim 1, wherein the solid additively manufactured cementitious structure further comprises at least one reinforcement component selected from the group consisting of: metal rebar, a reinforcement wire, a reinforcement cable, a tensioning mechanism, and combinations thereof.

18. The method of claim 1, wherein the method occurs without using any scaffolding to form the solid additively manufactured cementitious structure.

19. A method of additive manufacturing a cementitious structure comprising: depositing a printable cementitious composition in a toolpath by passing the printable cementitious composition through a printhead of a robotic additive manufacturing device to deposit the cementitious composition onto a target, wherein the depositing forms at least one layer of a printed shell structure with an open region and at least one internal feature within the open region defining an open conduit configured to receive a reinforcement component, wherein the printed shell structure and the open conduit comprising the reinforcement component together define an additively manufactured cementitious structure.

20. The method of claim 19, further comprising placing a reinforcement component into the at least one internal feature after the depositing.Attorney Docket No. 2115-OQ8422-WO-POA21. The method of claim 19, wherein the depositing occurs for a first duration, the method further comprises placing a reinforcement component into the at least one internal feature after the first duration, and the method further comprises continuing the depositing after the placing.

22. The method of claim 19, wherein the additively manufactured cementitious structure is topology optimized.

23. The method of claim 19, wherein the additively manufactured cementitious structure further comprises at least one reinforcement component selected from the group consisting of: metal rebar, a reinforcement wire, a reinforcement cable, a tensioning mechanism, and combinations thereof.

24. The method of claim 19, wherein the method occurs without using any scaffolding to form the additively manufactured cementitious structure.

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