• 한국세라믹학회지
• /
• 제44권2호
• /
• pp.103-109
• /
• 2007

In this study, the rheological properties of cement pastes containing blastfurnace slag of different fineness were investigated. The fluidity of cement pastes with low Blaine value blastfurnace slag was increased with decreasing the plastic viscosity and the yield stress of pastes. And the optimum dosage of polycarboxylate type superplasticizer to the cement pastes was confirmed according to the fineness and the replacement ratio of blastfurnace slag. All cement pastes showed the thixotropy behavior. And also it was formed that the segregation range of cement pastes was occurred below $10D/cm^2$ of the yield stress and below 350 cPs of the plastic viscosity by the coaxial cylinder viscometer.

• Computers and Concrete
• /
• 제7권1호
• /
• pp.17-38
• /
• 2010

This research aimed to investigate the influence of high-volume mineral admixtures (MAs), i.e., fly ash and slag, on the hydration characteristics and microstructures of cement pastes. Degree of cement hydration was quantified by the loss-on-ignition technique and degree of pozzolanic reaction was determined by a selective dissolution method. The influence of MAs on the pore structure of paste was measured by mercury intrusion porosimetry. The results showed that the hydration properties of the blended pastes were a function of water to binder ratio, cement replacement level by MAs, and curing age. Pastes containing fly ash exhibited strongly reduced early strength, especially for mix with 45% fly ash. Moreover, at a similar cement replacement level, slag incorporated cement paste showed higher degrees of cement hydration and pozzolanic reaction than that of fly ash incorporated cement paste. Thus, the present study demonstrates that high substitution rates of slag for cement result in better effects on the short- and long-term hydration properties of cement pastes.

• 콘크리트학회논문집
• /
• 제12권5호
• /
• pp.141-151
• /
• 2000

Compressive strength, sulfate deterioration factor(SDF) and length change of 5 types of mortars immersed in sodium sulfate solution were observed. As the results of tests, it was found that the sulfate resistance of blended cement mortars were superior to that of portland cement mortars. Pore volume with diameter larger than 0.1 $\mu\textrm{m}$ of 5 types of pastes indicated that the micro-structures of blended cement pastes were denser, due to pozzolan reaction and latent hydraulic properties, than those of portland cement pastes. The XRD, ESEM, EDS and TG analyses demonstrated that the reactants such as ettringite and gypsum were significantly formed in portland cement pastes. Besides, compared with the $Ca(OH)_2$ content of ordinary portland cement pastes immersed in water and sodium sulfate solution, the $Ca(OH)_2$ contents of fly ash blended cement and ground granulated blast-furnace slag cement paste were about 58% and 28% in water, and 55% and 20% in sodium sulfate solution, respectively.

• Computers and Concrete
• /
• 제19권1호
• /
• pp.19-31
• /
• 2017

This paper uses modelling and experiment to perform a quantitative analysis for the gypsum and ettringite formations in cement pastes subjected to sulfate attack. Firstly, based on Fick's law and chemical reaction kinetics, a diffusion model of sulfate ions in cement pastes is proposed, and then the model of the gypsum and ettringite formations is established to analyze its contents in cement pastes with corrosion time. Secondly, the corrosion experiment of the specimens with cement pastes immersed into 2.5%, 5.0% and 10.0% $Na_2SO_4$ solutions are carried out, and by using XRD-Rietveld method, the phases of powder samples from the specimens are quantitatively analyzed to obtain the contents of gypsum and ettringite in different surface depth, solution concentration and corrosion time. Finally, the contents of gypsum and ettringite calculated by the models are compared with the results from the XRD experiments, and then the effects of surface depth, corrosion time and solution concentration on the gypsum and ettringite formations in cement pastes are discussed.

• 도시과학
• /
• 제12권1호
• /
• pp.1-10
• /
• 2023

The cement industry is a major source of carbon dioxide emissions. Reduction in emissions in this sector is an important issue. Calcium silicate cement is a type of alternative to ordinary Portland cements which contributes to the reduction in carbon dioxide emissions. However, because the type of cement is a non-hydraulic material, there are limitations to its application in the field. The effects of pre-curing periods on the physical characteristics of ordinary Portland cement pastes with calcium silicate cement in the present study were investigated. The Independent variable is the pre-curing period. The pre-curing period varied from 0 to 5 hrs, considering the hydration characteristics of ordinary Portland cement. The carbonation curing of the ordinary Portland cement pastes with the calcium silicate cement after pre-curing was conducted. The concentration of gaseous CO₂ was fixed at 20 %. The test results showed that the pre-curing period led to the pore structural change of the pastes, which in turn could affect the further reaction under the long-term curing condition.

• 한국세라믹학회지
• /
• 제40권12호
• /
• pp.1229-1234
• /
• 2003

최근 광물 혼합재로서 메타카올린의 이용이 주목되어지고 있다. 본 연구에서는 메타카올린을 혼합한 시멘트 페이스트의 유동특성에 관해 조사하였다. 시멘트 페이스트의 레올로지는 실린더형 스핀들을 갖는 회전형 점도계를 사용하여 평가하였다. 메타카올린을 혼합한 시멘트 페이스트의 유동성은 물/고체비의 증가와 고성능 감수제의 치환량의 증가에 따라 증가하였다. 또한 메타카올린을 일부 치환한 시멘트 페이스트는 dilatant 거동을 나타내었다. Dilatancy는 물/고체비와 메타카올린의 양에 영향을 받았으며, 실리카 퓸의 경우는 thixotropy를 나타내었다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
• /
• pp.714-717
• /
• 2000

To consider sulfate resistance of cement pastes and motars for 3 types of portland cements which have different $C_3A$ contents an silicate ratio($C_3S/C_2S$), they were immersed in 5% sodium sulfate solution for 400 days. SEM analysis and ($Ca(OH)_2$ contents of cement pastes, and compressive strength and length change of cement mortars, were performed to investigate the effects of ($C_3$ and ($Ca(OH)_2$ contents. According to the results of this study, low heat portland cement pastes, and compressive strength and length change of cement mortars, were performed to investigate the effects of C3A and ($Ca(OH)_2$ contents. According to the results of this study, low heat portland cement had a good sulfate resistances because of a small quantity of gypsum and ettringite due to less ($Ca(OH)_2$ contents. However, ordinary portland cement had an adverse result. This was also confirmed by SEM analysis.

• 한국세라믹학회지
• /
• 제24권3호
• /
• pp.289-295
• /
• 1987

The changes of physical properties of portland cement pastes and mortars were investigated by addition of sodium gluconate. Flow table experiment and viscosity measurement were took in order to find dispersing effect, and time-dependent changesof viscosity and rates of hydration heat evolution were carried out for the sake of finding retardation effect of hydration. And changes of physical properties of cement pastes and mortars were discussed by setting time, compressive strength and porosity.

• 한국세라믹학회지
• /
• 제46권6호
• /
• pp.657-661
• /
• 2009

In this study, rheological properties of cement pastes containing ground Finex-slag (4000, 6000, 7000 c$m^2$/g) were investigated bymini-flow test and coaxial cylinder viscometer. And also blast furnace slag(4000, 6000, 7000 c$m^2$/g) were used for comparison. According to the experimental results, Finex-slag and blast furnace slag showed very similar trend in the rheological properties of the cement pastes. The fluidity of cement pastes blended Finex-slag and blast furnace slag powder were improved by high replacement ratio. In the relationship of plastic viscosity and yield stress appeared the tendency of the proportion greatly. And in the relationship of plastic viscosity, yield stress and mini-flow appeared the tendency of the inverse proportion.

• 한국재료학회지
• /
• 제13권2호
• /
• pp.94-100
• /
• 2003

The interface between low carbon steel and blended cement pastes containing slag was investigated using impedance spectroscopy. In addition, the pastes were characterized by several analytical methods (XRD, EDX, electrode potential, pH and ICP). The electrical behavior of the interface in the blended slag systems is correlated to its corresponding pore solution chemistry and the products present in the interface. Passivation occurred at the paste/steel interfaces, in cement pastes up to containing from 0 to 75% slag content. 100% slag paste induced corrosion of the low carbon steel, which could be explained by the influence of sulfur on the system.