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Analysis of Air Voids Evolution in cement pastes Admixed with Non-ionic Cellulose Ethers

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Journal of Wuhan University of Technology(Materials Science) 2018年第4期33卷 915-923页

作者：欧志华 XIAO Yi 王菁菁 MA Baoguo JIANG Longmin JIAN Shouwei School of Civil Engineering Hunan University of TechnologyZhuzhou 412007China State Key Laboratory of Silicate Materials for Architectures Wuhan University of TechnologyWuhan 430070China

Four cellulose ethers（CEs） were compared for their effects on the pore structure of cement paste using mercury intrusion porosimetry. The experimental results show that the total pore volume and porosity of cement pastes containing the four cellulose ethers are significantly higher than that of the pure cement pastes and the total pore volume and porosity of cement pastes containing HEC（hydroxyethyl cellulose ether） or low viscosity cellulose ethers are low in four CEs. By changing the surface tension and viscosity of liquid phase and the strengthening of liquid film between air voids in cement pastes, CEs affect the formation, diameter evolution and upward movement of air voids and the pore structure of hardening cement paste. For the four CEs, the pore volume of cement pastes containing HEC or low viscosity cellulose ethers is higher with the diameter of 30-70 nm while lower with the diameter larger than 70 nm. CEs affect the pore structure of cement paste mainly through their effects on the evolvement of the small air voids into bigger ones when the pore diameter is below 70 nm and their effects on the entrainment and stabilization of air voids when the pore diameter is above 70 nm.

关键词： cellulose ethers cement pastes pore structure air voids diameter evolution

Hydration Heat Effect of cement pastes Modified with Hydroxypropyl Methyl Cellulose Ether and Expanded Perlite

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Journal of Wuhan University of Technology(Materials Science) 2013年第1期28卷 122-126页

作者：苏雷 MA Baoguo JIAN Shouwei ZHAO Zhiguang LIU Min State Key Laboratory of Silicate Materials for Architectures Wuhan University of Technology

Hydration heat effect of cement pastes and mechanism of hydroxypropyl methyl cellulose ether （HPMC） and expanded perlite in cement pastes were studied by means of hydration exothermic rate, hydration heat amount, FTIR and TG-DTG. The results show that HPMC can significantly delay the hydration induction period and acceleration period of cement pastes. As mixing amount increased, hydration induction period of cement pastes enlarged and accelerated period gradually went back. At the same time, the amount of hydration heat gradually decreased. Expanded perlite had worse delay effects and less change of hydration heat amount of cement pastes than HPMC. HPMC changed the structure of C-S-H during cement hydration. The more amount of HPMC, the more obvious effect. However, EXP had little influence on the structure of C-S-H. At the same age, the content of Ca （OH）2 in cement pastes gradually decreased as the mixing amount increase of HPMC and expanded perlite, and had better delay effect than that single-doped with HPMC or expanded perlite when HPMC and expanded nerlite were both dooed in cement pastes.

关键词： hydroxypropyl methyl cellulose ether expanded perlite cement pastes hydration heat hydrationprocess

INFLUENCE OF GLASS CULLET IN cement pastes

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China Particuology 2006年第5期4卷 234-237页

作者： A.Karamberi E.Chaniotakis D.Papageorgiou A.Moutsatsou Laboratory of Inorganic and Analytical Chemistry Chemical Engineering Department National Technical University of Athens 9 Heroon Polytechniou Str. 157 73 Athens Greece "Titan"cement Company S. A. P. O. Box 18-GR 19200 Elefsis Greece

The present study investigates glass and cement compatibility with a view to use glass as a cement replacement. Amber, flint and green glasses were chosen due to their prevalence in the Greek market as packaging materials. The factors under investigation were the pozzolanicity of the glass cullet, the hydration rate and the mechanical strength development of the cement pastes, as well as the expansion of the specimens due to alkali-silica reaction. Moreover, the potential enhancement of glass pozzolanic activity was examined. The results of the study were encouraging to show the potentiality of utilising glass cullet in cementitious products.

关键词： glass cullet cement pastes pozzolanicity

Evaluation of the Properties of cement pastes and Mortars Used in the Encapsulation of Bituminized Waste to be Disposed in a Near-Surface Repository

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Journal of Environmental Science and Engineering(B) 2016年第11期5卷 541-548页

作者： Vanessa Mota Vieira Cledola Cassia Oliveira de Tello Nuclear Technology Development Center (CDTN/CNEN) Department of Radioactive Waste Belo Horizonte Pampulha Av.Presidente Ant6nio Carlos 6. 627 312 70-901 MG Brazil

The Brazilian repository is being planned to be a near-surface one. In Brazil, the low and intermediate level radioactive wastes are immobilized using cement and bitumen for nuclear plant Angra 1 and Angra 2, respectively. The major problems due to the disposal of bituminized wastes in repositories are swelling of the waste products and their degrad^ttion in the long term. To accommodate the swelling of the bituminized wastes, the drums are filled up to 70-90% of their volume, which reduces the structural the repository stability and the disposal availability. Countries, which use bitumen in the solidification of NPP＇s radioactive waste and have near-surface repositories, need to immobilize this bituminized waste within other drums containing cement pastes or mortars to disposal them. This study aims to evaluate the properties of bitumen, cement pastes and mortars to be used in the encapsulation of bituminized wastes. The formulations of two pastes and two mortars were selected for the pilot scale tests. The laboratory and pilot scales results were very similar, indicating that any of these formulations could be used. However, the better formulation will be chosen after the leaching test results, because it is an essential parameter in the long-term repository performance.

关键词： Radioactive wastes bitumen cement pastes mortars.

Influence of Silica Fume on Corrosion Behaviour of Reinforced Steel in Different Media

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Journal of Materials Science & Technology 2002年第1期18卷 83-88页

作者： Z.A.El-Hadi I.Z.Selim 等 DepartmentofChemistry UniversityCollegeforGirlsAinShamsUniversityEgypt PhysicalChemistryDepartment NationalResearchCenterCairoEgypt

Electrochemical and corrosion behaviour of reinforced steel embedded in cement pastes incorporating different amounts of silica fume as a partial replacement of cement has been studied in chloride and sulphate solutions by using different electrochemical techniques. The results indicate that, while steel passivity degree is low in the control samples' upon soaking in the corrosive media, it has been high in samples incorporating silica fume and increased with increasing silica fume content. The improvement effect of silica fume may be attributed to the pore solution structure of the cement paste, which limits the mobility of aggressive ions near the surface of the steel. The mechanism of steel corrosion due to chloride and sulphate attack and passivation effect of silica fume are discussed.

关键词： Corrosion Reinforced steel cement pastes Silica fume Aggressive ions