• Title/Summary/Keyword: Concrete properties

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Interaction of magnetic water and polypropylene fiber on fresh and hardened properties of concrete

  • Ansari, Mokhtar;Safiey, Amir
    • Steel and Composite Structures
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    • v.39 no.3
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    • pp.307-318
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    • 2021
  • Utilizing fibers is an effective way to avoid the brittle behavior of the conventional concrete and can enhance its ductility. In particular, propylene fibers can improve concrete properties, including energy absorption, physical and mechanical properties, controlling shrinkage cracks. The increase of fiber density leads to an increase of the overlapping surface of the fiber of concrete and, in turn, a decrease of cracks developed in the concrete. However, the workability of fiber reinforced concrete tends to be lower than the conventional concrete owing mainly to the hairline thickness and excessive concentration of fibers. The low slump of concrete impedes the construction of reinforced concrete members. In this research, we study if the utilization of magnetic water can alleviate the workability issue of young fiber reinforced concrete. To this end, the compressive and flexural strength of four types of concrete (conventional concrete, fiber reinforced concrete, magnetic concrete, magnetic fiber-reinforced concrete) is studied and compared at three different ages of 7, 14, and 28 days. In order to study the influence of the fiber density and length, a study on specimens with three different fiber density (1, 2, 5 kg of fiber in each cubic meter of concrete) and fiber length (6, 12, 18 mm) is undertaken. The result shows the magnetic fiber concrete can result in an increase of the flexural and compressive strength of concrete at higher ages.

Effect of horizontal joints on structural behavior of sustainable self-compacting reinforced concrete beams

  • Ibrahim, Omar Mohamed Omar;Heniegal, Ashraf Mohamed;Ibrahim, Khamis Gamal;Agwa, Ibrahim Saad
    • Advances in concrete construction
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    • v.10 no.5
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    • pp.455-462
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    • 2020
  • This study investigated the effect of horizontal casting joints on the mechanical properties and structural behavior of sustainable self-compacting reinforced concrete beams (SCRCB). The experimental research consisted of two stages. The first stage used four types of concrete mixtures which were produced to indicate the effects of cement replaced with cement waste at 0%, 5%, 10%, and 15% by weight of cement content on fresh concrete properties of self-compacting concrete (SCC) such as, passing ability, filling ability, and segregation resistance. In addition, mechanical properties such as compressive, tensile, and flexural strength were also studied. The second stage selected the best mixture from the first stage and studied the effect of horizontal casting joints on the structural behavior of sustainable SCRCBs. The effect of horizontal casting joints on the mechanical properties and structural behavior were at the 25%, 50%, 75%, and 100% of sample height. Load deflection, failure mode, and theoretical analysis were studied. Results indicated that the incorporation of replacement with cement waste by 5% to 10% led to economic and environmental advantages, and the results were acceptable for fresh and mechanical properties. The results indicated that delaying the time for casting the second layer and increasing the cement waste in concrete mixtures had a great effect on the mechanical properties of SCC. The ultimate load capacity of horizontal casting joints reinforced concrete beams slightly decreased compared with the control beam. The maximum deflection of casting joint beams with 75% of samples height is similar with the control beam. The experimental results of reinforced concrete beams were substantially acceptable with the theoretical results. The failure modes obtained the best forced casting joint on the structural behavior at 50% height of casting in the beam.

AN EXPERIMENTAL STUDY ON THE PROPERTIES & APPLICATION FOR FLY ASH OF CONBINED HEAT POWER PLANT - FOCUSSED HIGH STRENGTH CONCRETE - (열병합발전소 플라이애쉬의 특성 및 활용방안에 관한 실험적 연구 -고강도 콘크리트를 중심으로-)

  • 권영호;백명종;이보근;박칠림
    • Proceedings of the Korea Concrete Institute Conference
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    • 1994.10a
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    • pp.211-216
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    • 1994
  • This study dealt with the properties for fly ash of conbined heat power plant and application for concrete industry. For this purpose, fly ash sampled Ulsan conbined heat power plant and analyzed for physical and chemical properties. As analyzed results of fly ash, contents of $SiO_ and Al_O_ $in the fly ash of Ulsan were less than those of Thermo-electric power plant(Boryuing), but contents of CaO were tem times as much as those of Boryung, because of these differences, it is expected that pozzolanic activity of concrete using fly ash of Ulsan will be different from another fly ash. Concrete specimens were tested to evaluate concrete preformance when 10 to 50 percent of the portland cement by weight in the concrete mix was replaced with fly ash of conbined heat power plant. As test results, workability and consideration in the fresh concrete were increased and concrete strength was showed more than 400kg/$\textrm{cm}^2$ for the required age. This study would be provided valuable data for the practical utilization of fly ash(conbined heat power plant). In the future, properties of fly ash concrete including long term strength, elapsed time, pozzolanic activity, modulus of elasticity, sulfate resistance, shrinkage, freeze-thaw durability and so on will be studied.

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A Study on the Engineering Properties of Concrete Using Blast-furnace Slag Powder (고로슬래그 미분말을 사용한 콘크리트의 공학적 특성에 관한 연구)

  • Lee, Sang-Soo;Won, Cheol;Kim, Dong-Seok;Park, Sang-Jun
    • Journal of the Korea Concrete Institute
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    • v.12 no.4
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    • pp.49-58
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    • 2000
  • There are many methods to improve the performance of concrete. Especially, granuated blast furnace slag. by-products used in concrete as the replacement material of cement, could contribute to improve the fluidity, resistance of chemical attack and strength of concrete. Also, it could contribute to decrease the rate of generating hydration heat, in addition to cost-down of concrete and prevention of enviromental pollution. Therefore, in order to establish the systemical application of granuated blast furnace slag in normal concrete, the engineering properties of concrete, such as fluidity, strength, setting and hydration properties etc.. was evaluated. In this study, replacement ratio of granuated blast furnace slag was 0, 30, 50, 70(%), and target slump was 8, 12, 15, 18(cm). Results from the experiment, granuated blast furnace slag showed the outstanding effects of improving the engineering properties of concrete. From now on, positive application of granuated blast furnace slag is expected in the point of improving the performance and cost-down of concrete.

A Study on Reducing Deterioration in Long-span Slab Concrete (장스팬 슬라브 콘크리트의 열화저감에 대한 연구)

  • Kim, Dae-Geon;Cha, Hun;Choi, Sang-Hwan;Moon, Kyeong-Sik
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2014.11a
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    • pp.11-12
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    • 2014
  • In this study, fundamental properties of concrete mixed with fiber has been analysed. Compressive strength, tensile strength and plastic shrinkage has been tested to conduct the optimum addition ratio of fiber. Effect to control press concrete's cracking has been tested. The following results could be made as the conclusion. For the flowability, slump decreased about 41-79% when all types of fiber used in the concrete. When the addition ratio of fiber is 1.2%, the slump of concrete decreased about 45%. For the strength properties. all the specimens with different addition ratio of fiber shown higher compressive strength comparing with Plain. Comparing with Plain, cracking decreased when the fiber added. Especially, when NY fiber used in the concrete, the plastic shrinkage did not occurred. In addition, Latex modified concrete(LMC) has improved superior physical and chemical properties. The properties of latex, combined with the low water-cement ratio, produce a concrete that has improved flexural, tensile, and bond strength, lower modulus of elasticity, increased freeze-thaw resistance, and reduced permeability compared to conventional concrete of similar mix design.

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A Study on the Development of Corrosion Prediction System of RC Structures due to the Chloride Contamination (염해를 받는 철근콘크리트 구조물의 철근부식시기 예측시스템 개발에 관한 연구)

  • Kim, Do-Gyeum;Park, Seung-Bum
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.4 no.1
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    • pp.121-129
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    • 2000
  • In general. service life of the sea-shore concrete structures is largely influenced by the corrosion of reinforcing steel due to the chloride contamination, and the penetration of chloride ions into concrete is governed by concrete condition state as a micro-structure. In this study, characteristics of chloride diffusion in concrete are analyzed in accordance with the mixing properties and durability of concrete, by considering the facts that micro-structure of concrete varies with the mixing properties and can indirectly be analyzed by using the durability test. In order to predict the service life of existing concrete structures, chloride diffusion equation for the concrete structures under various service conditions and the major parameters used in that equation are formulated as the mathematical models. Based on the results of chloride diffusion analysis in accordance with the mixing properties and durability of concrete and mathematical models formulated in this study, a prediction system is developed to predict the corrosion initiation of reinforcing steel in the sea-shore concrete structures.

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Fresh and hardened properties of rubberized concrete using fine rubber and silpozz

  • Padhi, S.;Panda, K.C.
    • Advances in concrete construction
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    • v.4 no.1
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    • pp.49-69
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    • 2016
  • This work investigates the mechanical properties of conventional concrete (CC) and self compacting concrete (SCC) using fine rubber and silpozz were accompanied by a comparative study between conventional rubberized concrete (CRC) and self compacting rubberized concrete (SCRC). Fine rubber (FR) from scrap tires has replaced the fine aggregate (FA) and Silpozz has been used as a replacement of cement at the proportions of 5, 10 and 15%. Silpozz as a partial replacement of cement in addition of superplasticiser (SP) increases the strength of concrete. Fresh concrete properties such as slump test, compaction factor test for CRC, whereas for SCRC slump flow, $T_{500}$, V-funnel, L-box, U-box, J-ring tests were conducted along with the hardened properties tests like compressive, split tensile and flexural strength test at 7, 28 and 90 days of curing. The durability and microstructural behavior for both CRC and SCRC were investigated. FR used in the present study is 4.75 mm passing with fineness modulus 4.74.M30 grade concrete is used with a mix proportion of 1:1.44:2.91 and w/c ratio as 0.43. The results indicate that as FR quantity increases, workability of both CRC and SCRC decreases. The results also show that the replacement of natural fine aggregate (NFA) with FR particles decreases the compressive strength with the increase of flexural strength observed upto 5% replacement of FR. Also replacement of cement with silpozz resulted enhancement of strength in SCRC.

The Properties of Lightweight Concrete Using the Expanded Clay (경량골재 콘크리트의 역학적 특성)

  • 김태형;하상진;최영화;김동인
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.10a
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    • pp.249-252
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    • 1999
  • Recently, the use of lightweight concrete in architectural structures are increasing. It is considered important to control the quality of lightweight concrete. The purpose of this study is to find mechanical properties of lightweight concrete using the expanded clay. Thus, slump, air content, compressive strength, splitting tensile strength, length change ratio, unitweight change ratio and absorption of lightweight concrete have been investigated. As a result, it was shown that proper expanded clay replaced by coarse aggregate in concrete was considered as a good replacement of lightweight concrete.

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Diffusion of Chloride Ion in Antiwashout Underwater Concrete (수중불분리성 콘크리트의 염화물이온 침투저항성에 대한 고찰)

  • 김성수;김진철;김홍삼;김종필;김동현
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.10a
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    • pp.451-454
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    • 2000
  • Recently, the antiwashout underwater concrete has been increasingly used for underwater structure such as high strength massive concrete structures. However, Concrete has poor quality ad durability due to dilution with separating cementitious material. In this study, specimens were made with antiwashout underwater concrete replaced with mineral admixtures to improve their properties and were placed in air, water, and salt water. To estimation the chloride ion permeation in concrete, ASTM C 1202 Test was performed. The experimental results demonstrate that the increase of the admixtures improved the properties of antiwashout underwater concrete.

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A Study on the Properties of High Performance Concrete Using Low Heat Portland(Type IV) Cement (저열 포틀랜드(4종)시멘트를 사용한 고유동, 고강도콘크리트에 관한 연구)

  • 최광일;김기수;하재담;김동석;이순기;이동윤
    • Proceedings of the Korea Concrete Institute Conference
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    • 1997.10a
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    • pp.422-429
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    • 1997
  • In recent years, concrete construction have become larger and higher and are demanding high performance concrete with lower heat to prevent thermal cracking, far greater workability, high strength and durability. Application of low heat portland(Type IV) cement for the high performance concrete is the best solution to satisfied those requirements. Here are explained the basic properties of fresh concrete as well as hardened concrete of high performance concrete using low that portland cement.

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