Influence of Various Coal Energy Wastes and Foaming Agents on Foamed Geopolymer Materials’ Synthesis

Abstract

The regularities of obtaining foamed alkali-activated geopolymer materials based on different wastes of coal power engineering (fly ash, fuel (boiler) slag, ash, and slag mixture) were considered. The phase composition of the studied waste showed the presence of a significant amount of the amorphous phase, as well as a crystalline phase. mostly in the form of high quartz. The microstructure of studied the waste showed that the fly ash consisted of monodisperse hollow aluminosilicate microspheres, the fuel slag was represented by polydisperse irregular particles, and the ash and slag mixture included both of these materials in different ratios. Blowing agents such as aluminum powder, hydrogen peroxide, and sodium hypochlorite were chosen to achieve the porous structure of the geopolymer materials. The calculations of the geopolymer precursor compositions were carried out. Samples were synthesized, and their physical and mechanical properties, such as density, strength, porosity, and thermal conductivity, were analyzed. The micro- and macrostructure of the samples, as well as the pore distribution of the obtained geopolymers were studied. Conclusions were made on the choice of the most-optimal foaming agent and the optimal coal combustion waste suitable for the synthesis of the geopolymer materials.

Study on the Curing and Foaming of Surfactant-Modified Geopolymer Gels Based on Ash and Slag Waste from Coal Combustion

“…The newly formed exothermic peak (6) corresponds to heat release during the interaction between aluminum powder, alkali, and water, resulting in hydrogen release. The mechanism of this reaction was previously described in the research [26]. The endothermic peak (7) corresponds to the partial dissolution of SiO 2 and Al 2 O 3 present in ASW, as well as water evaporation from the gel, confirmed by the mass loss curve.…”

“…The thermal conductivity of the geopolymers was measured using a thermal conductivity meter (ITP-MG4"100/Zond", SKB StroyPribor, Chelyabinsk, Russia) employing the stationary heat flow method. The temperature of the hot and cold faces was set at 34 where λ-effective thermal conductivity, W/m•K; H-sample height, cm; q-density of stationary heat flux passing through the measured sample, W/m 2 ; T H -temperature of the sample's hot face, K; T C -temperature of the sample's cold face, K. The methodology and equipment necessary for determining the linear dimensions as well as certain physical-mechanical properties (volume, density, porosity, compressive strength) of porous geopolymers were described in the authors' previous research [26,64]. Each recorded test value is the medium of 4 measurements.…”

“…[10,24,25]; and various industrial waste materials include solid fuel residues (ashes, slag, and ash-slag mixtures), rice husk ash, etc. [26][27][28][29][30]. However, it is preferable to use raw materials with a high content of an amorphous phase due to improved reactivity [31].…”

Use of Alkaline-Activated Energy Waste Raw Materials in Geopolymer Concrete

“…In addition to gas emissions, the use of certain industrial waste products, including fly ash, is also important. Fly ash is a highly dispersed material consisting of spherical particles represented by hollow aluminosilicate balls, with a diameter of 0.1-100 µm, responsible for the binding properties in alkali-activated lightweight concrete [8][9][10][11][12]. It allows for the elimination of the problem of waste stacking on specially prepared landfills, which has a significant impact on the environment.…”

Use of Alkaline-Activated Energy Waste Raw Materials in Geopolymer Concrete

“…consisting of spherical particles represented by hollow aluminosilicate balls with a diameter of 0.1-100 μm, responsible for the binding properties in alkali-activated lightweight concrete [1,10,28,32,33]. It allows the elimination of the problem of waste stacking on specially prepared landfills, which has a significant impact on the environment.…”