Effect of Delay Time on the Mechanical Properties of Extrusion-Based 3D Printed Concrete

Marchment, Taylor; Xia, Ming; Dodd, Elise; Sanjayan, Jay; Nematollahi, Behzad

doi:10.22260/isarc2017/0032

Cited by 27 publications

(18 citation statements)

References 7 publications

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“…Table 2 gives the mix proportions of the 3D-printable geopolymer mortars prepared in this investigation. The results of the previous studies of the authors on 3D-printable OPC-based mortar were used to determine the preliminary proportions [29,30]. Following the findings of those previous studies, the proportions of sand were kept constant in all mixtures and the binder paste was changed, i.e., OPC and water were substituted by fly ash and alkaline activator.…”

Section: Materials and Experimental Proceduresmentioning

confidence: 99%

Effect of Polypropylene Fibre Addition on Properties of Geopolymers Made by 3D Printing for Digital Construction

et al. 2018

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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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Section: Materials and Experimental Proceduresmentioning

confidence: 99%

Effect of Polypropylene Fibre Addition on Properties of Geopolymers Made by 3D Printing for Digital Construction

et al. 2018

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“…Most of the printable cementitious materials used in extrusion-based 3DCP techniques are ordinary Portland cement (OPC)-based binders [11,12,14,15]. The production of OPC emits a significant amount of carbon dioxide (CO 2 ) into the atmosphere [16].…”

Section: Introductionmentioning

confidence: 99%

Method of Optimisation for Ambient Temperature Cured Sustainable Geopolymers for 3D Printing Construction Applications

2019

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Since the initial introduction of geopolymers, these materials have been characterised as environmentally-friendly sustainable substitutes for ordinary Portland cement (OPC). There is a routine increase in the application of geopolymers, especially in advanced technologies. Because of its better rheological characteristics compared to OPC, geopolymers are appropriate materials for extrusion-based 3D printing technologies. This paper focuses on the optimisation of an ambient temperature cured geopolymer for 3D printing construction applications. The effects of mixture parameters, including the type of hydroxide solution (HS), the type of silicate solution (SS) and the mass ratio of SS to HS on the workability, extrudability, shape retention ability and mechanical performance of different geopolymer mixtures were investigated. Accordingly, an optimum mixture was identified for geopolymers cured at ambient temperatures. Mechanical properties of the optimised mixture, including flexural and compressive strengths, were measured in different directions with respect to the printed layers. Further, uniaxial tension tests were also conducted on the optimised mixture to measure its interlayer bond strength. The results showed that among the activators investigated, the sodium-based activator composed of sodium hydroxide and sodium silicate solutions, with a SiO2/Na2O ratio of 3.22, was the most effective activator, providing appropriate workability and extrudability, along with reasonable strength and a high shape retention ability. The acquired mechanical properties exhibited anisotropic behaviour in different testing direction. The strength of the interlayer bond was found to be adequate to avoid interfacial shear failure.

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“…Herewith, a weak region with less hydrated cement than in the rest of the layer is prevalent. This could be complemented by the finding that moisture content of the bottom layer has an effect on interlayer strength, where a higher moisture content led to an increase in interlayer strength within the investigated boundary conditions [30,43].…”

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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Effect of Delay Time on the Mechanical Properties of Extrusion-Based 3D Printed Concrete

Cited by 27 publications

References 7 publications

Effect of Polypropylene Fibre Addition on Properties of Geopolymers Made by 3D Printing for Digital Construction

Effect of Polypropylene Fibre Addition on Properties of Geopolymers Made by 3D Printing for Digital Construction

Method of Optimisation for Ambient Temperature Cured Sustainable Geopolymers for 3D Printing Construction Applications

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

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