The inception of this experiment began during a construction process for an ongoing project located in a small town of Koni that is situated 90 km north of Mangalore. A sizable mass of soil from the excavation of a pond and debri from the demolition of a 120 year old house got collected. Engagement with the site over time got myself, my client and my team thinking about the possibility of using earth as a construction material. I embarked on my journey to learn about earth building techniques that led me to a workshop in Auroville. During my time there I got a glimpse of the various earth construction technologies like compressed stabilized earth blocks, rammed earth and was introduced to a lesser known technique of poured earth construction.
After returning to Mangalore, I was eager to bring my learnings back to the studio and start my exploration with rammed earth and poured earth construction. It was imperative for the entire team of architects, interns and workers, who had not been to the workshop, to get involved and really understand earth as a material and construction technique. Gaining an understanding of the theoretical process was just the starting point. The intention was to use this knowledge as a framework within which one could get playful and experimental. Learning and exploring earth as a construction material while developing a sense of its tactile nature was at the core.
In order to attempt earth as a construction material we had to understand the composition of earth and the role each of its components play in creating a soil mix.
- Gravel gives compressive strength
- Sand acts an a binder
- Silt and Clay give plasticity
Designing, building and constructing involves mixing the above in various proportions in accordance with the soil available. Along with soil, the addition of sand, aggregate and water creates an adequate and workable mix. A stabilizer like cement is added to increases strength and durability.
The first step of my journey with earth construction started with setting up a miniature lab to carry out my juvenile experiments of making scaled models in the studio. The shuttering was designed in a 1’: ¼“ scale and brought to life by the carpenters. With a couple of design revisions, I finally managed to get the shuttering ready to churn out the castings.
The next step was to gather soil, sand and aggregate from the various sites that we came across. In fact we always carry extra bags with us to pick up any soil that we find interesting. All the material is duly sieved and graded according to particle size. Backed with a general understanding of the theoretical process, the graded pure mix and the scaled shuttering, it was finally time to get started.
Since I first set my eyes on poured earth construction (PEC) I was intrigued by it and its possibilities. PEC is an easy to understand construction technique that utilizes majority soil with 8 to 10 percent of cement to produce a slurry mixture similar to the consistency of concrete. It has the highest compressive strength amongst all earth construction techniques. Along with the prepared mixture one can even mix pieces of quarry waste and/ or construction debri thereby decreasing the amount of solid filler needed to achieve the desired density and volume. This also increase the amount of usable construction by-product that goes back directly into the new construction.
Along with my team, I started of the PEC models by taking the graded soil, sand and jelly in varying permissible proportions by volume and added a percentage of cement by weight as is specified for this technique. The dry mix was combined to form a consistent mixture and water was added to form a slurry. The shuttering was lubricated with engine oil and the joints sealed with petroleum jelly. We DIY-ed our own vibrator using a drill machine, a pipe and a rod to be used to induce vibrations within the shuttering. At each stage of filling the poured earth into the shuttering, it was vibrated externally and internally till it was done. After checking the water level, it was left to rest undisturbed for 48 hours. After two days the models were deshuttered and cured consistently for a couple of weeks, watering it four times a day and sealing the moisture in with fabric and plastic.
Rammed earth is a construction technique that involves compacting of an earth aggregate mix with a stabilizer. For the rammed earth model the above material was taken in varying permissible proportions by volume and around 5 percent cement was added in by weight. The dry matter is combined to form a consistent mixture and water is added to form a concoction that was dense and plastic. The shuttering was lubricated and the joints were sealed before filling in mix. The mixture was added into the shuttering in stages and rammed at regular intervals. After casting the models, it was left to rest undisturbed for 12 hours while the curing process took a couple of weeks.
Throughout the process a record of the procedure, observations and inferences have been thoroughly documented. Various trials with varying proportions of mix have been experimented with and scrutinized. The results have fuelled the next round of experiments. The engineering of shuttering and vibrators and the designing of custom funnels have been delved into along the way. Over a period of learning and refining the procedure, the results achieved is getting closer to the desired outcomes. My intent is to engage with earth as a material through tactile play and explore its potential as a construction material.