Abstract: A heat-insulating constructional material based on an alkalized and flooded siliceous raw material fabricated by comminuting solid ingredients and mixing all the raw ingredients, steaming a raw mixture and thermally bloating intermediate products obtained from the steamed raw mixture is designed for utilisation as warmth-keeping fills and light-weight concrete aggregates (in a particulate form) and as structural elements for buildings and constructions (in the form of slabs or blocks). For the purpose of controlling the desired products in a wide range of dimensions and to achieve a greater stability in its mechanical strength and water adsorption the material is obtained by cooling the steamed raw mixture prior to its transition in a brittle condition and crushing the brittle mixture prior to bloating for obtaining the intermediate products.