A Look at Leca LWA Production


Simple ideas often last longer. Leca Lightweight Expanded Clay Aggregate is made from fresh clay, and produced through pre-treatment and high temperatures1m3 of fresh clay produces 5m3 of durable, natural aggregate to be used in anything from flower pots to structural concrete bridge elements in harsh Northern seas. Focus on a resourcefully efficient production process is always maintained with a focus on producing as little waste as possible in the process. Strict quality control is in place in all the Leca production plants to deliver high quality material with minimal environmental impact.

Leca Lightweight Expanded Clay Aggregate undergoes a number of processes in production from when the clay is collected from the clay field, until the finished product is packed into bagslorries and ships to be delivered to the customer. The 8 steps of the production cycle are described below. Also, watch the above video showing the steps one by one.

  1. Clay extraction: The clay is collected from the clay field and brought into the clay barn after separating larger stones from the clay.
  2. Clay substitutes: The clay is mixed with recovered waste products to preserve the natural raw material. The replacement products consist of surplus products/bio waste from other industries.
  3. Crushing: The smaller stones are crushed and the clay is pressed through small holes.
  4. Kneading: The clay is kneaded with a bit of water to make processing easier.
  5. Drying: The clay runs through the drying Kiln, where the water is evaporated and the clay is heated to 400 ⁰C. This is where the Leca pellets get their specific (0-4, 4-10 and 10-20 mm) size dimensions as the clay cracks into smaller particles.
  6. Burning: In the next part of the Kiln, the burning Kiln, the clay is heated to 1150 ⁰C, degrees initiating the expansion process creating light round lightweight clay aggregates. To operate this burning process, a combination of coal and waste fuels from other industries are used.
  7. Sifting: When the lightweight aggregate clay pellets are taken out of the Kiln, they are placed in a sieve system which divides them into 9 different fractions based on their grain size. These clay sizes have different properties to geotechnical requirements.
  8. Packing: In the last process, the lightweight aggregate clay pellets are packed into bags or filled directly onto the trucks and ships and taken directly to the customers.

Production in the Kiln for Leca Lightweight Aggregate

"Most of our manufacturing projects incorporates attempts to replace fossil fuels with waste fuels, or the raw material in the Leca mixture with residues", Jesper Schmidt, Project Manager at the Hinge Factory, Denmark.

The Hinge factory has 3 active Kilns, which each deliver 200,000 m3 lightweight aggregates a year. Of course, this requires a lot of fuel as the Rotary Kilns are heated to 400⁰C in the drying part of the Kiln and 1150⁰C in the burning Kiln. The Kilns run more or less 24/7, 365 days a year. In most Leca factories, biofuels are used in addition to coal combustion, in order to reduce the emissions as much as possible.

Leca UK imports lightweight expanded clay aggregate from a number of our most appropriately located manufacturing plants including Denmark, Portugal and Norway. Whilst each plant is guided by the ‘Leca Central Team’, they are targeted to source the most efficient and environmentally responsible methods and materials to aid manufacture and continually look to improve our green credentials.