Cold reaction sintering for preparation of ultra-dense geopolymer products

Geopolymers are attractive materials that contribute to carbon neutrality because they can significantly reduce CO2 emissions compared to traditional Portland-based cement manufacturing. Geopolymers generally take several days to weeks to cure and have low mechanical properties. This paper proposes a new hardening method using a warm press, called cold reaction sintering, in order to obtain a hardened body with high strength in a shorter time than conventional geopolymers. In general, to harden geopolymers use an alkaline solution such as NaOH. In this study, sodium metasilicate hydrate (Na2SiO3 center dot nH(2)O) was used instead of the alkaline solution. As a result of examining the composition, temperature and holding time, the maximum compressive strength value of 425 MPa was obtained when hardened at uniaxial pressure 100 MPa, 130 degrees C for only 10 min with fly ash: Na2SiO3: Na2SiO3 center dot 9H(2)O (68: 16: 16 wt%, respectively). In addition, dimensional change measurements during hardening, FTIR and NMR analysis were preformed to investigate and discuss the mechanism of geopolymer hardening.

Automated summary

This paper proposes a new hardening method using a warm press, called cold reaction sintering, to obtain a hardened body with high strength in a shorter time than conventional geopolymers. Sodium metasilicate hydrate was used instead of alkaline solution for the hardening process. The study found that the maximum compressive strength value of 425 MPa was achieved when hardened at uniaxial pressure 100 MPa, 130 degrees C for only 10 min.