• Title/Summary/Keyword: early strength

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Influence of $Na_2SO_4$ on Cement-flyash Paste and the Strength Development of Concrete ($Na_2SO_4$가 시멘트-플라이애쉬 페이스트 및 콘크리트 강도에 미치는 영향)

  • Lee, Chin-Yong;Bae, Sung-Yong;Song, Jong-Taek
    • Magazine of the Korea Concrete Institute
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    • v.11 no.2
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    • pp.85-94
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    • 1999
  • It was investigated to evaluate the characteristics of cement-flyash paste which was affected the replacement level, curing method and chemical admixtures. The strength of cement-flyash paste was lower than that of cement paste only and the differences increased with increasing the replacement level. However, in steam curing, the strength of cement-flyash pastes was improved and specially, the early strength was effectively increased. The inclusion of $Na_2SO_4$ increased the early strength of cement-flyash paste. In addition, the strength of concrete including 30% of fly ash and $Na_2SO_4$ has improved and obtained the highest strength compared to other concrete mixes.

Early-Age Compressive Strength of Magnesia-Phosphate Composite with Phosphate Type (인산염 종류에 따른 마그네시아-인산염 복합체의 초기 압축강도 특성)

  • Lee, Kyung-Ho;Yang, Keun-Hyeok
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2016.05a
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    • pp.185-186
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    • 2016
  • Four mortar mixes tested to evaluate the early-age compressive strength of magnesia-phosphate composite with phosphate type. Monopotassium phosphate, dipotassium phosphate, ammonium dihydrogen phosphate and diammonium phosphate used as phosphate. Test results show that the compressive strength of mortar used monopotassium phosphate as phosphate was highest, while compressive strength of mortars used dipotassium phosphate and diammonium phosphate as phosphate were not developed.

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Properties of Strength Development of Concrete Using High Fineness Cement and Blast Furnace Slag (고분말도 시멘트와 고로슬래그 미분말을 사용한 콘크리트의 강도발현 성상)

  • Kim, Han-Sic;Ha, Jung-Soo;Lee, Young-Do
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2018.05a
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    • pp.197-198
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    • 2018
  • As part of the effort to shorten the construction period, this study examined the strength expression characteristics at the early age of concrete using high fineness cement and blast furnace slag. accordingly to provide a basic data on how to solve the problem that the initial strength is lowered.

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Formulation design of chloride-free cement additive by response surface methodology

  • Zhu, Zi-chen;Gu, Ding-cheng
    • Advances in Computational Design
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    • v.1 no.1
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    • pp.27-35
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    • 2016
  • The influences of chloride-free components of the cement additive: triethanolamine, triisopropanolamine, sodium hyposulfite and calcium gluconate on the 1d, 3d and 28d compressive strength of cement were investigated by response surface methodology. It found the early strength activators, triethanolamine and sodium hyposulfite could enhance the 1d strength of cement effectively but they did not contribute to the 3d strength enhancement, and further their interaction was able to decrease the 28d strength of cement. Calcium gluconate was not that effective for the strength enhancement on 3 and 28 days when it's simply dosed. However the interaction effect of calcium gluconate with triisopropanolamine could strongly favor the strength enhancement of cement after 3 days. Results indicated it was necessary to focus attention on the potential interactions among the chemical components. And for the concern of four chemicals studied in this paper, it was feasible to formulated a kind of chloride-free cement additive that can be effective for the early strength of cement and its the strength after 3 days.

Determination of Removal Time of the Forms with the Strength Development of High Strength Concrete at Early Age (고강도 콘크리트의 초기강도 발현에 따른 거푸집 탈형시기의 결정)

  • 김은호;김영진;한민철;신병철;한천구
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2003.05a
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    • pp.99-102
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    • 2003
  • This study discusses the determination of removal time of forms with early strength development in high strength concrete. According to the results, as W/B increases by 10%, the setting time is shortened by about 2 hours. The time when compressive strength of 8 MPa is gained is about 20 hours. Bond strength between form and concrete is highest around final setting time, but decreases drastically after that. Amount of concrete sticking on the form is large before setting, but after that, it is little. The rebound value of P type schmidt hammer is measured faster by 2-3 hours than compressive strength. It is also confirmed that the removal of forms is possible when the rebound value of P type schmidt hammer is more than 34

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A Study and Evaluation of Super High Early Strength Concrete as Pavement Overlay Materials for Early Traffic Opening(3) (신속개방형 콘크리트 도로포장재의 설계를 위한 평가 연구(3))

  • 임채용;엄태선;유재상;이종열;엄주용;조윤호
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.05a
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    • pp.607-612
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    • 2002
  • In road pavements, it is known that cement concrete pavement has superior durability, safety compared. But in repairing pavement, cement concrete pavement is not usually applied because of the length of time while the road is interrupted when using Ordinary and Rapid-hardening Portland Cement. And Super High Early Strength Cement and Ultra Super High Early Strength Cement are not favorable for ready mixed concrete because of rapid setting time, high slump loss and other restrictions. We developed special cement developing 1 day strength of over 30.0N/mm$^2$ to open the road within 1 day and workable time is maintained over 1 hour so that it can be used as ready mixed concrete. We performed experimental overlay construction with the cement and evaluated the mechanical property and the durability. At curing temperature of 8-l8$^{\circ}C$,the flexural strength was 6.4N/mm$^2$at 1 day, so that the road can be open to traffic within 1 day. In durability test, the hardened concrete showed higher durability than Portland cement concrete.

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Durability of High Early Strength Concrete Using Fine Particles Cement (미립자 시멘트를 이용한 조강 콘크리트의 내구성 검토)

  • Kim, Yong-Jic;Park, Sang-Joon;Kim, Kyoung-Min
    • Journal of the Korea Concrete Institute
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    • v.23 no.6
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    • pp.757-763
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    • 2011
  • In order to secure the effective high early age strength of the concrete, the study was carried out with a goal of functional improvement of cement. This study was carried out as a follow up for the previous study, which analyzed the high early age strength and durability of concrete mixed with fine particle cement (FC) during cement production. The experimental results showed that the target range for each mix was satisfied at fresh state of concrete. Also, when mixed with fine particles cement, the setting time improved. Additionally, compressive strength and heat of hydration increased and remained same, respectively. Especially, the durability remained same even when mixed with fine particle cement.

An Experimental Study on Strength Properties of Early Strength Concrete for Reduction of Working Period in Apartment (공동주택 공기단축을 위해 개발된 조강 콘크리트의 강도 발현 특성에 관한 연구)

  • Jung, Yang-Hee;Lee, Jae-Hyun;Keum, Kyoung-Hun;Lee, Won-AM;Kim, Sun-Man
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2009.11a
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    • pp.157-160
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    • 2009
  • The decision of the Form removal time which leads the early assuring strength of the concrete from Apartment construction is the fact which is important from Reducing the period of works and the economical efficiency side. Especially, with Complex building of recent times the same Tall building and Multiple Apartment Site which only follows in upgrade of interior construction of apartment site and shortening the frame construction period becomes very, importantly is the actual condition where the effort which is various for this is attempted. But is caused by with limit and economical efficiency problem of case concrete early strength revelation of most and is not put to practical use is the actual condition. Develops concrete mixture which is a utility from the research which sees hereupon and the effect which is economic leads construction duration shortening under maximizing boil.

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Early-Age Shrinkage of Very-Early Strength Latex Modified Concrete (초속경라텍스개질콘크리트의 초기수축)

  • Lee Jung-Ho;Choi Pan-Gil;Choi Seung-Sic;Yun Kyong-Gu
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.269-272
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    • 2004
  • After concrete casts, temperature decent and shrinkage bring volume changes of concrete pavement. Microcracking and cracking in concrete pavement are caused by these volume changes. As a result, durability of concrete pavement is deteriorated. Recently, Very-Early Strength Latex Modified concrete(below:VESLMC) from the beginning of High-Way is used as urgent repair material for bridge deck. The advantage of VESLMC is that compressive and flexural strength at 3 hours age are 4.5MPa and 21MPa respectively. It allows the traffic to open in 3 hours. But, this material has the problem which is early-age shrinkage cracking caused by water self-dissipation with rapid hydration reaction and water evaporation with body dry. Unfortunately, until now, the research about early-age shrinkage of VESLMC leaves something to be desired. Therefore, the purpose of this study is to present the early-age shrinkage of VESLMC respect to latex contents and shrinkage ratio to maximum length change that can help field engineers' skill. Latex contents of 0, 5, 10, 15, $20\%$ in standard of same workability in VESLMC are selected by experimental variables. After initial set, shrinkage value was measured with 10mm LVDT for 3 days. The results of maximum shrinkage ratio were 0.019, 0.017, 0.023, $0.027\%$ respectively.

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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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