Additively Printed Cementitious Structures with Interlocking Contours

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Solution Overview

Problem

Existing additively printed cementitious structures, such as concrete wind turbine towers, face challenges in interlayer bonding due to the limited availability of cementitious material for crystallization and physical blockages during the hydration process, leading to inadequate structural integrity and increased void spaces between layers.

Innovation Solution

Incorporating contour coupling features in the cementitious structures that nest, mate, overlap, or interlock with each other, along with the use of an adhesive formulation to supplement interlayer bonding, allowing for improved mechanical coupling and reduced void spaces, while maintaining sufficient flowability and slump to ensure effective layer formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If cementitious material is allowed to cure rapidly to enable layer-by-layer printing, then printing productivity is improved, but interlayer bonding strength deteriorates due to limited availability of cementitious material for crystallization

Engineering Contradiction:

Improveprinting speedVSAvoidinterlayer bonding strength

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The patent introduces contour coupling features (protrusions and recesses) that are pre-formed into the cementitious material layers before curing completes. These mechanical interlocking features are created in advance during the printing process, ensuring that even with rapid curing that limits crystallization-based bonding, the layers will mechanically interlock through the pre-designed coupling geometries that engage across layer interfaces.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent divides the continuous cementitious material deposition into discrete contours with specific coupling features. Each layer is segmented into controllable portions that can be independently formatted with protrusions and recesses, allowing the bonding mechanism to be separated into mechanical interlocking (contour coupling) and chemical bonding (crystallization) components, thereby compensating for reduced chemical bonding due to rapid curing.

Inventive Principle:

Principle #1Segmentation

2Stability of the object's composition

If cementitious material cures quickly to support subsequent layers, then structural stability during printing is improved, but void spaces increase due to physical blockages during hydration

Engineering Contradiction:

Improvelayer stabilityVSAvoidvoid space volume

Core Design Contradiction:

Stability of the object's compositionVSQuantity of substance

Solution Approach 1:

The contour coupling features are pre-formed into the cementitious material during extrusion, creating defined pathways and engagement zones before the material fully cures. This preliminary structuring ensures that when material is deposited between contours, it has designated spaces to flow into and bond with adjacent layers, preventing random void formation that occurs when unstructured material tries to fill spaces after physical blockages have formed during rapid hydration.

Inventive Principle:

Principle #10Preliminary action

3Strength

If adhesive formulation is added to supplement interlayer bonding, then bonding strength is improved, but material flowability may deteriorate

Engineering Contradiction:

Improveinterlayer bonding strengthVSAvoidmaterial flowability

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The adhesive formulation is applied locally at the contour coupling interfaces rather than being uniformly mixed throughout the entire cementitious material. This localized application ensures that the adhesive enhances bonding strength at the critical interlayer contact zones without altering the rheological properties of the bulk material, thereby maintaining the necessary flowability for layer deposition while providing supplemental bonding where it is most needed.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enhances the structural integrity of additively printed cementitious structures by improving interlayer bonding through mechanical coupling and adhesive supplementation, reducing void spaces, and allowing for more efficient curing processes, resulting in stronger and more cohesive layers.

Implementation Method 1

cementitious materials such as concrete cure through a chemical reaction called hydration, whereby water reacts with calcium silicate and other hydration products form crystals which give cured cementitious materials their hardness

Methodology Applied

Scientific EffectHydration: Mineral Hydration

Implementation Method 2

Hydration products may form crystals that grow across interlayer boundaries and thereby bond layers to one another though interlayer crystallization

Methodology Applied

Scientific EffectInterlayer crystallization: Crystallisation

Data Source

PatentUS11511457B2Additively printed cementitious structures and methods of manufacturing same

Publication Date: 2022.11.29 GE INFRASTRUCTURE TECH LLC

AI summary

Methods of manufacturing a cementitious structure, such as a structure for supporting a wind turbine, include additively printing, via an additive printing device, one or more contours that include a cementitious material so as to form a cementitious structure in a layer by layer manner such that a first portion of the plurality of contours comprises a first plurality of contour coupling features that engage with a second plurality of contour coupling features of a second portion of the plurality of contours.