• Title/Summary/Keyword: Aggregate for concrete

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A Fundamental Property of Concrete Containing Atomized Steel Slag Fine Aggregate after Reforming Process (개질처리한 제강슬래그 잔골재 사용 콘크리트의 성질)

  • 문한영;유정훈;박영훈;김주용;윤표호;김얼
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.318-321
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    • 2003
  • Steel slag is produced during steel making process. Compared with the blast furnace slag, converter slag has the expansibility due to the reaction with water and free CaO. Therefore it is specified in Standard Specification for Concrete in Korea that steel slag aggregate must not be used in concrete. In this study, atomized steel slag aggregate is conducted from converter slag by the atomizing method. Atomized steel slag and conventional converter slag are same in its composite by nature in the converter but compounds of the composite become different because of different method of slag treatment. Especially atomized steel slag aggregate overcomes expansibility that is the weak point for usage. It is researched whether it has the possibility, suitability for fine aggregate in concrete. Slump and air content are measured in fresh concrete, compressive and bending strength in hardened concrete. These is compared with control concrete with washed sand.

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Application of Ceramic Aggregate for Ultra-High Strength Concrete (초고강도 콘크리트 제조를 위한 세라믹골재 개발)

  • Kim, Song-Ho;Kang, Suk-Hwa;Song, Yong-Soon;Kim, Kang-Min
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.389-392
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    • 2008
  • Ultra-high strength concrete becomes one of the main research areas because recently concrete structure is larger. The quality of aggregate (ultra-high strength and uniformity) as well as chemical admixture and mineral additives is a key factor for ultra-high strength concrete development. However, natural aggregate including crushed aggregate is inappropriate for ultra-high strength concrete because ultra-high strength quality cannot be maintained uniformly over whole natural aggregate lot. In this study ceramic aggregate was applied for ultra-high strength concrete in order to assure uniform quality of ultra-high strength aggregate. Ultra-high strength concrete was achieved by applying coated ultra-high strength ceramic aggregate to enhance the bonding strength between aggregate and cement paste. Also for actual application light weight ceramic aggregate(density 2.2 $g/cm^3$) with zero water absorption was tested.

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Freezing and Thawing Properties of High Strength Concrete Using Recycled Coarse Aggregate (재생굵은골재를 사용한 고강도 콘크리트의 동결융해 특성)

  • Sung , Chan-Yong;Im , Sang-Hyuk
    • Journal of The Korean Society of Agricultural Engineers
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    • v.46 no.2
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    • pp.59-66
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    • 2004
  • This study was performed to evaluate the freezing and thawing properties of the high strength concrete using recycled coarse aggregate. The recycled coarse aggregate replaced natural crushed aggregate by 0%, 25%, 50%, 75% and 100%. The compressive strength of the concrete using recycled coarse aggregate showed more than 300 kgf/$cm^2$ at the curing age 28 days. The mass loss ratio by freezing and thawing was less than 1% at all mix type. The relative dynamic modulus of elasticity was decreased with increasing the freezing and thawing cycles. Also, the durability factor by the freezing and thawing was decreased with increasing the content of recycled coarse aggregate. But, the recycled concrete except 100% recycled coarse aggregate showed 60 or more durability factor in the freezing and thawing 300 cycles. Accordingly, these recycled coarse aggregate can be used for high strength concrete.

A Fundamental Study on Supply Status and Use Plan of Fine Aggregates (잔골재의 수급현황 및 활용방안에 관한 기초적 연구)

  • Yu Myoung Youl;Lee Sea-Hyun;Lee Hyun-Soo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05b
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    • pp.101-104
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    • 2005
  • It analyzed the supply status of fine aggregate and find the point of issue related alternative fine aggregate through researches and interviews. The conclusions of the study are as follows. 1. Ready mixed concrete manufacture used crushed fine aggregate (15.5$\%$) and recycled fine aggregate (1.5$\%$) for alternatives aggregate than 1.3$\%$ in 1991. It is not allowed to use a recycled fine aggregate in ready mixed concrete, but they used it. 2. All alternative aggregate are satisfied the Korean Standard, But they showed low properties of mortar compared to when it replaced with natural fine aggregate. So, it is needed to make another special Korean Standard to use alternative aggregate in normal concrete by mixing method to recover the workability and compressive strength.

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Influence of coarse aggregate properties on specific fracture energy of steel fiber reinforced self compacting concrete

  • Raja Rajeshwari, B.;Sivakumar, M.V.N.
    • Advances in concrete construction
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    • v.9 no.2
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    • pp.173-181
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    • 2020
  • Fracture properties of concrete depend on the mix proportions of the ingredients, specimen shape and size, type of testing method used for the evaluation of fracture properties. Aggregates play a key role for changes in the fracture behaviour of concrete as they constitute about 60-75 % of the total volume of the concrete. The present study deals with the effect of size and quantity of coarse aggregate on the fracture behaviour of steel fibre reinforced self compacting concrete (SFRSCC). Lower coarse aggregate and higher fine aggregate content in SCC results in the stronger interfacial transition zone and a weaker stiffness of concrete compared to vibrated concrete. As the fracture properties depend on the aggregates quantity and size particularly in SCC, three nominal sizes (20 mm, 16 mm and 12.5 mm) and three coarse to fine aggregate proportions (50-50, 45-55, 40-60) were chosen as parameters. Wedge Split Test (WST), a stable test method was adopted to arrive the requisite properties. Specimens without and with guide notch were investigated. The results are indicative of increase in fracture energy with increase in coarse aggregate size and quantity. The splitting force was maximum for specimens with 12.5 mm size which is associated with a brittle failure in the pre-ultimate stage followed by a ductile failure due to the presence of steel fibres in the post-peak stage.

Genetic algorithm in mix proportion design of recycled aggregate concrete

  • Park, W.J.;Noguchi, T.;Lee, H.S.
    • Computers and Concrete
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    • v.11 no.3
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    • pp.183-199
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    • 2013
  • To select a most desired mix proportion that meets required performances according to the quality of recycled aggregate, a large number of experimental works must be carried out. This paper proposed a new design method for the mix proportion of recycled aggregate concrete to reduce the number of trial mixes. Genetic algorithm is adapted for the method, which has been an optimization technique to solve the multi-criteria problem through the simulated biological evolutionary process. Fitness functions for the required properties of concrete such as slump, density, strength, elastic modulus, carbonation resistance, price and carbon dioxide emission were developed based on statistical analysis on conventional data or adapted from various early studies. Then these fitness functions were applied in the genetic algorithm. As a result, several optimum mix proportions for recycled aggregate concrete that meets required performances were obtained.

Effect of the Pozzolanic Cement on Concrete Strengths with Recycled Aggregate (재생골재를 사용한 콘크리트의 강도에 미치는 포졸란 시멘트 효과)

  • 문대중;임남웅;김양배
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.217-220
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    • 2001
  • Due to the tendency of increase in demolished-concrete produced by alteration and deterioration of concrete structures, recycling of those demolished-concrete is necessary to solve the exhaustion of natural aggregate, in order to save resources and protect environment, especially being want of resources in Korea. For this purpose, concrete made with the pozzolanic cement and recycled aggregate was tested for compressive and tensile strength. The pozzolanic cement was a mixture of OPC(Ordinary Portland Cement) and pozzolans such as fly ash, other siliceous materials and early rapid hardening cement(ERC). It was found that the compressive strength of the pozzolanic cement was enhanced when 0.75% of ERC was dozed, as compared with OPC mortar. It was also shown that compressive and tensile strength of concrete with recycled aggregate and pozzolanic cement were higher than those of concrete with crushed stones and OPC. It was concluded that the pozzolanic cement influenced on the increase of concrete strengths with recycled aggregate.

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Properties of Fresh Concrete with Recycled fine Aggregates (순환잔골재를 사용한 굳지 않은 콘크리트의 특성)

  • Choi, Ki-Sun;You, Young-Chan;Yun, Hyun-Do;Kim, Keung-Hwan
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.373-376
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    • 2008
  • The objective of this study is to investigate the properties of fresh concrete with recycled fine aggregates. Three different kinds of fine aggregate with natural, high and low quality recycled aggregates were prepared. The concrete mixtures were produced with test parameters of replacement ratio of recycled fine aggregate. The properties of the fresh concrete were measured by means of slump and air content according to elapsed time. Quality control method to maintain the constant total mixing water for recycled aggregate concrete was suggested. The all concrete mixtures were produced with approximately the same slump on the job site after an hour. Test results indicated that compressive strength of the concrete mixtures with constant slump is not affected by the replacement ratio of recycled fine aggregate. Therefore, the practical way for the quality control of recycled aggregate concrete is to maintain the constant total mixing water.

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Performance Evaluation of Recycled Aggregate Concrete Made of Recycled Aggregate Modified by Carbonation (탄산화 개질 순환 골재를 사용한 순환 골재 콘크리트의 성능 평가)

  • Ha, Jung-Soo;Shin, Jin-Hak;Chung, Lan;Kim, Han-Sic
    • Journal of the Korea Concrete Institute
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    • v.28 no.4
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    • pp.445-454
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    • 2016
  • With the increase of decrepit facilities, construction waste increased to a certain level and now the increase is more or less stabilized. Yet construction waste still constitutes the largest portion of the overall wastes. Also, it is inevitable to spend a huge amount of the national budget due to the aggravating shortage of aggregate caused by prohibition on collection of natural aggregates as well as due to the damage to the land and environment caused by development of the sources of aggregates. As a countermeasure to the situation, the Ministry of Land, Infrastructure and Transport promulgated the quality standard for recycled aggregate to manage the usage of recycled aggregate according to its quality. But use of recycled aggregate for the purpose of high added value still remains nominal. Therefore, this research aims to study the applicability of recycled aggregate concrete as structural concrete by evaluating the quality improvement effects and the performance of the recycled aggregate concrete including recycled fine aggregate and recycled coarse aggregate that have undergone carbonation for 4 days and 14 days respectively in the condition of 60% RH, 20% $CO_2$ and $20^{\circ}C$ temperature, suggested for carbonation modifying from the advance research. The result shows carbonation modify contributed to quality improvement with 0.91% decrease in absorption rate for recycled fine aggregate and 0.7% decrease in absorption rate for recycled coarse aggregate. The physical properties and durability of the recycled aggregate made of aggregate modified by carbonation showed results similar to general concrete, which confirmed the possibility of applying the recycled aggregate made of recycled aggregate modified by carbonation to structural concrete.

Effects of Curing Method on the Mechanical Properties of Recycled Coarse Aggregate Concrete (양생방법에 따른 순환굵은골재 콘크리트의 강도특성)

  • Jeon, Esther;Yun, Hyun-Do;You, Young-Chan;Lee, Sea-Hyun;Shim, Jong-Woo;Choi, Ki-Sun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.525-528
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    • 2006
  • Recently, Korea government prepared Act on facilitation of construction waste recycling in December 2003 for effective recycling of rapidly increasing construction wastes, and has enforced the Act on Jan. 2005. This Act limits the definition of recycled aggregates to the aggregates which obtained quality certificate and for this purpose, government has operated quality standard and certificate system of recycling aggregate. The objective of this experimental study is to evaluate the mechanical properties of recycled coarse aggregate concrete according to curing method by ready-mixed concrete. Compressive strength ratio of recycled aggregate concrete under air-dry curing/wet curing was $74{\sim}91%$. KCI code for conventional concrete overestimated elastic modulus for recycled coarse aggregate concrete.

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