Rammed Earth Wall

This blog this year definitely has a reason to get me back to writing, so yes, read ahead.

This is about Rammed Earth walls.

The house construction is over. It actually even went through a few alterations based on the feedback from those who looked at the house and based on self-experience. Here are a few points before we start ramming:

• The roof overhanging was shorter than expected, and this meant water entering the house during heavy rains. Especially in the front side of the house that had a lot of Wooden Thoons and the side of the house where there was the wooden frame for the circular window, water is wood's enemy, so the overhanging was extended to about a foot. This meant another row of Roof tiles. We had them in excess, so that was sorted.

• The pressed clay tiles used in the Muttram needed a terracotta coating to prevent algae from growing on them.

• Roof tiles in the joint had a few gaps that leaked during heavy rains; this had to be closed using cement-sand mortar.

The Walls that Excite me

Now that said, I can't wait to talk to you about Rammed Earth walls that we raised.

As a part of the CSEB construction course that I learned from Pondicherry, I also learned the intro to rammed earth construction. We spent a day in Auroville Earth Institute mixing soil and ramming, and the next day we eagerly opened the formwork, and it was a Wow!

Wait, Are you asking me what that means?

Cool, here is an intro:

Rammed Earth Construction is basically making CSEB blocks in a larger size and building a wall as a homogeneous structure, unlike using CSEB blocks and cement-sand mortar to hold them together.

A mix of soil, sand, cement, and water is made (exactly the same as for CSEB). A formwork is created in the region where the wall is to be raised like for concrete but with proper supports on the side. Because unlike in concrete where the weight of the concrete is the only one pushing the formwork apart, here we are about to exert huge pressure on the soil to compact it. Therefore, it is very important to make sure the formwork is as strong and sturdy as your biceps.

The mix that we initially prepared is put into this, spread evenly or made into waves and rammed.

They are rammed.

Rammed.

Rammed.

Rammed.

Till you hear the sound of a bell from the soil.

Not even kidding,

You keep ramming it. It gets dense. Even more dense and sounds like metal. That is when you stop. There are, of course, hints on how to figure it out if you can't really trust your ears, but those details are in the later part of the blog.

So this is totally what happens the first day. The second day you remove the formwork and that's it! The wall is ready.

Let's slowly learn the technicalities behind it.

Why Rammed earth?

Rammed earth is actually stronger than the CSEB construction, well even the brick construction since it's a homogeneous structure. They totally gain their strength through compaction and the little cement added to it through proper curing. They are very similar to CSEB hence sustainable. They do not require burning which saves on fuel and energy.

What are the ingredients?

Breaking big Soil blocks before mixing

• Soil (locally called Gravel, it is found in multiple varieties. It is always best to try out a sample and then proceed with the actual wall)

• Sand or M Sand

• Cement +/ Lime - Usually about 5-6 % cement would be sufficient, but best to try out by working on a sample quantity.

• Water. Consistency is the key here XD. There should just be enough water to hold the particles together and let the cement react. Too much water can be a trouble to ram. The right consistency is that of Rice Flour Cake. If you know the consistency of Puttu (rice flour cake), you know how to mix this well.
  

Formwork

We made a formwork by coupling two plywoods (8’ X 4’). They had to be reinforced on the sides to prevent bending. This was achieved using Steel Pipes. A frame was prepared using Steel Pipes, and in them slots were made. While assembling, through these slots, threaded rods would be inserted and bolted. A PVC pipe could be placed in between the plywoods and the rod could be sent through it to ease the process of removing the rod after ramming.

The setup actually was an experiment as these formwork are actually available but at huge costs in the market.

Annas ramming in Unison

We reinforced them with 3” C Section Pipes, but they turned out very heavy. This meant more manpower to assemble them.

We also had built CSEB Pillars/ Columns at a gap of 8 ft. So this formwork was fit in between them. If we are to do a wall longer than an 8ft span, we might have to work out on a slightly different formwork as the usual size of plywoods is 8’. 2 or more such plywoods would be joined, and if there are no supports (like pillars here) we would have to close the lateral ends too.

Even though the entire formwork stood on its own in between the pillar since they were bolted together and heavy enough, we had planks supporting them on either side.

Workers positioned themselves on the pipes which made it easier to ram. Ramming from an external ladder could have been more difficult.

Creating the formwork was the most challenging, I would say.

Curing

It needs to be cured just like any concrete or brick masonry structure that has cement because we have mixed a proportion of cement and cement needs water to strengthen.

So best to wait till 28 days (the usual curing period) to test the strength. Or we could test after 7 days.

Behind the Scenes

It was a beautiful process. I am not making it up. But it indeed was beautiful.

The night we finished ramming a wall, I was sleepless because I was super anxious about opening it the next day. On my way to the site before opening the formwork, it felt like going to school to collect answer sheets.

And opening was the formwork to see the experiment turn out great was totally worth the hard work and totally a dopamine boost.

We initially experimented by creating a small formwork of 2’ L X 1’W X 1’D.

We tried different proportions of cement and sand, and the first one was a super failure. We added very little cement and no lime. After opening the formwork and letting it cure, we tried hitting it with a hammer and it broke easily.

The second one was strong on hitting, but when washed with water, we were able to see some soil washing away. It would still count to be strong but the durability might not be great.

The next was the successful attempt with about 6% cement and 6% lime. Which is quite high, but didn't want to risk it this time.

By the time we were doing experiments and doing the formwork, I had heard from at least 10 people that it would wash away in the rain.

But, not gonna lie there were helpful worker annas and akkas who trusted the process and helped throughout. They were curious to know how it would turn out and patted on my back when it did turn out great <3

So to all those still doubtful about the woman building a wall with mud, see it stand there - my beautiful fortress wall.