Abstract
It is well-known that CO2 process is the hardening method of sodium silicate bonded sand by carbon-dioxide and the process improves the efficiency of the work, but it is more expensive owing to the more consumption of carbon-dioxide than the theoretical volume.
The present investigation dealt with the dry-air hardening of the sand bonded with sodium silicate of high molecular ratio.
The following results were obtained.
1) The sand bonded by sodium silicate of molecular ratios 2.1 and 3.0 (mixed 1 : 1) was hardened by passing dry-air for 2-3 minutes with pressure 0.5-1.0 kg/cm2.
2) The strength after hardening increased slowly for 48 hours.
3) The dry strength increased very much, and the maximum strength was obtained heating at 120-160°C for 45-60 minutes.
4) In molding and casting tests, the results were similar to the CO2 process.
