TERRAPADS

Development and characterisation of ecological load-bearing blocks based on excavated soil

The construction sector, and in particular the Geneva construction sector, has to face two major challenges that are closely linked: on the one hand, the supply of raw materials (in particular with Geneva's exploitable reserves of gravel, which are dwindling) and on the other hand, the elimination of excavation materials (congestion of storage sites).

For example, in Geneva, more than 3.7 million tonnes of unpolluted excavated material are produced each year on building sites, which represents more than two thirds of the canton's total waste (5 million tonnes). In order to better understand the issues related to these volumes of excavated soil, legally considered as waste, it is necessary to specify that this corresponds to the monthly volume of 3 RTS towers, 2 Notre-Dame de Paris, 80 Olympic swimming pools and 13'500 trucks.

However, at a time when the dynamics around the circular economy are strong, when the problem of managing excavated soil is well known to all the players in the sector, we can only note that the conditions for a wide recovery of these materials are not met: only 15% of this soil is recycled, essentially for backfilling on site, filling sites and also for making compressed raw earth blocks for the manufacture of non-load-bearing walls.

Factors explaining this low recycling rate (especially as raw material for building materials) include:

• a poor image and fear of recycled materials, which are wrongly considered less reliable
• a lack of information and knowledge about recycled materials.

The objective of this project is to develop alternative and ecological construction practices through the development and full characterisation of large-format stabilised compressed earth blocks for interior and exterior load-bearing wall applications, in order to:

• certify their load-bearing capacities and thus validate the predictive calculations of civil engineers on the building structure;
• improve the image of these materials and to reassure the various actors in the construction industry.

More specifically, the project aims to:

• characterise a new «product» (material, construction system) for vertical load-bearing elements based on large-format compressed earth blocks, the «TERRAPADS»;
• characterise this product from the point of view of implementation, performance and durability;
• specify the field of application of the product and its integration in a construction project;
• contribute to filling the information gap in order to answer the questions of the various actors in the construction industry (engineers, architects, masons, project owners and users).