| 1. |
- Moosberg-Bustnes, Helena, et al.
(author)
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The function of fillers in concrete
- 2004
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In: Materials and Structures. - 1359-5997 .- 1871-6873. ; 37:2, s. 74-81
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Journal article (peer-reviewed)abstract
- The purpose of this investigation has been to evaluate the effect of quartz filler on concrete strength and microstructure, and to see if it is possible to replace cement with filler without loss of strength. Fillers are materials whose function in concrete is based mainly on size and shape. They can interact with cement in several ways; to improve particle packing and give the fresh concrete other properties, and even to reduce the amount of cement in concrete without loss of strength. Quartz was chosen as filler material, since it is inert and is available both as a by-product and a natural raw material. Different amounts of filler were used in the various experiments, as well as different particle size distributions. The results are positive: fillers can partially replace cement and at the same time improve the properties and the microstructure of the concrete. This research is part of a larger project that aims to find uses for by-products in concrete.
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| 2. |
- Westerholm, Mikael, et al.
(author)
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Rheological properties of micromortars containing fines from manufactured aggregates
- 2006
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In: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 40:6, s. 615-625
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Journal article (peer-reviewed)abstract
- This paper concerns the influence of fines from manufactured aggregates on the rheological properties of the micromortar phase of concrete. Fines from nine different aggregates were included in the experimental work. The zeta potential of five of them was measured at different additions of superplasticizer in order to study the interaction between the surface of the fines and the superplasticizer. The rheological properties of the micromortars were studied at different volume concentrations of fines and at different concentrations in the paste phase, i.e., w/c ratios. Furthermore, the micromortars were studied at different dosages of a superplasticizer. The results show that the fines have different surface properties, i.e., zeta potential, and indicate that the superplasticizer only is adsorbed on some of them. The results from the rheological characterisation of the micromortars indicate that the higher water demand of concrete with manufactured aggregates partly can be traced to the properties of the micromortar phase of the concrete.
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| 3. |
- Abramov, A.A., et al.
(author)
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Chemistry and optimal conditions for copper minerals flotation : theory and practice
- 2005
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In: Mineral Processing and Extractive Metallurgy Review. - : Informa UK Limited. - 0882-7508 .- 1547-7401. ; 26:2, s. 77-143
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Journal article (peer-reviewed)abstract
- Reliable information on the surface state of sulphide copper minerals and regularities of sulphidization and flotation of oxidized copper minerals, the composition of sorption layer on the mineral surface forming during its interaction with xanthate or dixanthogen, and the influence of collector forms sorption on the copper minerals floatability and on the optimal conditions for these minerals flotation and depression has been obtained at present. The determined physicochemical models in the form of quantitative equations have been derived for the optimal conditions of flotation and depression of copper minerals under changing pH value and of sodium sulphide, lime, cyanide, zinc–cyanide complexes additions. The equations derived were proven in the laboratory and industrial scale and can be used both in automatic control systems at plants and for improvement of technological processes of selective flotation of copper containing ores.
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| 4. |
- Ahlberg, E., et al.
(author)
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The surface oxidation of pyrite in alkaline solution
- 1990
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In: Journal of Applied Electrochemistry. - 0021-891X .- 1572-8838. ; 20:6, s. 1033-1039
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Journal article (peer-reviewed)abstract
- The collector-less flotation of pyrite has been studied by conventional techniques and is correlated to the electrochemical behaviour of pyrite in alkaline solution (1m NaClO4, pH 11). It was concluded that the initial oxidation of pyrite produces a hydrophobic sulphur rich surface together with hydrophilic iron hydroxide species. Also upon grinding, the surface is covered by hydrophilic species and therefore no significant flotation was obtained in the absence of a collector. However, collectorless flotation was readily obtained in an iron complexing solution like EDTA. This indicates that the remaining sulphur-rich layer is responsible for the floatability of pyrite under these conditions.
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| 5. |
- Alexandrova, L, et al.
(author)
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The influence of mixed cationic-anionic surfactants on the three-phase contact parameters in silica-solution systems
- 2011
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In: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 373, s. 145-151
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Journal article (peer-reviewed)abstract
- The formation of thin wetting films on silica surface from aqueous solution of (a) tetradecyltrimetilammonium bromide (C14TAB) and (b) surfactant mixture of the cationic C14TAB with the anionic sodium alkyl- (straight chain C12-, C14- and C16-) sulfonates, was studied using the microscopic thin wetting film method developed by Platikanov. Film lifetimes, three-phase contact (TPC) expansion rates, receding contact angles and surface tension were measured. It was found that the mixed surfactants caused lower contact angles, lower rates of the thin aqueous film rupture and longer film lifetimes, as compared to the pure C14TAB. This behavior was explained by the strong initial adsorption of interfacial complexes from the mixed surfactant system at the air/solution interface, followed by adsorption at the silica interface. The formation of the interfacial complexes at the air/solution interface was proved by means of the surface tension data. It was also shown, that the chain length compatibility between the anionic and cationic surfactants controls the strength of the interfacial complex and causes synergistic lowering in the surface tension. The film rupture mechanism was explained by the heterocoagulation mechanism between the positively charged air/solution interface and the solution/silica interface, which remained negatively charged.
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| 6. |
- Alexandrova, L., et al.
(author)
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Thin film studies in mixed cationic-anionic surfactant system
- 2003
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In: Proceedings of the XXII International Mineral Processing Congress. - Marshalltown, South Africa : South African Institute of Mining and Metallurgy. - 0958460922 ; , s. 838-846
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Conference paper (peer-reviewed)
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| 7. |
- Alexandrova, L, et al.
(author)
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Three-phase contact parameters measurements for silica-mixed cationic-anionic surfactant systems
- 2009
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In: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 348:1-3, s. 228-233
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Journal article (peer-reviewed)abstract
- The stability and interactions in thin wetting films between the silica surface and air bubble containing (a) straight chain C10 amine and (b) cationic/anionic surfactant mixture of a straight chain C10 amine with sodium C8, C10 and (straight chain) C12 sulfonates, were studied using the microscopic thin wetting film method developed by Platikanov [D. Platikanov, J. Phys. Chem. 68 (1964) 3619]. Film lifetimes, three-phase contact (TPC) expansion rate, receding contact angles and surface tension were measured. The presence of the mixed cationic/anionic surfactants was found to lessen contact angles and suppresses the thin aqueous film rupture, thus inducing longer film lifetime, as compared to the pure amine system. In the case of mixed surfactants heterocoagulation could arise through the formation of positively charged interfacial complexes. Mixed solution of cationic and anionic surfactants shows synergistic lowering in surface tension. The formation of the interfacial complex at the air/solution interface was confirmed by surface tension data. It was also shown, that the chain length compatibility between the anionic and cationic surfactants system controls the strength of the interfacial complex. The observed phenomena were discussed in terms of the electrostatic heterocoagulation theory, where the interactions can be attractive or repulsive depending on the different surface activity and charge of the respective surfactants at the two interfaces.
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| 8. |
- Antti, Britt-Marie, et al.
(author)
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Pulp chemistry in calcite flotation. : Modelling of oleate adsorption using theoretical equilibrium calculations
- 1989
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In: Mining engineering. - 0026-5187. ; 2:1, s. 93-109
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Journal article (peer-reviewed)abstract
- This paper considers the conditions required for direct flotation of calcite. Flotation experiments have been performed with oleate as the collector reagent and water glass as the dispersant and modifier. To be able to explain what happens in the flotation, solubility and adsorption experiments have been conducted parallel to, and under the same conditions as, the flotation experiments. Theoretical equilibrium calculations have been made with the help of data from the practical experiments for the purpose of modelling the adsorption experiments. With theoretical equilibrium calculations it is possible to predict that silicate ions will form complexes with calcium ions at the mineral surface.
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| 9. |
- Antti, Britt-Marie, et al.
(author)
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Pulp chemistry in industrial mineral flotation. Studies of surface complex on calcite and apatite surfaces using FTIR spectroscopy
- 1989
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In: Mining engineering. - : Elsevier BV. - 0026-5187. ; 2:2, s. 217-227
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Journal article (peer-reviewed)abstract
- Flotation experiments in a Hallimond tube have been performed on calcite and apatite at pH levels and oleate concentrations judged to be interesting from the point of view of adsorption isotherms. For the calcite system, adsorption isotherms indicate precipitation of calcium oleate after monolayer formation at pH 9, 10 and 11. In the apatite system, a double layer of oleate is formed. This means that apatite, unlike calcite, is sensitive to collector reagent overdosage. With the aid of FTIR techniques it is possible to demonstrate the existence of a surface complex in the apatite system with a calcium-oleate ratio of 1:1 at monolayer coverage of the surface. In conditions corresponding to bulk precipitation of calcium oleate, this compound can be detected by FTIR analysis of unfloated material.
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| 10. |
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