Rapid fabrication of highly dense geopolymers using a warm press method and their ability to absorb neutron irradiation

•Geopolymers with appropriate shape inside the mold could be fabricated for a few hours.•The hardening mechanism by a warm press method was discussed.•This highly dense geopolymer had an excellent ability to absorb neutron irradiation.

A highly dense pure phase geopolymer was fabricated in only a few hours using a warm press technique. The resultant geopolymer had a high compressive strength of 149 MPa after pressing at 200 MPa and 130 °C for 1 h. The heat and pressure applied during the processing accelerated the geopolymerization and solidification of the starting materials, which consisted of fly ash, a sodium hydroxide solution, and water glass. This highly dense geopolymer had an excellent ability to absorb neutron irradiation, compared to geopolymers fabricated by a conventional curing process.