To produce a glassy lightweight, high-strength and inexpensive board excellent in processability and further freeze damage resistance performances by mutually bonding glassy lightweight aggregates with a melt solidified layer of sodium silicate formed on the surfaces of the glassy lightweight aggregates.

This glassy lightweight board is produced by mutually bonding glassy lightweight aggregates with a melt solidified layer of sodium silicate formed on the surfaces of the glassy lightweight aggregates. Nearly spherical and high-strength lightweight aggregates having uniform grain dimensions are used as the glassy lightweight aggregates used as a raw material. The method for producing the glassy lightweight board comprises sticking the sodium silicate to the surfaces of the glassy lightweight aggregates, hardening the glassy lightweight aggregates, then filling the resultant hardened aggregates in a container 1 and sintering the filled hardened aggregates at 700-900°C. The form of carrying out the method for production is shown in the figure. Rods 2, made of the same material as that of the container 1 and having a triangular cross section are laid and arranged side by side on the bottom of the container 1 and sodium silicate is made to stick to the glassy lightweight aggregates 3, which are hardened and then filled therein. A lid is placed thereon and the glassy lightweight aggregates 3 are baked to thereby produce the glassy lightweight board. The resultant glassy lightweight board has 0.3-0.6 specific gravity, 4.0-20.0kg/cm2 flexural strength and ≥15% intergranular porosity.