Effect of printing parameters on interlayer bond strength of 3D printed limestone-calcined clay-based cementitious materials: An experimental and numerical study

This paper investigates the effect of polypropylene (PP) fibres on the fresh and hardened properties of 3D-printed fibre-reinforced geopolymer mortars. Different percentages of PP fibres ranging between 0.25% and 1.00% by volume were added to an optimised geopolymer mixture. All samples showed reasonable workability and extrudability. In addition, shape-retention ability in the fresh state was investigated as a major requirement for 3D-printing. The compressive strength of the printed specimens was tested in the hardened state in three loading directions, viz. longitudinal, perpendicular, and lateral. The flexural strength of samples was also tested in the longitudinal and lateral directions. In addition, the interlayer bond strength was investigated. Fibre addition seems to influence compressive strengths positively only when the loading is perpendicular to the interface plane. This is due to the preferential fibre alignment parallel to the direction of extrusion. The addition of fibre significantly enhanced the flexural performance of the printed samples. The use of fibre dosages of 0.75 and 1.00 vol % caused deflection-hardening behaviour of the 3D-printed geopolymers and, hence, a significantly higher fracture energy in comparison to specimens without fibre or with lower fibre content. However, an increase in the fibre volume caused some minor reduction in interlayer bond strength. With respect to properties in the fresh state, higher fibre volumes caused better shape-retention ability in the printed samples. The results indicate the possibility of printing fibre-reinforced geopolymers which meet all the necessary properties in both the fresh and hardened states.

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Effect of Type of Fiber on Inter-Layer Bond and Flexural Strengths of Extrusion-Based 3D Printed Geopolymer

Materials Science Forum ◽

10.4028/www.scientific.net/msf.939.155 ◽

2018 ◽

Vol 939 ◽

pp. 155-162 ◽

Cited By ~ 24

Author(s):

Behzad Nematollahi ◽

Ming Xia ◽

Jay Sanjayan ◽

Praful Vijay

Keyword(s):

Flexural Strength ◽

Bond Strength ◽

Fused Deposition Modeling ◽

Shear Failure ◽

Cementitious Materials ◽

Tensile Failure ◽

Layer By Layer ◽

Fused Deposition ◽

Rate Of Increase ◽

3D Printed

Extrusion-based 3D concrete printing is analogous to fused deposition modeling method, which extrudes cementitious materials from a nozzle to build a complex concrete structure layer-by-layer without the use of expensive formwork. This study aims to investigate the influence of type of fiber on inter-layer bond strength and flexural strength of extrusion-based 3D printed geopolymer. An extrudable fly ash-based geopolymer composition previously developed by the authors was reinforced by three types of fibers, namely polyvinyl alcohol (PVA), polypropylene (PP) and polyphenylene benzobisoxazole (PBO) fibers. Control geopolymer specimens with no fiber were also 3D printed for comparison purposes. The results indicated that the incorporation of fibers reduced the inter-layer bond strength of 3D printed geopolymer. This pattern was true regardless of the type of fiber. On the other hand, the flexural strength of 3D printed fiber-reinforced geopolymer mixtures was substantially higher than that of the 3D printed geopolymer with no fiber. The rate of increase in the flexural strength depended on the type of fiber. The flexural failures of the specimens were due to the tensile failure of the bottom layer, rather than the shear failure of the interfaces.

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Effect of Structural Build-Up on Interlayer Bond Strength of 3D Printed Cement Mortars

Materials ◽

10.3390/ma14020236 ◽

2021 ◽

Vol 14 (2) ◽

pp. 236

Author(s):

Tinghong Pan ◽

Yaqing Jiang ◽

Hui He ◽

Yu Wang ◽

Kangting Yin

Keyword(s):

Bond Strength ◽

Surface Moisture ◽

Cement Mortars ◽

Nano Clay ◽

3D Printed ◽

Time Gap ◽

The Relationship ◽

Insight Into ◽

Interlayer Bond ◽

Operational Time

Understanding the relationship between the intrinsic characteristics of materials (such as rheological properties and structural build-up) and printability and controlling intrinsic characteristics of materials through additives to achieve excellent printability is vital in digital concrete additive manufacturing. This paper aims at studying the effects of material’s structural build-up on the interlayer bond strength of 3DPC with different time gaps. Structural build-up can indirectly affect the interlayer bond strength by affecting the surface moisture of concrete. Based on the structural build-up of 3DPC, a new parameter, maximum operational time (MOT), is proposed, which can be considered as the limit of time gap to ensure high interlayer bond strength. Slump-retaining polycarboxylate superplasticizer (TS) slightly slows down the physical flocculation rate, but increases the maximum operational time of the cement paste. Nano clay significantly increases the sort-term structural build-up rate and has the function of internal curing and water retaining. Composite with nano-clay and TS can reduce the loss of surface moisture of 3D printed layers, prevent the formation of interface weak layer, and increase the interlayer bond strength between printed layers. This contribution can provide new insight into the design of 3D-printed ink with good extrudability, outstanding buildability, and excellent interlayer bond strength.

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Chloride Induced Corrosion and Carbonation in 3D Printed Concrete

Infrastructures ◽

10.3390/infrastructures7010001 ◽

2021 ◽

Vol 7 (1) ◽

pp. 1

Author(s):

Jean De’M Malan ◽

Algurnon Steve van Rooyen ◽

Gideon P. A. G. van Zijl

Keyword(s):

Carbon Dioxide ◽

Flexural Strength ◽

Bond Strength ◽

Lack Of Fusion ◽

Durability Properties ◽

Chloride Induced Corrosion ◽

3D Printed ◽

Strength And Durability ◽

Durability Performance ◽

Interlayer Bond

The durability of reinforced concrete structures is dependent on the ability of the concrete cover to combat the ingress of chlorides and carbon dioxide in marine and urban environments. In recent years, interest in additive manufacturing), specifically referring to extrusion based three-dimensional concrete printing (3DCP), has been growing in the construction industry. Despite this being a promising technology that can save construction time, costs and resources, certain issues regarding the lack of fusion between subsequent printed layers have been brought to light. Research has shown that the lack of fusion at the interlayer regions can act as ingress pathways for corrosion contaminants, such as carbon dioxide and chloride aqueous solution, that can cause deterioration. This study investigates the interlayer bond strength (flexural strength) and durability performance of 3D printed concrete subjected to pass times between 0 and 30 min and compares the results to reference cast concrete of the same concrete mixture. The durability study includes Durability Index testing (oxygen permeability, water sorptivity and chloride conductivity index), accelerated concrete carbonation and chloride-induced corrosion. The results show that the cast samples outperform printed samples, yielding greater flexural strength and durability properties, and emphasize the importance of improving the 3DCP interfacial bond. Cast samples are shown to have randomly distributed, compact voids compared to the interconnected and elongated pores located at the interlayer regions of printed samples. In addition, printed samples yield lower interlayer bond strength and durability properties with an increase in pass time, which is attributed to surface moisture evaporation as well as the thixotropic behaviour of the concrete mixture. Good relationships between the mechanical strength and durability performance are also presented.

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A Concise Review on Interlayer Bond Strength in 3D Concrete Printing

Sustainability ◽

10.3390/su13137137 ◽

2021 ◽

Vol 13 (13) ◽

pp. 7137

Author(s):

Adewumi John Babafemi ◽

John Temitope Kolawole ◽

Md Jihad Miah ◽

Suvash Chandra Paul ◽

Biranchi Panda

Keyword(s):

Bond Strength ◽

Critical Parameters ◽

Printing Process ◽

Interface Reactions ◽

Current State ◽

Concise Review ◽

Established Fact ◽

3D Printed ◽

Key Aspects ◽

Interlayer Bond

Interlayer bond strength is one of the key aspects of 3D concrete printing. It is a well-established fact that, similar to other 3D printing process material designs, process parameters and printing environment can significantly affect the bond strength between layers of 3D printed concrete. The first section of this review paper highlights the importance of bond strength, which can affect the mechanical and durability properties of 3D printed structures. The next section summarizes all the testing and bond strength measurement methods adopted in the literature, including mechanical and microstructure characterization. Finally, the last two sections focus on the influence of critical parameters on bond strength and different strategies employed in the literature for improving the strength via strengthening mechanical interlocking in the layers and tailoring surface as well as interface reactions. This concise review work will provide a holistic perspective on the current state of the art of interlayer bond strength in 3D concrete printing process.

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The Effect of Material Fresh Properties and Process Parameters on Buildability and Interlayer Adhesion of 3D Printed Concrete

Materials ◽

10.3390/ma12132149 ◽

2019 ◽

Vol 12 (13) ◽

pp. 2149 ◽

Cited By ~ 26

Author(s):

Biranchi Panda ◽

Nisar Ahamed Noor Mohamed ◽

Suvash Chandra Paul ◽

GVP Bhagath Singh ◽

Ming Jen Tan ◽

...

Keyword(s):

Bond Strength ◽

Process Parameters ◽

Control Sample ◽

Cementitious Materials ◽

Nano Particles ◽

High Yield ◽

Adhesion Properties ◽

Low Viscosity ◽

Main Challenge ◽

3D Printed

The advent of digital concrete fabrication calls for advancing our understanding of the interaction of 3D printing with material rheology and print parameters, in addition to developing new measurement and control techniques. Thixotropy is the main challenge associated with printable material, which offers high yield strength and low viscosity. The higher the thixotropy, the better the shape stability and the higher buildability. However, exceeding a minimum value of thixotropy can cause high extrusion pressure and poor interface bond strength if the printing parameters are not optimized to the part design. This paper aims to investigate the effects of both material and process parameters on the buildability and inter-layer adhesion properties of 3D printed cementitious materials, produced with different thixotropy and print head standoff distances. Nano particles are used to increase the thixotropy and, in this context, a lower standoff distance is found to be useful for improving the bond strength. The low viscosity “control” sample is unaffected by the variation in standoff distances, which is attributed to its flowability and low yield stress characteristics that lead to strong interfacial bonding. This is supported by our microscopic observations.

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