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

Materials ◽  
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.

Modelling the interlayer bond strength of 3D printed concrete with surface moisture

2021 ◽  
Vol 150 ◽  
pp. 106559
Author(s):  
Gerrit Marius Moelich ◽  
Jacques Kruger ◽  
Riaan Combrinck
Keyword(s):  
Bond Strength ◽  
Surface Moisture ◽  
3D Printed ◽  
Interlayer Bond

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

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2352 ◽  
Author(s):  
Behzad Nematollahi ◽  
Praful Vijay ◽  
Jay Sanjayan ◽  
Ali Nazari ◽  
Ming Xia ◽  
...  
Keyword(s):  
3D Printing ◽  
Bond Strength ◽  
Fibre Volume ◽  
Interface Plane ◽  
Flexural Performance ◽  
Fresh State ◽  
Hardened State ◽  
3D Printed ◽  
Shape Retention ◽  
Interlayer Bond

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.

scholarly journals Effects of slicing parameters on measured fill density for 3D printing of precision cylindrical constructs using Slic3r

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Prashanth Ravi ◽  
Panos S. Shiakolas
Keyword(s):  
3D Printing ◽  
Open Source ◽  
Matrix Material ◽  
Maximum Error ◽  
Drug Release Rate ◽  
Reasonable Degree ◽  
3D Printed ◽  
Parametric Relationships ◽  
The Relationship ◽  
Insight Into

AbstractThe goal of this research is to develop and verify an algorithm to predict the fill density of 3D printed cylindrical constructs as a function of critical slicing parameters. Open-source 3D printing is being applied to the pharmaceutical and biomedical domains where characteristics including drug release rate and compressive strength depend on fill density. Understanding how slicing parameters affect fill density in the printed construct is important to appropriately tailor these characteristics. In this study, we evaluated the relationship between slicing fill density (SFD), extrusion width (EW), layer height (LH), construct diameter and measured fill density (MFD). The developed algorithm provides novel insight into the effects of interconnects and rasters on the distribution of intra-matrix material. We analyze 27 combinations involving 3 levels of EW (0.40, 0.44, 0.48 mm), SFD (15, 25, 35%) and LH (0.15, 0.20, 0.25 mm). The SFD is smaller than and deviates from MFD with a maximum error of 18.62% and from predicted fill density (PFD) with a maximum error of 19.50% compared to the maximum error of 4.30% between PFD and MFD. The predicted interconnect contribution and error reduce with increasing SFD and cylinder diameter but are more prominent at lower values. Our work highlights the perils of employing open-source 3D printing without a sound understanding of the underlying parametric relationships. The proposed predictive model could be used in conjunction with Slic3r, an open-source slicing software, to predict fill density to a reasonable degree of accuracy (less than 5% error) for relatively smaller cylindrical constructs.

scholarly journals Chloride Induced Corrosion and Carbonation in 3D Printed Concrete

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.

scholarly journals Time gap effect on bond strength of 3D-printed concrete

2018 ◽  
Vol 14 (1) ◽  
pp. 104-113 ◽  
Author(s):  
Yi Wei Daniel Tay ◽  
Guan Heng Andrew Ting ◽  
Ye Qian ◽  
Biranchi Panda ◽  
Lewei He ◽  
...  
Keyword(s):  
Bond Strength ◽  
Gap Effect ◽  
3D Printed ◽  
Time Gap

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

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.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

On Metaphysics and the Political: A Polemics of Reading Baudelaire in the 1930s

2019 ◽  
Vol 58 (2) ◽  
pp. 249-259
Author(s):  
Joseph Acquisto
Keyword(s):  
Twentieth Century ◽  
Political Crisis ◽  
The Political ◽  
Modern Poetry ◽  
Progressive Politics ◽  
The World ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

This essay examines a polemic between two Baudelaire critics of the 1930s, Jean Cassou and Benjamin Fondane, which centered on the relationship of poetry to progressive politics and metaphysics. I argue that a return to Baudelaire's poetry can yield insight into what seems like an impasse in Cassou and Fondane. Baudelaire provides the possibility of realigning metaphysics and politics so that poetry has the potential to become the space in which we can begin to think the two of them together, as opposed to seeing them in unresolvable tension. Or rather, the tension that Baudelaire animates between the two allows us a new way of thinking about the role of esthetics in moments of political crisis. We can in some ways see Baudelaire as responding, avant la lettre, to two of his early twentieth-century readers who correctly perceived his work as the space that breathes a new urgency into the questions of how modern poetry relates to the world from which it springs and in which it intervenes.

The Annual Reports of the Prison Commissioners for Scotland and Religion, 1903–1931

2019 ◽  
Vol 48 (1) ◽  
pp. 83-101
Author(s):  
Cameron McKay
Keyword(s):  
Annual Report ◽  
Annual Reports ◽  
Individual Choice ◽  
Drinking Habits ◽  
Parental Neglect ◽  
Late Nineteenth ◽  
Causes Of Crime ◽  
Criminological Theories ◽  
The Relationship ◽  
Insight Into

During the late nineteenth and early twentieth century penologists began to explore the possibility that environment and upbringing, as opposed to individual choice, were the causes criminality. The Prison Commissioners for Scotland, the devolved body who administered prisons north of the border, were not immune to this wider trend. Smith has argued that from the 1890s onwards the Commissioners began to accept that criminality was caused by social problems, namely alcoholism, but also parental neglect, poor education and poverty. In their efforts to test these new criminological theories, the Commissioners began to make more careful enquiries into the backgrounds of their charges. From 1896 to 1931 the Commissioners interviewed a sample of prisoners each year and included the findings in their annual report. Although the main focus of these interviews was on the upbringing and drinking habits of prisoners; by the 1900s the Commissioners seem to have added irreligion to the growing list of etiological causes of crime, and from 1903 onwards prisoners were asked to give details on their religious habits. Although it is debateable how much the Prison Commissioners revealed about the relationship between religion and crime, they did however provide a useful insight into the religiosity of the average prisoner.

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