Abstract
Six matrices based on alkali-activated aluminosilicate with different amounts of potassium phosphate were prepared for the production of six-layer composite plates. The addition of potassium phosphate in the matrix was 2 wt%, 4 wt%, 6 wt%, 8 wt% and 10 wt% of its total weight. The matrix without the potassium phosphate was also prepared. The aim of this study was to determine whether this addition has an effect on the tensile strength or Young’s modulus of composites at temperatures up to 800 °C. Changes in the thickness and weight of the samples after this temperature were also monitored. Carbon plain weave fabric was chosen for the preparation of the composites. The results show that under normal conditions, the addition of potassium phosphate has no significant effect on the mechanical properties; the highest measured tensile strengths were around 350 MPa. However, at temperatures of 600 °C and 800 °C the addition of potassium phosphate had a positive effect, with the tensile strength of the composites being up to 300% higher than the composites without the addition. The highest measured values of composites after one hour at 600 °C were higher than 100 MPa and after 1 h at 800 °C higher than 85 MPa.
Highlights
Alkali-activated aluminosilicates are one of the most researched materials in recent decades
Aluminosilicates are most often represented by metakaolin, but the content of aluminum and silicon can be supplied in the form of industrial waste, such as fly ash or blast furnace slag
Inorganic matrix (A-matrix) based on alkali-activated aluminosilicates was prepared using commercial metakaolinite-rich material [31,32] produced by the calcination of kaolinitic claystone in a rotary kiln at cca 750 ◦C (Ceské lupkové závody, a.s., Nové Strašecí, Czech Republic), silica fume (Ceské lupkové závody, a.s., Nové Strašecí, Czech Republic), commercial potassium silicate with a molar ratio SiO2:M2O equal to 1.7 (Vodní sklo, a.s., Prague, Czech Republic), potassium hydroxide pellets (89.9%, Lach-Ner, s.r.o., Neratovice, Czech Republic), potassium phosphate anhydrous (Penta, s.r.o., Prague, Czech Republic) and distilled water
Summary
Alkali-activated aluminosilicates are one of the most researched materials in recent decades. Aluminosilicates are most often represented by metakaolin, but the content of aluminum and silicon can be supplied in the form of industrial waste, such as fly ash or blast furnace slag. These alternative materials give rise to a more environment friendly and cost-effective inorganic material [4,5,6,7]. The liquid alkaline activator in which the aluminosilicate powder is dissolved is most often represented by a solution of water glass, oxides and hydroxides of sodium or potassium or their mixtures [4,8]
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