• Bulletin of the Korean Chemical Society
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• 제9권5호
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• pp.298-303
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• 1988

Kinetic studies on cupric ion ($Cu^{2+}$) oxidation of 1-benzyl- and 1-aryl-1,4-dihydronicotinamides (XNAH) in aqueous solution were performed. In the presence of dioxygen ($O_2$), the reaction followed first order kinetics with respect to both XNAH and $Cu^{2+}$. The oxidation reaction was found to be independent and parallel to the acid-catalyzed hydration reaction of XNAH. The catalytic role of $Cu^{2+}$ for the oxidation of XNAH in the presence of $O_2$ was attributed to $Cu^{2+}/Cu^+$ redox cycle by the reactions with XNAH and $O_2$. The second order rate constants of the Cu2+ oxidation reaction kCu, and acid-catalyzed hydration reaction $k_H$ were strongly dependent on the nature of the substituents in 1-aryl moiety. The slopes of log $k_{Cu}$ vs log $K_H$ and log $k_{Cu}$ vs ${\sigma}_p$ of the substituents plots were 1.64 and -2.2, respectively. This revealed the greater sensitivity of the oxidation reaction rate to the electron density on the ring nitrogen than the hydration reaction rate. A concerted two-electron transfer route involving XNAH-$Cu^{2+}$ complex was proposed for mechanism of the oxidation reaction.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.25-28
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• 2006

This study investigated pre-mixed cement combined with ordinary portland cement, BF and SF, in order to manufacture cement binder, which is possible to produce 150MPa ultra high strength concrete. The BF used in this study reduces and control hydration heat. It can also improve concrete fluidity, while AP increases hydration product and accelerates reaction of BF. SF has micro filler effect and makes pozzolanic reaction. It also fabricates high density internal organization. This developed pre-mixed cement can reduce hydration heat and increase hydration product. It is possible to fabricate high density organization and to secure homogeneity. The mock-up test of ultra high strength concrete showed excellent dispersibility and workability and indicated compressive strength more than 150MPa at 28 days.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.261-262
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• 2010

POSCO 글로벌 R&D 센터 구조실험동에 시공되는 반력상 및 반력벽은 구조실험을 수행하여야하기 때문에 구조물의 균열이나 손상은 치명적이다. 따라서 매스콘크리트 타설시 발생할 수 있는 온도균열을 최소화하기 위하여 수화열 해석을 시행하였다. 수화열 저감을 위해 몇가지 방법이 제안되었으며, 해석의 주요 변수는 타설 콘크리트의 종류, 타설 주기가 검토되었다.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.123-127
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• 2005

EVA Powder modified high strength concretes were prepared by varying polymer/binder mass ratio with a constant water/binder mass ratio of 0.3. The effect of EVA powder on the slump, hydration heat, compressive and flexural strength, toughness and water absorption ratio was studied. In hydration heat test, temperature of hydration reaction displayed almost fixed level regardless of containing rate of EVA powder, but peak time of hydration reaction displayed late inclination as containing rate of powder increases. With the same water/binder mass ratio, the compressive strength and water absorption of EVA powder modified concretes decreased slightly when EVA powder was added and the flexural strength of EVA powder modified concretes rised slightly when EVA powder was added. Also, the toughness of the modified concretes can be improved markedly. The interpenetrating structure between the polymeric phase and cement hydrates formed at a $2{\sim}6%$(containing rate of EVA powder). The properties of the polymer modified concretes were influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases.

• 도시과학
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• 제9권1호
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• pp.7-16
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• 2020

Application of nanomaterials to cementitious composites has been attempted with the rapid development of nanotechnology since the 1990s. Various nanomaterials such as carbon nanotube, graphene, nano-SiO₂, nano-TiO₂, nano-Al₂O₃, nano-Clay, and nano-Magnetite have been applied to cementitious composites to improve the mechanical properties and the durability, and to impart a variety of functionality. In-depth information on the effect of nanomaterials on the hydration reaction, the microstructure, and the mechanical properties of cementitious nanocomposites is provided in the present study. Specifically, this paper mostly deals with the previous studies on the heat evolution characteristics of cementitious nanomaterials at an early age of curing, and the pore and the compressive strength characteristics of cementitious nanocomposites. Furthermore, the effect of nanomaterials on the cementitious nanocomposites was systematically discussed with the reviews.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.129-130
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• 2020

This paper attempted to examine the characteristics of heat of hydration and calorific value of concrete according to the formwork material in Hot weather environment. As a result of the experiment, it was found that there were no problems such as temperature cracking and delay in hydration reaction when a synthetic resin form was used.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.153-154
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• 2020

The purpose of this paper is to examine the characteristics of heat and hydration of concrete according to formwork materials. As a result of the experiment, it was found that there were no problems such as concrete heat loss and delay in hydration reaction due to the use of synthetic resin formwork.

• 한국건설순환자원학회논문집
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• 제10권1호
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• pp.15-22
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• 2022

이 연구에서는 매년 대량으로 발생하는 커피찌꺼기를 건설소재로 재활용하기 위해 커피찌꺼기와 커피찌꺼기 애시를 혼입한 시멘트 모르타르의 수화반응성을 검토하고 강도 특성을 조사하였다. 연구 결과, 커피찌꺼기의 소성온도가 높아질수록 유기물의 연소로 인한 질량 손실은 커졌으나 밀도는 증가하는 것으로 나타났다. 또한 커피찌꺼기를 혼입했을 때는 시멘트 수화반응성이 저조하여 압축강도가 현저히 낮아졌다. 반면, 800 ℃에서 소성시킨 커피찌꺼기 애시는 수화반응이 원활하였으며, 압축강도는 OPC 모르타르와 동등한 수준으로 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.565-566
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• 2009

Supplementary cementing materials (SCM), such as silica fume, slag, and low-calcium fly ash, have been widely used as mineral admixtures in high strength and high performance concrete. Due to the chemical and physical effect of SCM on hydration, compared with Portland cement, hydration process of cement incorporating SCM is much more complex. This paper presents a numerical hydration model which is based on multi-component concept and can simulate hydration of cement incorporating SCM. The proposed model starts with mixture proportion of concrete and considers both chemical and physical effect of SCM on hydration. Using this proposed model, this paper predicts the following properties of hydrating cement-SCM blends as a function of hydration time: reaction ratio of SCM, calcium hydroxide content, heat evolution, porosity, chemically bound water and the development of the compressive strength of concrete. The prediction results agree well with experiment results.

• 한국세라믹학회지
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• 제35권2호
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• pp.185-195
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• 1998

This experiment carried out in order to investigate the effect of the chemical activators for acceleration of hydration the system of Fly ash-Cao The paste was consisted of 80wt% Fly ash and 20wt% CaO with 1. 3. 5wt% of 4 activators(N{{{{ alpha _2 }}S{{{{ OMICRON _4 }}, CaC{{{{ {l }_{2 } }}, NaOH, Ca(N{{{{ OMICRON _3 {)}_{2 } }} and W/S ratio of 0.42 After curing for 1, 3, 7, 14, 28 days the paste hydration was characterized by the measurement of compressive strength XRD analysis SEM observation the combined water and the reaction amount of Ca(OH)2 determination. As a result of this ex-periment all of the system which involved Na2SO4 or NaOH had a god compressive strength. In the case of 7 days curing a system which added CaCl2 showed the highest compressive strength among all especially NaOH system showed a high increase in strength as a dosage of it increased. Hydration products were different according to activatores added. Only C-S-H was observed in NaOH system. As the reaction amount of Ca(OH)2 and combined water were increased the compressive strength increased. There were few differences in the comparision of strength between ignited loss 3.1% and loss 9.3% of fly ash.