Calcium aluminates

About: Calcium aluminates is a research topic. Over the lifetime, 490 publications have been published within this topic receiving 9200 citations.

Interaction of Alumina Inclusions in Steel with Calcium-containing Materials

Abstract: Clogging of tundish and submerged entry nozzles (SENs) adversely impacts productivity and quality in the continuous casting of aluminum-killed steels. Clogging results from an accretion layer that develops on the inside surface of the nozzle and restricts steel flow. Current nozzle refractories often react with molten steel to form solid by products that promote clogging. Nozzle materials that are inert with the liquid steel or react with accretions to form liquid reaction products could inhibit or eliminate clogging. Static experiments were conducted to investigate the stability between calcium-based materials and aluminum-killed steel. The results indicate that both calcium titanate and calcium zirconate react with alumina to form calcium aluminates. However, only the reaction between alumina and calcium titanate yielded calcium aluminate chemistries that were molten at steel casting temperatures. Liquid reaction products are preferred since they would be removed from the nozzle by the steel flow, thereby preventing accretion formation and clogging.

Reactions of soil minerals with cement and chemicals

Abstract: THE NATURE OF REACTIONS ACCOMPANYING THE STABILIZATION OF SOIL WITH LIME AND CEMENT AND THE MECHANISMS INVOLVED IN THE ALTERATION OF SOIL-CEMENT /OR SOIL-LIME/ REACTION BY CHEMICAL ADDITIVES WERE STUDIED WITH TWO SOIL MINERALS. MIXTURES OF MONO-MINERAL SOILS AND 10 PERCENT CEMENTING COMPOUNDS, WITH OR WITHOUT SODIUM ADDITIVES, WERE EXAMINED AFTER COMPACTION AND VARIOUS CURING PERIODS BY A NUMBER OF ANALYTICAL TECHNIQUES, INCLUDING FLAME PHOTOMETRY, COLORIMETRY, X-RAY DIFFRACTION, AND DIFFERENTIAL THERMAL ANALYSIS. BOTH MONO-MINERAL SOILS /QUARTZ AND KAOLINITE/ REACTED WITH THE THREE CALCIUM STABILIZERS /HYDRATED LIME, TRICALCIUM SILICATE AND TYPE I PORTLAND CEMENT/. ADDITION OF SODIUM ADDITIVES GREATLY INTENSIFIED THE REACTION BETWEEN THE SOIL AND THE STABILIZER AND INCREASED THE ABUNDANCE OF REACTION PRODUCTS. REACTIVITY OF KAOLINITE WITH ANY ONE OF THE CEMENTING COMPOUNDS WAS HIGHER THAN THAT OF QUARTZ. THE PRINCIPAL REACTION PRODUCTS PRODUCED IN QUARTZ MIXTURES WERE HYDROUS CALCIUM SILICATES OF VARIOUS COMPOSITIONS WITH CAO TO SIO2 RATIO VARYING FROM 0.2 TO 1, AND IN KAOLINITE MIXES WERE HYDROUS CALCIUM SILICATES, HYDROUS CALCIUM ALUMINATES AND A MIXED CALCIUM ALUMINOSILICATE. SODIUM FROM THE ADDITIVE ASSOCIATED WITH SOLUBLE COMPOUNDS EARLY IN CURE AND LATER WITH INSOLUBLE MIXED SODIUM-CALCIUM SILICATES OR ALUMINATES. /AUTHOR/

Thermodynamics of Reactions Among Al2O3, CaO, SiO2 and Fe2O3 During Roasting Processes

Abstract: The thermodynamic of the chemical reactions among Al2O3, CaO, SiO2 and Fe2O3 in the roasting processes was investigated in this chapter. The chemical reactions are classified into SiO2-Al2O3 system, Fe2O3-Al2O3 system, SiO2-Fe2O3 system, CaO-Al2O3 system, SiO2-CaO system, SiO2-calcium aluminates system, CaO-Fe2O3 system, Al2O3-calcium ferrites system and Al2O3-CaO-SiO2-Fe2O3 system. When the roasting temperature is over 1100K, 3Al2O3·2SiO2 is preferentially formed in SiO2-Al2O3 system; FeO·Al2O3 can be formed in Fe2O3-Al2O3 system; ferric oxide and SiO2 could not generate iron silicate; 12CaO·7Al2O3 is preferentially formed in CaO-Al2O3 system when one mole Al2O3 reacts with CaO; 2CaO·SiO2 is preferentially formed in SiO2-CaO system; except for CaO·2Al2O3 and CaO·Al2O3, the other calcium aluminates can transform into calcium silicate by reacting with SiO2 in SiO2-calcium aluminates system; 2CaO·Fe2O3 is preferentially formed in CaOFe2O3 system; alumina is unable to form 3CaO·Al2O3 with calcium ferrites(2CaO·Fe2O3 and CaO·Fe2O3), but able to form 12CaO·7Al2O3 with 2CaO·Fe2O3; when CaO, Fe2O3, Al2O3,SiO2 coexist, they are more likely to form ternary compound 2CaO·Al2O3·SiO2 and 4CaO·Al2O3·Fe2O3.

Study of the hydration of calcium zirconium aluminate (Ca7ZrAl6O18) blended with reactive alumina by calorimetry, thermogravimetry and other methods

Abstract: The reactivities of hydratable alumina, calcium zirconium aluminate and their binary mixtures were investigated by calorimetric method, X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), differential thermal/thermogravimetric analysis (DTA–TG) and scanning electron microscope observations. The rate of heat evolution illustrates only one distinct exothermic peak in the mixtures containing calcium zirconium aluminate which corresponds the subsequent precipitation of hydrated material mainly in the form of amorphous CaO–Al2O3–H2O phases and crystalline C4AH19 occurs simultaneously after wetting of Ca7ZrAl6O18 grains. Nevertheless, coexistence of both unstable calcium aluminate hydrates (CAH10, C2AH8, C4AH19) and thermodynamically more stable C3AH6 detected by FT-IR and DTA–TG in the paste cured at 20 °C may have originated in the thermally induced partial conversion reaction due to the considerable amount of heat generated by the Ca7ZrAl6O18 hydration. It is also found that curing temperature affected the hydration products formed in the hydration products of both Ca7ZrAl6O18 and Ca7ZrAl6O18/Al2O3 blends. Reactive alumina influences the hydration behavior of Ca7ZrAl6O18 facilitating the nucleation and growth of hydration products, causes characteristic changes in the microstructure of hardened blended pastes and favors recrystallization of dehydrated calcium aluminates.