Alexander Gorokhovsky

Cementitious composites of pulverised fuel ash and blast furnace slag activated by sodium silicate: effect of Na2O concentration and modulus

Abstract Pastes of pulverised fly ash (PFA) and blast furnace slag (BFS) in proportions of 100–0, 75–25, 50–50, 25–75 and 0–100 (wt-%) were chemically activated using sodium silicate with modulus (SiO2/Na2O) of 0, 0·75, 1, 1·5 and 2; the %Na2O was added at 4, 6 and 8% relative to the binder weight. The pastes were cured for 24 h at 75°C and then 28 days at 20°C. For 100%PFA pastes, the higher %Na2O, the better the strength; 4%Na2O was ineffective, whereas the highest strength of 25 MPa was reached using modulus 1. For 100%BFS pastes, the highest strengths were for 4%Na2O (80–85 MPa); the optimum modulus was 1·5. The addition of BFS to PFA rich pastes was favourable; for 50% blends, the strengths were between the above mentioned figures and the best modulus was 1–1·5 (45–48 MPa). The lower glass content of PFA (70%) compared with the BFS (>90%), together with the porous nature of the PFA, were considered to have reduced the strength in PFA blends.

Glass–ceramic materials with regulated dielectric properties based on the system BaO–PbO–TiO2–B2O3–Al2O3

Vitrification and crystallization properties of glasses of the system BaO-TiO 2 -PbO-Al 2 O 3 (B 2 O 3 ) were investigated. The fields of vitrification based on ternary diagrams of BaTiO 3 -PbTiO 3 -(TiO 2 +Al 2 O 3 +B 2 O 3 ) with varied contents of Al 2 O 3 (10, 13, 16 mol%) and B 2 O 3 (3, 15 mol%) were identified. The glass compositions obtained had relatively low melting temperature (1450°C). These stable glasses could be thermally treated to produce glass-ceramics characterized by fine-crystalline structures and regulated permittivity associated to the contents of ferroelectric phases. The phase composition of such glass-ceramics included different Pb x Ba 1-x TiO 3 solid solutions depending on the starting chemical composition. Permittivity of the obtained materials (f=800 kHz, T=25°C) varied from 20 to 680 relatively to the time of crystallization.

EFFECT OF GEOTHERMAL WASTE ON STRENGTH AND MICROSTRUCTURE OF ALKALI-ACTIVATED SLAG CEMENT MORTARS

Abstract Mortars of blast furnace slag replaced with 10% of a geothermal silica waste were cured for 90 days. The binder was activated by 6 wt.% Na 2 O equivalent of NaOH and water glass. The presence of the silica enhanced the formation of hydration products as shown by nonevaporable water (NEW) results. Backscattered electron images indicated that the microstructures of blended slag had less porosity than those of neat slag mortars and the interfacial zone between aggregate and hydration products was dense and of homogeneous composition similar to the matrix of hydration products. The main hydration products were C-S-H and for NaOH a hydrotalcite type phase was found as finely intermixed with the C-S-H.

Inorganic wastes in manufacturing of glass-ceramics: slurry of phosphorous fertilizer production and oil shale ash

The use of bicomponent raw material mixtures of industrial wastes to produce pyroxene glass ceramics was investigated. It is shown that oil shale ash from heat power stations can promote the production of crystalline phases and the slurry from phosphorous fertilizer production can provide sufficient concentration of nucleating agents. Mechanical and chemical properties, as well as the structure and crystallization mechanism were characterized. An increase of phosphorous oxide and fluorine concentrations leads to a change of the crystallization mechanism.

Modification of the float-glass surface by treatment with urea aqueous solution

Abstract The thermo-chemical modification of float-glass surface structure and properties by the aerosol of aqueous solution of urea was investigated. It is shown that the character of the modification depended on the temperature of treatment. The chemical interaction of urea and water vapor with the soda–lime–silicate glass yielded different products under various treatment conditions; the effects of such products on the glass properties were also analyzed. For industrial application of the investigated treatment, the temperature range of 140–160 °C has been identified as optimal, promoting increased mechanical strength and enhanced adhesion of glass surface to poly(vinyl butiral); also this is not related to atmosphere contamination. The effectiveness of the proposed method was tested and confirmed under industrial conditions of float-glass production.