Foam Glass Gravel Experimentally Made in A 10 KW-Microwave Oven

                                                         The experimental manufacture of foam glass gravel from glass waste has been quantitatively extended by increasing the power of the microwave oven from 0.8 to10 kW, the authors' interest being focused on the quality of the foamed product. The work equipment was rather improvised, the existing used oven not being adequate except to small extent for the requirements of the experiment, but it allowed obtaining a product similar to those industrially manufactured by conventional techniques. Using a recipe previously tested on the 0.8 kW-microwave oven composed of 1 wt.% glycerol as a liquid foaming agent together with 8 wt.% water glass as an enveloping agent and 8 wt.% water as a binder, the main features of the foam glass gravel lumps were: bulk density of 0.22 g/cm3, porosity of 88.9%, thermal conductivity of 0.057 W/m·K, compressive strength of 5.9 MPa and pore size between 0.10-0.30 mm. The specific energy consumption was negatively influenced by the excessive internal volume of the oven, but even under these conditions its value was relatively low (between 1.53-1.69 kWh/kg)

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). &nbsp

Cellular Glass Manufactured by Microwave Irradiation of Residual Glass, Eggshell and Borax

The paper presents an improved method of manufacturing cellular glass using residual glass (91 %), sodium borate (5 %), eggshell waste (4 %) and added water (9 %). Compared to methods using eggshell as an expanding agent producing cellular glass with low compression strength, the technique adopted by the authors is original by the addition of sodium borate, which contributes to increasing the compression strength and the use of the unconventional electromagnetic wave heating method, which ensures very economical specific energy consumption. The optimal variant of cellular glass had the following characteristics: density of 0.40 g/cm3, porosity of 81 %, heat conductivity of 0.086 W/m·K, compression strength of 4.3 MPa and the cell dimension between 0.3-0.9 mm. The specific energy consumption of the process was 0.80 kWh/kg. The product has adequate features for using as a heat insulation material under conditions of quite high mechanical loading. &nbsp