• Scarlett Lee

Is it possible to build fabric formed rammed earth with an electric rammer?

Updated: Sep 18

While I have gained earthen construction knowledge and experiences, I have not had a chance yet to use an electric rammer. Have been developing fabric formed rammed earth technology, I have been really drawn to uncover the world of fabric - how durable, versatile, and flexible fabric can be. Despite of that, I have been sceptical about using an electric rammer at fabric formwork for building rammed earth because I assumed that fabric will be easily torn. However, it just turned out that I underestimated the capability of fabric.


From this blog post, I would like to share what challenges I experienced while using an electric rammer for building fabric formed rammed earth walls and the benefits of using it, and also the interesting findings.


What was the challenge of using an electric rammer?

One of the biggest challenges was the weight of an electric rammer. It is too heavy for me to compact soils properly while holding the rammer. Therefore, technicians made the ramming course easier for me by hanging the rammer at a pulley of a gantry. However, the gantry at the research workshop could not go higher to compactsoils properly to build 1-metre-height of rammed earth walls. So, the technician Malcolm hung the electric rammer with a Kevlar strop at the mezzanine level’s balcony. This provided a sufficient space to compact soils up to 1 metre height of rammed earth walls, but the handle of the rammer was higher than my height, so I compacted soils at a raised level. Once the issue of lifting the heavy electric rammer was resolved, the ramming process was much easier since all I had to do was just pulling the rammer to compact soils.



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Building fabric formed rammed earth with an electric rammer

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The heavy rammer was hung at a pulley so that it was easier to compact soils

Another challenge was associated with a pulley at which the electric rammer was hung. Because the intensity of the rope of pulley was controllable - either tight or loose, I had to fasten or loose the bolt of the pulley to change the intensity of the rope when rammer earth walls became higher and when I had to change a rammer head – a long or short one. Because this adjustment took some time, the moisture contents of the mixture was changed quickly if lime-stabilised mixtures are prepared beforehand. Building a fabric formed rammed earth wall for practice, I have got to know what I have to prepare before mixing soil mixtures. The fabric formed rammed earth wall built for practice has come out generally nice but there is a lime-stabilised layer that is not smooth. That is because lime started a chemical reaction hardening the soil components while I adjusted the pulley.


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Fabric formed rammed earth wall built with an electric rammer

It is not a challenge but another important consideration for building rammed earth walls with the electric rammer was how to produce its form making the construction process simple. I asked the technician Paul Charlton to create three different types of rammer heads for me. One with a rectangular head, and the other two had rounded heads – 50cm and 100cm height. For the construction of fabric formed rammed earth walls, it was inevitable to have two different heights of rounded rammers in order to maintain the shape of fabric formwork. (For a manual rammer, it is possible to compact soils by putting hands between the steel frames (or any frames that control fabric), however, for an electric rammer, the handle of the rammer is located at the top, so it is only possible to compact soils above the formwork.)


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Different sizes and shapes of rammer heads for an electric rammer

What was the benefits of using an electric rammer?

The major reason why I has decided to use an electric rammer is for the consistent compaction and quality at rammed earth walls that I am going to build. This is important factor for a comparative test that I am currently working on to compare each wall more exactly by maintaining other factors (e.g., compaction and quality) identical. If rammed earth is built by a manual hammer, it is very much difficult to control its consistent quality because the level of compaction varies according to the condition, mood and strength of builder. For example, a first layer is generally more densely compacted than a last layer of a rammed earth wall because a builder becomes tired.


Another benefit of employing an electric rammer is that it makes the construction process of rammed earth walls less heavily intensive. Although there is an impact on the hands due to prolonged use and vibration, if a builder doesn’t need to lift an electric rammer (such as through a pulley, which I am currently doing this way ), the construction process is easier than using a manual rammer.


The findings

I have found that less water is required for compacting rammed earth with an electric rammer compared to a manual rammer. That is because higher compaction is given by an electric rammer, so that less water is needed, thereby increasing the density of rammed earth walls.


At the next blog post, I am going to showcase the outcome of fabric formed rammed earth wall built with an electric rammer. To keep updated, follow my Instagram or Facebook Page.


https://www.instagram.com/scarlettleearchitecture/


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Acknowledgement

Without a kind help, support and insight of the Minto House Workshop technicians Malcolm Cruickshank, Paul Charlton, and Paul Diamond and my PhD supervisor Chris Beckett, I would not be able to find that it is possible to build fabric formed rammed earth with an electric rammer. I great appreciate their big supports.



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