keramzite

Keramzite, also spelled keramzit or ceramsite in different languages, is a lightweight, porous aggregate produced from expanded clay. It is a type of expanded clay aggregate (ECA) used in construction and engineering to reduce weight and improve insulation and drainage.

Production and properties: Raw clay or shale is dried, formed into granules, and fired at high temperatures in rotary kilns, typically around 1100–1250°C. The rapid expansion of gases inside the grains creates hollow, glassy ceramic spheres with high porosity. The resulting material has a low bulk density (typically in the range of 400–900 kg/m3 depending on grade), good thermal and fire resistance, and chemical inertness. Water absorption is usually in the range of 15–25% by weight, and the product can be produced in various sizes for different applications.

Applications: Keramzite is used as a lightweight coarse aggregate in structural and non-structural concrete, as well as in mortars and precast elements. It also serves as drainage and insulation material in foundations, retaining walls, and green roofs, and as a filtration or media substrate in horticulture and wastewater treatment. Common particle sizes span from fine to coarse, typically in the 2–20 mm range, with specific grades tailored to concrete or drainage needs.

Standards and regional use: Standards for lightweight aggregates in concrete exist in many regions (for example, EN 13055 in Europe and ASTM C330 in the United States). Keramzite production and use are prevalent in Europe, Russia, and parts of Asia, where it is marketed under local trade names.

Environmental aspects: The production process is energy-intensive, but the resulting insulation and reduced structural weight can lead to energy savings in buildings. Considerations include strength class, durability, and compatibility with cementitious systems.