PURPOSE: To permit to take a balance easier for ground development work by an artificial lightweight material made by foamed polystyrene and foamed cement hardened bodies compounded together.

CONSTITUTION: Foam polystyrene 2 crushed to the size of 20 to 25 mm, and cement foam slurry made from cement, water, a higher alcohol, a sulfuric ester- based compound foaming agent are mixed together, and a compound of foam polystyrene, cement, water, and air bubbles is obtained and used as artificial lightweight material for ground and earth filling. According to this, mass balance can be taken more easily when carrying out the ground development work such as prevention of settlement of soft ground, earth pressure reduction for developing sloped land or the like.