Mechanical Response of Geopolymer Foams to Heating—Managing Coal Gangue in Fire-Resistant Materials Technology

Abstract

Two geopolymer foams were prepared from a thermally activated coal gangue containing kaolinite. As the foaming agent, aluminium powder and 36% hydrogen peroxide were used to obtain two levels of porosity. The materials’ high temperature performances were investigated: tensile and compressive strength evolution with temperature. This study shows that the mechanical performances of developed geopolymer foams are similar to foam concrete of the same apparent density. The geopolymer foams from coal gangue present stable mechanical performances up to 600 °C. When the glass transition temperature is achieved, sintering occurs and mechanical performance increases. SEM observations confirm the glass transition and densification of the matrix at temperatures above 800 °C. Moreover, the XRD measurements revealed a high amount of mullite that forms at 1000 °C that explained the observed strength increase. The synthesis of good-quality geopolymer foams from coal gangue and its application as a thermal barrier is feasible. The constant level of porosity and its stable character in the range of temperatures 20–1000 °C ensures stable thermal insulation parameters with increasing temperature, which is extremely important for fire protection.

Investigation of Mechanical Properties and Microstructure of Construction- and Demolition-Waste-Based Geopolymers

“…Some amount of ferrous oxides-Fe x O y -was detected. This compound is mostly Fe 2 O 3 [28,29]. The particle distribution for clay brick and concrete waste used as raw materials is presented in Figure 1.…”

Fabrication and application of porous materials made from coal gangue: A review

“…In addition to the CG microspheres, several recent reports, respectively, used 100% calcined CG 109 and selfignition CG 110,111 as aluminosilicate raw material to prepare porous geopolymers. Sitarz et al 109 prepared geopolymer foams with two levels of porosity using calcinated CG as raw material, aluminum powder and hydrogen peroxide as foaming agent, and hydroxyethyl cellulose as foaming stabilizer. Li et al 110 obtained porous geopolymers rapidly within 15 min under the microwave energy after simply mixing the alkali activator with self-ignition CG (Figure 11A).…”

Influence of elevated temperatures on the mechanical properties of foamed geopolymer materials

“…Foamed geopolymers were tested in the temperature range from 20 °C to 1000 °C. Showed stable mechanical properties up to a temperature of 1000 °C À 5.4 MPa compressive strength and 1.30 MPa flexural strength [26].…”