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MATERIAL DESIGN AND PROPERTIES OF GEO POLYMER MORTAR FOR APPLICATIONS IN 3DPRINTING
ABSTRACT
The objective of this research was to design a 3D printable alkali-activated metakaolinbased geopolymer formula and to explore the effect of its components on material properties of fresh and hardened binder. These objectives were fulfilled by performing a series of experiments to determine the flowability, shape stability and strength of the geopolymer based binder.
A statistical mixture design technique was adopted to formulate 21 mixtures with predetermined content ranges of each component (water, sodium metasilicate, metakaolin and basalt) for the regression model creation and investigation of each component’s effect on the response variables, i.e., flowability, initial setting time and final setting time. The regression results showed water content governed the change of flowability and sodium metasilicate content had the largest effect on both the initial setting time and final setting time among the four components investigated.
Based on layer deposition simulation results, the optimal mixture for 3D printing was determined for its satisfactory flowability and fast-growing shape stability among the five potentially printable mixtures candidates. Also, these five candidates served as verifications of the response variables’ regression model. The final setting time’s high variance observed in the experimental results of the candidates confirmed the high standard deviation mentioned in ASTM 191-13 and the regression model’s poor prediction ability.
The compressive strength of the designed geopolymer was found to be significantly reduced with the increase of water/solid ratio, and the increase in the content of sodium metasilicate designed specifically for geopolymers had variable effects on the 28d compressive strength. A novel geopolymer superplasticizer enhanced the flowability and the 24h compressive strength with the increase of the superplasticizer dosage. However, the 7d compressive strength decreased with the increasing dosage of superplasticizer.
The results of this study indicated: 1. Water content and sodium metasilicate have the largest effect on the flowability and setting time, respectively. 2. Metakaolin based geopolymer can serve as a potential candidate for 3D printing. 3. The increasing water content reduced the compressive strength, while sodium metasilicate below a certain content can enhance the 28d compressive strength of geopolymer. 4. The superplasticizer increased the flowability, increased the 7d compressive strength, and decreased the 28d compressive strength of geopolymer.
Table of Contents
List of Figures vii
List of Tables x
Acknowledgements xii
Chapter 1 Objectives and Organization 1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Research Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Chapter 2 Description of geopolymer concrete for 3D printing 3
2.1 3D Technology Applied in Architecture . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Introduction to Geopolymer Concrete . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Printablity and Buildability in 3D Material Design . . . . . . . . . . . . . . . . 23
Chapter 3 Materials and Testing Procedures 31
3.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.2 Mixing Procedure & Solution pH Measurement . . . . . . . . . . . . . . . . . . 33
3.3 Flow Table Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.4 Setting Time Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.5 Compressive Strength Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Chapter 4 Experimental Design, Results and Discussion 38
4.1 Design of Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.2 Experiment Result Analysis and Response Variable Model Formation . . . . . . 40
4.2.1 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.2.2 Flowability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.2.3 Initial Setting Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.2.4 Final Setting Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.3 Model Verification, Empirical Layer Deposition Simulation and Compressive
Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.3.1 Model Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.3.2 Empirical Layer Deposition Simulation . . . . . . . . . . . . . . . . . . . 51
4.3.3 Compressive Strength Analysis . . . . . . . . . . . . . . . . . . . . . . . 53
4.4 Superplasticier Effect on Flowability and Compressive Strength . . . . . . . . . 57
Chapter 5 Conclusions and Further Research 59
5.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
5.2 Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
References 63
Appendix 70
Chapter 1 Objectives and Organization
1.1 Introduction
3D printing technology, also called additive manufacturing, is becoming more and more prevalent in engineering fields. This technology is being adopted by the construction industry due to its advantages over the traditional approach, including decreased cost of labor, accelerated construction, improved work safety, and more. However, unlike traditional concrete, 3D printing has its own unique material requirements, as during the 3D printing operation, the mixture is printed layer by layer through a nozzle. Printable materials require high flowability before being extruded and sufficient hardening rate is required to maintain shape stability after being deposited. In comparison with cement-based materials, geopolymers typically possess a shorter setting time, i.e., the layer is able to harden faster and subsequently increases the printing rate. As such, these materials were investigated to a great depth in this research.
In order to achieve the goal of successful printing, flowability and setting time are two parameters adopted for the evaluation of the material’s feasibility in 3D printing. The statistical mixture design was used in this work to explore the effect of each mixture component on the responses variables and their models were also created for seeking the optimal mixture for printing. This was achieved by finding a balance between three responses properties (i.e., flowability, initial setting time and final setting time) and layered deposition simulation results. The compressive strength of the material was concurrently investigated and a novel superplasticizer was explored for promoting material’s behavior in 3D printing.
1.2 Research Objective
The purpose of this thesis is to design new geopolymer mixtures that could be successfully 3D printed and to experimentally investigate the mixture components and superplasticizer’s effect on fresh and hardened material properties.
1.3 Outline
This thesis contains 5 chapters. Chapter 1 includes background information and research objectives. Chapter 2 summarizes the literature review on the current progress in material advancement for 3D Printing. Chapter 3 presents experimental methods conducted in this research. Chapter 4 describes the experimental results, data analysis and optimal mixture determination for 3D printing. Chapter 5 concludes the findings and discussions of this research and proposes potential improvements for further research on 3D printable materials.
MATERIAL DESIGN AND PROPERTIES OF GEO POLYMER MORTAR FOR APPLICATIONS IN 3DPRINTING
