• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.223-231
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• 1998

Existing cast in place piles made by grouting cement mortar have many problems that cracks by autogeneous and drying shrinkage bring about the deterioration of force for piles, segregations by the submersion of ground water occur and also, high cement contents lead to rise the manufacturing cost. Therefore, this study is intended to investigate the mechanical properties of high performance mortar, incorporating expansive additives and fly ash. for cast in place piles. According to the experimental results, as the contents of expansive additives increase in mortar mixture, fluidity decrease and air contents shows inverse tendency. Setting time is delayed. Although compressive strength at 7days shows a decline tendency. compressive strength at 28days and 91days increase slightly with 5% of expansive additives. As fly ash increase in mortar mixture, high fluidity is shown, air contents increase and setting time is delayed at fresh state, and additives are, the larger length change is, whereas shrinkage decrease with the increase of fly ash.

• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.480-484
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• 2012

Concrete, the mixture of cement, sand, gravel and water, is a suspension substance extensively used to construct building materials. When a concrete mortar is applied to the underwater construction, the rheology of concrete is of great importance to its flow performance, placement, anti-washout and consolidation. In this research, the anti-washout and rheological properties of concrete have been investigated with concrete admixtures prepared by adding anionic surfactants, cationic surfactants, and polymeric thickeners. The concrete mortar formulated by pseudo-polymeric systems with the electrostatic association of anionic and cationic surfactants, showed high viscosities and suitable anti-washout properties, but poor pumpabilities. The addition of poly methyl vinyl ether to the mixed surfactant system exhibits synergistic effects by improving the concrete mortar properties of the concrete mortar such as fluidity, visco-elastic property, self-leveling, and anti-washout.

• Geophysics and Geophysical Exploration
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• v.13 no.1
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• pp.69-79
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• 2010

In order to reduce leakage from a reservoir, a large amount of cement milk (grout) was injected from boreholes drilled around the shores of the reservoir, and monitored to establish the infiltration of cement milk into the bedrock under the reservoir. From laboratory tests using rock core samples, it was revealed that the resistivity of cement milk is much lower than that of the groundwater at this location. Therefore, it was expected that the resistivity of the zones filled with cement milk would be significantly reduced. Geophysical surveys are expected to be suitable methods to check the effectiveness of grouting in improving the water-retaining performance of a reservoir. DC electrical surveys (seven in total) and two Controlled Source Audio-frequency Magneto-Telluric (CSAMT) surveys were conducted along survey lines in the reservoir to monitor the infiltration of cement milk during the grouting. Extremely low resistivity zones ($10\;{\Omega}m$ or less) were observed in resistivity sections obtained by 2D inversion. The zones are inferred to be fractured zones filled with cement milk. In sections showing the rate of change of resistivity, three zones that showed significant change showed gradual expansion to deeper parts as the grouting progressed. These zones correspond to highly permeable zones detected by Lugeon tests at grout boreholes. We have confirmed that it is possible to measure the resistivity change by DC electrical and CSAMT surveys from the surface of the reservoir. It seems that such monitoring results could be reflected in future grouting plans.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.85-94
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• 2016

In this study, the hydrophilic chemical grout using silanol (HCGS) was introduced to overcome the limitations of conventional epoxy resin which have been used for strengthening reinforced concrete (RC) structures. Then, flexural tests on the RC slabs strengthened by FRP sheets were conducted. Three slab specimens were tested in this study; a control specimen with no strengthening, and two specimens strengthened by a typical epoxy resin or HCGS, respectively, as a binder between the slabs and the FRP sheets. In addition, an analytical model was developed to evaluate the flexural behavior of strengthened slab members, considering the horizontal shear force at the interface between concrete slabs and FRP sheets. The analysis results obtained from the proposed model indicated that the strengthened specimens showed fully composite behavior before their flexural failure. Especially, the specimen strengthened by HCGS, which can overcome the limitations of conventional epoxy resin, showed a similar flexural performance with that strengthened by a conventional epoxy resin.

• Journal of the Korean GEO-environmental Society
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• v.18 no.7
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• pp.13-20
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• 2017

Soil nailing is ground reinforcement method using the shear strength of ground and the pullout shear resistance force of nail. It is mainly used for reinforcement of cut slopes, earth retaining structures and retaining walls, etc. It may be designed considering the pullout resistance of nail in the case of earth retaining structure and retaining wall, but it should be designed considering not only pullout resistance but also shear and bending resistance in the case of slope. However, conservative designs considering only pullout resistance are being done and most of the studies are about increasing pullout resistance by improving of material, shape and construction method of nail. Actually, Shear bending deformations occur centering on the active surface in ground reinforced with the nail. The grout with relatively low strength is destroyed and separated from the reinforcing material. As a result, the ground is collapsed while reducing the frictional resistance rapidly. Therefore, it is necessary to develop the method to increase the shear resistance while preventing separation of nail and grout body. In this study, an experimental study was conducted on new soil nailing method which can increase shear resistance by forming protrusions through pressurized grouting after installing a packer on the outside of deformed bar.

• Journal of the Korean Geosynthetics Society
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• v.18 no.1
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• pp.67-77
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• 2019

The grouting method is utilized to reinforce and waterproof poor grounds, enhance the bearing capacity of structures damaged resulting from settlement due to elevation and vibration or differential settlement, and for cutoff. The purpose of this research is to enhance the compressive strength of grout materials by using aramid fiber and develop a high-strength ground improvement method by using blast furnace slag powder. In this regard, this study has conducted a uniaxial compression test after checking the high charge (higher than 50%) of the ratio of blast furnace slag powder and cement at 100:0, 70:30 and 40:60%, adding the aramid mixture based on 0, 0.5 and 1.0% of the cement and furnace slag powder weight and creating sand gels based on surface oiling rate of 0.7 and 1.2%. For the environmental review evaluation, a heavy metal exudation test and a pH test measurement have been conducted. The experiment results showed that 1% increase of aramid fiber led to 1.3 times greater uniaxial compression intensity. As for the hexavalent chrome, a 30% increase in blast furnace slag powder led to approximately 50% decrease in heavy metal exudation. However, the pH test revealed that a 30% increase in blast furnace slag powder resulted in approximately 0.5 increase in pH. Further research on the pH part is needed in the future.

• Magazine of the Korea Concrete Institute
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• v.7 no.6
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• pp.233-241
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• 1995

In this thesis, the fatigue tests were performed on a series of R /C beams repaired with co& crete-lmlyrner composites to investigate the fatigue bahavior. The three point loading system is used in the fatigue tests. In these tests, relations between the repeated loading cycles and mid-span deflections, number of repeated loading cycles when repaired beams were fractured, the bonding performance of repair materials were observed. On this basis, the mid-span deflections, the crack growth and failure mode of repaired R /C beams were studied. A S-N curve was drawn to present the fatigue strength of repaired beams. From the test results, it was shown that behavior of R /C beams repaired with polymer-cement series were very sirnillar to control beam about bonding performance, mid-span deflections and fatigue strength according to S-N curve drawn by the regression anlysis on the fatigue test results.

• Journal of Korean Society of Disaster and Security
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• v.7 no.2
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• pp.25-34
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• 2014

This study researches on global technology trend in each of composing technology, such as grouting material, grouting equipment, and construction management technology, which grouting technology has been founded upon to improve relatively inadequate domestic grouting technology and to establish the global standard for overseas expansion in the future. As far as grouting material is concerned, while High-Penetration and High-Strength micro cement ($1.5{\mu}m$) has been developed in 2000's in Japan, JinChun Kim et al. (2014) has been developing hybrid type micro cement grouting material and examining specifications of different kinds of projects and countries to analyze the trend of grouting equipment development. The specification contains detailed requisite specification for materials, mixers, pumps, agitators, and packers and it has to satisfy the standard of different countries to win global contracts. Grouting management technology can be divided into four different generations and Scandinavian countries, such as Sweden, Norway, and Finland, Japan, and South Korea are recently doing vigorous researches on the Fourth generation which merges grouting technology with ICT.

• Journal of the Korean Geosynthetics Society
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• v.20 no.2
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• pp.23-33
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• 2021

In Korea, many reservoirs have been built for the purpose of solving the food shortage problem and supplying agricultural water. However, the current 75.6% of the reservoirs are in serious aged as more than 50 years have passed since the year of construction. In the case of such an aging reservoir, the stability due to scour and erosion inside the reservoir is very reduced, and if concentrated rainfall due to recent abnormal weather occurs, the aging reservoir may collapse, leading to a lot of damage to property and human life. Accordingly, each agency that manages aging reservoirs uses Ordinary Portland Cement (OPC) as an injection material and applies the grouting method. However, in the case of OPC, it may deteriorate over time and water leakage may occur again. And there are environmental problems such as consumption of natural resources and generation of greenhouse gases. So, there is a need to develop new materials and methods that can replace the OPC. In this study, an laboratory test and analysis were performed on the grout material developed to induce a curing reaction similar to that of OPC by recycling power plant byproduct. In addition, test in the field such as electric resistivity survey, Standard Penetration Test (SPT), and field permeability test were performed to analyzed to reinforcement effect and determine the possibility of using instead of OPC. As a results of the test, in the case of recycled power plant byproduct, the compressive strength was 2.9 to 3.2 times and the deformation modulus was 2.3 to 3.3 times higher, indicating that it is excellent in strength and can be used instead of OPC. And it was analyzed that the N value of the reservoir was increased by 1~2, and the coefficient of permeability (k) decreased to the level of 8.9~42.5%. showing sufficient reinforcing effect in terms of order.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.5
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• pp.773-786
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• 2018

In this paper, viscosity features of sealant (bentonite-cement slurry), which is used for umbrella arch method in tunnel, were studied. The sealant must secure optimal strength and capacity for the waterproof and stabilization of borehole as well as to satisfy groutability. In this study, the variation of viscosity was measured with different mixing processes. With an increase of initial mixing period with water and bentonite mixture, the required time for the rapid increase of viscosity of the sealant is shorten. With increase of mixing period, the possibility of swelling of bentonite will increases and this can lead increase of the viscosity of the mixture. In addition, the behaviors of sealant vary with a drastic increase of the viscosity: thixotropy and rheopexy. Furthermore, the bentonite/water mixing period influences on the bleeding features of the sealant. Further study is required to introduce the guideline, which can be applicable in the field in the aspect of required capacity of the sealants and mixing processes of the ingredients.