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 H2O2 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/m3 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.
Highlights
In recent years, the need to limit the consumption of natural, non-renewable resources and to progressively lower the energy demand has led to the design of sustainable and environmentally-friendly materials, technologies and processes
The two samples are qualitatively similar in terms of phase composition of the reaction products, as for both formulations the detected crystalline phases mostly derive from the biomass ash, besides some traces of quartz, anatase and muscovite resulting from the metakaolin
Biomass actively participate in the formation of the reaction the the biomass ash ash did did not not actively participate in the formation of the reaction products of the geopolymer and its crystalline phases remained unchanged in the consolidated matrix, products of the geopolymer and its phases remained unchanged in the consolidated acting as a as partially reactive filler.filler
Summary
The need to limit the consumption of natural, non-renewable resources and to progressively lower the energy demand has led to the design of sustainable and environmentally-friendly materials, technologies and processes. Two of the major industrial branches in terms of impact on global emissions and energy consumption, namely the construction and transportation sectors, are increasingly asked to prioritize ecological manufacturing processes and firmly integrate recyclability in the design phase of any component, to produce value-added sustainable solutions. Insulating and flame-resistant materials have been recently developed as greener alternatives to the more traditional petrochemical-derived solutions [6]: an increasing use of renewable resources and new manufacturing processes integrating wastes are being largely adopted in the production of insulating products [1,4,7,8,9].
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