• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.186-187
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• 2022

The purpose of this study was to give fluidizing properties to non-sirtered cement made using by-products that can replace Portland cement by using a fluidizing agent. Blast furnace slag, C-type fly ash, and F-type fly ash were used for non-sirtered cement, and sand was used for aggregate. The amount of fluidizing agent used was fixed at 1%, and the water-cement ratio (W/C) was different by setting the binder blending ratio of the non-sintered cement differently, and the fluidity test and flow were compared. As a result of the experiment, when the flow standard was 170mm when the fluidizing agent was used, the fluidizing properties were shown at an average water-cement ratio (W/C) of 36%. Through this study, it was confirmed that the fluidizing properties appeared when the fluidizing agent was used in non-sintered cement.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.2
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• pp.57-66
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• 2015

The purpose of this study was to improved the durability of a improved movable weir by replacing the improved movable weir's metal gate with a hybrid steel/glass fiber reinforced polymer composites panel gate. Because the metal gate of a improved movable weir is always in contact with water, its service life is shortened by corrosion. This study made four type of hybrid steel/glass fiber reinforced polymer composites panel gate with different steel gate surface deformation (control, sand blast, scratch and hole), flexural. Fracture properties tests were performed depending on the steel gate surface deformation. According to the test results, the flexural behavior, flexural strength and fracture properties of hybrid steel/glass fiber reinforced polymer composites panel gate was affected by the steel panel gate surface deformation. Also, the sand blast type hybrid steel/glass fiber reinforced polymer composites panel gate shows vastly superior flexural and fracture performance compared to other types.

• Journal of the Korean Geotechnical Society
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• v.37 no.10
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• pp.13-25
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• 2021

The most widely used method for determining the blast effects of explosives is the Trauzl test. This test is used to measure the explosive power (strength) of a substance by determining volume increase, which is produced by the detonation of a tested explosive charge in the cavity of a lead block with defined quality and size. In this paper, Trauzl lead block test and High speed 3D-DIC (Digital Image Correlation) system were conducted to evaluate the stemming effect of the blast hole. The effects of stemming materials can be expressed as the expansion of the cavity in a standard lead block through explosion of the explosives. The blasting experiment was conducted with emulsion explosives. The stemming material in the blast hole of lead block, which was adopted in this study, were using sand and stone chips. Results of blasting experiment and numerical analysis showed that the expansion rates of lead block were most affected by stone chips followed by sand. Also, as result of dynamic strain measurement on the lead block surface of High speed 3D-DIC system, the displacement and surface strain on the block were the highest in the experiment case of stone chips stemming.

• Explosives and Blasting
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• v.41 no.1
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• pp.1-18
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• 2023

Stemming is a process applied to blast holes to prevent gases from escaping during detonation. A stemming material helps confine the explosive energy for longer and increases rock fragmentation. This study developed a stemming material based on a shear-thickening fluid (STF) that reacts to dynamic shock. Two blasting experiments were conducted to Field-verify the performance of the STF-based stemming material. In the first experiment, the pressure inside the blast hole was directly measured based on applying the stemming material. In the second field verification, tunnel blasting was performed, and the blasting results of sand stemming and, that of the STF-based stemming case were compared. The measurement results of the pressure in the blast hole showed that when the STF-based stemming material was applied, the pressure at the top of the blast hole was lower than in the sand stemming case, and the stemming ejection was also lower. The results of the field application verify that the excavation performance of the STF-based stemming case in the tunnel blasting was superior to that of the sand stemming case.

• Advances in concrete construction
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• v.5 no.3
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• pp.183-199
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• 2017

This paper reports an experimental study into the rheological behaviour of Smart Dynamic Concrete (SDC). The investigation is aimed at quantifying the effect of the varying amount of mineral admixtures on the rheology, setting time and compressive strength of SDC containing natural sand and crushed sand. Ordinary Portland cement (OPC) in conjunction with the mineral admixtures was used in different replacement ratio keeping the mix paste volume (35%) and water binder ratio (0.4) constant at controlled laboratory atmospheric temperature ($33^{\circ}C$ to $35^{\circ}C$). The results show that the properties and amount of fine aggregate have a strong influence on the admixture demand for similar initial workability, i.e., flow. The large amounts of fines and lower value of fineness modulus (FM) of natural sand primarily increases the yield stress of the SDC. The mineral admixtures at various replacement ratios strongly contribute to the yield stress and plastic viscosity of SDC due to inter particle friction and cohesion.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.667-670
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• 2003

The purpose of this study is to present data for the reusing, reinforcement and estimation of safety of the RC structure damaged by fire, and for the prevention of explosive spalling by checking the character of explosive spalling according to kinds of fine aggregate, admixture and water-cement ratios. The materials used fine aggregates were sea sand, crushed sand and recycled sand, and the admixtures were fly ash and blast-furnace slag. Also the water-cement ratios was 55% and 30.5%. After those were heated respectively for 30 and 60 minutes in accordance with Standard Time-Temperature Curve. And then conditions of explosive spalling were divided into five grades, and characters of explosive spalling were investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.755-758
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• 2004

Self-compactability is defined as a capability of concrete to be uniformly filled and compacted in every corners of formwork by its self-weight without vibration during placing. To evaluate the self compactability of self compacting concrete, the slump flow, the time of slump flow at 500mm and U-box apparatus testing methods are used. In this research, the fresh and hardened properties of self compacting concrete using ground granulated blast furnace slag as a part of cement were investigated for the volume contents of sand in the mortar. The workability, flowing characteristics, air content and compressive strength of concrete were tested and the results were compared with the different volume contents of sand in the mortar. In the experiment, we acquired satisfactory results at the point of flowing characteristics and strengths of self compacting concrete.

• International Journal of Concrete Structures and Materials
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• v.9 no.3
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• pp.381-390
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• 2015

Investigating the microstructure of hardened cement mixtures with the aid of advanced technology will help the concrete industry to develop appropriate binders for durable building materials. In this paper, morphological, mineralogical and thermogravimetric analyses of autoclave-cured mixtures incorporating ground dune sand and ground granulated blast furnace slag as partial cementing materials were investigated. The microstructure analyses of hydrated products were conducted using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), differential thermal analysis (DTA), thermo-graphic analysis (TGA) and X-ray diffraction (XRD). The SEM and EDX results demonstrated the formation of thin plate-like calcium silicate hydrate plates and a compacted microstructure. The DTA and TGA analyses revealed that the calcium hydroxide generated from the hydration binder materials was consumed during the secondary pozzolanic reaction. Residual crystalline silica was observed from the XRD analysis of all of the blended mixtures, indicating the presence of excess silica. A good correlation was observed between the compressive strength of the blended mixtures and the CaO/$SiO_2$ ratio of the binder materials.

• Tunnel and Underground Space
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• v.21 no.4
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• pp.320-327
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• 2011

In this study, for stemming effect in blast of the mortar block body, the crushed granite sand as fine aggregate, which is waste rock obtained at the ○○ limestone mine, was investigated to compare with stemming materials such as sea sand, river sand, clayed soil and water can be acquired easily at the field. The mortar block body was manufactured with the dimensions of 50 cm width, 50 cm length and 70 cm height. The direct shear and sieve separator test were performed, and the properties of friction resistance were analyzed by the extrusion test for five stemming materials. Axial strain of steel bar and ejection velocity of stemming materials due to the explosive shock pressure in blasthole with the stemming length of 10 cm and 20 cm in the mortar blast test were measured by the dynamic data acquisition system. Among stemming materials, axial strain showed the largest value at the crushed granite sand as fine aggregate, and the ejection velocity was the smallest value at the stemming of water. The results has shown correlate with harden unit weight in blasthole, particle size distribution, shear resistance, and extrusion strength of stemming materials. The ejection velocity of stemming material at the mouth of blasthole and the axial strain of steel bar in the inside of blasthole tend to be inversely proportional to each other, represent exponentially.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1212-1217
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• 2008

In this study, in order to clarify the effect of the direction of cyclic shear on the post-earthquake settlement the multi-directional shear tests were carried out for Toyoura Japan standard sand, Genkai natural sand and the Granulated Blast Furnace Slag (GBFS). In a series of tests, number of strain cycles was changed as n=5-200 and the shear strain amplitude varied from 0.1% to 1.0%. The relative density was also changed as Dr=50, 60 and 70%. From the test results for Toyoura sand and GBFS, it is clarified that the post cyclic settlement is relatively large at the small relative density and becomes large with the shear strain amplitude. When the influence of the direction of cyclic shear is decreases, the post cyclic settlement strain for Toyoura sand is converged to a constant value, but the GBFS is increased with the number of strain cycles.