CHEMICAL REACTIVITY ASSESSMENT METHOD OF NANOSTRUCTURED LOW CALCIUM ALUMINOSILICATES

Nowadays, the production of high-performance composites is a relevant objective in construction industry. Normally, geological and/or technological conditions of phase formation are responsible for chemical and structural characteristics of raw materials. In this regard, the use of a certain material dictates terms to optimizing production process, efficient use and, therefore, requires to develop a method for quality evaluation of raw materials. This approach allows a considerable time saving and raw materials sources, while the evaluation of final performance characteristics of designed materials is being done. The biggest interest in this area is focused on new types of developed and poorly-studied composite systems which results in a lack of capacity to design materials with known performance and, therefore, constrains the areas of application of construction composites Among such composite systems there are zero cement alkali-aluminosilicate systems or geopolymers. For geopolymers production a wide range of different aluminosilicates with varied characteristics potentially can be used. And also, in each certain case, the quality evaluation methods for aluminosilicates should be different. This study is focused on chemical reactivity assessment method of crystalline (mainly, nanocrystalline) low calcium aluminosilicates exposed to high-alkali media. The solubility degree in high-alkali media and compressive strength performance were evaluated in this study in order to define chemical reactivity of low calcium aluminosilicates. The compressive strength data demonstrated a positive correlation with the crystallinity degree of aluminosilicates.

Formation Mechanism of Gehlenite-Anorthite Materials Containing ZrO2 from Andalusite, CaCO3 and ZrO2

This paper reports the results of using natural andalusite (Al2SiO5) in combination with CaCO3 and ZrO2 in order to obtain aluminosilicate product. This work was devoted to the study of the mechanism of new phases creation in the Al2SiO5-CaO-ZrO2 phase system during heating at different temperatures (1000, 1100, 1200, 1300 and 1400°C). Al2SiO5, CaCO3, and ZrO2 were used in a weight ratio of 45:50:5, respectively. According to the phase composition and chemical analysis in microareas, it was found, that andalusite reacted with CaO giving two calcium aluminosilicates: gehlenite and anorthite at 1400°C. ZrO2 was presented as the separated phase at this temperature. Other occurring transition phases were: CaZrO3 at 1000 and 1200°C, Ca2SiO4 at 1000, 1100 and 1200°C, Ca3ZrSi2O9 at 1300°C. The synthesis mostly depended on the diffusion of Ca2+ ions.

EXTRA-FURNACE STEEL PROCESSING BY RECYCLED SECONDARY ALUMINUM WASTE

The paper presents the results of research on the use of recycled aluminum waste (RAW) during extra-furnace steel processing in ladle refining furnace. It has been established that simultaneously with the deoxidation of refining slags before desulfurization of steel, their liquid mobility increases, which eliminates the need for using fluorspar for these purposes.A thermodynamic analysis of possible reactions of formation of aluminates and calcium aluminosilicates in the refining slag has been carried out. It has been suggested that the cause of thinning of refining slags from the addition of RAW is the formation of a number of low-melting eutectics containing aluminates and calcium aluminosilicates. The composition of briquettes based on RAW for liquefaction of refining slags is proposed. Dependence of the friability and breaking load of briquettes on the content of CaO, the temperature and drying time is established. The data on the composition and properties of the refining slag after treatment with a diluent based on RAW are given.

Sorption Properties of Nanostructured Calcium Aluminosilicate with Respect to Cesium Ions

Long–lived 134Cs and 137Cs isotopes with half-cycle of 2.06 and 30 years respectively refer to the most dangerous and wide-spread radionuclides in ecological facilities. The efficient way of removing cesium radioisotopes from the living environment is to bind them into the compounds insoluble in water. This paper presents the findings on the sorption properties of synthetic nanostructured calcium aluminosilicates (CAS) with AI:Si correlation equal to 2:2, 2:6, 2:10 and obtained in CaCI2—AICI3—КОН--SiO2—H2O multiple-component system. An isotherm investigation of cesium ion sorption produced from aqueous solution with Cs+1 from 0.2 till 6.0 mmol/L-1 concentration was carried out. Maximum sorption capacity of calcium aluminosilicates (CAS) as well as Langmuir constant was defined. The kinetics data was received and the activation energy of cation exchange in the process of sorption was estimated. The impact of 1% КCI + 6% NaCI saline background on the values of interfacial distribution coefficient (Kd) and recovery rate of cesium ions were determined.