3D Printed Cementitious Structures with Graded Lightweight Aggregates
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Solution Overview
Problem
Existing methods for additive manufacturing with cementitious materials struggle to achieve a balance between low density and high compressive strength, often resulting in inhomogeneous curing and cracking due to excessive heat release during hydration.
Innovation Solution
A method using a combination of cement, slag, and suitable activators as a cementitious binder, paired with lightweight aggregates of optimized particle size distribution, to create 3-dimensional objects with low density and high compressive strength, while minimizing heat release during curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If standard aggregate is replaced by lightweight fillers to lower density, then density decreases, but compressive strength decreases
Solution Approach 1:
The patent changes the particle size parameters of lightweight fillers by classifying them into coarse (0.63-5.00 mm), medium (0.16-0.63 mm), and fine (0.006-0.16 mm) categories. By optimizing the proportion of each size class within the total filler content, the patent achieves improved packing density that maintains compressive strength while preserving low density characteristics.
Solution Approach 2:
The patent creates a composite filler system combining multiple sizes of lightweight fillers (expanded clay, expanded perlite, or pumice) with cementitious binder. This composite approach allows smaller particles to fill voids between larger particles, optimizing the overall packing structure and achieving both low density and adequate compressive strength.
2Strength
If cement content is increased to counteract reduced compressive strength from lightweight fillers, then compressive strength improves, but heat flow from hydration increases
Solution Approach 1:
The patent optimizes the cement content parameter within a specific range (30-60 wt% of total dry mixture) rather than simply increasing it. This controlled parameter adjustment, combined with optimized filler proportions, achieves adequate compressive strength while limiting excessive heat generation from cement hydration.
Solution Approach 2:
The patent creates local density variations through the graded particle size distribution of fillers, where different size classes are strategically distributed. This allows for optimized packing in different regions of the material structure, achieving strength requirements without uniformly increasing cement content throughout the entire mixture.
3Strength
If increased cement content is used to improve compressive strength, then compressive strength increases, but inhomogeneous curing and cracking occur
Solution Approach 1:
The patent adjusts the water-to-cement ratio parameter within the range of 0.20-0.40 and optimizes cement content to 30-60 wt% of total dry mixture. These parameter changes ensure adequate strength development while maintaining uniform curing by preventing excessive heat localization that would cause thermal gradients and cracking.
Solution Approach 2:
The patent achieves homogeneous curing by creating a uniform distribution of graded lightweight fillers throughout the cementitious matrix. The optimized particle size distribution ensures consistent packing and stress distribution, preventing localized weak zones that would lead to cracking during curing.
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
The method achieves 3-dimensional objects with densities not exceeding 1800 kg/m3 and compressive strengths of at least 15 MPa after 1 day of curing, offering improved mechanical properties and reduced thermal issues.
Implementation Method 1
mixing a dry cementitious composition with water... curing the 3-dimensional object
Implementation Method 2
applying the mixture obtained under a) from said print head to form a 3-dimensional object
Data Source
AI summary
A method of printing a 3-dimensional object, the method including the steps of mixing a dry cementitious composition with water, conveying the mixture obtained to a print head, applying the mixture from the print head layer-by-layer to form a 3-dimensional object, curing the 3-dimensional object, wherein the dry cementitious composition includes at least one cement, at least one type of slag, at least one activator for the slag, and at least two lightweight aggregates of different particle size.