Saint-Gobain’s fresh look at earth

09/09/2020

Innovation around construction practices and techniques is now central to creating a more sustainable and more environmentally friendly model for buildings and cities. Saint-Gobain Distribution Bâtiment France and Norper have joined forces to develop a new building system that breaks away entirely from existing systems. This construction method, using raw and excavated earth, has many advantages: high thermal inertia, efficient hydro-thermo behavior, high acoustic insulation, etc. It also provides a circular-economy solution while also optimizing worksite logistics.

Just one meeting

Saint-Gobain Distribution Bâtiment France has for several years been working with EPAEM (Euroméditerranée Public Development Authority) under an agreement aimed at boosting open innovation initiatives to develop the sustainable Mediterranean city of the future. The “experiment permit” introduced by France’s “confidence law” smooths the way for construction projects and supports the emergence of new approaches in many areas, including construction. One of the flagship projects involves experimenting with raw earth as a new eco-responsible building material and upcoming main resource for future sustainable construction projects. Seeking a partner with which to develop this new basic raw material, Saint-Gobain Distribution Bâtiment France contacted the family-owned company Norper, which specializes in projecting decorative concrete.

Excavation earth: recycled material used as a new resource

A natural resource considered worksite waste, raw earth is available throughout the entire country. Its use as a recycled material is now more crucial than ever as limestone quarries are facing gravel shortages.

Harking back to ancestral techniques, it has many advantages for building low-cost and environmentally friendly buildings. With its high thermal inertia, it can store heat and acts as an efficient hydro-regulator. Its acoustic performance is another of its outstanding features for a dense urban context.

Norper’s unique process

Norper has come up with a natural lightweight concrete compliant with France’s RE 2020 thermal regulations. It uses so-called “site earth”, excavation earth or quarry waste, and does not contain any cement binder.

The application process involves several stages:

  • Preparation of the earth

 The first step involves calibrating the site’s earth to obtain material with the desired particle size. The earth is passed through a sieve and the product collected in a container.

 After sieving and calibrating, the earth is mixed with various other components including gravel and natural fiber (hemp, rice husks, etc.).

  • Production of natural earth concrete

Next, the formula preparation involves the following steps: 

• The calibrated site earth is placed in the mixer

• Gravel is added

• Natural fiber (hemp, rice husk or other) is added

• The machine’s volumetric system adds water

• Binders are added (without the use of cement)

• Longer mixing (3 to 5 mins) to obtain the smooth consistency of concrete

The site concrete is now ready for projection.

  • Projection of natural earth concrete

Several operations must be completed before the actual projection:

• Installation of a screw pump connected to the mixer using various hoses

• Connection of the projection hose and nozzle with the appropriate cross-section

• The natural earth concrete is projected onto wooden frames attached to OSB board, which in turn is screwed to a timber structure; a welded mesh metal grid is placed mid-frame to allow for the components traditionally used by the building trades to be included.

• The concrete is projected in successive passes of 7 to 8 cm. The time between passes is 30 minutes (for bigger panels on large construction sites, this time has to be increased to 1 to 2 hours). The finished panel is perfectly solid and it can be finished using standard processes (rule, float, trowel, etc.).

Norper has filed a patent application for the binder used to project and hold the earth as a construction material.

This process can also be used for concrete walls, slabs and screeds, double walls, cinder blocks, etc.

Meeting circular economy needs

This new construction method is an ideal illustration of a project meeting circular economy needs.

98% of the panel is sourced from:

◦ Local excavation or construction sites

◦ Industrial waste (blast furnace slag, steel production waste, etc.)

◦ Bio-sourced waste depending on the region (e.g., in southern France, rice husk is locally available), earth (geo-sourced waste)

◦ Local construction timber industry for the frame, etc.

Training and expertise

This project, along with its network of projectors and 22 certified trainers (Datadock) allows for a systematic approach to recognizing and promoting an entire building trade.

Plans are underway to eventually provide training through CFA-apprenticeship training centers as part of the support that Saint-Gobain Distribution Bâtiment France provides its professional customers and this business.

Upcoming projects 

Eiffage and Euroméditerranée are sponsoring the project with the construction of two buildings in the Euroméditerranée region. A consortium of partners is backing this innovation: CEMEX, Ginger, Bessis, to name a few.

Various projects could see the light of day:

• 2 buildings built by Eiffage in the Euroméditerranée region

• The new La Plateforme du Bâtiment depot in Nanterre, Paris region.

Photo Credit: ©Joseph Melun.