Influence of time and temperature on ageing and phases synthesis in the MgO–SiO2–H2O system

Szczerba, Jacek; Prorok, Ryszard; Śnieżek, E; Madej, Dominika; Maślona, Konrad

doi:10.1016/j.tca.2013.01.018

Cited by 87 publications

(71 citation statements)

References 15 publications

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“…However, after 200 accelerated aging cycles, the control samples suffer a significant loss of flexural strength as has been demonstrated by other authors [9,53], whereas the optimized MgO-SiO 2 formulation increases in modulus of rupture (MOR). This suggests that the hydration reactions of MgO-SiO 2 system continue beyond 28 days of age, in accordance with the findings of other researchers [38,27].…”

Section: Fiber-cement Bending Testssupporting

confidence: 92%

Optimization of the MgO SiO2 binding system for fiber-cement production with cellulosic reinforcing elements

et al. 2016

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Section: Fiber-cement Bending Testssupporting

confidence: 92%

Optimization of the MgO SiO2 binding system for fiber-cement production with cellulosic reinforcing elements

et al. 2016

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“…The structure of M-S-H gel produced by reacting MgO and silica fume (SF) with water has recently been reported using x-ray diffraction, IR spectra, DTA-TGA-EGA and NMR studies [9][10][11]14].…”

Section: Introductionmentioning

confidence: 99%

“…Sodium hexametaphosphate(Na-HMP) is a hexamer of sodium metaphosphate, which is used in the ceramics and food industries and in nanotechnology as a deflocculant and/or sequestering agent [13][14][15]. The addition ofNa-HMP to the mix water has been reported to significantly improve the rheology and properties of MgO/SF pastes and mortars and this enables the production of materials with high strength, high density and low porosity [10,13].…”

Section: Introductionmentioning

confidence: 99%

Role of sodium hexametaphosphate in MgO/SiO2 cement pastes

Jia

Wang

et al. 2016

Cement and Concrete Research

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The extent of reaction between magnesium oxide (MgO) and silica fume (SiO2) is normally limited and mixes require high water contents to give suitable rheology. The use of considerably lower water contents and the formation of magnesium silicate hydrate (M-S-H) gel as a binding phase is made possible by adding sodium hexametaphosphate (Na-HMP) to the mix water prior to the addition of MgO and SiO2. This results in the formation of extensive reaction products and cured samples with high compressive strength and low porosity. In this work, the effect of Na-HMP on the hydration of MgO/SiO2 mixes is investigated using high water to solids ratio samples to allow monitoring of pH and the solution chemistry during hydration. It is shown that a relatively small amount of Na-HMP inhibits the formation of Mg(OH)2 when MgO is hydrolyzed. It is proposed that this is due to adsorption of phosphate species on the MgO which inhibits the nucleation of the Mg(OH)2.. This gives rise to high Mg 2+ species in solution and elevated pH (>12) conditions relative to when Mg(OH)2 forms. In contrast, the phosphate does not suppress formation of M-S-H gel. In combination with the enhanced dissolution rate of SiO2 at high pH, M-S-H gel can form quickly without competition for Mg 2+ ions by Mg(OH)2 precipitation. Incorporating the optimum concentration of Na-HMP into the mix water therefore transforms the properties of cement paste and mortar samples formed by reacting MgO and SiO2.

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“…Magnesia (MgO) is widely used in the production of refractory materials due to its ultra-high melting point and ability to form the binding system based on M-S-H (M:MgO, S:SiO 2 , H:H 2 O) phase under moist conditions and in the presence of, for example, silica fume [1][2][3][4]. Magnesium oxide with high chemical activity can be obtained by optimizing the technological parameters including calcination temperature and soaking time.…”

Section: Introductionmentioning

confidence: 99%

An experimental investigation of hydration mechanism of the binary cementitious pastes containing MgO and Al2O3 micro-powders

Madej

Prorok

Wiśniewska

2018

J Therm Anal Calorim

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The reactivity of the binary mixtures of reactive magnesia and hydratable alumina micro-powders with various compositions was investigated by calorimetric method, X-ray diffraction, simultaneous DSC-TGA with thermal evolved gas analysis-mass spectrometry and scanning electron microscope observations. The effect of the MgO/Al 2 O 3 molar ratio (2:1, 1:1 and 1:2) and temperature on the hydration behavior of pastes has been explored using the TAM Air isothermal calorimetry system at 25 and 50°C. Some structural aspects of a M-A-H (M:MgO, A:Al 2 O 3 , H:H 2 O) binding phase formed upon the hydration of MgO-Al 2 O 3 micro-powders at different curing time have been explored. The main hydrate considered to be important in this system is hydrotalcite Mg 6 Al 2 CO 3 (OH) 16 Á4H 2 O formed via the isomorphous substitution of Mg 2? ions by trivalent Al 3? one in the brucite-like sheet. This was expressed as a systematic shift of the peak at 2-theta value corresponding to the (003) reflection. Since both hydrotalcite and brucite are identified in the hydrating samples, the thermal stability of hydroxyls in these hydration products can be placed in the decreasing order as follows: (Mg2Al)-OHhydrotalcite group [ (Mg3)-OH-brucite group [ (Mg3)-OH-hydrotalcite group.

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Influence of time and temperature on ageing and phases synthesis in the MgO–SiO2–H2O system

Cited by 87 publications

References 15 publications

Optimization of the MgO SiO2 binding system for fiber-cement production with cellulosic reinforcing elements

Optimization of the MgO SiO2 binding system for fiber-cement production with cellulosic reinforcing elements

Role of sodium hexametaphosphate in MgO/SiO2 cement pastes

An experimental investigation of hydration mechanism of the binary cementitious pastes containing MgO and Al2O3 micro-powders

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