Combination of chemical foaming and direct ink writing for lightweight geopolymers

Abstract

In this work, the possibility of combining direct ink writing and chemical foaming to create geopolymer lattices with interconnecting porosity at different scales is investigated. Chemical foaming was achieved by introducing aluminum powder into the paste, in order to produce a foam which was then 3D printed. Homogeneous foams with interconnected pores were generated, by combining polyethylene glycol, hexadecyltrimethylammonium bromide and aluminum powder. Porosity was characterized by X-ray tomography, mercury intrusion porosimetry and helium pycnometry. The samples obtained after the 3D printing of the foams have a similar open porosity than foams directly molded. However, their pore access diameters are very different since the 3D printing process tends to close the channels generated by the gas escape during chemical foaming. This loss is compensated by the porosity created by 3D printing, which is due to the space between the filaments.