What is argex (expanded clay aggregate)?

Argex (also known as LECA, hydroton or expanded clay aggregate) is a lightweight building material consisting of fired clay pellets with a porous core and a hard outer shell. The pellets are made by heating clay to approximately 1,200 °C, causing the clay to expand and form light, round balls.

Properties

• Lightweight — bulk density of roughly 300–600 kg/m³, much lighter than sand or gravel
• Thermally insulating — the air pockets inside the pellets provide insulating value
• Moisture resistant — the hard outer shell absorbs virtually no water
• Load-bearing — despite the low weight, argex can withstand considerable pressure
• Non-combustible — Euroclass A1, completely fireproof
• Free-draining — water flows easily between the
  

  pellets

Application

Argex is used in construction in many ways:

• Crawl space — as insulating fill beneath the ground floor
• Roof — as a screed-to-falls layer on flat roofs, combined with insulation
• Lightweight fill — beneath floors or behind retaining walls to reduce weight
• Drainage — around foundations and in planters
• Concrete aggregate — as a lightweight aggregate in lightweight concrete

Application in the crawl space

1. Lay a root barrier membrane on the ground
2. Fill the crawl space with argex to approximately 5 cm below the floor
3. The pellets insulate and prevent rising damp

The insulation value is limited (lambda approx. 0.09–0.12 W/mK), but it significantly improves the climate in the crawl space.

Related terms

• Insulation
• Drainage
• Crawl space
• Lightweight concrete
• Falls (gradient)

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