• Title/Summary/Keyword: Engineering Properties of concrete

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Study on Anti-Washout Properties and Shear-Thickening Behaviors of Surfactant Added Cement Grouts (계면활성제 혼화제를 첨가한 시멘트 그라우트의 수중 불분리 특성 발현과 점도 증가 효과 연구)

  • Jang, In-Kyu;Seo, Seung-Ree;Park, Seung-Kyu
    • 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.

Time-dependent properties of lightweight concrete using sedimentary lightweight aggregate and its application in prestressed concrete beams

  • Chen, How-Ji;Tsai, Wen-Po;Tang, Chao-Wei;Liu, Te-Hung
    • Structural Engineering and Mechanics
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    • v.39 no.6
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    • pp.833-847
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    • 2011
  • We have developed a lightweight aggregate (LWA) concrete made by expanding fine sediments dredged from the Shihmen Reservoir (Taiwan) with high heat. In this study, the performance of the concrete and of prestressed concrete beams made of the sedimentary LWA were tested and compared with those made of normal-weight concrete (NC). The test results show that the lightweight concrete (LWAC) exhibited comparable time-dependent properties (i.e., compressive strength, elastic modulus, drying shrinkage, and creep) as compared with the NC samples. In addition, the LWAC beams exhibited a smaller percentage of prestress loss compared with the NC beams. Moreover, on average, the LWAC beams could resist loading up to 96% of that of the NC beams, and the experimental strengths were greater than the nominal strengths calculated by the ACI Code method. This investigation thus established that sedimentary LWA can be recommended for structural concrete applications.

Effects of environmental temperature and age on the elastic modulus of concrete

  • Yang, Shuzhen;Liu, Baodong;Li, Yuzhong;Zhang, Minqiang
    • Structural Engineering and Mechanics
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    • v.72 no.6
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    • pp.737-746
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    • 2019
  • Concrete mechanical properties change constantly with age, temperature, humidity and the other environmental factors. This research studies the effects of temperature and age on the development of concrete elastic modulus by a series of prism specimens. Elastic modulus test was conducted at various temperatures and ages in the laboratory to examine the effects of temperature and age on it. The experimental results reveal that the concrete elastic modulus decreases with the rise of temperature but increases with age. Then, a temperature coefficient K is proposed to describe the effects of temperature and validated by existing studies. Finally, on the basis of K, analytical models are proposed to determine the elastic modulus of concrete at a given temperature and age. The proposed models can offer designers an approach to obtain more accurate properties of concrete structures through the elastic modulus modification based on actual age and temperature, rather than using a value merely based on laboratory testing.

An approach of using ideal gradating curve and coating paste thickness to design concrete performance-(2) Experimental work

  • Wang, H.Y.;Hwang, C.L.;Yeh, S.T.
    • Computers and Concrete
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    • v.10 no.1
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    • pp.35-47
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    • 2012
  • The ideal gradating curve is used in this study to estimate densified aggregate blended ratio and total surface area of aggregate, there by under assigned paste amount of concrete, and coating paste thickness can then be deduced. Four groups of concrete mixtures were prepared and the corresponding concrete properties, such as workability, compression strength, ultrasonic velocity, surface resistivity and chloride ion penetration, were measured and finally the results are interpreted in terms of "coating thickness". The result shows as the coating thickness of the concrete is higher than critical one, the coating thickness on aggregate does affect the workability, and whatever workability is required the superplasticizer can be adjusted to achieve the demand workability. Under a fixed paste quality at the same age, coating paste thickness is inversely proportional to the concrete properties, especially as the coating thickness gets thinner.

A Study on the Engineering Properties of Concrete Using Cement Kiln Dust (킬른더스트를 사용한 콘크리트의 공학적 특성에 관한 연구)

  • 김기정;황인성;차천수;김성수;한천구
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.05a
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    • pp.267-270
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    • 2003
  • This study is intended to investigate the engineering properties of concrete, in which cement and fine aggregate are replaced with cement kiln dust(CKD), such as the properties of fresh concrete and hardened concrete and hydration heat history, for effective using method of CKD, a by-product produced in the process of making cement. According to the results, as the replacing ratio of CKD increases, slump and air content of concrete decreases remarkably due to an increase of viscosity and filling of the pores. As the properties of setting, initial and final setting time are shortened with an increase of the replacing ratio of CKD, and as the replacement of CKD for fine aggregate increases, setting time is shortened more greatly. Compressive strength increases due to filling of the pores and reduction of air content in comparison with plain concrete. When the replacement ratio of CKD for cement is 10% and 15%, peak temperature of hydration heat lowers slightly, but it goes up in the case of replacement of CKD for fine aggregate. Also, when cement and fine aggregate is replaced with CKD by 2.5% and 7.5% respectively(1C3S) in the case of replacement of CKD for cement and fine aggregate, it is highest.

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Mechanical properties of natural fiber-reinforced normal strength and high-fluidity concretes

  • Kim, Joo-Seok;Lee, Hyoung-Ju;Choi, Yeol
    • Computers and Concrete
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    • v.11 no.6
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    • pp.531-539
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    • 2013
  • An experimental investigation of mechanical properties of jute fiber-reinforced concrete (JFRC) has been reported for making a suitable construction material in terms of fiber reinforcement. Two jute fiber reinforced concretes, called jute fiber reinforced normal strength concrete (JFRNSC) and jute fiber-reinforced high-fluidity concrete (JFRHFC), were tested in compression, flexure and splitting tension. Compressive, flexural and splitting tensile strengths of specimens were investigated to four levels of jute fiber contents by volume fraction. From the test results, Jute fiber can be successfully used for normal strength concrete (NSC) and high-fluidity concrete (HFC). Particularly, HFC with jute fibers shows relatively higher improvement of strength property than that of normal strength concrete.

Durability properties of concrete containing metakaolin

  • Nas, Memduh;Kurbetci, Sirin
    • Advances in concrete construction
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    • v.6 no.2
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    • pp.159-175
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    • 2018
  • The main aim of this study is to investigate the possible effects of metakaolin on strength and durability properties of concrete. For this purpose, concrete mixtures are produced by substituting cement with metakaolin 0, 5, 10 and 20% by weight. The amount of binder for the concrete mixtures are 300 and 400kg/m3 with a constant water to cement ratio of 0.6. Compressive and bending strengths, freeze-thaw and high-temperature resistances, capillary coefficients and rapid chloride permeability properties were determined and compared each other. Because of all the experiments conducted, it has been found that the use of metakaolin as a pozzolanic additive in concrete have positive effects especially on compressive and bending strengths, capillary, rapid chloride permeability, freeze-thaw resistance, and high temperatures, up to 800C. The results indicated that the performance of concrete can be enhanced by metakaolin. Particularly, compressive strength and durability properties have found to be improved with increasing metakaolin content which is attributed to pozzolanic activity and filler effect. Furthermore, metakaolin has relatively positive impacts under elevated temperatures and freeze-thaw effects. However, almost all the strengths of entire concrete specimens are lost at 800C. Consequently, the optimum metakaolin substitution ratio can be suggested to be 20% as per this study.

Fundamental Properties of Porous Concrete by Aggregate Size

  • Kim, Moo-Han;Kim, Gyu-Yong;Baik, Yong-Kwan;Kim, Jae-Hwan;Cho, Bong-Suk
    • International Journal of Concrete Structures and Materials
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    • v.18 no.2E
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    • pp.117-124
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    • 2006
  • Porous concrete has been used recently for the purpose of decreasing the load on the earth environment. It consists solely of cement, water and coarse aggregate of uni form size. Its fundamental properties are considerably affected by the physical properties of aggregate because the aggregate is the main material for the most part in its mix proportion. Because of this reason, this study carried out an investigation of the influence of the size and type of aggregate on the fundamental properties of porous concrete. It is shown that the fundamental properties of porous concrete was seldom affected by the size of aggregate except for the case of using 2.55mm aggregate but varied significantly by the type of aggregate. In particular, the compressive strength of porous concrete using 2.55mm aggregate was much higher than that using other aggregate, and its void ratio and coefficient of permeability was lower. Moreover, the capacity to maintain the permeability of porous concrete was found to vary by the size and type of aggregate. Of particular notice was that it decreased greatly when 2.55mm aggregate was used. Unlike ordinary concrete, porous concrete exhibited very high dynamic modulus of elasticity at early age and continued to increase but slowly afterwards.

Mechanical properties and damage constitutive model of self-compacting rubberized concrete

  • Ke, Xiaojun;Xiang, Wannian;Ye, Chunying
    • Computers and Concrete
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    • v.30 no.4
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    • pp.257-267
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    • 2022
  • Two different types of rubber aggregates (40 mesh rubber powder and 1-4 mm rubber particles respectively) were devised to substitute fine aggregates at 10%, 15%, 20% and 30% by volume in self-compacting concrete to investigate their basic mechanical properties. The results show that with the increase of rubber content, the reduction of compressive strength, splitting tensile strength and static modulus of elasticity gradually increase, and energy dissipation performance gradually increase. The rubber addition significantly reduces brittleness and decelerates damaged process. Whilst, the effect of rubber particles is greater when they are finer. Considering the mechanical properties, the optimal rubber content is 10%. It is recommended that the rubber volume content in rubberized concrete (RC) should not be higher than 20%. In addition, a constitutive model under uniaxial compression was proposed basing on the strain equivalent principle of Lemaitre and the damage theory, which was in good agreement with the test curves.

Properties of Shrinkage in Concrete Incorporating Shrinkage Reducing Agent and Expansive Additive (수축저감제와 팽창재를 병용 치환한 콘크리트의 수축 특성)

  • 김광화;문학룡;심영태;이병상;정용희;한천구
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2004.05a
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    • pp.61-64
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    • 2004
  • This study is to investigate the engineering and shrinkage properties of concrete incorporating shrinkage reducing agent(SRA) and expansive additive(EA) in order to reduce shrinkage of concrete. According to results, as for the properties of fresh concrete, increase in, SRA and EA content leads to reduce the fluidity but to increase the air content, and as for setting time, there is little difference. For strength properties, it decreased with an increase in SRA dosage and increased up to 5% of EA content. For the properties of drying shrinkage, it shows decline tendency with an increase in SRA and EA content reiteratively. It alto reduces significantly with the combination of SRA-EA systems due to the combined effect of the admixture. In the scope of this paper, it is found that the use of SRA with 0.5% and EA with 5% has optimum effects on the various properties of concrete. And under the combination of SRA and EA, it can reduce drying shrinkage about 37%.

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