Experimental Prediction of Material Deformation and Toolpath Design Compensation in Large-Scale Additive Manufacturing of Concrete

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- Author:
- Ashrafi, Negar
- Graduate Program:
- Architecture
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- March 10, 2022
- Committee Members:
- Jose Pinto Duarte, Chair & Dissertation Advisor
Sven Bilén, Outside Unit Member
Ali Memari, Outside Field Member
Nicholas Alexander Meisel, Special Member
Aleksandra Radlinska, Outside Field Member
Ute Poerschke, Program Head/Chair
Shadi Nazarian, Dissertation Co-Advisor - Keywords:
- Additive Manufacturing of Concrete
Robotic Fabrication
3D printing concrete
Toolpath Design
Toolpath Compensation
Shape Grammar - Abstract:
- In extrusion-based Additive Manufacturing (AM), parts are produced by extruding material through a nozzle, which is deposited layer by layer along a trajectory defined by a toolpath. In recent years, there has been a growing interest in applying AM at the construction scale, which can bring many advantages, including increased labor safety and reduced use of resources, construction time and cost. This may lead to more affordable and sustainable buildings, including housing, an important outcome in the context of strong population growth and urbanization processes. Concrete is the most common building material worldwide due to the availability of its raw materials, strength, durability, fire resistance, and cost. Because of its fluid state before setting, concrete can be extruded through a nozzle and, therefore, it is suitable material for use in AM. However, such an application encounters many challenges as extruded concrete takes time to harden and, therefore, presents a behavior that is radically different from that of materials used for small-scale AM. As such, the software used to generate toolpaths in small-scale AM cannot be efficiently used in AM of concrete, as it may be necessary to compensate for material deformation in toolpath design. This dissertation presents a methodological framework to slice geometries for concrete printing purposes and generate compensated toolpaths based on material deformation. The study is comprised of two main parts. In the first part, concrete deformation behavior was modeled using an experimental approach and regression analysis. Different mathematical models were developed to predict the material deformation under the influence of different variables such as extrusion rate, time, number of printed layers, and printed beads. In the second part, the developed equations were used to develop an algorithm to compensate for material deformation in the design of the toolpath. Subsequently, a shape grammar that captures existing toolpath design strategies was developed. The algorithm was then incorporated into the grammar to generate compensated toolpaths. In the last step of this research, two other experiments were conducted to print compensated toolpaths, validating the algorithm and the shape grammar. Although the developed equations are valid for the specific material used, with its specific mix design, or for materials with similar rheological and hardening properties, the same research methodology can be used to infer equations for other materials, which can then be incorporated into the proposed algorithm.
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