Pitchstone reacted with CaO in hot water(9$0^{circ}C$) and increased its sedimentary volume by forming Ca(OH)2 and calcium silicate hydrates. ALC was prepared from gel at 9$0^{circ}C$ and subsequently autoclaved at 18$0^{circ}C$ by using the property of swelling and the physical properties of ALC was investigated with experimental conditions. When the ratio of pitchstone/CaO was 2 (CaO/SiO2 mol ratio=0.81), bulk density, modulus of rupture and thermal conductivity of the ALC were 0.75g/㎤, 73kg/$ extrm{cm}^2$ 0.150 kcal/m.hr.$^{circ}C$, respectively. The crystalline phase of it was mainly tobermorite. Therefore ALC was turned out to be much lightweighted and good thermal insulation.