Porous Geopolymer Insulating Core from a Metakaolin/Biomass Ash Composite

Abstract

Ashes derived from the combustion of vegetal and animal biomass still represent a mostly unexplored secondary raw material for the production of alkali-activated materials, given their peculiar chemical nature. In this work, calcium phosphate biomass ashes were successfully used as partially reactive fillers in a metakaolin-based geopolymer composite to produce, by direct foaming, sustainable and lightweight boards with thermal insulating properties. The investigated materials were obtained by activating a blend of metakaolin and biomass ash in a weight ratio of 1: 1 and foamed with the addition of H 2 O 2 in measure of 5 wt. %, to maximize the volume of disposed ash and ensure adequate properties to the material at the same time. The obtained geopolymer composite was characterized by microstructural, chemical-physical, mechanical and thermal analysis: the obtained results showed that biomass ash and metakaolin well integrated in the microstructure of the final porous material, which was characterized by a density of about 310 kg/m 3 and a thermal conductivity of 0.073 W/mK at a mean test temperature of 30 • C, coupled with an acceptable compressive strength of about 0.6 MPa. Dilatometric and thermogravimetric analysis, performed up to 1000 • C, highlighted the thermal stability of the composite, which could be regarded as a promising material for low-cost, self-bearing thermal insulating partitions or lightweight cores for thermostructural sandwich panels.

Rice Hulls as a Renewable Complex Material Resource

“…Ashes derived from the combustion of vegetal wastes represent a secondary raw material for the production of alkali-activated materials. The porous geopolymer composite appears to be a promising thermal insulating material, suitable for being used as a lightweight heat barrier [21]. Such a porous geopolymer represents the best balance in terms of low density (313 kg/m 3 ) and mechanical strength (0.63 MPa).…”

Evaluation of Urban Tree Leaf Biomass-Potential, Physico-Mechanical and Chemical Parameters of Raw Material and Solid Biofuel

“…This is very important in case of an attempt of further use. Ash from biomass combustion is used in the production of cement or soil fertilizers [40,61].…”

“…The amount of ash generated during combustion depends on the origin of the fuel and ranges from about 1% (wood biomass) to over 10% (agro biomass) [38]. Ash rich in silica can be used as an additive, so it can be successfully used in the ceramic and cement industry [39,40]. It can also be used as a raw material or component of granulated fertilizers [41].…”

Effect of Hydrogen Peroxide on the Thermal and Mechanical Properties of Lightweight Geopolymer Mortar Panels

“…Considering this effect, metakaolin-based geopolymers have the potential to meet these thermal insulation requirements due to two main effects: their higher thermal reflectance due to the whitish coloration provided by metakaolin, and their thermal insulation capacity when modified to porous geopolymer. Numerous articles have been published in recent years on porous geopolymers [5][6][7][8][9][10]. The most commonly used strategy to produce porous geopolymers involves mixing an air-incorporating agent, such as hydrogen peroxide, to the geopolymers paste.…”