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Thermoset polymer composite was made in an original version less expensive than the known techniques, in which alumina-borosilicate glass recycled from used laboratory glass was chosen as filler into the mixture of starting materials together with polyurethane resin as a matrix. The matrix/filler weight ratio was modified during the experiment from 0.67 to 1.22 and this change influenced the features of manufactured products. The temperature and time of the thermoset polymer curing process played an important role. It was opted for the electric heating of the material mixture up to 300-305 ℃ with the heating rate between 3.06-3.22 ℃/min, keeping at the maximum temperature for 100 min, and cooling in about 30 min. Results showed making a dense material type with relatively low heat conductivity. Tensile strength was around 40 MPa and compressive modulus of elasticity registered around 19 GPa, above the level of thermoplastic polymer.

The paper exposes testing results corresponding to the process of manufacture cellular glass from consumed drink glass packaging, a vegetable expanding agent (beech leaves) used for the world premiere, and borax as a flux agent. The process of sintering/expanding the powder material mixture was performed by microwave irradiation at 825-834 ºC, as a process improved by the authors of this paper and applied in previous experiments, unlike the conventional procedures used in processes of the same type. The nonconventional heating has allowed a higher energy efficiency of the process and reduced energy consumption (0.78 kWh/kg). The optimal version of the manufacturing process with 30 % beech leaves, 65 % consumed drink glass packaging, and 5 % borax led to obtaining a cellular glass with features adequate for its use as heat insulating material in civil engineering having density of 0.60 g/cm3, heat conductivity of 0.124 W/mK, compression resistance of 5.0 MPa, absorbing the water of 1.5 vol. %, and cells dimension between 0.7-1.0 mm.

The paper presents experimental results obtained in the manufacturing process of porous high-strength glass foam for thermal insulation in buildings made of glass waste and kaolin clay as raw materials and dolomite as a foaming agent. The paper’s originality is the use of the unconventional microwave heating technique. The best product manufactured by this technique was that sintered at 1050 ºC using 18 wt.% kaolin clay and 3.5 wt.% dolomite. The product characteristics were: the apparent density of 0.66 g·cm-3, the thermal conductivity of 0.155 W/m·K, the compressive strength of 5.3 MPa and a microstructural homogeneity with pore size between 0.20-0.50 mm.

The paper presents an innovative technique for manufacturing glass foams from recycled glass waste at room temperature by using aluminum powder and an aqueous solution of calcium hydroxide. The physical, thermal, mechanical and morphological characteristics of the foamed products (porosity between 82.9-86.2%, thermal conductivity in the range 0.061-0.081 W/m·K and compressive strength between 1.15-1.28 MPa) were similar to those of the foams manufactured by sintering at high temperatures. Glass foams produced by this new technique are suitable for use as thermal insulation materials for buildings.

A glass foam with typical characteristics for a foam glass gravel usable as a thermal insulating material in difficult climatic conditions and with mechanical stress was made by sintering at 834 ºC a powder mixture composed of colorless glass waste (93.1 wt.%), glycerol (1.0 wt.%), sodium silicate (4.8 wt.%), calcium carbonate (0.8 wt.%), kaolin (0.2 wt.%) and water addition (14.5 wt.%). The physical, thermal, mechanical and morphological characteristics of the product were: apparent density of 0.28 g/cm3, porosity of 86.67%, thermal conductivity of 0.063 W/m·K, compressive strength of 7.3 MPa, water absorption of 4.3% and pore size between 0.10-0.35 mm. The specific energy consumption of the manufacturing process was 0.78 kWh/kg. The originality of the work is the use of a nonconventional heating technique based on the microwave energy.

The paper presents experimental results obtained in the manufacturing process of high-strength glass foam by combined use of two solid foaming agents (calcium carbonate and graphite) in variable weight ratios. The originality of the work is applying the unconventional microwave heating method, unlike the conventional techniques currently used in similar industrial processes. The optimal experimental variant, composed of 89.1 % glass waste, 0.9% calcium carbonate, 1 % graphite and other additives, was sintered at 828 ºC with a very low energy consumption (0.73 kWh/kg). The main characteristics of the optimal product were apparent density of 0.39 g/cm3, thermal conductivity of 0.088 W/m·K and compressive strength of 3.6 MPa, being usable in fields that requires resistance to mechanical stress and relatively difficult environmental conditions.

Another experimental application of the nonconventional microwave heating technique in the manufacturing process of a porous glass foam with high mechanical strength confirmed the high energy efficiency of this procedure compared to the conventional techniques. The specific energy consumption of the manufacturing process was very low (0.72-0.73 kWh/kg). Due to its physical, thermal, mechanical and microstructural characteristics (apparent density of 0.23-0.27 g/cm3, porosity of 87.7-89.5%, thermal conductivity of 0.063-0.070 W/m·K, compressive strength of 6.4-6.8 MPa and pore size between 0.2-0.6 mm) the product can enter in the foam glass gravel category usable as a thermal insulating material in construction in application fields that require mechanical, chemical and thermal shock resistance.

The manufacture of glass foams from container glass waste, silicon carbide as a foaming agent (1.75-1.9 wt.%) and an addition of 1:6 aqueous solution of KNO3 (0-1.75 wt.%) was performed at sintering temperatures between 913-952 ºC. Using the effect of the microwave power conversion into heat, the predominantly direct and partially indirect microwave heating reached high heating rates (25.2-28.8 ºC/min) and the specific energy consumption had very low values (0.70-0.83 kWh/kg), generally, below the values of industrial manufacturing processes. The characteristics of the glass foam products were excellent, the optimal sample obtained with 1.9% SiC and 1% KNO3 having an apparent density of 0.28 g/cm3, porosity of 87.3%, compressive strength of 5.1 MPa and pore size between 0.25-0.45 mm. The material is a very good thermal insulator for civil engineering.

A glass foam obtained by sintering at 790 ºC using borosilicate glass waste, carbon black (1%) as a foaming agent, Na2HPO4 (5.9%) as a stabilizing agent, Sb2O3 (0.8%) as an oxygen supplying agent and water addition (10%) as a binder was manufactured by microwave irradiation. The glass foam characteristics were: apparent density of 0.34 g/cm3, porosity of 84.5%, thermal conductivity of 0.06 W/m·K, compressive strength of 2.2 MPa. The pore size was between 0.4-0.7 mm. The specific consumption of energy had an extremely low value (0.68 kWh/kg) below the level of the consumptions of glass foam industrially made by conventional techniques.

The paper presents experimental results aiming the enhanced manufacturing technique of cellular glass-ceramic using a mixed microwave heating method (predominantly direct and partially indirect). A SiC and Si3N4 ceramic tube with a wall thickness of 3 mm was used as a screen placed between the microwave radiation source and the material subjected to heating. The optimal sample was made by sintering at 980 ºC of 87.5% glass waste, 9.5% coal ash, 3% silicon carbide and 10% water addition. The product had the apparent density of 0.24 g/cm3, porosity of 88%, thermal conductivity of 0.052 W/m·K and compressive strength of 1.25 MPa. The material microstructure was homogeneous, with pores uniformly distributed, having the size between 0.4-1.2 mm.

The paper presents experimental results obtained in the manufacturing process of a lightweight aggregate using a finely ground mixture of wastes (clay, glass and coal ash) expanded with silicon carbide as a foaming agent. The originality of the work consists in the use of microwave radiation in a direct heating process, the energy efficiency being remarkable (0.58-0.85 kWh/kg), unlike all the manufacturing processes known in the world, industrial or experimental on a small scale. Given that glass alone is not suitable for foaming by direct microwave heating, but the favorable effect of adding glass to clay on the physical and mechanical characteristics of lightweight (expanded) clay aggregate is known, the experiments aimed to determine the maximum allowable proportion of glass in clay without affecting the microstructure of the material. The characteristics of the experimental samples were almost similar to those of industrially manufactured products by conventional methods (0.60-0.69 g/cm3 the apparent density, 0.100-0.116 W/m·K the thermal conductivity, 7.8-8.3 MPa the compression strength, 9.3-17.5% the water absorption).

A cellular glass-ceramic with very high compressive strength (14.1 MPa) from a mixture 40/60 of blast furnace slag and container glass waste, calcium carbonate (6.5%), borax (7.8%), titanium oxide (5%), sodium phosphate (3%) and water addition (8%) was experimentally manufacture by sintering at 900 ºC using the microwave radiation. The main advantage of the nonconventional heating technique was the very low specific energy consumption (0.90 kWh/kg). The physical, mechanical and morphological characteristics of the best cellular glass-ceramic sample were: apparent density of 0.82 g/cm3, porosity of 75.9%, thermal conductivity of 0.135 W/m·K, water absorption of 3.4%, pore size between 0.3-0.6 mm. Due to the mentioned characteristics the cellular glass-ceramic is suitable for construction applications.

Experimental results of the process of manufacturing cellular glass from glass waste and calcium carbonate (between 1.1-1.4 wt.%) in a microwave reactor are presented in the paper. Compared to all previous experiments, a significantly larger amount of raw material powder mixture was heated to 817-828 ºC in a 3 kW-microwave reactor. The physical characteristics of the cellular glass samples were excellent: apparent density between 0.13-0.16 g/cm3, porosity between 92.7-94.1% and thermal conductivity in the range 0.041-0.046 W/m·K. The compressive strength had low values (1.09-1.18MPa), but in acceptable limits for using the cellular glass as an insulating material in construction. The specific energy consumption was higher (1.59-1.84 kWh/kg) due to the 15 mm-thickness of the wall of the silicon carbide crucible that fully absorbs the microwave radiation, the heating of the glass being indirect.

The paper presents a microwave based-nonconventional technique of manufacturing a cellular glass obtained by a heat treatment at 803 C of a powder mixture composed of glass waste from cathode ray tube (93 wt.%), MnO2 (7 wt.%) as a foaming agent and water addition (10 wt.%). The cellular glass has excellent characteristics as an insulating material: apparent density of 0.19 g/cm3, porosity of 91.4%, thermal conductivity of 0.043 W/m·K and an acceptable compressive strength of 1.17 MPa. An economical specific energy consumption (1.16 kWh/kg) was obtained.

The paper presents experimental results obtained in the manufacturing process of a glass foam with good characteristics of insulating material (porosity of 90%, thermal conductivity of 0.042 W/m·K and compressive strength of 2.1 MPa) usable in construction. The basic raw material was recycled panel glass from cathode ray tube (CRT) waste. The heating technique was unconventional by using the microwave energy unlike the conventional techniques applied both in the industrial glass foam manufacture and in the numerous small-scale experiments known in the literature. The tests have shown an excellent energy efficiency, the specific energy consumption (0.72 kWh/kg) being more economical than that corresponding to the industrial manufacturing processes of glass foam.

The paper presents experimental results of the manufacture by a microwave heating technique of a fine porosity lightweight glass foam with high compression strength (up to 5.8 MPa) using a liquid carbonic foaming agent (glycerol) associated with "water glass" and water. The advantage of using the microwave irradiation was evidenced by the very low specific energy consumption (0.81-0.88 kWh/ kg) at the level of the lowest consumption obtained in industrial production by conventional techniques of similar products. Considering that a high power microwave equipment (industrial type) could have a higher energy efficiency (up to 25%) compared to the experimental oven, the superiority of the tested nonconventional method is theoretically obvious.

The paper presents recent achievements in the microwave use for manufacturing foam glass gravel from recycled glass waste and silicon carbide. The aim was to obtain a product with physical and mechanical characteristics almost similar to those of industrially manufactured materials by conventional heating techniques, but with a higher energy efficiency. A foam glass with the thermal conductivity of 0.075 W/m·K and the compressive strength of 7.5 MPa was experimentally obtained. The specific energy consumption was of 1.0 kWh/kg comparable with the industrial processes and it could reach values up to 25% lower by using a high power industrial microwave equipment.

The paper presents an unconventional technique for manufacturing foam glass gravel. The numerous experimental results obtained by the authors in the last year using various manufacturing recipes common in the world industrial production by conventional techniques were selected and subjected to a qualitative and energy efficiency comparative analysis, aiming to determine the best foam glass gravel manufacturing procedure under the conditions of the use of the microwave energy. The optimum recipe was composed of 83% glass waste, 1 % glycerol, 8 % sodium silicate and 8 % water. The maximum heating temperature reached 823 ºC with a very economical energy consumption of 0.88 kWh/kg. The sample characteristics were apparent density-0.24 g/cm3, porosity-89.1% with pore size between 0.3 - 0.6 mm, thermal conductivity-0.063 W/m·K and compressive strength - 5.9 MPa, almost similar to those industrially obtained.

The paper presents the results of the research for the production by a nonconventional method (using microwave irradiation) of a cellular glass with high mechanical strength from flat glass waste (86 – 95%), calcium carbonate (1%) as a foaming agent and an addition of sodium silicate also called “water glass” (4 – 13%). The cellular glass samples had the apparent density between 0.40 – 0.45 g/ cm3, the thermal conductivity in the range 0.076 – 0.081 W/ m·K and the compressive strength between 4.9 – 6.2 MPa, having the characteristics of a foam glass gravel industrially manufactured by conventional methods and used in construction as materials resistant to high mechanical loads. The morphological characteristic specific for the thermal insulating materials, i.e. a homogeneous distribution of the pores, have been fulfilled, even in case of using a raw material (flat glass waste) which is, generally, avoided because it causes structural inhomogeneity of the glass foam. The energy efficiency of the making process is remarkable, the specific energy consumption having low values between 1.13 – 1.19 kWh/ kg.

The paper presents the results of experimental research for manufacture a high mechanical strength thermal insulating material using the microwave energy. Clay brick waste (75 - 83 mass %) and coal ash (15 - 23 mass %) as raw material and silicon carbide (2%) as a foaming agent have been used as a powder mixture. The porous product obtained by a sintering/ foaming process at 1115 - 1145 ºC had relatively low density and thermal conductivity (0.50 - 0.68 g/cm3 and 0.078 - 0.095 W/mK, respectively) and high compressive strength (up to 7.5 MPa). This remarkable combination of some physical and mechanical characteristics of the insulating material allows its use in applications involving mechanical stress resistance.

The paper presents experimental results obtained in the process of making glass foam from glass waste using a cheap foaming agent (natural dolomite). The originality of the work is the application of the microwave energy, unlike the conventional techniques commonly used in the world. The main advantage highlighted by the experiments is the very low specific energy consumption (below 1.5 kWh/kg), due to the peculiarities of the microwave heating technique. The foamed product has physical, mechanical and morphological characteristics (density between 0.30-0.32 g/cm3, thermal conductivity between 0.064-0.067 W/m·K, compressive strength in the range 2.2-2.6 MPa), which are similar to those of foams made by conventional methods and are suitable for its use as insulating material in construction.

The paper presents an aluminum foam experimental technique using the microwave energy. The raw material was recycling aluminum waste processed by ecological melting and gas atomizing to obtain the fine powder required in the foaming process. The powder mixture was completed with dolomite as a foaming agent. The products had a fine and homogeneous porous structure (pore size between 0.4-0.9 mm). The density (1.17-1.19 g/cm3), the compressive strength (6.83-7.01 MPa) and the thermal conductivity (5.71-5.84 W/m·K) had values almost similar to the foams made by conventional methods.

The paper contains testing results of an intensification method of the remarkable microwave absorbing capacity of a silicon carbide crucible coated with a yttrium oxide layer, applied in the sintering/ foaming process of the glass waste. Using the same type of microwave oven and same composition of raw material and foaming agent as in previous tests, the functional parameters of the process were significantly enhanced without altering the characteristics of products made by known conventional and nonconventional techniques.

The use of microwaves as a nonconventional energy source in the manufacturing process of glass-ceramic foam is presented in the paper. The main raw materials, representing 88wt.% of the load, are bottle glass waste and old clay brick waste, available in very large quantities. The weight ratio of the two waste types was varied between 3/1 – 3/2, aiming the improvement of the glass-ceramic foam mechanical strength. Substituting 40% from the glass waste mass with clay waste, it was obtained a high compressive strength of 3.35 MPa, in conditions where the apparent density and the thermal conductivity had relative low values (0.78 g/ cm3 and 0.099 W/ m · K, respectively). Due to his physical, mechanical and morphological features, the foamed product is usable in construction as replacer of similar materials existing on the market.

The work refers to an innovative recycling solution of wastes from demolition and rehabilitation of buildings to produce more cost-effective lightweight aggregates. The adopted method is based on the use of microwave energy as a nonconventional source, replacing conventional energy sources and expanding the powder mixture of raw material with silicon carbide as a foaming agent. The final product has a porous structure and a high compressive strength (over 6 MPa), being suitable for use as a lightweight aggregate for concrete manufacture.

In the work experimental results on the manufacture of glass foam with high mechanical strength from glass waste are presented. By replacing the usual conventional energy source with a nonconventional energy (electromagnetic waves) the heating efficiency allows a fast and economical manufacturing process. Calcium carbonate as a foaming agent and an addition of sodium silicate (aqueous solution) as a binder were used. By their physico-mechanical and morphological features (0.40-0.66 g/ cm3 the apparent density, 0.054-0113 W/ m·K the thermal conductivity, 2.2-6.3 MPa the compressive strength, below 1.2 % the water absorption and under 2 mm the pore size), the foams are appropriate for their use as replacer of existing similar building materials on the market.

The paper presents experimental results of producing glass foam from borosilicate glass waste (laboratory ware) using the microwave energy. More variants of foaming agents (silicon carbide, calcium carbonate and activated carbon) and additives (coal ash and disodium phosphate) were tested in the Romanian company Daily Sourcing & Research. The glass foams have characteristics specific to those made of borosilicate glass waste by conventional heating, i. e. relatively low apparent density (0.34 – 0.47 g/ cm3), but higher than those resulting from soda-lime glass waste and compressive strength (1.5 – 2.5 MPa) higher than theirs. As glass foams mainly made of soda-lime glass waste, and those made of borosilicate glass waste are suitable for use as insulating material in construction.

The paper presents results of research conducted by the Romanian company Daily Sourcing & Research on the use of microwave energy in the manufacture process of glass foams. Compared to similar products manufactured by conventional heating techniques, the physical, mechanical and morphological features of the experimental samples are close and meet the requirements for materials used as thermal insulators. The apparent densities and thermal conductivities are low (0.16 – 0.24 g/ cm3 and respectively 0.037 – 0.043 W/ m · K) and the compressive strength has acceptable values (1.14 – 1.25 MPa). The manufacturing technique of glass foam in microwave field, in experimental stage in the Romanian company Daily Sourcing & Research, has already confirmed its effectiveness in numerous tests conducted in the last two years.

Results of the research conducted by the Romanian company Daily Sourcing & Research Bucharest to obtain glass foams from clear flat glass waste with good macrostructural homogeneity are presented in the paper. The favourable influence of the microwave heating was proved experimentally on a 0.8 kW-microwave oven. The most significant achievement was obtaining good macrostructural homogeneity, which is difficult to obtain under conditions of conventional heating methods. The pores of the samples are uniformly distributed and their size varies between 0.6 - 2 mm (foaming with calcium carbonate) and 0.9 - 3 mm (foaming with silicon carbide).

Experimental results obtained in the process of manufacturing dense glass foam using the microwave energy are presented in the work. The glass foam is produced from bottle glass waste, calcium carbonate as foaming agent and borax as fluxing agent. The high compressive strength (2.5 - 6.2 MPa) is the main mechanical feature of this product, which together with other physical and morphological features (apparent density 0.60 – 0.90 g/cm3, porosity 59.1 – 72.7%, thermal conductivity 0.081 – 0.105 W m K, water absorption 0.5 – 1.0%, pore size 0.5 – 3 mm), are appropriate for using as a substitute for similar building materials existing on the market.

An industrially manufacturing recipe of foam glass gravel (FGG) from glass waste by an unconventional heating technique, using simultaneously a liquid foaming agent (glycerol) and a solid one (calcium carbonate) was tested on a 10 kW-microwave oven. Using a ceramic crucible based on silicon carbide with large dimensions, placed in a horizontal position, inside which a metal mold containing the finely ground pressed raw material mixture was inserted, the conditions were created to experiment the manufacture of a much higher quantity and on a significantly extended surface of 725 cm2 of foamed product compared to previous tests performed on a 0.8 kW-microwave oven. In terms of quality, the results were appropriate, the characteristics of FGG samples manufactured by sintering at 834-840 ºC using the conversion of microwave power to heat being within the limits of values required for this type of thermal insulation material (bulk density of 0.20-0.25 g/cm3, thermal conductivity of 0.062-0.070 W/m•K, compressive strength of 7.1-7.4 MPa, water absorption below 3% and pore size between 0.10-0.65 mm).

The paper presents a new technique for making foam glass gravel by expanding at high temperature recycled glass waste with a liquid carbonic foaming agent (glycerol) in combination with sodium silicate (also called “water glass”). Unlike the conventional methods known worldwide in similar technological processes, the paper proposes a fast, economical and clean unconventional technique (microwave irradiation), applied to a very small extent in the industrial sector, although in the household it is a widely used process. The experiments carried out by the Daily Sourcing & Research Company on a 0.8 kW-microwave oven aimed at the manufacture of foam glass gravels with physical and mechanical characteristics almost similar to those industrially obtained by conventional methods, simultaneously demonstrating the superior energy efficiency of the technique of using microwave energy as an unconventional source. The products experimentally made had low thermal conductivity (between 0.057-0.063 W/ m·K), high compressive strength for this material type (up to 5.9 MPa) and very low pore size (below 0.9 mm). The specific energy consumption had values between 0.83-0.88 kWh/ kg comparable to those industrially achieved, but it should be considered that the use of a high power microwave equipment could improve the process efficiency by up to 25%.

Experimental results of manufacturing the cellular glass from container glass waste using an unconventional heat treatment technique (microwave energy) are presented in the paper. The cellular glass has physical, mechanical and morphological characteristics suitable for using as an insulating material in construction constituting an alternative for existing building materials. By comparison with these materials, the cellular glass has a higher resistance to mechanical stress, fire, humidity, attack of rodents, insects, bacteria, etc. The apparent density and thermal conductivity of the product are low (below 0.34 g/ cm3 and 0.062 W/ m·K, respectively), the compressive strength is acceptable (over 1.2 MPa) and the material structure is homogeneous with closed pores evenly distributed. The originality of the manufacturing technique of cellular glass presented in the paper is the use of microwave energy, unlike the conventional methods currently applied in the world. The advantages of the use of this unconventional technique are the low specific energy consumption (around 1 kWh / kg) and its non-polluting character.

Huge amounts of vegetable waste, mainly resulting from the food industry, need large areas for storage, as they could cause hazardous environmental impact, leading to soil and water pollution or to CO2 emissions during accidental incineration. This work was aimed at recycling certain lignocellulosic waste (walnut shells, kernels of peach, apricot, and olive) to design advanced carbon material precursors (ACMP) to be used for obtaining nano-powders with high applicative potential in pollution abatement. Both waste and ACMP were characterized using proximate and elemental analysis, and by optical microscopy. Complex characterization of raw materials by FTIR, TGA-DTG, and SEM analysis were carried out. The ACMP were synthetized at 600–700 °C by innovative microwave heating technology which offers the advantages of lower energy consumption using 3.3 kW equipment at laboratory level. The ACMP ash < 3% and increased carbon content of 87% enabled the development of an extended pore network depending on degassing conditions during heating. TEM analysis revealed a well-developed porous structure of the synthesized ACMP carbonaceous materials. Due to the presence of oxygen functional groups, ACMPs exhibit adsorption properties highlighted by an iodine index of max. 500 mg/g and surface area BET of 300 m2/g, which make them attractive for removal of environmental pollutants such as dyes having molecule sizes below 2 nm and ions with pore dimensions below 1 nm, widely used industrially and found in underground waters (NO3−) or waste waters (SO42−).