Processing math: 100%
  • Title/Summary/Keyword: Engineering Properties of concrete

Search Result 2,674, Processing Time 0.039 seconds

Fishes distribution and their connection to artificial reefs off Bukchon, Jeju Island using geographic information system (지리정보시스템을 활용한 제주도 북촌의 인공어초해역에서 어류 분포와 어초와의 관계)

  • KANG, Myounghee;FAJARYANTI, Rina;JUNG, Bongkyu;YOON, Eun-A;MIN, Eunbi;LEE, Kyounghoon;OH, Woo-Seok;PARK, Geunchang;SHIN, Young-Jae;CHOI, Yong-Suk;YI, Byung-Ho;HWANG, Doojin
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.55 no.2
    • /
    • pp.121-128
    • /
    • 2019
  • Various artificial reefs provide the fish habitat and nursery, and contribute the improvement of fisheries productivity. The evaluation methods of fishery resources in the artificial reefs have been done by fishing, scuba diving, underwater camera, and scientific echo sounder/sonar. There are a number of studies using echosounders on the quantitative and qualitative evaluations of artificial reefs in various seas around the world. This study focused on the spatial distribution of fishes around artificial reefs and the influential area of reefs off Bukchon, Jeju Island. Not only acoustic data but also various properties of artificial reefs were used in the geographic information system to extract relevant results. As a result, the major material of reefs on this study site was concrete and the number of reefs with that material was the most. The volume of reefs consisted of steel only and steel with riprap was considerably large compared to other reefs. The average NASC in the vertical distribution of fishes in artificial reefs was 31.6m2/nm2 in April, and that was 61.3m2/nm2 in June. The distance between the fish school and their nearest reef in June morning had a wide range from 750 to 3250 m. On the basis of the influence ray of artificial reefs, it had a tendancy of NASC to decrease with distance from the reef in the June morning. It is a preliminary study to present the geospatial analysis example to understand a better way of comprehensive artificial reef environments.

Possibility of Using Landfill Coal Ash as CLSM Material for Emergency Restoration of Ground and Road Joint Parts (지반 및 도로 공동부의 긴급복구용 CLSM 재료로 매립 석탄저회 활용 가능성)

  • Jin-Man Kim;Sang-Chul Shin;Kyoung-Nam Min;Ha-Seog Kim
    • Journal of the Korean Recycled Construction Resources Institute
    • /
    • v.11 no.1
    • /
    • pp.55-61
    • /
    • 2023
  • This study aims to develop CLSM fill material for emergency restoration using landfill coal ash. As a result of examining physical properties such as particle size distribution and fines content of landfill coal ash, bottom ash, fly ash, and general soil were mixed, and SP was found to have a density of 2.03 and a residual particle pass rate of 7.8 %. CLSM materials that secure fluidity in unit quantities without using chemical admixtures such as glidants and water reducing agents have a high risk of material separation due to bleeding. As a result of this experiment, it was found that the bleeding ratio did not satisfy the standard in the case of the specimen with a large amount of fly ash and a lot of addition of mixing water. As a result of the compressive strength test, the strength development of 0.5 MPa or more for 4 hours was found to be satisfactory for the specimens using hemihydrate gypsum with a unit binder amount of 200 or more, and the remaining gypsum showed poor strength development. Although it is judged that landfill coal ash can be used as a CLSM material, it is necessary to identify and apply the physical and chemical characteristics of coal ash buried in the ash treatment plant of each power generation company.

Examination of Color Difference in Elastic Pavement that uses EPDM Chip using Ultraviolet Ray Accelerated Weathering Test (자외선 촉진 내후성 시험에 의한 EPDM Chip을 사용한 탄성포장의 색차분석)

  • Hong, Chang Woo
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.31 no.1D
    • /
    • pp.91-98
    • /
    • 2011
  • Recently, the usage of elastic paving using EPDM Chip instead of pedestrian sidewalk blocks or permeable concrete used mostly for pedestrian walk, trails and in parks has been increassed as it can absorb impact during walking and produce wide range of colors and designs. However, the properties of EPDM Chip including elasticity and durability are decreased when exposed to ultraviolet ray and scenic paving functions through various colors are lowered due to the yellowing phenomenon. In this study, ultraviolet ray accelerated weathering test has been conducted to analyze the color changes in EPDM Chip and polyurethane resin, which are the main ingredients of elastic paving, when exposed to ultraviolet ray. The color differences are quantitatively analyzed through the color value coordination of the colored space by using the color difference scheme. The experimental results show that the color changes in BL polyurethane resin which is used most frequently at present was larger than that of EPDM Chip. Moreover, the total color difference, ΔE, of BC polyurethane resin are 3.162 on the 14th day of commencement of acceleration, which is 6 times greater color change resistance against ultraviolet ray than that of BL polyurethane resin with total color difference of 20.639. Therefore, the usage of BC polyurethane resin, which is manufactured to have chain-type molecular structure by using the isocyanate as the HMDI at the time of producing polymer, as binder in elastic paving with EPDM Chip is found to be a highly efficient method of restraining the color changes due to the ultraviolet ray.

Experimental Study on the Proposal of an Assessment Method and Quality Standard for Identifying the Fine Particles of Clay Components in Fine Aggregates (잔골재의 토분 평가방법 및 품질기준 제안을 위한 실험적 연구)

  • Choi, Hyun-Kyu;Han, Min-Cheol
    • Journal of the Korea Institute of Building Construction
    • /
    • v.22 no.6
    • /
    • pp.585-596
    • /
    • 2022
  • The purpose of this study is to propose an assessment method to analyze clay collectively referred to as fine particles of clay components contained in fine aggregates, and to propose quality standards for clay use through correlation with the performance of concrete to verify the properties of clay measured according to the method. As a result, it is analyzed that it will be suitably utilized as a method to assess the fine particles of the clay component of fine aggregates through the component analysis of XRF. Regarding the related quality standards, considering the error rate of about 10% of KCS 14 20 10, the related quality standards were analyzed to be safe when Al2O3+Fe2O3+MgO is 23.5% or less and SiO2+K2OSiO2+K22O is 66.5% or more. To build on this study, it is expected that a comprehensive review will be conducted through additional follow-up studies such as on clay of coarse aggregates and durability analysis to establish a system for quality control of the soil fraction of aggregates.

Evaluation of Properties of Warm-Mix Recycled Asphalt Binder for Promoting the Recycled Asphalt (순환골재 활성화를 위한 중온 재생 아스팔트 바인더 특성 평가)

  • An, Ji Hun;Kim, Nakseok
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.36 no.6
    • /
    • pp.1101-1107
    • /
    • 2016
  • As an increase in the amount of RAP, there are growing interests in recycling asphalt concrete. In case of using the RAP as recycled asphalt pavement, it tends to be quality deteriorate. Therefore, the amount of RAP using is advised to be limited or has to be used with rejuvenator. In this study, asphalt mixture containing WMRA was analyzed to be used up to 50% for the sake of convenience on the process. As the results of evaluation, there was no significant difference in case of using 30% of RAP in the test of Marshall stability. However, in case of WMRA using up to 50%, it was satisfied criteria by flow value at 34.7. Further, result of toughness test was found that the crack resistance showed 55% higher than using straight asphalt when using WMRA binder up to 50%. According to the results of directly comparing crack resistance through repeated direct tensile test, it was shown that the fatigue crack resistance of WMRA pavement was increased by 263%. Therefore, it was shown that WMRA binder was effective in recycling RAP because WMRA binder could increase the percentage of RAP using up to 50%.

A Behavior Test on a Frictional-Wedge-Type Vibration Isolation Device for Vibration Reduction of a Railway Track (열차 진동 저감을 위한 마찰쐐기형 방진장치의 거동 시험)

  • Lee, Chanyoung;Choi, Sanghyun;Lee, Yooin;Kwon, Segon;Koh, Yongsung;Ji, Yongsoo
    • Journal of the Society of Disaster Information
    • /
    • v.11 no.1
    • /
    • pp.45-54
    • /
    • 2015
  • In the case of railway facilities in cities such as a railway station or a bridge, the significance of design for reducing vibration and noise is getting more significant. The vibration control solution is in need especially for an elevated railway station to block vibration of a train and secondary noise effectively. Even though a vertical vibration isolation device is able to be applied effectively to railway facilities such as elevated railway stations which transfer vibration directly from a train to a structure, the development of the vertical device is much slower than a horizontal vibration isolation device. In this paper, a vibration isolation device using wedge type friction material which is currently developing to reduce train-induced vibration effectively is introduced and test results for verification of dynamic performance is also presented. The vibration test on a concrete structure equipped with the developed vibration isolation device is conducted through which the isolation performance and dynamic properties are verified and needs for improving the performance of the device is identified.

Strength and Durability Characteristics of Low-alkali Mortar for Artificial Reefs Produced by 3D Printers (인공어초 3D 프린터 출력을 위한 저알칼리 모르타르의 강도와 내구성능)

  • Lee, Byung-Jae;Kim, Bong-Kyun;Kim, Yun-Yong
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.26 no.1
    • /
    • pp.67-72
    • /
    • 2022
  • Concrete prevents corrosion of reinforcing bars due to its strong alkalinity. However, in the sea, strong alkali components with a pH of 12 to 13 are eluted, which adversely affects the ecological environment and growth of marine organisms. In this study, the mechanical properties and durability of the low alkali mortar were evaluated for the development of a low alkali mortar for the 3D printed artificial reefs. As a result of evaluation of strength characteristics, the α-35 mixture, which were produced with fly ash, silica fume and α-hemihydrate gypsum, satisfied the strength requirement 27 MPa in terms of compressive strength. As a result of pH measurement, it was found that mixing with alpha-type hemihydrate gypsum resulted in minimizing pH due to the the formation of calcium sulfate instead of calcium hydroxide production. As a result of the chloride ion penetration resistance test, the α-35 mixture exhibited the best performance, 3844C. As a result of measuring the length change over time, the α-35 mixture showed the shrinkage 33.5% less compared to the Plain mix.

Development of Surface Pavement Materials for Environment-Friendly Farm Road (환경친화형 경작로를 위한 표층포장재료의 개발)

  • Sung, Chan-Yong;Kim, Young-Ik
    • Korean Journal of Agricultural Science
    • /
    • v.31 no.2
    • /
    • pp.105-114
    • /
    • 2004
  • This study was performed to examine the physical and mechanical properties of eco-concrete using soil, natural coarse aggregate, soil compound and polypropylen fiber. The mass loss ratio was decreased with increasing the content of coarse aggregate and soil compound. The compressive strength, flexural strength, ultrasonic pulse velocity and dynamic modulus of elasticity were increased with increasing the content of coarse aggregate, soil compound and polypropylene fiber. The compressive and flexural strengths were showed in 8.07 MPa and 2.641 MPa at the curing age 28 days, respectively. The coefficient of permeability was decreased with increasing the content of coarse aggregate and soil compound, but it was increased with increasing the content of polypropylene fiber. The lowest coefficent of permeability was showed in 5.066×109cm/s.

  • PDF

A Consideration on the Electromagnetic Properties of Road Pavement Using Ground Penetrating Radar (GPR) (지표투과레이더(GPR)에 의한 도로포장의 전자기적 특성값 고찰)

  • Rhee, Jiyoung;Shim, Jaewon;Lee, Sangrae;Lee, Kang-Hyun
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.40 no.3
    • /
    • pp.285-294
    • /
    • 2020
  • This study investigated the use of Ground Penetrating Radar (GPR) over a two-decade period on public roads, focusing on the electromagnetic characteristics of the pavement dielectrics and attenuation. From the results, a typical range of characteristic value, influencing factors, and a correction method were suggested. The typical dielectrics of asphalt pavements were 4-7, as measured by an air-coupled 1 GHz GPR antenna. The dielectrics of concrete pavements were very large in the early age, but were drastically reduced with ageing. Ten years on, collection was in the range of 6-12. The dielectrics were proportional to the relative humidity (R.H.) of the atmosphere. The effects were reduced to one eighth with an overlay. Attenuation generally increased with thickness of the road layer, and also increased where there was damage. The GPR results could also vary depending on the weather conditions as well as on the characteristics of the GPR equipment, even at the same frequency. Therefore, GPR surveys should be performed on road surfaces without debris on a single, fine day. The reliability of the GPR analysis could be improved by cores and equipment calibration with other non-destructive test surveys.

A Fundamental Approach for Developing Deformation Strength Based on Rutting Characteristics of Asphalt Concrete (소성변형과의 상관성에 근거한 아스팔트 콘크리트의 변형강도 개발을 위한 기초연구)

  • Kim, Kwang-Woo;Lee, Moon-Sup;Kim, Jun-Eun;Choi, Sun-Ju
    • International Journal of Highway Engineering
    • /
    • v.4 no.4 s.14
    • /
    • pp.23-39
    • /
    • 2002
  • This study dealt with developing a new approach for finding properties which might represent rut resistance characteristics of asphalt mixture under static loading. Two aggregates, a normal asphalt (pen 60-80) and 5 polymer-modified asphalts were used in preparation of 12 dense-graded mixtures. Marshall mix design was used in determination of OAC and each mixture at the OAC was prepared for a newly-developed Kim test on Marshall specimen (S=10cm) and gyratory specimen (S=15cm), and for wheel tracking test. Kim test used Marshall loading frame and specimens were conditioned for 30min at 60C before loading through Kim tester an apparatus consisting of a loading column and a specimen and column holder Diameter (D) of column was 3cm and 4cm with each column having different radius (r) of round cut at the bottom. The static load was applied at 50mm/min in axial direction of the specimen, not in diametral direction. The maximum load (Pmax) and vertical deformation (y) at Pmax point were obtained from the test. A strength value was calculated based on the Pmax r, D and y by using the equation KD=4Pmax/π(D2(r2ryy2))2 and is defined as the deformation strength (kgf/cm2). The values of Pmax/y and KI=KD/y were also calculated. In general the leading column diameter and radius of round cut were significant factors affecting KD and Pmax values while specimen diameter was not. The statistical analyses showed the KD had the best correlation with rut depth and dynamic stability. The next best correlation was found from Pmax which was followed by Pmax/y and KI in order.

  • PDF