Unconventionally Made-Cellular Glass Aggregate

Improving the original manufacturing process in microwave field of a cellular glass aggregate using a recipe containing colored consumed drinking bottle, calcium carbonate (CaCO3) as an expanding agent, sodium borate (borax) as a fluxing agent and sodium silicate (Na2SiO3) as a binder is shown in the work. The main adopted technological measures were the advanced mechanical processing of residual glass at a grain dimension below 100 μm and especially the use of a high electromagnetic wave susceptible ceramic tube with a wall thickness reduced from 3.5 to 2.5 mm for the protection of the pressed glass-based mixture against the aggressive effect of microwave field and, in the same time, to achieve a preponderantly direct heating with electromagnetic waves. Of the tested variants, a recipe with 1.6 % calcium carbonate, 6 % borax, 8 % sodium silicate and the rest residual glass was determined to be optimal. The cellular glass aggregate had the bulk density of 0.22 g/cm3, heat conductivity of 0.079 W/m·K and compression strength of 5.9 MPa. The specific consumption of energy was very low (0.71 kWh/kg) below the range of reported values of the industrial processes consumption (between 0.74-1.15 kWh/kg).

Potential use of alluvial clays from Monoun in ceramics by adding feldspar from Batie (West-Cameroon) as a fluxing agent

The present study focuses on the use of feldspars from Batie granites (West-Cameroon) as a fluxing agent in ceramic applications, in order to reduce the energy cost of brick manufacture. Three alluvial clays were collected in the field using an auger and the feldspar sample was collected by hammering. Mineralogical, physical and geochemical analysis of alluvial clays samples were carried out, as well as the microscopy analysis of feldspar. The specimen of fired bricks was formulated with different proportions of feldspar (0%, 10%, 15%, 20%, and 25%) and calcined respectively at 750 °C, 850 °C, 950 °C and 1050 °C in an electric furnace. The physical analysis of the clay material showed a well graded granulometry composed of 3% gravel, 10% coarse sand, 23% fine sand, 13% silt and 51% clay. Thin section microscopic analysis revealed essentially perthites. The mineralogical analysis obtained by XRD on total powder shows that the alluvial clays are composed essentially of: 55.8% of total clays; 19.2% quartz; 14.2% goethite; 8.5% K feldspar; 1.2% anatase; 0.7% hematite and 0.4% gibbsite. Geochemical analysis shows that clay material consists of: SiO2, Al2O3, Fe2O3, TiO2, P2O5, MgO, CaO and K2O. The ceramic tests carried out on these bricks showed that their colors were red for all the formulations and temperatures tested. The sound of the bricks is metallic for the formulations of 20 and 25% of feldspar as from 850 °C. The flexural strength (greater than 3 MPa) and compressive strength (10–20 MPa) obtained at 20 and 25% of feldspar meet the standard of traditional ceramics requirements. The bricks obtained at 20 and 25% of feldspar and at a sintering temperature below 850 °C have good technological properties. It was observed that brick formulations with 0% of feldspar fired between 950 and 1000 °C are similar to those of 20 and 25% of feldspar fired at 850 °C).Highlights The alluvial clays from Monoun characterized have highest proportion of kaolinite and good mechanical properties (950 and 1050 °C). Thin section microscopic analysis of Batie feldspar revealed essentially perthites. The brick formulations with 0% of feldspar fired between 950 and 1050 °C are similar to those of 20 and 25% of feldspar fired at 850 °C.

Effect of White Mud Addition on Desulfurization Rate of Molten Steel

Fluorspar (CaF2) is commonly used to control the fluidity of slag in ladle-refining of steel. However, because it is desirable to reduce CaF2 consumption because of its environmental impacts, the industrial waste material such as white mud (WM) was investigated as a potential substitute for fluorspar. Steel sample (Fe-0.3C-0.9Mn-0.3Si-0.03Al-0.05S, mass pct) was melted in a high-frequency induction furnace, followed by additions of ladle slag (CaO-Al2O3-SiO2-5MgO-xCaF2, CaO/Al2O3=3, x = 0 to 10 mass pct) and fluxing agent (WM) at 1823 K (1550 °C). The desulfurization experiments were carried out by reducing CaF2 content in the ladle slag and increasing the addition of WM. Ladle slag with added WM showed an overall mass transfer coefficient of sulfur (kO) equivalent to or higher than that of conventional 10 mass pct CaF2-containing ladle slag. In a slag melting experiment based on DIN 51730 standard, the melting rate of mixed slag increased with the amount of WM added, which is considered to have a positive effect on the initial desulfurization rate. In addition, adding WM provided sulfide capacity of the slag equivalent to that of CaF2-containing slag. Consequently, the use of WM yielded slag having $$k_{{\text{O}}}$$ k O equivalent to or higher than that of conventional ladle slag with 10 pct CaF2, and thus, WM shows promise as a partial replacement for fluorspar.

Effect of Basicity and Boron Oxide in Slags of the AOD Process on the Equilibrium Interphase Distribution of Sulfur and Boron

The use of fluorspar in modern metallurgical slags, incl. slags of the argon-oxygen decarburization (AOD) process, as a fluxing agent, is associated with many disadvantages. Those disadvantages can be solved by using boron oxide as an alternative, which also provides conditions for direct microalloying of steel with boron. The paper presents the results of thermodynamic modeling of the effect of basicity and boron oxide content in slags of the CaO–SiO2–B2O3–Cr2O3–Al2O3–MgO system on the equilibrium interphase distribution of sulfur and boron, and their equilibrium content in the metal. Modeling was carried out using the HSC 8.03 Chemistry software package (Outokumpu). Slag from the desulfurization period of the AOD-process was used as the oxide phase. As a result, it was shown that, in the range of basicities 2.0-2.5 and a content of 2-4% B2O3, it is possible to carry out desulfurization of the metal, providing a sulfur content of 0.001-0.007%, and simultaneous microalloying of steel with boron in an amount of up to 0.0103%.

Differential Scanning Calorimetry as a New Method to Evaluate the Effectiveness of Rejuvenating Agents in Bitumens

To date, few methods allow distinguishing a fluxing effect of an additive for bitumen from a regenerating effect. This research aims at identifying a method to accurately establish whether an oxidized bitumen has been regenerated or has simply been fluxed by a softener. Oxidized bitumens, simulating the aging process that results in road pavement lifetime, were prepared by the Rolling thin film oven test (RTFOT) procedure for 225 min and the Pressure Aging Vessel (PAV) procedure. Their asphaltene parts were extracted and analyzed by calorimetry (Differential Scanning Calorimetry DSC), and the results were compared with the presence and absence of a fluxing agent and real rejuvenators. The self-consistent results showed that the thermal properties of the asphaltene fractions is a sound probe to monitor the effect of rejuvenation clearly distinguishable from the mere fluxing effect. This preliminary study might allow the creation of standard protocols capable of identifying a priori the rejuvenating effect of an additive in the future. Furthermore, given the widespread use of calorimetry for the characterization, it tends to become a widely accessible and useful tool for this purpose in material characterization laboratories.

Phase Transformation of Kaolin-Ground Granulated Blast Furnace Slag from Geopolymerization to Sintering Process

The main objective of this research was to investigate the influence of curing temperature on the phase transformation, mechanical properties, and microstructure of the as-cured and sintered kaolin-ground granulated blast furnace slag (GGBS) geopolymer. The curing temperature was varied, giving four different conditions; namely: Room temperature, 40, 60, and 80 °C. The kaolin-GGBS geopolymer was prepared, with a mixture of NaOH (8 M) and sodium silicate. The samples were cured for 14 days and sintered afterwards using the same sintering profile for all of the samples. The sintered kaolin-GGBS geopolymer that underwent the curing process at the temperature of 60 °C featured the highest strength value: 8.90 MPa, and a densified microstructure, compared with the other samples. The contribution of the Na2O in the geopolymerization process was as a self-fluxing agent for the production of the geopolymer ceramic at low temperatures.