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Structural Integrity and Shrinkage Behavior of 3D Printing Concrete · 2019-12-10 · Structural...

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Structural Integrity and Shrinkage Behavior of 3D Printing Concrete Discipline : Civil Engineering More Information Concrete Extrusion 1. Introduction mixtures is lower than the conventional concrete mixtures. The higher surface exposure of freeform concrete can result in higher evaporation rate, leading to very low moisture content and a lower hydration degree of printed products. Mohsen Rezaei Shahmirzadi PhD Candidate Supervisors: Prof. Tuan Ngo, Dr. Alireza Kashani E-mail: [email protected] Room B404, Building 175, Department of Infrastructure Engineering https://infrastructure.eng.unimelb.edu.au/people/research-students/#Rezaei Concrete 3D printing and conventional concrete casting processes are different in many aspects. In 3D printing, no formwork exists to cover the surface of freshly printed concrete, and water-to-binder ratio of printable a. Construction Practice & Mix Design - Using coarse aggregate limitation - Higher amount of Cement - Lower W/C ratio b. Curing Condition: - Higher surface exposure - Almost impracticable post- processing - Layered structure and final product’s lower structural integrity Local capillary water-intake at the interfaces and Cracks Non-uniform Shrinkage Effective parameters in controlling the shrinkage behavior of printing concrete are divided into two main categories: 3D Printing Environment, and Construction Practice. Concrete 3D-Printing Vs. Conventional Concrete Casting How the freeform nature of 3D printing and climatic parameters (T, RH, Wind) affect the structural integrity and shrinkage behavior of 2. Methodology Simulating the Printing Environment and Free-form condition by Changes in T and %RH and Removing Mould after Initial Setting Time respectively. A thixotropic 3D printing concrete with a following composition was developed. The workability and printing quality have been studied by using a drop flow table and concrete rheology tests. Drying shrinkage experiments have been started according to different international standards with different S/V ratio. Samples have been cast in prismatic mould and kept in different curing condition of temperature and relative humidity for 28 days. To simulate freeform condition, all the samples have been de- moulded after their initial setting time of nearly 4 hours. Real 3D Printed samples also will be tested with the same condition and the mass loss and dimensional stability will be compared. OPC Based 3D Printing concrete mix composition *in percentage of cement mass S/C W/C Silica Fume* High Range Water Reducer* Thicker Agent* 0.8-1.2 0.35 2% 0.26% 0.01% H=Humidity T= Temperature H L T L 45% - 15 C H L T H 45% - 35 C Standard 50% - 24 C H H T L 85-90% - 15 C H H T H 85-90% - 35 C H: high L: low Standard Designation Size Initial Curing Condition S/V AS 1012.13-2015 AS 1012.8.4-2015 75 x 75 x 280 mm3 23 ± 2 ̊ C 50 ± 5% RH 0.60 BS EN 12617-4: 2002 BS EN 196-1: 2005 40 x 40 x 160 mm3 21 ± 2 ̊ C 60 ± 10% RH 1.125 ASTM C157 ASTM C511 ASTM C490 25 x 25 x 285 mm3 23 ± 2 ̊ C 50 ± 4% RH 1.67 Curing Condition Standard Designation and Experiments Condition 3. Result & Discussion In this study, a 3D printing concrete has been successfully developed based on initial yield strength and spread diameter within an optimum control range of 200-2000 Pa and 214-243 mm respectively. Drying shrinkage strain of these printable mixes is being measured in four different conditions obtained from the combination of High and Low humidity and temperature. The results of this study can be helpful to provide better curing condition considering the relationship between the printing environment condition and dimensional stability of printed products. printable Geopolymer and Concrete compare to casting condition? Research Question Shrinkage Measurements of Printed Parts
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Page 1: Structural Integrity and Shrinkage Behavior of 3D Printing Concrete · 2019-12-10 · Structural Integrity and Shrinkage Behavior of 3D Printing Concrete Discipline : Civil Engineering

Structural Integrity and Shrinkage Behavior of 3D Printing Concrete

Discipline : Civil Engineering

More Information

Concrete Extrusion

1. Introduction

mixtures is lower than the conventional concrete mixtures. The highersurface exposure of freeform concrete can result in higher evaporationrate, leading to very low moisture content and a lower hydration degree ofprinted products.

Mohsen Rezaei ShahmirzadiPhD CandidateSupervisors: Prof. Tuan Ngo, Dr. Alireza Kashani

E-mail: [email protected] B404, Building 175, Department of Infrastructure Engineering

https://infrastructure.eng.unimelb.edu.au/people/research-students/#Rezaei

Concrete 3D printing and conventional concrete casting processes aredifferent in many aspects. In 3D printing, no formwork exists to cover thesurface of freshly printed concrete, and water-to-binder ratio of printable

a. Construction Practice & Mix Design

- Using coarse aggregate limitation- Higher amount of Cement- Lower W/C ratio

b. Curing Condition:- Higher surface exposure- Almost impracticable post-

processing - Layered structure and final

product’s lower structural integrity

✓ Local capillary water-intake at the

interfaces and Cracks✓ Non-uniform Shrinkage

Effective parameters in controlling the shrinkage behavior of printingconcrete are divided into two main categories: 3D Printing Environment,and Construction Practice.

➢ Concrete 3D-Printing Vs. Conventional Concrete Casting

How the freeform nature of 3D printing andclimatic parameters (T, RH, Wind) affect thestructural integrity and shrinkage behavior of

2. MethodologySimulating the Printing Environment and Free-form condition by Changes in T and%RH and Removing Mould after Initial Setting Time respectively.

A thixotropic 3D printing concrete with a following composition was developed. Theworkability and printing quality have been studied by using a drop flow table andconcrete rheology tests. Drying shrinkage experiments have been started according todifferent international standards with different S/V ratio. Samples have been cast inprismatic mould and kept in different curing condition of temperature and relativehumidity for 28 days. To simulate freeform condition, all the samples have been de-moulded after their initial setting time of nearly 4 hours. Real 3D Printed samples alsowill be tested with the same condition and the mass loss and dimensional stability willbe compared.

OPC Based 3D Printing concrete mix composition

*in percentage of cement mass

S/C W/CSilica

Fume*High Range

Water Reducer*Thicker Agent*

0.8-1.2 0.35 2% 0.26% 0.01%

H=HumidityT= Temperature

HL TL 45% - 15 C

HL TH 45% - 35 C

Standard 50% - 24 C

HH TL 85-90% - 15 C

HH TH 85-90% - 35 C

H: highL: lowStandard Designation Size

Initial Curing

ConditionS/V

AS 1012.13-2015

AS 1012.8.4-201575 x 75 x 280 mm3

23 ± 2 ̊C

50 ± 5% RH0.60

BS EN 12617-4: 2002

BS EN 196-1: 200540 x 40 x 160 mm3

21 ± 2 ̊C

60 ± 10% RH1.125

ASTM C157

ASTM C511

ASTM C490

25 x 25 x 285 mm323 ± 2 ̊C

50 ± 4% RH1.67

Curing Condition

Standard Designation and Experiments Condition

3. Result & Discussion

In this study, a 3D printingconcrete has been successfullydeveloped based on initial yieldstrength and spread diameterwithin an optimum control rangeof 200-2000 Pa and 214-243 mmrespectively. Drying shrinkagestrain of these printable mixes isbeing measured in four differentconditions obtained from thecombination of High and Low humidity and temperature. The results ofthis study can be helpful to provide better curing condition consideringthe relationship between the printing environment condition anddimensional stability of printed products.

printable Geopolymer and Concrete compare to casting condition?

➢Research Question

➢Shrinkage Measurements of Printed Parts

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