• Journal of the Korean GEO-environmental Society
• /
• v.18 no.10
• /
• pp.15-22
• /
• 2017

The soil improvement method so far has been developed with an emphasis on enhancing the strength of the ground. A soil improvement method using a excellent cementitious stabilizer in economical efficiency and handling property is mainly used. The soil improvement method using cementitious stabilizer is effective but environmental and human harmful substances are detected and environmental problems such as carbon dioxide emission and groundwater pollution are pointed out. Therefore, as part of an alternative method capable of solving such problems, researches on the soil improvement method incorporating biological technology are being actively carried out. This study was conducted to investigate the characteristics of strength change when mixed with environmentally friendly soil binder and microorganism in clay, and it was analyzed by uniaxial compression test, direct shear test, SEM, XRD. As a results of the test, we confirmed the cementation caused by microbially induced calcite precipitation and the strength increase enhancement by it.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.991-996
• /
• 2001

The long-term durability characteristics of high-early-strength concrete were assessed. The effect of long-term durability characteristics of high-early-strength concrete were investigated. In experiment, two different types of fiber were adopted for improvement of durability. High-early-strength fiber reinforced concretes using regulated-set cements are compared with high-early-strength concrete without fiber. The durability performance of the laboratory-cured high-early-strength concrete specimens was determined by conducting an accelerated chloride permeability, abrasion resistance, freeze-thaw, surface deicer salt scaling and wet-dry repetition test. The results indicated that incorporation of fibers enhance durability performance.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.11a
• /
• pp.199-200
• /
• 2022

In this study, the material properties of UHPC mixed with graphene was investigated. The compressive strength, the bending strength and the permeability test was conducted. As a result, there was no improvement in compressive strength by the graphene, but the bending strength increased by 20% by the graphene. The water penetration amount decreased by 80% by the graphene.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.2
• /
• pp.117-124
• /
• 2015

Currently, Eco-friendly construction materials are widely utilized for reducing $CO_2$ emission in construction. Furthermore various engineering fibers are also added for improving a brittle behavior in concrete. In the paper, concrete specimens with 10% and 20% replacement ratio with RHA (Rice Husk Ash) are prepared, and engineering behaviors in RHA and OPC concrete are evaluated with different addition of coconut fiber from 0.125~0.375% of volume ratio. Several basic tests including compressive strength, tensile strength, flexural strength, impact resistance, and bond strength are performed, and crack width and deflections are also measured in flexural test. RHA is evaluated to be very effective in strength development and 0.125% of fiber addition leads significant improvement in tensile strength, ductility, and crack resistance. RHA and coconut fiber are effective construction material both for reutilization of limited resources and performance improvement in normal concrete.

• International Journal of Advanced Culture Technology
• /
• v.8 no.3
• /
• pp.307-315
• /
• 2020

The physique and health status of Chinese college students have received a generous concern in recent years. The physical condition of Chinese college students is not good and this phenomenon is especially obvious among female college students, which has been an disputable fact. This study starts from exercise intervention to study the concrete influence of taijiquan (a kind of traditional Chinese shadow boxing) and five-animal exercises on human body balance ability; the study uses experimental apparatus to measure the specific impact of exercise intervention on human body balance ability; meanwhile, the study also applies data analysis to longitudinally study whether the two studied sports items affect body balance, and whether there is difference in terms of the influence of two sports items on human body balance ability. The conclusions are as follows: firstly, 24-style taijiquan and five-animal exercises can improve ankle muscle strength, and the focus and degree of the improvement are different; secondly, five-animal exercises have a better improvement effect on the flexor and extensor muscles of ankle joint and 24-style taijiquan is in the second place. Moreover, compared with 24-style taijiquan, there is no significant difference in terms of the improvement caused by five-animal exercises; thirdly, 24-style taijiquan has a better effect on the improvement of internal rotation and evertors muscle strength. Compared with 24-style taijiquan, five-animal exercises have no significant difference in terms of the improvement degree.

• Clinical Pain
• /
• v.20 no.2
• /
• pp.105-121
• /
• 2021

Objective: Physiologically, the vastus medialis muscle is the first muscle to undergo muscle atrophy, and it was thought that pain in patients with knee osteoarthritis could be reduced if this muscle could be strengthened and stabilized. The purpose of this study was to prove the effectiveness in knee osteoarthritis using polydioxanone sutures that have been tried in other musculoskeletal areas. Method: Forty knee osteoarthritis patients voluntarily participated in the study, and divided into 30 polydioxanone suture needle (MEST-B2375 produced by Ovmedi Co.) and 10 sham needle (without suture). And the needles were inserted into the vastus medialis muscle. In all patients, safety evaluation including blood tests and ultrasonography as well as efficacy evaluation including isometric maximal contractile strength of quadriceps muscle, weight bearing pain, impression of change, quadriceps angle, rescue drug intake were evaluated up to 30 weeks after the procedure. Results: Isometric maximal contractile strength showed a significant improvement at 4 weeks after the procedure in the polydioxanone suture group, and the weight-bearing pain showed a significant improvement at every visit in the polydioxanone suture group compared with baseline values. Patient global impression of change score showed significant improvement at 20 and 30 weeks, and clinical score showed improvement at every visit. Conclusion: Insertion of polydioxanone sutures showed improvement in muscle strength and knee pain by supporting and fixation of the vastus medialis muscle in patients with degenerative knee osteoarthritis. Insertion of polydioxanone sutures is considered to have a therapeutic effect in knee osteoarthritis patients.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09a
• /
• pp.527-532
• /
• 2010

Soil-cement has been broadly used for eco friendly pavement, slope protection and soft soil improvement since it used for the increase of soil strength with cement. Recently, additional agents are mixed with existing soil-cement so as to improve specific properties or functions such as strength, color and permeability of it. This study aims at figuring out the physical and mechanical properties of a soil-cement mixed with crashed oyster shell and loess. The study is specially focused on the applicability of oyster shell as an alternative material for sands. To have his objective achieved a series of uniaxial compression tests were conducted. As a result, it appears that usage of oyster shell may have effect on strength improvement of mixed soils.

• International Journal of Concrete Structures and Materials
• /
• v.4 no.2
• /
• pp.113-118
• /
• 2010

This article aims to study the effects of adding steel fibers to concrete on the mechanical behavior of steel fiber concrete (SFC) slabs. After formulating the SFC, an experimental work was, first, conducted on $160\;{\times}\;320$ mm cylindrical specimens and $70\;{\times}\;70\;{\times}\;280$ mm prisms. Then, this study was carried out on 20 rectangular $1,100\;{\times}\;1,100\;{\times}\;60$ mm small slabs submitted to a distributed load. Two types of fibers with hooked ends were used: long fibers (LF) of a length of 50 mm and short fibers (SF) of a length of 35 mm. The studied parameters are compressive and tensile strengths and Young's modulus. Plain concrete (PC) small slabs were also prepared to be compared to the SFC specimens. The results showed that the compressive strength of SFC increased up to 25% while the splitting tests showed an improvement of the SFC reaching 45%. Tests on SFC small slabs also showed that a smaller deflection is obtained with respect to PC, which indicates an improvement in strength (up to 100%), in ductility and in resistance to cracking. The LF gives a better improvement in strength than the SF for a 70% $kg/m^3$ of steel proportioning.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.2
• /
• pp.115-123
• /
• 2000

Piezocone Penetration Test has been performed in the soft ground over the site preparation area at Inchon International Airport(IIA). With the pore pressure dissipation test results, the changes in the permeability and the coefficient of consolidation in clayey soil were checked and the differences of the undrained shear stength verified the soft ground improvement effect from vane test and piezocone test both before and after the improvement. From the results, thin sand seam was found and this caused a big difference in the coefficient of permeability and consolidation. The coefficient of consolidation was high in the upper marine deposit and relatively low in lower marine deposit. It was found that the reduction of void ratio by preloading resulted in the reduction of coefficient of consolidation after the ground improvement. In addition, there were some variations of undrained shear strength when the number of 15 or 18 was used as the coefficient of piezocone(Nkt). However, when the average value of undrained shear strength calculated using Nkt=10 was applied, the result indicated the similar average value with the result of vane test and the increasing rate of strength( Δsu/Δ$\sigma$≒0.38) also showed the similar distribution.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.5
• /
• pp.45-51
• /
• 2010

This study is to evaluate an application of technology to the soft ground stability using quick lime pile in the field. We investigated properties of Korean quick lime by conducting loading test and theoretical consideration about a principle and property of soft ground improvement by quicklime. According to the test results, it was estimated that quick lime pile method has dehydration effect by absorption of quick lime, consolidation effect by swelling of pile, increasing bearing by strength of pile itself and decreasing sinking effect, etc. A material property of quick lime is favorable for construction and considerable strength. In the case of higher strength is required, using cement as additive would increase material strength.