• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.131-136
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• 2019

Buildability of fresh concrete, a key element of Concrete 3D printing, is the ability to build filaments at a desirable height without excessive deformation or collapse. Buildability is closely related to yield stress, and the higher the yield stress, the better. Also, the shear stress of fresh concrete increases as it hardens over the time after extruded, and consequently the buildability increases. Therefore, in concrete 3D printing, proper time gaps between printed layers (Printing Time Gap, PTG) are required to ensure the buildability of fresh concrete. As the PTG increases, the buildability increases; however, an excessive PTG reduces the bond performance between the printed layers, and the extrudability can be lowered as the printing time increases. In this research, therefore, 3D printing experiments were conducted with the variable of PTG to examine the buildability of 100 MPa-high strength concrete. In addition, a pseudo-layer loading method was applied to simulate the buildability test for 3D concrete printing and its applicability was examined.

• Advances in concrete construction
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• v.11 no.2
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• pp.141-149
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• 2021

This study is a basic research for evaluating the buildability of cementitious materials for three-dimensional (3D) printing. In the cement paste step, the thixotropy behavior according to the resting time, which represents the time interval between each layer, was analyzed. In addition, the relationship between the thixotropy behavior and 3D concrete printing buildability was derived by proposing a measurement method that simulates the 3D concrete printing buildup process. The analysis of the tendency of the thixotropy behavior according to the resting time revealed that the area of the hysteresis loop (AHyst) showed a tendency to increase and then converge as the resting time increased, which means hysteresis loop approach critical resting time for sufficient buildability. In the thixotropy behavior analysis that simulates the 3D concrete printing buildup process, the buildup ratio, which is the recovery rate of the shear stress, showed a tendency to increase and then converge as the resting time increased, which are similar results like hysteresis loop. It was concluded that AHyst and the buildup ratio can be used as parameters for determining the resting time, and they have close relationships with 3D concrete printing buildability.

• 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.

• Korean Journal of Construction Engineering and Management
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• v.23 no.6
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• pp.54-64
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• 2022

The continuous aging of the domestic construction industry and the shortage of human resource are no longer a problem for the future, but must be solved for the survival of the domestic construction industry, given the characteristics of the labor-intensive construction industry and the continuing negative image of young people toward the construction industry. It is undoubtedly a prerequisite. This study is aimed to tackle the fundamental problem of the construction labor shortage faced by the domestic construction industry by comparing and analyzing the case of MMC technology development in the UK, which has been preparing fast-track response measures for the past 5 years to solve the labor shortage problem, and the case of Buildability technology development in Singapore, which is seeking mid- to long-term countermeasures for about 20 years. Also, This research provides the initial research & development roadmap for Korean Countermeasures Strategy.

• 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.

• 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 Korea Institute of Building Construction
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• v.2 no.2
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• pp.157-164
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• 2002

In this study, attempts to analyze the case study of production design were carried out through: 1) exploration of the factors influencing the interface between architectural and production design phases; 2)application of precast technologies. Building design and construction planning in Japan may be characterized by ample use of Production Design which extends over the whole projects phases. Taking a composite construction system for apartment buildings which allow for alternative combination of different technologies as a case study object, three projects have been chosen to analyze actual process of determining product sub-system and their specification. And the expectancies of this paper are that it can be used as efficient data for improvement of system to systematize Constructability(Buildability) in korea.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.41-49
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• 2021

3D printing techniques have been recently adopted in the construction industry. It mainly utilizes additive manufacturing which is the fabrication process depositing successive layers of materials without any formworks. Conventional cementitious materials may not be directly applicable to 3D printing because 3D printable cementitious materials is required to satisfy such characteristics as pumpability, extrudability, and buildability in a fresh state. This study aimed to investigate rheological properties and required performances of 3D printable cementitious materials, by reviewing existing studies. Test methods and equipments, evaluation results and characteristics of mixture additives were compared. Based on reviews of existing studies, this study indicates that the viscosity is mainly relevant to the pumpability of 3D printable materials whereas the yield stress and thixotropy are important in securing buildability of the materials.

• 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.23 no.7
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• pp.104-112
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• 2019

The material properties of the 3D printing cement composite mortar were evaluated, and the performance range in which printing was possible was calculated using the void ratio in a fresh state as a single index. As a results of the tests, as the water-binder ratio (W/B) increased, the mortar flow value increased and the density and strength decreased. As the sand-binder ratio (SS/B) increased, the mortar flow value decreased. However, strength and density increased and decreased up to a certain SS/B. As admixture-binder ratio (Ad/B) increased, mortar flow value, density, and strength decreased. These trends make it difficult to mix-design to meet the target performances of 3D printing mortars, represented by extrudability and buildability. The value of mortar flow increased proportionally with the void ratio, while the density and strength apparently decreased as the void ratio increased. This indicates that void ratio can be utilized as a single index for controlling the material properties in the design of mortar mixtures. It was found that mortar mixture could be printed by a 3D printer when the void ratio was in the range from 0.6 to 0.7. This was verified by printing a mortar which has the void ratio of 0.634. The mortar was produced with the mixture design of W/B 35.0%, SS/B 60.0%, and Ad/B 0.1%. Further research applying diverse admixtures is needed to improve the quality of 3D printing output mortars.