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Carbonation of low heat portland cement paste precured in water for different time

Journal of University of Science and Technology Beijing 2007年第2期14卷 178-184页

作者： Deping Chen Etsuo Sakai masaki daimon Yoko Ohba Civil and Environmental Engineering School University of Science and Technology Beijing Beijing 100083 China Graduate School of Science and Engineering Tokyo Institute of Technology Tokyo 152-8552 Japan

The carbonation technique was applied to accelerate the hydration of low heat portland cement （LHC）. Before carbonation, the demoulded pastes were precured in water for 0, 2, 7, and 21 d, respectively. The results show that precuring time in water strongly influences the carbonation process. The phenolphthalein test indicates that the paste precured in water for a shorter time is more quickly carbonated than that for a longer time. The content of calcium hydroxide increases with increasing the precuring time in water, whereas, the amount of absorbed carbon dioxide changes contrarily. Scanning electron microscope （SEM） observation shows that portlandite always fills up big air bubbles in the paste during precuring in water, and the mercury intrusion porosimetry （MIP） results show that there are less large capillary pores in the paste precured in water for a longer time. It is found that the paste without precuring in water has more carbon dioxide absorption during curing in carbon dioxide atmosphere, and its total pore volume decreases remarkably with an increase in the carbonation time than that precured in water. X-ray diffraction （XRD） and Brunauer-Emmett-Teller （BET） surface area analyses indicate that the carbonate products are vaterite and calcite; CxSHy formed from carbonation has low BET surface area in comparison with that of C-S-H formed from curing in water.

关键词： carbonation carbon dioxide absorption vaterite BET surface area pore size distribution

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DISPERSION MECHANISMS OF COMB-TYPE SUPERPLASTICIZERS CONTAINING GRAFTED POLYETHYLENE OXIDES

DISPERSION MECHANISMS OF COMB-TYPE SUPERPLASTICIZERS CONTAIN...

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第五届水泥与混凝土国际会议

作者： SAKAI Etsuo daimon masaki Tokyo Institute of Technology 2-12-1 OokayamaMeguro-kuTokyoJAPAN152-8552

This paper discusses on graft chain length of comb-type superplasticizers affecting the adsorption and dispersion mechanisms, and their subsequent effect on the fluidity of limestone powder suspensions. Contrary to the results obtained from interparticle potential calculations, the fluidity of concentrated suspension is improved by the use of comb-type polymers having shorter grafted chain length. The dispersion mechanism of comb-type polymers in a concentrated suspension is evaluated from the perspective of molecular structure, the amount of adsorbed polymer, and the amount of entrapped water in the clusters of CaCO3 particles. Furthermore, the addition of certain soluble salts, which can effect the concentration of Ca2+ in liquid phase of CaCO3 suspensions, has been observed to decrease the adsorption of comb-type polymers on CaCO3. Thus, the polymer adsorption process can be selectively influenced by certain types of ions

关键词： comb-type superplasticezer grafted chain dispersion mechanisms steric hindrance

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CONTROL METHODS FOR THE EARLY HYDARTION IN Ca3Al2O6--GYPSUM SYSTEM WITH SUPERPLASTICIZERS

CONTROL METHODS FOR THE EARLY HYDARTION IN Ca3Al2O6--GYPSUM ...

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第五届水泥与混凝土国际会议

作者： Sakai Etsuo Kang Jin-Kyu daimon masaki Tokyo Institute of Technology 2-12-1 OokayamaMeguro-kuTokyoJAPAN152-8552

It is necessary to control the early hydration of aluminate phase in order to control the fluidity. The object of this paper is to obtain the basic data for the fluidity control of cement and concrete with superplasticizers. This paper discusses the influence of superplasticizers on the early hydration of C3A-calcium sulfates by quantitative XRD. And the control methods of the hydration in C3A-gypsum system with supperplasticizers have been proposed. The early hydration of C3A is retarded, as there is much content of SO42- in the gel formed around C3 A. Adding of comb-type superplasticizers in C3A-calcium sulfates systems accelerates early hydration of C3 A, because the supply of SO42- to gel is inhibited. The early hydration of C3A in C3 A-gypsum system is retarded by replacement of gypsum to hemihydrate or increasing free-CaO contents. It is proposed that the replacement of about 50% of gypsum to hemihydrate or the increase of CaO contenets would be effective for controlling the early hydration of cement with comb-type superplasticizers.

关键词： wuperplasticizers early hydration C3A calcium sulfates free-CaO

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5%乙烯-醋酸乙烯共聚物复合低热水泥浆体的碳化促进养护

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硅酸盐学报 2006年第10期34卷 1263-1269页

作者：陈德平坂井悦郎大场阳子大门正机北京科技大学土木工程系北京100083 东京工业大学大学院理工学研究科

采用碳化养护方法促进5%乙烯-醋酸乙烯共聚物复合低热水泥浆体的水化。通过X射线衍射定性及定量分析测定了养护后样品的组成及水泥中硅酸三钙(3CaO·SiO2,C3S)、硅酸二钙(2CaO·SiO2,C2S)的水化率;利用带固体样品测试装置的全有机碳素... 详细信息

采用碳化养护方法促进5%乙烯-醋酸乙烯共聚物复合低热水泥浆体的水化。通过X射线衍射定性及定量分析测定了养护后样品的组成及水泥中硅酸三钙(3CaO·SiO2,C3S)、硅酸二钙(2CaO·SiO2,C2S)的水化率;利用带固体样品测试装置的全有机碳素分析仪测定了样品所吸收的CO2量;采用水银压入法检测了样品的孔径分布。结果显示:碳化养护大大促进了低热水泥的水化,并有球霰石生成。样品中的总孔隙体积也明显减少,但有大量较大孔径的毛细孔隙存在。碳化养护前,对样品进行水中预养护可以减少这些毛细孔隙,但不利于水泥的水化并导致CO2吸收量及抗折强度显著降低。

关键词：碳化乙烯-醋酸乙烯共聚物低热水泥球霰石二氧化碳吸收孔径分布

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