Building Inovative Prototypes
The programm of the second and third weeks of our Poured Earth workshop in Montemor-o-Novo (Portugal) focused on learning how to build formworks and formulate mixes for building with this technique. We splitted our group of participants in 3 teams named by the provenance of each earth they would work with: Cano, Nelia and Vendas Novas.
The objective for each team was to build two wall prototypes of 80x80x30cm that would then be tested exposing them to weathering, with the purpose of determining the best mix and formwork design for future constructions in the area.
First, each team had to characterize the soil that was assigned to them by doing field tests (cigars, sedimentation in a bottle, pellets, etc.) and laboratory tests (granulometry, sedimentometry, retraction tests).
Then they had to determine the strategies they would adopt to build their first prototype in order to have a mix:
1) fluid enough to be poured (by adjusting the water content and possibly adding dispersing agents and/or modifying the granulometry)
2) solid enough to take the formwork out few time after (by using any hydraulic binder or coagulant to harden the mortar or by increasing the breathability of the formwork in order to accelerate the drying).
Once this was defined they started to work and we could observe a fascinating agitation in the Earth Lab : canes beeing cuted and knotted together wirh sisal rope, different types of dispersing products being tested on mud samples, gravels and sand being mixed in different proportions with the earth in order to improve the granulometry, mortars consistency being tested with the so-called “Abrams cone”, samples of 10x10x10 cm being poured, etc. We also put on disposal of the groups different types of materials (fabrics, wood, cork, etc) that could be used in order to create different textures on the surface of the final materials, with an aesthetic or functional purpose.
After one week of intense experimentation, each group, help by the others, managed to pour a prototype:
Cano’s group worked with a double formwork with an inner breathable skin made of common canes (A.Donax) with a mortar containing only their earth and dispersants in order to reduce the water content.
Nelia’s group designed with a mix of earth, gravels and gypsum poured into a formwork with 3 horizontal chamfered timbers that would posteriorly be removed in order to include ceramic tiles as an “anti-erosion” system.
Vendas Novas group created an original formwork with an Alentejo traditional fabric and poured in it a mix of earth, sand and gravel stabilized with gypsum.
At the beginning of the third week, the formworks were taken out and we gathered all the participants to analyze the results of the tests and draw some conclusions, before each group could start thinking about what to test or improve for the following prototype and started implementing their ideas:
Cano’s group decided to improve the cane formwork in order to make it more resistant and they fine-tuned their mix formulation, being able to reduce the quantity of additives.
Nelia’s group decided to take out the gypsum of their mix formulation and work with a breathable formwork made out of jute fabric, playing with the deformation of the surface with an aesthetic purpose. In order to reduce the water content, they added a dispersant to the mix.
Vendas Novas group’s strategy was similar to Nelia’s but using a superposition of 2 types of metal meshes instead of jute fabric.
As all the prototypes of this new serie were all based on breathable formwork (no hydraulic binder was used), we had to wait until the following week to take the formworks out and see the results.
During these second and third weeks of the workshop the work mainly happened in the Earth Lab with “hands on approach” but we managed to organize two breaks to listen to two Guest Lectures by:
Arch. Martin Pointet from BETerre (Grenoble, France), a company specialized into assessment on earth building with a special expertise on Poured Earth technique
Pr. Guillaume Habert from ETH (Zürich, Switzerland), associate professor and director of the Chair of Sustainable Construction, who we have been fortunate to receive in person in Montemor-o-Novo. This day was also the occasion to organize a visit to Tânia Teixeira’s house, a traditional “casa alentejana” entirely renovated with low-impact building techniques.