Leca is initial letters for: Light Expanded Clay Aggregate.
LECA consists of small, lightweight, bloated particles of burnt clay. The thousands of small, air-filled cavities give LECA its strength and thermal insulation properties.
The base material is plastic clay which is extensively pretreated and then heated and expanded in a rotary kiln.
Finally,the product is sintered at about 1200 °C to form the finished LECA product.