Effect of Basicity on the Structure, Viscosity and Crystallization of CaO-SiO2-B2O3 Based Mold Fluxes

In this study, the structure, viscosity characteristics, and crystallization behavior of CaO-SiO2-B2O3 based melts were studied combining molecular dynamics (MD) simulation, Fourier transform infrared (FTIR) spectroscopy, rotating viscometer test, and FactSage thermodynamic calculation. The results showed that, in the ternary CaO-SiO2-B2O3 glass system, stable structural units of [SiO4]4− tetrahedral, [BO3]3− trihedral and [BO4]5− tetrahedral were formed, and the Si-O and B-O structure depolymerize with the basicity increase from 1.15 to 1.25, then the B-O structure become complex with the basicity further increase to 1.35. In fluorine-free mold fluxes, with the basicity increases, the viscosity at 1300 °C increases, the liquidus temperature decreases and then increases, the network structure polymerizes, it indicates that the structural complexity rather than the melting property change plays a predominant role in increasing the viscosity at 1300 °C. Moreover, due to the changes in crystallization phase and solid solution ratio, the viscosity-temperature curve of fluorine-free slag shows the characteristics of alkaline slag and the break temperature increase with the basicity increase. The MD simulation, FTIR experiment, viscosity test, and FactSage calculation results are verified and complemented each other.

Corrosion resistance dry building mortars base on alkaline slag binder for using in aggressive sulfate medium

Dry Building Mortars (DBM) are new in terms of building technology, and they sometimes substitute different kinds of concrete and mortar mixes. DBM have been successfully used in construction and their performance has been as efficient as the one of commercial mortar mixes, i.e. they boost labour efficiency, and bring down material consumption. They can be also kept in stock for a long time, and shipped with no compromise in quality. Today DBM are based on cementing components. And some famous mix mortars are based on gypsum, polymer, and some other types of cementing components which contain fine-dispersed additives of ground slag, fly ash, and raw sludge. These mix mortars are applied as smoothing, aligning, waterproof, and safety types of coverage. This article studies the possibility of involving slag cementing components in manufacturing DBM. Due to their high waterproof resistance in salt-affected water, these sorts of mixes may be used as protective coatings and plasters for concrete frames in corrosive medium. Slag Cementing Components (SCC) are hydraulic cementing agents, which harden both in water and in open air. They are produced by mixing electric-furnace slag or furnace clinkers with some solutions of alkaline metals (to trigger alkaline reaction), or by mixing together all these agents.

Apparent Absence of Microbial Life inside an Alkaline Slag Dump

An extremely alkaline slag dump in Germany was investigated for its mineralogy and colonization with microorganisms. The dump material originated from a metallurgical processing plant for steel production and consisted of a magnetic concentrate of cohenite, metallic iron and magnetite interwoven or associated with various slag related phases such as glasses of variable chemistry, RO-, C2F- and C4AF- phases, and phases originating from the ovens, steel additives, sand and construction fragments. After deposition, reactions in the surface layer generated a number of secondary phases such as gels (NaCO3-rich or -poor), calcite, mirabilite, natron, and others. To explore the microbiology inside the approximately 15 m high dump, 35 samples were taken over the whole depth range via core drilling. Total cell counts were determined via acridine orange staining and living cells were enumerated on R2 agar plates for heterotrophs. Both methods allowed for the detection of microbial life on the dump surface down to about 1 m depth. In this depth range the pH values were between 8 and 12. Below, microbial life was not detected, most likely because of the high pH values of 12 and the low availability of organic carbon inside the dump. In contrast to all previously studied sulfidic dumps the interior of the alkaline slag dump did not appear to be a habitat for microorganisms.