Showing papers by "Francisca Puertas published in 2010"
TL;DR: In this article, the use of three Slovak poor metakaolin sands with different metakolin content (36.0%, 31.5%, and 40.0%) and specific surface has been deeply studied as mineral addition for Portland cement.
84 citations
TL;DR: In this paper, a clinker and a cement obtained from a raw mix containing ceramic waste as an alternative raw material were characterized, and their hydration, physical-chemical properties and leaching behaviour in different acid media were also explored.
Abstract: A clinker and a cement obtained from a raw mix containing ceramic waste as an alternative raw material were characterized in the present study. Their hydration, physical–chemical properties and leaching behaviour in different acid media were also explored. The findings showed that both the clinker and the cement met all the requirements set out in European standards EN 197-1 [1] , although they had higher ZnO, ZrO 2 , and B 2 O 3 contents than an industrially produced reference product. According to the hydration studies, initial hydration was somewhat retarded in the new cement, which exhibited longer initial and final setting times and lower 2-day mechanical strength. The SEM/BSE/EDS microstructural study showed, however, that morphologically and compositionally, the hydration products formed were comparable to unadditioned Portland cement paste products. While low concentrations of Zn and B were observed to leach in acid media, the biotoxicity trials conducted confirmed that these concentrations were not toxic. Zr was retained in the cement pastes.
63 citations
TL;DR: In this paper, a quantitative method based on thermal analyses has been used for the determination of the chemical composition of the C-S-H gel together with the degree of hydration and quantitative evolution of all the components of the pastes.
Abstract: This research is part of a European project (namely, CODICE project), main objective of which is modelling, at a multi-scale, the evolution of the mechanical performance of non-degraded and degraded cementitious matrices. For that, a series of experiments were planned with pure synthetic tri-calcium silicate (C3S) and bi-calcium silicate (C2S) (main components of the Portland cement clinker) to obtain different calcium–silicate–hydrate (C–S–H) gel structures during their hydration. The characterization of those C–S–H gels and matrices will provide experimental parameters for the validation of the multi-scale modelling scheme proposed. In this article, a quantitative method, based on thermal analyses, has been used for the determination of the chemical composition of the C–S–H gel together with the degree of hydration and quantitative evolution of all the components of the pastes. Besides, the microstructure and type of silicate tetrahedron and mean chain length (MCL) were studied by scanning electron microscopy (SEM) and 29Si magic-angle-spinning (MAS) NMR, respectively. The main results showed that the chemical compositions for the C–S–H gels have a CaO/SiO2 M ratio almost constant of 1.7 for both C3S and C2S compounds. Small differences were found in the gel water content: the H2O/SiO2 M ratio ranged from 2.9 ± 0.2 to 2.6 ± 0.2 for the C3S (decrease) and from 2.4 ± 0.2 to 3.2 ± 0.2 for the C2S (increase). The MCL values of the C–S–H gels, determined from 29Si MAS NMR, were 3.5 and 4 silicate tetrahedron, for the hydrated C3S and C2S, respectively, remaining almost constant at all hydration periods.
62 citations
TL;DR: In this paper, the results showed that this metakaolin sand (MK-1) is a pozzolanic material apt for use as a cement addition and for making mortars, and the hydration reactions taking place in the blends were assessed with conduction calorimetry, X-ray diffraction and differential thermal analysis-thermogravimetry (DTA-TG).
Abstract: The kaolin sand resource at the Vysný Petrovec quarry in Slovakia comes to a total of 20 megatonnes. The metakaolin material obtained by heating kaolin sand at 650 oC contains from 31.5 to 40% (wt) metakaolinite, as well as illite, muscovite, quartz and feldspar. The aim of this study was to verify whether this calcined sand (MK1) is a pozzolanic material and characterize the cements and mortars prepared with it. The hydration reactions taking place in the blends were assessed with conduction calorimetry, X-ray diffraction (XRD) and differential thermal analysis-thermogravimetry (DTA-TG). Blend and mortar strength development and pore structure were also evaluated. The results obtained showed that this metakaolin sand (MK-1) is a pozzolanic material apt for use as a cement addition and for making mortars.
3 citations
TL;DR: In this paper, the problem of recycling mixed cullet, a constituent of solid common wastes, remains topical and it is shown that the method of mechanochemical activation makes it possible to obtain a mixed alkaline binding substance which is promising for the production of unfired heat-insulating materials with high mechanical properties.
Abstract: Methods for recycling mixed cullet, which is a constituent of solid common wastes, are analyzed It is shown that the problem of recycling wastes of this form remains topical It is established experimentally that the method of mechanochemical activation makes it possible to obtain a mixed alkaline binding substance which is promising for the production of unfired heat-insulating materials with high mechanical properties
2 citations