Abstract

This paper examines the influence of the type of fly ash and activating solution in the development of fly ash-based geopolymers used to manufacture panels with fire resistance properties. Two fly ashes with different vitreous phase contents, from coal combustion and from coal and pet-coke co-combustion, were used as the aluminosilicate source. Two activating solutions were also used: sodium silicate and potassium silicate. Geopolymers, after 28 days of curing at 20 degrees C and 45% of relative humidity, were subjected to different tests: physicochemical (porosity, density, volumetric expansion, water absorption and moisture content), mechanical (flexural and compressive strength) and fire resistance tests. Panels prepared with both alkali silicates present a similar insulating capacity. Mechanical properties were improved with sodium silicate. The best mechanical properties and the worst fire resistance capacity were observed in the geopolymer panels manufactured using the fly ash with the highest amorphous content. All geopolymer panels were subjected to the Dutch standard leaching test NEN 7345, a common leaching test for monolith samples. The type of ash is the most important factor in leaching behaviour, while the type of activating solution has no influence on the leachability of the geopolymer panels.