What was the method of measuring the shear strength of concrete?

A water-binder ratio of 0.28 was selected to achieve over 100 MPa compressive strength concrete based upon a previous study of ultra high performance concrete [18].

How was the effect of workability on the extrudability of the concrete?

Concerning the effect of workability on the extrudability, a shear strength in the range of 0.3 to 0.9 kPa (controlled by superplasticiser dosage) was optimum for printing Mix 4.

What is the effect of superplasticiser on the workability of concrete?

using high dosage of superplasticiser would result in deformed filaments as discussed previously, i.e. reducing the buildability.

How was the compressive strength of the mix determined?

The compressive strength of this mix, determined by casting 100 mm cube specimens, was measured at 1, 7, 28 and 56 days in accordance with BS EN 12390-2:2009 [20], and found to be 20, 80, 110 and 125 MPa, respectively.

How long did it take to increase the shear strength of the concrete?

1% superplasticiser needed approximately 15 minutes to increase the shear strength by 0.3 kPa while 1.5 - 2.0% needed over 60 minutes (Fig. 10).

What properties were used to investigate and optimise the other fresh properties?

As Mix 4 was the optimum in terms of extrudability, it was subsequently used to investigate and optimise the other fresh properties, i.e. workability, open time and buildability.

What was the effect of retarder on the workability of the concrete?

In the series without retarder and accelerator, increasing the superplasticiser dosage from 0 to 2% by weight of binder increased the workability, i.e. reduced the shear strength, see Fig.

What is the effect of retarder on the workability of the printing concrete?

Unlike the effect of superplasticiser on the workability of the printing concrete, increasing the retarder or accelerator dosage reduced the workability, i.e. increased the shear strength.

How much binder was used in the mixes?

The binder content of 25 and 30% in these mixes appear to be insufficient to create a suitable extrudability to cope with this printing process.

What was the strategy used to test the extrudability of concrete?

The strategy was to use very practical indications of successful printing, in terms of the ability to extrude filaments into a layer (extrudability) and to then build-up multiple layers (buildability).

What was the mix for printing?

The dosages of superplasticser, retarder, accelerator and polypropylene fibres were varied to identify optimum mix proportions for printing.

Open AccessJournal Article10.1617/S11527-012-9828-Z

Mix design and fresh properties for high-performance printing concrete

Thanh T. Le, +6 more

- 19 Jan 2012

- Materials and Structures

- Vol. 45, Iss: 8, pp 1221-1232

995

TL;DR: In this article, the authors present the experimental results concerning the mix design and fresh properties of a high-performance fiber-reinforced fine-aggregate concrete for printing concrete, which has been designed to be extruded through a nozzle to build layer-by-layer structural components.

Abstract: This paper presents the experimental results concerning the mix design and fresh properties of a high-performance fibre-reinforced fine-aggregate concrete for printing concrete. This concrete has been designed to be extruded through a nozzle to build layer-by-layer structural components. The printing process is a novel digitally controlled additive manufacturing method which can build architectural and structural components without formwork, unlike conventional concrete construction methods. The most critical fresh properties are shown to be extrudability and buildability, which have mutual relationships with workability and open time. These properties are significantly influenced by the mix proportions and the presence of superplasticiser, retarder, accelerator and polypropylene fibres. An optimum mix is identified and validated by the full-scale manufacture of a bench component.

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Most frequently asked questions

1. What are the contributions in this paper?

This paper presents the experimental results concerning the mix design and fresh properties of a high-performance fibre-reinforced fine-aggregate concrete for printing concrete.

2. What are the main methods used to evaluate the workability of concrete?

Conventional methods evaluating workability include slump, compacting factor and flow tests, for which various national standards are available.

3. What is the reason why a 90 mm diameter vane was used in this research?

A 90 mm diameter vane was used in this research because of the relatively low shear strength, where the factor to convert the outer reading of the shear vane apparatus to shear strength is 0.022.

4. What are the properties of concrete printing?

Experiments showed that the most critical properties in the fresh state of this printing process are extrudability and buildability.

Fig. 5. Particle size distribution of mixes

Fig. 2. Schematic of concrete delivery system

Fig. 6. Effect of superplasticiser dosage on workability

Fig. 4. Diagram of a shear vane test with measuring positions

Citations

Journal Article•10.1016/J.AUTCON.2016.08.026

Additive construction: State-of-the-art, challenges and opportunities

Nathalie Labonnote, +3 more

- 01 Dec 2016

- Automation in Construction

TL;DR: In this paper, the central concept of additive construction was defined, and a systematic mapping study was performed in order to assemble relevant publications selected according to a well-defined set of criteria.

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502

Journal Article•10.1016/J.CONBUILDMAT.2018.03.232

Effect of surface moisture on inter-layer strength of 3D printed concrete

Jay Sanjayan, +3 more

- 30 May 2018

- Construction and Building Materials

TL;DR: In this article, the effects of print-time interval on the inter-layer strength, along with compressive and flexural strengths of extrusion-based 3D printed concrete in different directions were investigated.

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498

Journal Article•10.1016/J.CONBUILDMAT.2017.12.051

Printable properties of cementitious material containing copper tailings for extrusion based 3D printing

Guowei Ma, +3 more

- 20 Feb 2018

- Construction and Building Materials

TL;DR: In this article, an environmental friendly cementitious mixture that is compatible with an extrusion-based printing process was proposed, where the authors investigated the six replacement ratio of tailing to sand from 0% to 50% and developed a single nozzle printing system.

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•Journal Article•10.1016/J.CEMCONRES.2019.105780

Digital Concrete: A Review

Timothy Wangler, +4 more

- 01 Sep 2019

- Cement and Concrete Research

TL;DR: A review of the state of the art in the newly forming field of digital fabrication with concrete, and aims to provide some direction in terms of the research challenges encountered thus far is provided in this article.

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Journal Article•10.1016/J.MEASUREMENT.2017.08.051

Measurement of tensile bond strength of 3D printed geopolymer mortar

Biranchi Panda, +4 more

- 01 Jan 2018

- Measurement

TL;DR: In this article, the tensile bond strength of 3D printed geopolymer mortar with respect to printing time gap between layers, nozzle speed and nozzle standoff stance was analyzed and shown that the bond strength is a function of state of interface material between two nearby layers which can be influenced by material strength development rate and 3D printing parameters.

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443

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References

•Journal Article•10.3151/JACT.1.5

Self-Compacting Concrete

Hajime Okamura, +1 more

- 01 Jan 2003

- Journal of Advanced Concrete Technology

TL;DR: Ozawa and Maekawa as mentioned in this paper developed a self-compacting concrete, which can be compacted into every corner of a formwork, purely by means of its own weight and with out the need for vibrating compaction.

...read moreread less

2.1K

•Journal Article•10.1016/J.AUTCON.2006.05.002

Freeform construction: mega-scale rapid manufacturing for construction

Richard A. Buswell, +3 more

- 01 Mar 2007

- Automation in Construction

TL;DR: In this article, the authors outline some of the major issues facing construction technology and give examples of the use of large scale Digital Fabrication in the industry and define the term Freeform Construction.

...read moreread less

511

Journal Article•10.1016/J.CEMCONRES.2009.07.005

Flow conditions of fresh mortar and concrete in different pipes

Stefan Jacobsen, +3 more

- 01 Nov 2009

- Cement and Concrete Research

TL;DR: In this article, the authors investigated the variation in fresh concrete flow rate over the pipe cross section on differently coloured and highly flowable concrete mixes flowing through pipes of different materials (rubber, steel, acryl).

...read moreread less

114

Journal Article•10.1016/J.CEMCONCOMP.2009.04.010

Effect of absorption of limestone aggregates on strength and slump loss of concrete

Abdulrahman M. Alhozaimy

- 01 Aug 2009

- Cement & Concrete Composites

TL;DR: In this article, the effect of absorption of limestone aggregates on the effective w/c ratio and on the strength and slump loss of concrete was investigated, and it was found that the absorption of dry aggregates in all concrete mixes considered in this study occurred mainly in the first 15min after the start of mixing and diminished substantially thereafter.

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Journal Article•10.1617/S11527-006-9186-9

Final report of RILEM TC 188-CSC ‘Casting of self compacting concrete’

Rilem Technical Committe

- 17 Oct 2006

- Materials and Structures

TL;DR: In this article, the authors developed a self-compacting concrete (SCC) material that does not need vibration for compaction and is now increasingly being used in routine practice and the major impact of the introduction of SCC is connected to the production process.

...read moreread less

...

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Mix design and fresh properties for high-performance printing concrete

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Most frequently asked questions

1. What are the contributions in this paper?

2. What are the main methods used to evaluate the workability of concrete?

3. What is the reason why a 90 mm diameter vane was used in this research?

4. What are the properties of concrete printing?

5. What was the method of measuring the shear strength of concrete?

6. How was the effect of workability on the extrudability of the concrete?

7. What is the effect of superplasticiser on the workability of concrete?

8. How was the compressive strength of the mix determined?

9. How long did it take to increase the shear strength of the concrete?

10. What properties were used to investigate and optimise the other fresh properties?

11. What was the effect of retarder on the workability of the concrete?

12. What is the effect of retarder on the workability of the printing concrete?

13. How much binder was used in the mixes?

14. What was the strategy used to test the extrudability of concrete?

15. What was the mix for printing?

Figures

Citations

Additive construction: State-of-the-art, challenges and opportunities

Effect of surface moisture on inter-layer strength of 3D printed concrete

Printable properties of cementitious material containing copper tailings for extrusion based 3D printing

Digital Concrete: A Review

Measurement of tensile bond strength of 3D printed geopolymer mortar

References

Self-Compacting Concrete

Freeform construction: mega-scale rapid manufacturing for construction

Flow conditions of fresh mortar and concrete in different pipes

Effect of absorption of limestone aggregates on strength and slump loss of concrete

Final report of RILEM TC 188-CSC ‘Casting of self compacting concrete’

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