• Title/Summary/Keyword: Early-high strength

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Estimation of the Compressive Strength of the Concrete incorporating Mineral Admixture based on the Equivalent Age Method (등가재령방법에 의한 혼화재 종류별 콘크리트의 압축강도 증진해석)

  • Han, Min-Cheol;Han, Cheon-Goo
    • Journal of the Korea Institute of Building Construction
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    • v.7 no.1 s.23
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    • pp.71-77
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    • 2007
  • This paper is to investigate the effect of the curing temperature on strength development of concrete incorporating cement kiln dust(CKD) and blast furnace slag (BS) quantitatively. Estimation of the compressive strength of the concrete was conducted using the equivalent age equation and the rate constant model proposed by Carino. Correction of Carino model was studied to secure the accuracy of strength development estimation by introducing correction factors regarding rate constant and age. An increasing curing temperature results in an increase in strength at early age, but with the elapse of age, strength development at high curing temperature decreases compared with that at low curing temperature. Especially, the use of BS has a remarkable strength development at early age and even at later age, high strength is maintained due to accelerated pozzolanic activity resulting from high temperature. Whereas, at low curing temperature, the use of BS leads to a decrease in compressive strength. Accordingly, much attention should be paid to prevent strength loss at low temperature. Based on the strength development estimation using equivalent age equation, good agreements between measured strength and calculated strength are obtained.

The Effect of Dry Environment on Strength of Cement Mortar Immediately after Casting (성형직후 건조환경이 시멘트 모르터의 강도에 미치는 영향)

  • 오무영;김준희
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.33 no.2
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    • pp.61-72
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    • 1991
  • This study was carried out to research the strength drop of concrete in dry environment. The mixing ratio of cement-fine aggregate was 1: 1, 1 : 2, 1: 3 and 1 : 4. The curing was compared standard curing with dry curing immediately after casting. It is analysis of strength change by water-proof mixing. The curing age of cement mortar was 3days, 7days, l4days and 28days. The result obtained from this study are summarized as follows. 1. The compressive and bending strength change by increasing the curing age, dry curing mortar the increasing rate of strength was decreased than standard curing mortar. 2. The compressive and bending strength change in early curing, strength difference between standard curing mortar and dry curing motar was gradually closed by increasing the W/C. 3. The dry curing mortar was decreased than standard curing mortar in decreasing rate of compressive and bending strength by increasing the W/C. 4. The compressive strength of water-proof mortar in early curing, liquid water-proof mortar was shown high strength in dry curing than standard curing. The powder and liquid water-proof mortar have a small effect in dry environment. The liquid water-proof mortar was high strength without relation change of curing age in dry environment than standard curing. 5. The compressive strength of liquid water-proof mortar in poverty mix, dry curing was shown high strength than standard curing. 6. The bending strength was increased than compressive strength by decreasing the volume of cement in early curing. The increasing rate of bending strength was decreased to compressive stength by increasing the curing age.

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Estimation of Compressive Strength of Concrete Incorporating Admixture (혼화재 치환 콘크리트의 압축강도 증진해석)

  • Joo Eun-Hee;Pei Chang-Chun;Han Min-Cheol;Sohn Myoung-Soo;Jeon Hyun-Gyu;Han Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2005.11a
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    • pp.75-78
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    • 2005
  • This raper investigates the effect of curing temperature on strength development of concrete incorporating cement kiln dust(CKD) and blast furnace slag (BS) quantitatively. Estimation of compressive strength of concrete was conducted using equivalent age equation and rate constant model. An increasing curing temperature results in an increase in strength at early age, but with the elapse of age, strength development at high curing temperature decreases compared with that at low curing temperature. Especially, the use of 35 has a remarkable strength development at early age and even at later age, high strength is maintained due to accelerated pozzolanic activity resulting from high temperature. Whereas, at low curing temperature, the use of BS leads to a decrease in compressive strength. Accordingly, much attention should be paid to prevent strength loss at low temperature. Based on the strength development estimation using equivalent age equation, good agreements between measured strength and calculated strength are obtained.

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Relationship between Compressive Strength of Geo-polymers and Pre-curing Conditions

  • Kim, Hyunjung;Kim, Yooteak
    • Applied Microscopy
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    • v.43 no.4
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    • pp.155-163
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    • 2013
  • Meta-kaolin (MK) and blast furnace slag (BS) were used as raw materials with NaOH and sodium silicate as alkali activators for making geo-polymers. The compressive strength with respect to the various pre-curing conditions was investigated. In order to improve the recycling rate of BS while still obtaining high compressive strength of the geo-polymers, it was necessary to provide additional CaO to the MK by adding BS. The specimens containing greater amounts of BS can be applied to fields that require high initial compressive strength. Alkali activator(s) are inevitably required to make geo-polymers useful. High temperature pre-curing plays an important role in improving compressive strength in geo-polymers at the early stage of curing. On the other hand, long-term curing produced little to no positive effects and may have even worsened the compressive strength of the geo-polymers because of micro-structural defects through volume expansion by high temperature pre-curing. Therefore, a pre-curing process at a medium range temperature of $50^{\circ}C$ is recommended because a continuous increase in compressive strength during the entire curing period as well as good compressive strength at the early stages can be obtained.

A Study on the Cold Weather Concrete using High Early Strength Concrete (조강시멘트를 이용한 한중콘크리트의 특성평가 연구)

  • 임채용;엄태선;유재상;이종열;이순기;이동호
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.261-264
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    • 2003
  • Cold weather can lead to many problems in mixing, placing, setting time, and curing of concrete that can have harmful effects on its properties and service life. Korean Concrete Institute (KCI) defines cold weather as a period when the average daily air temperature is less $4^{\circ}C$ and recommends to cast concrete with special care such as shielding, heating and so on. The use of high early strength cements may improve the rate of hardening characteristics of concrete in cold weather by making it possible to achieve faster setting time and evolving more hydration heat than ordinary Portland cement. Higher early strength can be achieved using Type III cement especially during the first 7 days. The strength increase property of Type III cement at low temperature was studied. As a conclusion the heat or heat insulation curing period can be reduced to 50~75%. So, it can be used for cold weather concreting to reduce construction cost and extend the construction season.

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Improvement of the Early Age Strength of Low Cement Concrete Using High Volume Mineral Admixture

  • Park, Jong-Ho;Kim, Yong-Ro;Song, Young-Chan;Song, Dong Yub;Kim, Gyu-Yong
    • Journal of the Korea Institute of Building Construction
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    • v.12 no.6
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    • pp.566-574
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    • 2012
  • To address the problem of global warming, consumption of cement, the main material of concrete, should be decreased. Unfortunately, when industrial by-products are used in large quantities as admixture, the early age strength of concrete will be decreased, reducing its viability for use in concrete structures. Therefore, in this study, the application of an ionization accelerator and alkaline activator as addition agent of superplasticizer were investigated to secure a similar early age strength to that of normal concrete, thus increasing the viability of low cement concrete. Through the investigation, it was found that specimens that used a combination of Alkaline-activator (Na2Sio3) and ionization accelerator (Amine) had the highest early and long-age compressive strength. From this, we can determine an appropriate range of application of superplasticizer to improve early-age compressive strength of low cement concrete.

The On-site Quality Characteristics of the Cold Weather Concrete using High Early Strength Portland Cement (조강포틀랜드시멘트를 사용한 한중콘크리트의 현장품질 특성)

  • Lee, Won-Am;Um, Tae-Sun;Ryu, Jae-Sang;Lee, Jong-Ryul;Kang, Ji-Hun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.05a
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    • pp.224-227
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    • 2004
  • The cement can be influenced by the temperature. Especially, when it is cold weather, it causes some problems in such properties as mixing, placing and curing of concrete. According to the Concrete Standard Specification(2003), in case of the average daily outdoor temperature below $4^{\circ}C$, it recommends to use the cold weather concrete. In this research, the on-site quality characteristics of the cold weather concrete using high early strength portland cement(Type III cement) were studied. As a result, the cold weather concrete using high early strength portland cement can obtain its excellent properties and benefit the cost of construction.

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A Study of Blast Furnace Slag Cement of High Early Strength and Replacement Ordinary Portland Cement (조강형 고로 슬래그 시멘트 및 보통 포틀랜드 시멘트 대체용 고로 슬래그 시멘트에 관한 연구)

  • 권기동;최현국
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.10b
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    • pp.1211-1214
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    • 2000
  • The purpose of this paper was to study of blast furnace slag cement of high early strength and replacement ordinary portland cement. we prepared the specimens of cement and concrete with various mixing proportions of elementary materials. For example, clinker, gypsum(1~10%), fineness $4, 000~6, 000cm^2/g$ of blast furnace slag(30~50%), limestone etc. As a result of this study, fineness $(4, 000cm^2/g)$ blast furnace slag was of used replacement ordinary portland cement and fineness $(6, 000cm^2/g)$ blast furnace slag was of used blast furnace slag cement of high early strength.

Evaluation of Strength of Normal and Lightweight Aggregate Concrete Using Ultrasonic Velocity Method in Early Age (초기 재령에서 초음파 속도법을 활용한 보통 및 경량 골재 콘크리트의 강도 발현 평가)

  • Nam, Young-Jin;Kim, Won-Chang;Choi, Hyeong-Gil;Ryu, Jung-Rim;Lee, Tae-Gyu
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2023.05a
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    • pp.55-56
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    • 2023
  • Recently, large and high-rise buildings are increasing, and accordingly, concrete weight reduction is required. Lightweight aggregate concrete can provide economic feasibility and large space, but safety can be reduced due to problems such as low strength and poor durability. Since the development of such low strength of concrete is important in the early construction stage, it is necessary to evaluate the vertical formwork demolding period at the early age. The correlation was analyzed by measuring the compressive strength and ultrasonic pulse velocity. As a result, the ultrasonic pulse rates of normal and lightweight aggregate concrete at the time of 5 MPa expression, which is the time of vertical mold deformation, were 3.07 km/s and 2.77 km/s for W/B 41, and 2.89 km/s and 2.73 km/s for W/B 33.

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Strength Characteristics of Ultra High Performance Concrete at early age

  • Kim, Sung-Wook;Park, Jung-Jun;Ryu, Guem-Sung;Koh, Kyoung-Taek;Hong, Ki-Nam
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.563-564
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    • 2009
  • Ultra-High Performance Concrete (UHPC) compared to normal concrete is exhibiting extremely high strength characteristics with compressive strength and tensile strength reaching 200MPa and 15MPa, respectively. The mechanical characteristics of UHPC can be thus exploited advantageously in the construction of structure through the reduction of the cross-sectional area and fabrication of slim and light-weight of the structural members. In the case where the structural member is made of UHPC, the occurrence of crack can be prevented by releasing the restraint provided by the form in due time. This research performs parametric study of the failure characteristics of concrete such as failure energy and softening curve suggested by the viscous crack model approximating the failure of concrete. The scope of this research contains the results of tests performed to investigate the strength of UHPC during early elapsed time.

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