Synthesis and Characterization of Industrial Casting Sand Based Silica Aerogel

In this study, a commercial foundry sand (Seydisehir Eti Aluminium Co. Inc.) was provided as the starting material. Using this supplied casting sand, silica aerogel production was carried out by sol-gel method. Starting materials chemical components were determined by doing XRD and XRF analyses to starting industrial casting sand respectively. After analysing studies, sodium silicate solution was produced from commercial casting sand. During silica aerogel synthesize, 5 different pH degree was investigated including 2-4-6-8 and 9. Silica aerogel modification (Super hydrophobic) was made by choosing the optimum pH value. Afer then, on the synthesized experiment sample, FT-IR, BET, SEM and contact angle characterization studies were realised respectively. As a result of preliminary experiments done with different pH experiments, sample with the lowest density was determined as pH 8 value. Keywords: Casting sand, Sol-gel, Silica aerogel

Granulated Expanded Glass Manufacturing Method Using Electromagnetic Waves

The paper presents experimental results obtained in the process of experimental manufacture in a microwave oven of lightweight granulated glass aggregates. The process was conducted to obtain the highest dimensional class (between 18-23 mm), the almost spherical shape of the aggregates being facilitated by cold processing of raw spherical pellets (between 11-15 mm) containing the powder mixture formed by glass waste, borax. calcium carbonate, aqueous sodium silicate solution and water addition and then rotation of the high electromagnetic wave susceptible ceramic crucible containing raw pellets during the heat treatment at temperatures between 822-835 ºC. In terms of quality, the expanded glass aggregate granules are almost similar to those manufactured in conventional rotary kilns heated by burning fuel, having the following characteristics: bulk density of 0.17 g/cm3, compressive strength of 2.2 MPa, thermal conductivity of 0.047 W/m·K, water absorption of 1 vol. % and pore size between 0.3-0.6 mm. The experimental product has not yet been tested as a raw material in the manufacture of some light weight concretes, but the use of similar granulated glass aggregates manufactured in the world confirms the ability of this aggregate type to produce light weight and energy efficient concretes for building construction.

Granulated Expanded Glass Manufacturing Method Using Electromagnetic Waves

The paper presents experimental results obtained in the process of experimental manufacture in a microwave oven of lightweight granulated glass aggregates. The process was conducted to obtain the highest dimensional class (between 18-23 mm), the almost spherical shape of the aggregates being facilitated by cold processing of raw spherical pellets (between 11-15 mm) containing the powder mixture formed by glass waste, borax. calcium carbonate, aqueous sodium silicate solution and water addition and then rotation of the high electromagnetic wave susceptible ceramic crucible containing raw pellets during the heat treatment at temperatures between 822-835 ºC. In terms of quality, the expanded glass aggregate granules are almost similar to those manufactured in conventional rotary kilns heated by burning fuel, having the following characteristics: bulk density of 0.17 g/cm3, compressive strength of 2.2 MPa, thermal conductivity of 0.047 W/m·K, water absorption of 1 vol. % and pore size between 0.3-0.6 mm. The experimental product has not yet been tested as a raw material in the manufacture of some light weight concretes, but the use of similar granulated glass aggregates manufactured in the world confirms the ability of this aggregate type to produce light weight and energy efficient concretes for building construction.

Remediation of Annular Gas Migration along Cemented Wellbores Using Reactive Mineral Fluids: Experimental Assessment of Sodium Bicarbonate and Sodium Silicate-Based Solutions

Achieving zonal isolation along wellbores is essential for upholding the containment integrity of subsurface reservoirs and preventing fluid seepage to the environment. The sealing performance of Portland cements conventionally used to create barriers can be severely compromised by defects like fractures or micro-annuli along casing–cement–rock interfaces. A possible remediation method would be to circulate reactive fluids through compromised cement sections and induce defect clogging via mineral precipitation. We assess the sealing potential of two prospective fluids: sodium bicarbonate and sodium silicate solutions. Reactive flow-through experiments were conducted on 6-m-long cemented steel tubes, bearing ~20-μm-wide micro-annuli, at 50 °C and 0.3–6 MPa fluid pressure. For the sodium bicarbonate solution (90 g/kg-H2O), reactive flow yielded only a minor reduction in permeability, with values remaining within one order. Injection of sodium silicate solution (37.1 wt.%, SiO2:Na2O molar ratio M= 2.57) resulted in a large decrease in flow rate, effectively reaching the setup’s lower measurement limit in hours. However, this strong sealing effect can almost certainly be attributed to gelation of the fluid through polymerisation, rather than defect clogging via mineral precipitation. For both fluids investigated, the extent of solids precipitation resulting from single-phase injection was less than anticipated. This shortfall is attributed to ineffective/insufficient liberation of Ca-ions from the alkaline phases in the cement.

Red Mud-Blast Furnace Slag-Based Alkali-Activated Materials

The aluminum Bayer production process is widespread all over the world. One of the waste products of the Bayer process is a basic aluminosilicate bauxite residue called red mud. The aluminosilicate nature of red mud makes it suitable as a precursor for alkali-activated materials. In this work, red mud was mixed with different percentages of blast furnace slag and then activated by sodium silicate solution at different SiO2/Na2O ratios. Obtained samples were characterized by chemical–physical analyses and compressive strength determination. Very high values of compressive strength, up to 50 MPa, even for high percentage of red mud in the raw mixture (70 wt.% of RM in powder mixture), were obtained. In particular, the higher compressive strength was measured for cubic samples containing 50 wt.% of RM, which showed a value above 70 MPa. The obtained mixtures were characterized by no or scarce environmental impact and could be used in the construction industry as an alternative to cementitious and ceramic materials.

Installation of Bored Piles with a Protective Silicate Shell of a New Design in Saline Silty-Clayey Soils

Designing advanced methods of corrosion protection and increasing the bearing capacity of pile foundations on saline clayey soils is a priority geotechnical task in Kazakhstan. The formation of a suffusion-resistant waterproof shell was achieved by silicatization of a borehole before concreting, by the installation of a mold into the borehole and the impregnation of a sodium silicate solution into the space between the mold and the soil under pressure. After coagulation of the silicate solution, the mold was removed and the formed shell was filled with corrosion-resistant concrete. Full-scale static pile load tests were conducted in the construction site “Retaining wall on Mount Koktobe” in Almaty. The bearing capacity of the piles with the protective silicate shell exceeded the bearing capacity of an ordinary pile by 2.5 times on average without wetting the site, and 3.2 times after prolonged wetting. The numerical model had a close relationship with the average experimental curve obtained when conducting six static pile load tests with the protective shell. A large economic effect of the developed piling technology with a protective shell was achieved, with a significant reduction in the cost of piling, equal to 27.85%.

Possible Recycling of End-of-Life Dolomite Refractories by the Production of Geopolymer-Based Composites: Experimental Investigation

Production and characterization of geopolymers prepared by mixing metakaolin, end-of-life dolomite refractories, sodium silicate solution, and sodium hydroxide solution have been performed. The as-received refractory was crumbled in order to obtain products having, respectively, 250 μm, 1 mm, and 2.5 mm maximum particles size. Each batch of powder was added in different proportions to a blank geopolymeric matrix. It has been observed that the addition of waste refractory reduces workability of the reference refractory-free slurry. After hardening, only the set of samples prepared with powders with maximum size of 250 μm maintain integrity while the others resulted affected by the presence of fractures caused by volumetric instabilities; samples with composition R100 showed the highest compressive strength, whereas higher refractory addition lowers strength. Specific surface area appears independent by materials composition; conversely pore volume slightly increases with the addition of dolomite refractory powder. During the thermodilatometric tests all compositions display a shrinkage of about 0.1% between 170 and 400 °C; however, sintering starts at higher temperature (above 600 °C) and samples melt in the range between 650 and 750 °C as a function of their composition, thus showing that the resulting materials loose refractoriness with respect to both the reference geopolymer and the dolomite refractory. Graphical Abstract