• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.3
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• pp.66-77
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• 2022

Digitization and automation technologies have rapidly maximized productivity and efficiency in all industries over the past few decades. Construction automation technology has either stagnated over the same period or has not kept pace with overall economic productivity. According to the research studies up to now, the output of concrete structures using coarse aggregates (8mm or more) is very limited due to the limitations of equipment and materials. In this study, information on the development process of 3DCP equipment that can print concrete structures with the printing width (100 mm or more) and printing thickness (30 mm or more) using a 3DCP material mixed with coarse aggregate (8 mm or more) is provided. To verify the performance of the developed 3DCP equipment, experimental data are provided on output variables, the number of layers, and the inter-layer printing time interval. The evaluation and verification data of various mechanical properties (compressive and splitting tensile strength) of printed materials using coarse aggregates are provided.

• Advances in concrete construction
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• v.8 no.2
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• pp.155-163
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• 2019

The objective of this study was to derive a cementitious material for three-dimensional (3D) concrete printing that fulfills key performance functions, extrudability, buildability and bondability for 3D concrete printing. For this purpose, the rheological properties shown by different compositions of cement paste, the most fundamental component of concrete, were assessed, and the correlation between the rheological properties and key performance functions was analyzed. The results of the experiments indicated that the overall properties of a binder have a greater influence on the yield stress than the plastic viscosity. When the performance of a cementitious material for 3D printing was considered in relation with the properties of a binder, a mixture with FA or SF was thought to be more appropriate; however, a mixture containing GGBS was found to be inappropriate as it failed to meet the required function especially, buildability and extrudability. For a simple quantitative evaluation, the correlation between the rheological parameters of cementitious materials and simplified flow performance test results-time taken to reach T-150 and the number of hits required to reach T-150-in consideration of the flow of cementitious materials was compared. The result of the analysis showed a high reliability for the correlation between the rheological parameters and the time taken to reach T-150, but a low reliability for the number of hits needed for the fluid to reach T-150. In conclusion, among several performance functions, extrudability and buildability were mainly assessed based on the results obtained from various formulations from a rheological perspective, and the suitable formulations of composite materials for 3D printing was derived.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.4
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• pp.227-233
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• 2022

The 3D-printing technique is used for manufacturing objects by adding multiple layers, and it is relatively easy to manufacture objects with complex shapes. The 3D concrete printing technique, which incorporates 3D printing into the construction industry, does not use a formwork when placing concrete, and it requires less workload and labor, so economical construction is possible. However, 3D-printed concrete is expected to have a lower strength than that of molded concrete. In this study, the properties of 3D-printed concrete were analyzed. To fabricate the 3D-printed concrete samples, the extrusion path and shape of the samples were designed with Ultimaker Cura. Based on this, G-codes were generated to control the 3D printer. The optimal concrete mixing proportion was selected considering such factors as extrudability and buildability. Molded samples with the same dimensions were also fabricated for comparative analysis. The properties of each sample were measured through a three-point bending test and uniaxial compression test, and a comparative analysis was performed.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.74-86
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• 2020

This study discussesresearch and development of large-sized 3D printers that can be applied to construction and civil engineering for various designs of protective casing on foam liner for concrete exteriors. The consistent use of concrete represents the current surroundings. However, concrete exteriors in Korea have not considered the regional characteristics, but the concrete has been poured solely for economical aspects for the last decade or two. There are many cases of poor installation and not enough design development projects to correct it. This study was conducted to apply various patterns, regional characteristics, and 3D printing for protective casing design for foam liner to create various designs for the concrete walls. Therefore, we started researching on a large 3D printer, and designed and developed this system. Considering the chronological process, the properties of concrete structures were identified, the application of designs for concrete in Korea and abroad and the 3D printing materials for the protective casing were surveyed and analyzed, and a stereotype was produced in the first year to study designs for the beauty of concrete surfaces. In the second year, images of regional characteristics were gathered, design ideas for regional promotion were derived, virtual images were produced along with design modeling to simulate the appearances, and verify the effect of application and promotion. Finally, in the third year, the 3D printer for concrete foam liner was constantly improved to analyze the 3D printing program and the various library elements to complete an actual large-sized 3D printer.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.2
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• pp.35-42
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• 2024

This study evaluated the buildability and mechanical properties of 3DP concrete printed in air and underwater environments. Buildability was evaluated by green strength test on fresh concrete and height and deflection immediately and 1 hour after printing. The green compressive strength of the concrete was 5.0 kPa after 30 minutes and 7.9 kPa after 3 hours, an increase of 1.6 times the initial strength. The total height of the laminated parts met the design height regardless of the printing environment. The amount of deflection in air and under water 1 hour after printing was 1 mm and 0.2 mm, respectively, indicating a small amount of deflection under water. The apparent density of the sample appeared in the order of A-M > A-P > UW-P. This is believed to be because a large amount of air is mixed into the concrete during the printing process, and water infiltrates during the underwater printing process. The compressive strength ratio of UW-P/A-P was 0.86 at 1 day, but the compressive strength of the underwater printed concrete was high from 7 days.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.199-208
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• 2021

The extrudability of 3D printed concrete and its member strength can be highly influenced by water cement ratio (W/C) and printing time gap (PTG). In this study, mold cast specimens and 3D printed specimens were fabricated with variables of W/C ratio and PTG, and their shear bond strength and interlayer surface moisture content were measured and analyzed. The test results showed that the shear bond strength is greatly influenced by the amount of interlayer surface moisture. It is thus recommended that proper amount of interlayer surface moisture with respect to PTG needs to be maintained to have a required interlayer shear bond strength. In addition, further research is required to estimate the effect of many environmental factors that can influence the interlayer surface moisture content.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.1
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• pp.33-40
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• 2024

The volume of shells, a prominent form of marine waste, is steadily increasing each year. However, a significant portion of these shells is either discarded or left near coastlines, posing environmental and social concerns. Utilizing shells as a substitute for traditional aggregates presents a potential solution, especially considering the diminishing availability of natural aggregates. This approach could effectively reduce transportation logistics costs, thereby promoting resource recycling. In this study, we explore the feasibility of employing wasted shell aggregates in 3D concrete printing technology for marine structures. Despite the advantages, it is observed that 3D printing concrete with wasted shells as aggregates results in lower strength compared to ordinary concrete, attributed to pores at the interface of shells and cement paste. Microstructure characterization becomes essential for evaluating mechanical properties. We conduct an analysis of the mechanical properties and microstructure of 3D printing concrete specimens incorporating wasted shells. Additionally, a mix design is proposed, taking into account flowability, extrudability, and buildability. To assess mechanical properties, compression and bonding strength specimens are fabricated using a 3D printer, and subsequent strength tests are conducted. Microstructure characteristics are analyzed through scanning electron microscope tests, providing high-resolution images. A histogram-based segmentation method is applied to segment pores, and porosity is compared based on the type of wasted shell. Pore characteristics are quantified using a probability function, establishing a correlation between the mechanical properties and microstructure characteristics of the specimens according to the type of wasted shell.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.375-382
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• 2019

In this study, an experimental study on the buildability of the structure using the developed printing materials and equipment was performed. Experimental variables included the moving speed of nozzles(=80 and 100mm/s), the revolutions per minute (RPM) of screw in discharge buckets, and the aspect ratio(=1.67 and 5.00) reflecting wall length of the structures. Buildability of the 3D printed concrete structures was analyzed based on the maximum decomposition layer and collapse patterns of the structures according to the experimental variables. The nozzle movement speed of 80mm/s and the aspect ratio of 1.67 were favorable for 3D printing in this study. The collapse process of structure due to uneven layer decomposition was also analyzed through the relative displacement measurement of the lower part of the structure during printing.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.68-69
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• 2019

Integrating 3D printing into architecture is gaining attention because it allows construction of construction structures without formwork. Among them, 3D printing construction materials must have high flow performance and at the same time ensure the performance that does not collapse during lamination. Therefore, in this study, we tried to determine the fluidity and lamination properties of mortar formulations, and set the thickener incorporation ratio as the formulation parameters. As a result of this experiment, it was confirmed that the lamination performance was secured from the thickening agent mixing rate of 1.5%.

• Advances in concrete construction
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• v.13 no.4
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• pp.281-289
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• 2022

3D printing cement-based materials (3DPCBM) is an innovative rapid prototyping technology for construction materials. This study is tested on the rheological behavior, printability and buildability of steel slag (SS) content based on the extrusion system of 3D printing. 0, 8 wt%, 16 wt%, 24 wt%, 32 wt% and 40 wt% SS was replaced cement, The test results revealed that the addition of SS would increase the fluidity of the printed paste, prolong the open time and setting time, reduce the plastic viscosity, dynamic yield stress and thixotropy, and is beneficial to improve the pumping and extrudability of 3DPCBM. With the increase of SS content, the static yield stress developed slowly with time which indicated that SS is harmful to the buildability of printing paste. The content of SS in 3DPCBM can reach up to 40% at most under the condition of satisfying rheological property and buildability, it provides a reference for the subsequent introduction of SS and other industrial solid waste into 3DPCBM by explored the influence law of SS on the rheological properties of 3DPCBM.