Using Leca® Aggregate Clay in Geotechnical Construction


Using Leca® Lightweight Aggregate in Geotechnical Construction

Leca® Lightweight Aggregate (LWA) provides numerous alternative types of application for construction projects. Lightness combined with good bearing capacity and thermal insulation properties of the material makes it a material of choice in construction on a soft, poor bearing subgrade. Leca® LWA is made from fired clay and is a mechanically and chemically sustainable material, which remains unchanged throughout the lifetime of a completed structure.


Helix Project for Scotland - Kelpies
Leca® LWA was utilised to provide the stable foundations to construct the world famous Kelpies.

When constructing over weak underground voids or soils with low bearing capacity, the load compensation method may be considered using Leca® LWA.

By extracting a volume of existing soil from beneath the new construction, the equivalent volume of Leca® LWA replacing that soil will reduce the load on the subformation by up to four times. By using Leca® LWA extraction can be kept to a minimum in order to achieve nil settlement.

Reducing Soil Pressure

Earth pressure of fill soil affects a supporting structure on a boundary surface between the supporting structure and earth. Supporting structures loaded by earth pressure include, among others, retaining walls, sheet pile walls, back fill of bridges, basement walls, and foundations.

Backfill of a bridge
Transition structure in backfill area of bridge. Leca® LWA also reduces soil pressure impact on bridge abutment.

As a fill material, Leca® LWA can effectively decrease the earth pressure. Due to its light weight, the vertical earth pressure impacting the structure is up to 75% lower that induced by the natural rock fill. Lower earth pressure enables optimized dimensioning of supporting structures; and therefore application of Leca® LWA as backfill in these circumstances is usually a cost-efficient solution.

Underground Fill Using LecaUnderground FillUnderground Fill

Description of underground fill

When Leca® LWA is applied to decrease the earth pressure, the following design aspects shall be taken into account:

  • Properties of underlying subgrade and its loading history
  • Pore water pressure in subgrade soil
  • Groundwater and/or perched water level and possible open water level
  • Allowed settlements and displacement of structure and its vicinity
  • Adjacent buildings and foundations
  • Dead and live loads
  • Construction reliability and feasibility of a structure

Principles of earth pressure reduction by using Leca® LWA are shown in Figure 4.6. Diagrams of the lateral earth pressure on the retaining wall in relation to the depth for Leca® LWA and conventional soil fill are presented in different colours.

Stability of subgrade soil and fill structure must be evaluated using commonly accepted geotechnical calculations to ensure safety and suitability.

         Using Leca for fill material reduces earth pressure 

        Using traditional fill material increases Earth pressure

Figure 4.6. Lateral earth pressure produced by back fill on retaining wall in relation to depth. Lateral earth pressure of Leca® LWA is shown (above); corresponding impact of the conventional soil material is indicated (below).



When used in house and commercial buildings, the Leca® LWA material offers high levels of thermal and acoustic comfort and contributes to improved energy performance and home environment quality. The unique material properties provide solutions for stabilizing and restoring foundations of historical buildings while preserving the original structures.

Using Leca in construction and housing development

Housing Leca® lightweight aggregate is used extensively in new buildings, the restoration of historical buildings and renovation projects.


Expanded clay can be used in all elements of construction from foundations to rooftop. It is primarily used in internal and external masonry walls, both in blocks and mortar as well as providing insulating layers in floors, roofs and basements.

Using Leca in housing and construction work

We have a team of representatives in the UK with extensive experience and knowledge on utilising Leca® Lightweight Aggregate on a variety of Geotechnical Civil Engineering projects.


For a free consultation on Leca® Lightweight Aggregate contact us now


TEL: 0844 3351770