Citric acid as anti-hydration additive for magnesia containing refractory castables

Salomão, R.; Pandolfelli, V. C.

doi:10.1016/j.ceramint.2011.03.050

Cited by 74 publications

(37 citation statements)

References 15 publications

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“…Comparing to the other SAS grades, MS particles have a much lower internal mesoporosity (IP = 10.7 %) and specific surface area. Due to this, its reduces the amount of voids amongst particles at the compacting step 1,6,8,48 . During the initial heating, no significant densification was observed up to 1000ºC (Fig.…”

Section: Samples Sintered At 1100ºcmentioning

confidence: 99%

“…1d) particles are spherical, dense and individualized and their broad particle size distribution ranges from 50 to 500 nm. They are obtained as a precipitated by-product during the production of elemental silicon and are widely used in civil construction for enhancing the packing of high performance concrete, and in refractories for the production of mullitebased bricks and castables 1,7,8,15,38,39,48,49 . After physical characterization, the SAS particles were combined with calcined alumina to produce in situ mullite dense parts.…”

Section: Introductionmentioning

confidence: 99%

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Preparation and Characterization of Mullite-Alumina Structures Formed "In Situ" from Calcined Alumina and Different Grades of Synthetic Amorphous Silica

Fernandes

Salomão

2018

Mat. Res.

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The in situ reaction between alumina and silica to obtain mullite (Al 6 Si 4 O 13 ) can be significantly affected by using synthetic amorphous silica (SAS) sources instead of crystalline ones (quartz and cristobalite). For instance, SASs promote early mullite formation (below 1300°C) and greater densification during sintering. This paper reports the "in situ" formation of mullite-alumina structures from fine calcined alumina (α-Al 2 O 3 ) and four grades of SAS of different particles' morphology, specific surface area and internal porosity. After sintering assisted by dilatometry (up to 1500°C), the samples' total porosity, density and flexural strength were measured. The relative density and strength levels of some of these structures were greater than or comparable to other studies in which similar compositions were sintered at higher temperatures (1600-1700°C). Their microstructure assessment indicated that the specific surface area and internal porosity of SAS particles showed a major influence in the development of these physical properties.

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Section: Samples Sintered At 1100ºcmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Preparation and Characterization of Mullite-Alumina Structures Formed "In Situ" from Calcined Alumina and Different Grades of Synthetic Amorphous Silica

Fernandes

Salomão

2018

Mat. Res.

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“…In the first set of experiments, where MgO was added to water, the pH and the amount of species precipitate onto the surface of MgO particle [17]. This [6MgOH + ·(PO3)6 6-](insoluble)layer forms a stable protective coating on MgO particles which prevents further hydrolysis of MgO [18].…”

Section: Mg 2+ (Aq) + 2oh -(Aq) → Mg(oh)2(s)mentioning

confidence: 99%

“…The aqueous dissolution of MgO and precipitation of magnesium hydroxide (Mg(OH)2) has been extensively studied [15][16][17]. Protonation (Eq.…”

Section: Hydrolysis Of Mgo and Dissolution Of Sf Influences The Formamentioning

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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“…In particular, in the production of lightweight concrete Heidun Oil platform in its structure silica fume added in an amount of 20 kg/m 3 [7]. Silica fume reduces the volume changes in concrete, thereby reducing the number of micro-cracks [13].…”

Section: The Scientific Journal Of Cihan University -Sulaimanyiamentioning

confidence: 99%

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2017

SJCUS

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Abstract. Concrete ships (floating docks, hotels, houses, marinas, oil platforms) are being built in many countries around the world. For such ships previously used mainly heavy concrete. Recently, for concrete floating structures often use lightweight aggregate concrete. Using expanded clay lightweight concretes reduces the weight of the construction. At reducing the weight load lifting of the floating structure is increased. The use of lightweight concrete improves people's occupation and equipment on a reinforced concrete ship.Influence of composition expanded clay concrete on its properties has been found. At the first stage, were investigated lightweight concrete based on the processed by hydrophobisator gravel. In the second phase were investigated concretes with silica fume. Planned three-factor experiment was conducted. Such concrete composition were varied: the amount of cement (500-600 kg/m 3 ), silica fume (0-50 kg/m 3 ) and superplasticizer S-3 (0.5-1%). Concretes were made from equal mixtures mobility P2 (4-6 cm). It is found that the compressive strength of concrete is in the range of 32 to 43 MPa. By increasing the amount of cement strength increases, but this increase is not linear type. Tensile strength of concrete was in the range of 5.6 to 7.0 MPa. Water-resistant concrete was in the range of W4 to W12. When administered to 30-35 kg/m 3 silica fume of about 2 MPa increases compressive strength expanded clay lightweight concrete and 0.3 MPa the tensile strength increases with bending. By increasing the amount of additive S-3 is significantly increased compressive strength concrete. However, the introduction of additives increases tensile strength is less when bending. Due to the introduction of the optimal amount of silica fume and S-3 water resistance of concrete is increased by about 40-50%.Thus, the modified expanded clay lightweight concrete has a relatively low bulk density with high strength. They can be used in thin-walled construction of hydraulic structures, in particular floating docks, houses and hotels.Keywords: shipbuilding reinforced concrete, expanded clay lightweight concrete, silica fume, plasticizer, experimental and statistical modeling.

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Citric acid as anti-hydration additive for magnesia containing refractory castables

Cited by 74 publications

References 15 publications

Preparation and Characterization of Mullite-Alumina Structures Formed "In Situ" from Calcined Alumina and Different Grades of Synthetic Amorphous Silica

Preparation and Characterization of Mullite-Alumina Structures Formed "In Situ" from Calcined Alumina and Different Grades of Synthetic Amorphous Silica

Role of sodium hexametaphosphate in MgO/SiO2 cement pastes

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