Rammed Earth + Fabric Formwork
Updated: Sep 10, 2020
When I travelled to Jeju island with my family, Suwolbong (수월봉) has left a great impression on me. Its stratification and exposed rocks were incredibly beautiful, and I felt, these geographical features were very much similar to rammed earth. Conventionally, rammed earthen walls were built as plain straight rectangular shapes, but I thought about how these beautiful curved forms can be also transferred to rammed earthen walls bringing advanced aesthetic quality and durability.
Since I have learnt fabric formwork at the University of Edinburgh, I was so much drawn to its flexibility, affordability, and great potential to design. Fabrics have a wide range of types and diverse properties. For example, according to the percentage of spandex on fabrics, the extent of elasticity is significantly different. This means that forms created by fabric formwork are limited only by designers’ imagination. Furthermore, fabrics are generally cheaper and lighter than wood, so that it is expected to bring a crucial contribution to reducing construction fees and times compared to traditional timber formwork.
I have created fabric formwork for a rammed earth model stabilised with lime and cement. One side of fabric formwork was made of a rigid synthetic fabric and wooden panels which confine the shape of the model. This stiff fabric was intentionally used in order to prevent the form was bulged out too much, and it was fastened securely to withstand the tension pressure of a cast.
The other sides of fabric formwork are created with polystyrene moulds and fabrics having a high percentage of spandex which is stretched adequately to catch the fine details of polystyrene moulds.
Three types of mixtures were poured and rammed into the fabric formwork from bottom to top; sand and lime mixture, concrete mixture with plasticiser, and sand and lime mixture with plasticiser. The minimum amount of water was used, and several layers of coloured mixtures were added between.
After the formwork was dissembled, the elevation pressed against 4 wooden panels displayed an interesting fabriclike texture. Fabric wrinkles created between ridges of wooden panels were embedded on rammed earth. If it is examined more carefully, it is noticeable that even the delicate weaving pattern of the fabric was expressed on the façade. Furthermore, the middle and top layers which are mixed with plasticiser are less porous than the bottom layer so that weaving pattern of the fabric is more clearly visible.
On the other hand, the other 3 elevations had shapes controlled by polystyrene moulds. Despite big sizes of aggregates, fine details were relatively well expressed maintaining haptic textures.
It was very interesting to see that fabric formwork is successfully working on fabricating rammed earth. At the later stage, I would like to develop this technique further at a bigger scale of models.
I am very much interested in designing the façade of rammed earth not just because it is visually pleasing but also it enhances the resistance to the impact of rainwater and wind. For example, an aerodynamic shape of a rammed earth wall is more efficient on withstanding wind forces than a plain straight wall, and it also contributes to reducing the erosion caused by rainwater which is accelerated by prevailing wind force. Considering the fact that diverse designs of rammed earthen can be produced with fabric formwork, this technology will definitely bring a great benefit to increase the life span of rammed earth buildings minimising environmental loads.