ECA (Expanded Clay Aggregate) is a perfect material for lightweight fill material when creating underground structures. It offers an extremely high strength-to-weight ratio, due to its unique construction, with thousands of tiny holes and pores throughout the structure of the clay.
In addition, ECA is very strong and noncompressible, and will not deform under load. It’s also a highly-efficient insulator, with a low thermal conductivity coefficient. Since it’s lightweight, it’s also inexpensive to transport, which can help keep costs low for your project. It can even be combined with other fill materials, such as concrete while maintaining its unique properties.