Hardened properties of 3D printed concrete: The influence of process parameters on interlayer adhesion

Wolfs, Rob; Bos, Freek; Salet, Theo A.M.

doi:10.1016/j.cemconres.2019.02.017

Cited by 444 publications

(215 citation statements)

References 22 publications

(35 reference statements)

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“…The average results of the compressive test are listed in Table 4 and shown in Figure 6a. The performance of the cast specimens is almost identical to results reported by Wolfs, Bos, and Salet (2019), while the performance of the printed specimens is slightly better. The addition of fibres seems to cause a minor decrease in strength for the cast specimens.…”

Section: Compressive Strengthsupporting

confidence: 79%

“…Cast and printed specimens without and with Fibraflex FF15E0 high-strength steel fibres were subjected to 3 mechanical tests: compressive cube strength, flexural bending test and crack-mouth opening displacement (CMOD). The printed specimens were tested in two directions, namely directions I (parallel to the print direction) and III (vertically perpendicular to print direction, as defined by (Wolfs, Bos, and Salet 2019). Printed specimens with Cem-FIL minibars 24 mm glass fibres were subjected CMOD testing, in direction I.…”

Section: Methodsmentioning

confidence: 99%

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On-demand additive manufacturing of functionally graded concrete

Ahmed

Bos

Brunschot

et al. 2020

Virtual and Physical Prototyping

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The rapid development of additive manufacturing of cementitious materials has enabled the emergence of a new design paradigm, namely functional grading of material properties by location. Target performance parameters could be material weight and insulation value or (particularly important) ductility. A generic concept to achieve this, is through the selective addition of fibres or aggregates. In 3D concrete printing (3DCP), this concept can be developed into two strategies: by adding particles (i) to the bulk mixture through a second stage mixing process at the printer head (Simultaneous Process, SP), or (ii) in between the layers of deposited cementitious filament (Repetitive Sequential Process, RSP). The present paper presents the development of specific equipment required to obtain on-demand functional grading of the printed material. Subsequently, the application of these systems in print trials is shown. The current study focussed on ductility by creating fibre-reinforced 3D printed concrete through both strategies. The mechanical performance of the obtained material has been established through compressive, flexural, and crack-mouth opening displacement tests. To underline the generic nature of the strategies, a trial with lightweight aggregates has also been performed. It was shown that particularly the SP is capable of achieving improvements in ductility and selfweight.

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Section: Compressive Strengthsupporting

confidence: 79%

Section: Methodsmentioning

confidence: 99%

On-demand additive manufacturing of functionally graded concrete

Ahmed

Bos

Brunschot

et al. 2020

Virtual and Physical Prototyping

Self Cite

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“…Other study such as Wolfs et al, Hosseini et al and Marchment et al focused on the bond between layers [38][39][40][41]. As previously reported in the literature, the interlayer adhesion between two printed layers is time sensitive [38].…”

Section: State Of the Art And Research Objectivesmentioning

confidence: 92%

Experimental Approach for Printability Assessment: Toward a Practical Decision-Making Framework of Printability for Cementitious Materials

et al. 2019

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The objective of this paper is to propose a pre-experimental framework of printability pre-assessment of cementitious materials. This study firstly presents a general review of additive manufacturing in construction and then examines the main characteristic of the material formulation and printability properties based on extrusion technique. This framework comes with experimental tests to determine a qualitative printability index of mixtures. It uses mix-designs reported in the literature to define interval ratio of mixture design to be investigated in this study. The focus was put on two criteria that influence the formulation namely flowability and buildability. Two practiced based tests, mini slump and cone penetrometer, were used to draw the flowability and buildability dimensionless index. The results were analyzed by introducing an optimal printability coefficient and examining their time evolution. An optimal time of printing was determined Toptimal. Finally, a 3D mortar printing system and its operational process are presented. Then, based on the measurement, the optimal mixture is identified and printed in a large-scale geometry.

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“…Up to now, the effect of interlayer strength in the context of 3D printing has mainly been observed with extrusion-based techniques. Anisotropic behaviour was observed for mechanical strength of 3D-printed specimen [34][35][36][37], which is attributed to the oriented interface properties [38]. In [39], a flexural strength of a cement-based mortar with a water-to-binder-ratio of 0.42 for layers oriented perpendicular to a loading direction of 10.1 MPa was reported, whereas, for layers with parallel orientation, a reduced flexural strength of 5.3 MPa (approximately 48% strength loss) was determined.…”

Section: Effects On Interlayer Strengthmentioning

confidence: 92%

“…In addition to this, the process of applying the layer has been identified to affect interlayer strength. In [34], it is stated that there is no significant effect on interlayer strength of 3D printed concrete when the distance from the nozzle to layer is changed. By contrast, [49] found an increase of the nozzle height to have a negative effect on interlayer strength of geopolymers mortars.…”

Section: Effects On Interlayer Strengthmentioning

confidence: 99%

The Effect of Accelerator Dosage on Fresh Concrete Properties and on Interlayer Strength in Shotcrete 3D Printing

2020

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Recently, the progress in 3D concrete printing has developed enormously. However, for the techniques available, there is still a severe lack of knowledge of the functional interaction of processing technology, concrete rheology and admixture usage. For shotcrete 3D printing technology, we present the effect of accelerator dosages (0%, 2%, 4% and 6%) on fresh concrete properties and on interlayer strength. Therefore, early yield stress development up to 90 min is measured with penetration resistance measurements. Deformation of layers under loading is investigated with digital image correlation and a mechanical testing machine. One point in time (10 min after deposition) is examined to quantify vertical buildability of elements depending on the accelerator dosage. Four different interlayer times (0, 2, 5 and 30 min), which occur for the production of small and large elements as well as due to delay during production, are investigated mechanically as well as quantitatively with computed tomography regarding the formation of cold joints. With increased accelerator dosage, an instantaneous increase in early age yield stress and yield stress evolution was observed. An increase in interlayer time leads to a reduced strength. This is mainly attributed to the observed reduced mechanical interlocking effect of the strands. Finally, a model to describe interlayer quality is presented. In the end, advantages as well as limitations of the findings are discussed.

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Hardened properties of 3D printed concrete: The influence of process parameters on interlayer adhesion

Cited by 444 publications

References 22 publications

On-demand additive manufacturing of functionally graded concrete

On-demand additive manufacturing of functionally graded concrete

Experimental Approach for Printability Assessment: Toward a Practical Decision-Making Framework of Printability for Cementitious Materials

The Effect of Accelerator Dosage on Fresh Concrete Properties and on Interlayer Strength in Shotcrete 3D Printing

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