• Magazine of the Korea Concrete Institute
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• v.6 no.1
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• pp.111-119
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• 1994

The strength of vertical joints of precast concrete large panel structures depends on the many factors, such as the bond strength of grout concrete (or mortar), the interlocking of the shear keys, the dowel action of horizontal bars. Many experimental studies have been conducted to in vestigate the shear strength of the vertical joints. In domestic, a few design formulas to predict shear strength of the vertical joint were proposed by some investigators, but formulas were based on limited experimental results. The objective of this paper is to propose a suitable formula for the shear strength of vertical joints with 94 vertical joints experimental data using the modified Mohr-Coulomb's 4ield theory and regression analysis. From the comparison of the proposed formula with others, it is shown that the proposed formula can be used economically for the design of vertical joints.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.665-678
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• 2007

It was applied the grouting method to fill densely the space between the bottom of the caisson and the ground with the grout mixture mixed with anti-washout admixture after locating accurately the precast caisson on three concrete landing pads but it is far different from a costly conventional method, which place concrete to build the foundation of reinforcement concrete on the spot after excavating inside of the temporary coffering wall for the bridge foundation in the sea. To verify the grouting method in advance, the full-scale trial test was performed twice on the land. After confirming the fluidity of material for the injection and some possible problems during construction and then enhancing the original design, the main process is ongoing and it has been finished 12 spots until now. The purpose of this study is to introduces for the first time in Korea the grouting method including the automatic and the manual monitoring process applied to, based on the main process of the caisson foundation finished already in the site. In a similar construction it is sincerely expected to be referred to in the future.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.111-116
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• 2010

The treatment of heavy metal, in the waste ash from incinerator and mine solid waste, by using alkali-soluble acrylic copolymer emulsion, that is effective in the absorption of heavy metal has been studied. It seemed that alkali soluble acrylic copolymer emulsion was very effective in the absorption of Hg, Pb, Cd and Cu in this test. Also, eco-friendly thixotropic grout, using alkali soluble acrylic copolymer emulsion, that is effective in the absorption of heavy metal, for the recycling of waste ash from incinerator and mine solid waste has been tested. It was observed that waste ash could be used as a raw material of eco-friendly thixotropic grout mortar due to the effectiveness of alkali soluble acrylic copolymer emulsion in the fixation of heavy metals including $Cr^{6+}$ from waste ash in this test.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.229-239
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• 2008

This paper compares the load transfer efficiency between precast concrete pavement specimen and typical concrete pavement specimen by means of laboratory and field tests. An experimental method was developed to evaluate the load transfer efficiency of the dowel bars buried in the concrete pocket and grouted with cement mortar. The test results showed that the load transfer efficiency of the specimen for the dowel bars repaired with grout was equivalent to that of the control specimen. In addition, a series of FWD field tests were conducted on the precast pavement to evaluate the joint stiffness. The field test results revealed that the central deflection of the precast slab slightly increased but the load transfer efficiencies at the joints were almost the same as those in the typical concrete pavement slab.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.77-84
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• 2006

Unlike homogeneous material structure, the behavior of masonry structure is not perfectly elastic even in the range of small deformations because it is a non-homogeneous and anisotropic composite structural material, consisting of masonry units, mortar, and grout. This paper proposes a simplified way of investigating the evolution of the deformation and damage of the structure subjected to a series of successive ground motions with varying shaking. Especially, the most simple but useful algorithm of Fast Fourier Transformation (FFT) has been adopted to investigate the evolution of the deformation and damage of the structure tested on the shaking table. Moreover, the development of a hi-linear curve for an equivalent SDOF system which is obtained by exploiting the frequency and stiffness relationship was discussed. Finally, some important findings related to inelastic properties of the URM are summarized.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.4
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• pp.651-668
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• 2017

For initial stability of the tunnel, the primary support, Shotcrete and rockbolt shall be placed in the most appropriate time. This is because the role of such support plays a vital role in long-term and short-term tunnel stability. In this study, the rock bolt is an important supporting system that receives the external pressure generated by the stress relaxation during tunnel excavation as axial force and transmits it to the shotcrete on the tunnel excavation surface. Until now, most of the materials of rock bolts have been used in the field, but there have been many problems such as uncertain quality of Chinese materials entering the market, poor packing due to falling down of rock bolts when filled with mortar, and corrosion due to water. Therefore, in this study, we have developed a high strength steel pipe rock bolt using Autobeam material to solve and improve various problems of existing rock bolts. In order to evaluate the performance of the developed bolt, field tests were carried out and the existing mortar filler in order to improve the performance of the rock bolt, the design and construction criteria were studied and the results were included in this paper.

• Journal of Industrial Technology
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• v.3
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• pp.103-116
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• 1983

Recent developments in multi-storey buildings for residential purpose have led to the extensive use of shear walls for the basic structural system. When the coupled shear wall system is used, joined together with cast-in-place concrete or mortar (or grout), the function of the continuous joints is a crucial factor in determining the safety of L.P. Precast concrete shear wall structures, because the function of the continuous joints(Vertical wall to wall joints) is to transfer froces from one element(shear wall panel) to another, and if sufficient strength and ductility is not developed in the continuous joints, the available strength in the adjoining elements may not be fully utilized. In this paper, the influence of the stiffness of vertical joints(wet vertical keyed shear joints) on the behaviour of precast shear walls is theoretically investigated. To define how the stiffness of the vertical joints affect the load carrying capacity of L.P.Precast concrete shear wall structure, the L.P.Precast concrete shear wall structure is analyzed, with the stiffness of the vertical joints varying from $K=0.07kg/mm^3$(50MN/m/m) to $K=1.43kg/mm^3$(1000MN/m/m), by using the continuous connection method. The results of the analysis shows that at the low values of the vertical stiffness, i.e. from $K=0.07kg/mm^3$(50MN/m/m) to $K=0.57kg/mm^3$(400MN/m/m), the resisting bending moment and shearing force of precast shear walls, the resisting shearing force of vertical joints and connecting beams are significantly affected. The detailed results of analysis are represented in the following figures and Tables.

• Explosives and Blasting
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• v.27 no.1
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• pp.32-37
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• 2009

To look over the effect of mixed proportion of cement, sand and water on strength, 162 tests were made for 9 mix proportions. It was observed that strength increased as water in the mixture is reduced. As a result of the control of sand ratio by 50%, the execution strength increased when the sand ratio is raised. Strength was consistent during curing period on each mix proportion, but there were sections where it suddenly increased. Poisson's ratio widely ranged from 0.13 to 0.27, and Young's modulus also broadly ranged from 13.79MPa to 33.25MPa. Poisson's ratio had nothing to do with uniaxial compressive strength, wheras Young's modulus was concerned with it. Young's modulus from theory and experiment showed similar outcome on the 3rd curing day, however, the strength from theory was higher than that from test after 3rd day. In consequence, there was a great change of strength between 3rd and 7th curing day. In addition, it is more efficient to use field strength value between the 3rd and 7th day and to apply Young's modulus on it for determining the exact time.

• Resources Recycling
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• v.27 no.6
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• pp.30-37
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• 2018

A series of experiment was conducted to evaluate basic performances of low-pH, anti-washing grouts incorporating gypsum which applied for reinforcing underwater cavities in limestone- grounds. Various types of mix proportions were designed and the fluidity, strength and environmental impact of these mixtures were evaluated. The flowability was evaluated under two conditions, i.e., flows without and with pressing, respectively. Strength was measured for the hardened mixtures fabricated under conditions of air and water injections. The environmental impacts including the pH of the suspension and the suspended solids concentration for the mixtures were evaluated. The low pH of fresh mixture suspension, below than 10, was achieved by incorporation of gypsum. The mix proportions of cement-quartz powder-gypsum binders and chemical agents resulted in mortar natural flow 7-10 cm and uniaxial compressive strength 4 MPa were derived.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.115-127
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• 2019

The low-flow grouting injection technique, the target construction method for this study, is a method of pouring mortar into the ground by non-emission replacement principle, which can be expected to increase the density of the ground, and, in some cases, be used as a base file using the strength of the high injection solids, along with low noise, low pollution, and high durability. To verify that the dynamic characteristics of the ground are improved by the low-flow injection technique, the test work was conducted on the site and physical tests were performed, and the quality of the improvement formed in the ground was verified through the indoor test on the core and core recovery rate was analyzed. The density logs test layer calculated the volume density of the ground layer by using the Compton scattering of gamma-rays, and the sonic logs was tested on the ground around the drill hole using a detector consisting of sonar and receiver devices inside the drill hole. As a result of the measurement of the change in physical properties (density and sonic logs) before and after grouting, both properties were basically increased after infusion of grout agent. However, the variation in density increase was greater than the increase in speed after grouting, and the ground density measurement method was thought to be effective in measuring the fill effect of the filler. Strength and core recovery rates were measured from specimens taken after the age of 28 days, and the results of the test results of the diffusion and strength test of the improved products were verified to satisfy the design criteria, thereby satisfying the seismic performance reinforcement.