Rammed earth farm house - Soil Testing

Soil

I started looking for suitable soil to build the structure. I stumbled upon a possibly good soil sample. Look and feel of the soil was good. It had lightly rained couple of days before I found the soil. Holding a handful of soil and pressing it made a nice and compact soil ball - which also gave an indication of good soil. Soil had bright red colour indicating no organic content. FYI - soil with organic content is usually dark/black/brown and smells like decayed organic matter. I decided to take this soil sample for further testing.

I did these tests:

1. Mason jar or sedimentation test.
2. Cigar test.
3. Biscuit test.

Soil Test : Mason jar / sedimentation test

I decided to begin with Mason Jar test or sedimentation test. This is a simple test needing little time, effort and material. Take a mason jar with water tight lid. If you don't know what is mason jar - don't worry, use a 1-2 kg/litre sized cylindrical glass bottle/jar with wide mouth as shown in the picture. Don't use fancy shaped bottle because it becomes difficult to see the ratio of different contents after sedimentation. Take soil sample and remove large pebbles from it (don't sieve it though). Put this soil to 1/3rd level in the jar. Pour water up to 2/3rd level of the jar. Close the lid tightly and shake the jar vigorously for few minutes so that soil particles mix well with water. Keep the bottle on a stable surface and wait for 1 minute. Heavy particles like sand settle down within first minute. After that silt particles settle down - within first 30 minutes. Fine clay particles remain suspended further and settle down within first 24 hours. Anything that remains suspended in water is too fine clay particle - ignore that. We should see several clear layers (typically 1-4 layers) of particles indicating how much gravel, sand, silt and clay is present in the soil.

After 10 minutes.

This is the result of the soil sample I picked up.

This picture was taken 10 minutes after shaking the jar. You can see a clear water layer at the top and soil suspended in water at the bottom. Clear water layer indicates there are no fine particles at all. But the soil looked pretty fine. I expected some fine particles to remain suspended in water. But this result does not show fine particles. I thought - may be I did a mistake and did not take right sample or did not shake the jar well when mixing soil sample with water. Therefore I repeated the test with another sample from the same pile of soil.

After 24 hours

Second sample also showed similar result. Clear water layer appeared after 10 minutes. Everything settled down within first 30 minutes leaving almost clear water at the top.

Even then I waited till 24 hours to see whether more particles settle. Nothing happened - it did not show any changes after 24 hours.

Conclusion: No pebbles or large particles in the bottom layer. This soil probably has only sand and silt because it settles very fast. There is no clay in this soil - because if there is clay it should have remained suspended in water for longer duration. Clay is the binder to hold the soil particles together when we ram the soil. Without clay, the wall may not be strong enough to withstand the load (both vertical and lateral) and wear & tear of normal usage. Wall built from soil without clay tends to weather easily. So what to do now? Is this soil unfit for rammed earth walls?

Soil test : Cigar test

Cigar test

Remove pebbles / stone pieces from the soil. Don't sieve it, just hand pick pebbles from some soil; couple of fist full is enough. Mix enough water to make plastic dough. Take a medium lemon size dough ball and roll it between your palms to make cigars. When you push it out of your palm, it bends, hangs and ultimately breaks. It should break between 2-6 inch length. It is considered too sandy if it breaks below 2 inches (too fragile/brittle). It is considered too clayey if it breaks above 6 inches (too sticky). 

My soil sample never went beyond 3-4 inch. Sometimes broke at 2 inches too. Soil is not clayey, it is more sandy/silty. This is largely in agreement with mason jar test.

Soil test : Biscuit test

Prepare soil sample similar to cigar test by removing pebbles / stone pieces. Mix enough water to make malleable dough. Make approximately 2 inch diameter and slightly thicker then quarter inch biscuits.

Biscuit test

First dry them in shade for couple of days and later couple of days in sun so that they dry completely. Keeping them in sun first may lead to cracks since the soil dries too quickly. After the biscuits dry completely, take a biscuit and snap it in 2 pieces with your fingers. Soil is too sandy if it shatters or breaks into too small pieces or crumbles into powder. Soil is too clayey if it is hard to break it. Soil is considered good if it snaps into 2-3 pieces easily. 

My soil sample turned out to be good in this test because it snapped into 2-3 pieces without too much effort.

Soil Composition

Particle ratio of 40% sand + gravel, 40% silt and 20% clay is well suited (all ratios approximate) for rammed earth. Soil is a complex material. Science (science of soil is called Soil Mechanics; you Civil Engineers - remember 2nd/3rd year?) has not been able to understand soil properly because soil does not follow precise scientific rules and formulas. Formulas and rules mentioned in soil mechanics are empirical. Therefore any rule (including the soil composition rule) is only indicative, not deterministic. Therefore soil without having one or more types of these particles or particle types in very different ratios can also make good/acceptable rammed earth walls; especially with some stabilizers like lime or OPC (ordinary portland cement). Lime is used with clayey soils. OPC does not play well with clay because clay is soft and expands when wet. Cement is hard and brittle after setting. Therefore OPC should not be used for stabilizing clayey soil. OPC is best suited for sandy and/or gravely soils. OPC with sandy and/or gravely soil results in soilcrete (like concrete - but with soil instead of gravel and sand [called coarse aggregate and fine aggregate in structural engineering] in concrete).

Proof of the pudding ... rather proof of the wall!

Soil suitability for rammed earth construction can be verified by making a sample rammed earth block and testing it. I made a small box of 12 inch x 5 inch x 5 inch for ramming a test block. Don't jump on me for the unorthodox size - I ended up with this size because I used some wooden boards lying around.

Test block

I was too lazy to cut the boards to regular brick size. Box sides are held with screws so that I can disassemble the box to take the block out after ramming. Well, that turned out to be a bad decision in hind sight because pressure of ramming caused the screws to pull out and the box disassembled itself! After that I made a tourniquet setup to hold the boards of the box tightly in place.

I rammed first block without any stabilizer. Block came out looking well - in the sense there was no shrinkage and no cracks. Probably I ended up using less water than needed while ramming. Therefore this block did not come out that strong. Rammed layers of soil separated and broke when I dropped it on the ground from shoulder height. Conclusion: 1st attempt is a failure. No worries, failures are stepping stones of success!

I stabilized second block with 5% cement. Block looked better than the previous block. Probably I used less water for this block too. I allowed it to cure for 7 days and then dropped it from shoulder height. It fared far better than the block without stabilizer. Rammed earth layers did not separate out when dropped from shoulder height. But the block broke into 2 pieces. Rammed earth layers separated when one of those pieces was dropped from 15 ft. height. Conclusion: 2nd attempt is a moderate success. I told you - first attempt was the stepping stone ;-)

I stabilized 3rd block with 5% cement . I used more water than earlier blocks. After 3 days of curing it is looking really good. I did a drop test after 7 days of curing. Block passed drop tests from shoulder height and 15 ft. height without major damages. What I mean by that is - block was intact, rammed layers did not separate, only the corners got damaged when dropped; which is expected.

Later I had put the third block in the farm under irrigation sprinkler for testing the effect of water on the block. This irrigation sprinkler sprays water every day for 1 hour. I did not find major erosion of the block after keeping it under the sprinkler for 15 days. Looks good and I feel confident of using 5% cement stabilization with little higher water content than usually recommended in rammed earth literature. Slightly more water content is better than less water content. Lower water content does not allow us to compact the soil to needed extent. Higher water content also affects compaction, but not as much as lower water content. Therefore it is ok to have slightly higher water content than lower water content.

Note: After having rammed the whole building, I know slightly higher water content is better for sure. There are instances where my helpers put in little more water. After ramming such soil mixture we found it "sweating". We saw sweating on the inside of the form work when we removed the form work and also on the surface of the rammed wall. It is extra water oozing out of the rammed soil. Later, after curing, I found such walls to be dense and nice. On the other hand, walls with lower water content did not turn up that well. I found them to be less dense and porous. Therefore slightly higher water content is better than lower water content.

Rammed earth farm house - Structure

The structure

I started construction of my house in the farm (farm house) this year (2017-2018). Building will use eco-friendly materials - rammed earth walls and Mangalore tile roof. As famous Indian mud architect Laurie Baker says, house should go back to the earth after we stop living in them (rather ... after we stop maintaining them). Today's fancy concrete buildings remain on earth for thousands of years after people stop living in them. Nature cannot destroy and recycle concrete. Concrete buildings will stand for ever like ghost structures. Unlike the concrete buildings, soil buildings will go back to earth if people stop maintaining them. Almost all the parts of the building (mainly walls and roofing) will weather and go into the soil in few decades if the building is abandoned. Also, another very important feature of soil buildings is - they use very little energy and resources when compared to concrete monsters.

Therefore my home is going to be a soil structure. Different techniques like cob, adobe, rammed earth, and stabilized earth blocks can be used for building soil structure. I decided to use rammed earth because of some advantages with rammed earth. More about advantages of rammed earth will be provided in a future blog article.

Apart from lot of information available on the internet, good reference books for rammed earth structures are:

1. Adobe and Rammed Earth Buildings. Design and Construction. - Paul Graham McHenry, Jr.

 

 2. Rammed Earth Structures, A Code of Practice. - Julian Keable and Rowland Keable

"Keable & Keable" book is the bible of rammed earth. This book is the standard for rammed earth buildings in Zimbabwe (and other African countries I believe). This is expensive book (more you feel so when you see the thickness of the book), but very well worth the price tag because it covers minutest subject areas of rammed earth technique.

By the way - fact that I am a qualified structural engineer helped a lot. My engineering background made it easy to understand the technical terms and techniques mentioned in the books, reference materials, and WWW.

Also, I was the engineer, designer, and contractor for the project. I used Google SketchUp for 3D layout of the building. Basic version is free for personal use. Only catch is - for the reason best known to Google, it is available only for Windows and Mac (no luck Linux users like me). I had to struggle a lot to run it under Wine. Under Linux/Wine it crashes few times in a day. I had to bear it because I don't want to pay for Windows OS or buy a Mac just for using SketchUp.

Foundation trench outlines.

I printed SketchUp drawing layout on paper for the use of building workers. I then used 2 ft long 10mm steel bar (rebar) pieces as stakes to mark the center line on the ground. 18 inch wide foundation trench outlines were marked with lime powder. Stakes and string line tied to the stakes for marking the layout are visible in the picture (click to view full size). Blue/yellow plastic sheets are for covering soil procured for rammed earth walls. White pile of stone pieces on the remote corner is for laying concrete bed for the foundation.

Rammed earth farm house - Intro

Low foot print living

This year (2017-2018) I started construction of my farm house. Laterite stone blocks, portland cement and reinforced cement concrete (RCC) are popular building materials in this place now. All of them are playing havoc with the environment in different ways.

However, the picture was different few decades back. Traveling in the villages shows us the true picture of how the people built their homes. People were using locally available natural building materials. Buildings older than few decades are either cob or sun dried mud blocks (adobe bricks) with thatched roof or Mangalore tile (clay roofing tile) roof.

I am deeply committed to eco-friendly and sustainable life style. Therefore I wanted to build my home with locally available natural materials. I decided to make it a rammed earth structure. Load bearing rammed earth walls and clay roofing using Mangalore roofing tiles.

As famous Indian mud architect Laurie Baker says, house should go back to the earth after we stop living in them (meaning - after we stop maintaining them). Today's modern and fancy concrete buildings remain on earth for thousands of years after people stop living in them. Nature cannot easily destroy and recycle concrete. Unlike the concrete buildings, soil buildings will go back to earth if people stop maintaining them. Almost all the parts of the building will weather and go into the soil in few decades once the building is abandoned.

One important feature of soil buildings is - they use very little embodied energy and resources when compared to conventional structures (like wood, stone, or concrete). Bulk of the material used for the building (which is soil) is taken from the site or transported from nearby area if the soil in the site is not suitable for construction. Compared to this, a conventional structure fetches building material from distant quarries/forests causing large scale environmental destruction in the process and burns precious fossil fuel for transportation adding to the ecological destruction.

Thanks to my farm helpers, lot of heavy physical work has gone into the building. This is how the building looks now. It is not yet complete. I have lot of work to do. I will explain each part of the building in the coming days in a series of articles.

Rammed earth building under construction.

Monsoon season vegetables

Farmer should be self-sufficient. Food is a very important department of self-sufficiency. We are growing our staple food - paddy. Next in the list are vegetables. These are the vegetable crops we planted so far in this monsoon.

A female pumpkin flower
(a bee is busy pollinating the flower - click to see full size image)

Pumpkin (ಕುಂಬಳ/ಚೀನಿ ಕಾಯಿ) creeper
(a colocasia plant and a coconut
plant are seen in the background) 

Growing pumpkin with a smaller one in the background and buds

Colored cucumber creeper (ಮಗ್ಗೆ/ಮೊಗೆ/ಮಂಗಳೂರು ಸೌತೆ ಕಾಯಿ ) 

Large cucumber creeper (ದೊಡ್ಡ ಸೌತೆ/ಮುಳ್ಳು ಸೌತೆ)

Red pumpkin creeper (ಕೆಂಪು/ಗೋವೆ ಕುಂಬಳ)

Bitter gourd creeper (ಹಾಗಲ)

Flame flower/Purslane/Talinum (ನೆಲಬಸಳೆ)

Paddy cultivation

Last year I had written a detailed post about paddy cultivation. This year also we did almost the same - with one change. Decided to bring some old technologies. Brought in Bangarappa's (our farm neighbour and farm helper) traditional skills and his animals for ploughing the field. It is lot of hard work both for human and the animals. But it is far less destructive compared to machines - they burn so much fossil fuel, throw lot of carbon into the air and also over-till the ground damaging the soil biology.

Last year I had borrowed seeds from Bangarappa. I did completely natural farming - I did not use chemicals and fertilisers of any kind. My crop had got some diseases. Plants resisted diseases and grew well. I got one generation of seeds grown without chemicals. Hopefully this year they will improve further in disease resistance and adaptation to local environment.

I should have treated seeds with biological agents like pseudomonas. My bad - I missed it because of my bad planning. I will for sure do it in the next season. I have to wait for one more year for that though :-(

We sowed seeds on 30-Jun. Saplings were transplanted on 16-Jun. We ran out of saplings though because of a minor mistake. Our saplings were little younger than the usual age transplanting. Transplanting workers did not consider that. They planted usual thickness of plants - ending up planting one or two extra samplings in each group. Because of that we ran out of saplings when one small terrace was still to be planted. Thanks to Bangarappa - he borrowed some saplings from another farmer who had some excess saplings and completed the job.

Will keep you posted about how it goes this year.

Monsoon time

It is the time of the year everybody in India is eagerly looking forward to - monsoon time. Monsoon not only brings lot of water; it also brings lot of interesting things (see below). It is the single biggest event of the year for farmers like me because it makes or breaks the plans for the next whole year. Everything gets delayed if monsoon is delayed. Year is ruined because of lack of water if monsoon is short. Lives and property lost if monsoon is in excess. Therefore, our lives hang in fine balance setup by monsoon!

So far (June-2017) monsoon had been disappointing for South India this year. Government statistics say our district (Shimoga district in Karnataka state) had 40% less rain this year compared to long term average. However, it has started raining well in last few days. Hopefully it will pick up now and cover up the shortage in rest of this monsoon season.

Some pictures of this monsoon:

One day came out of the house and found this beautiful orchid on a tree in front of the house. Such a beautiful creation of nature it is. See the close-up for more details of the compound flower. Pictures are not as good as I wanted them to be - continuous rain and less than satisfactory light conditions because of heavy cloud cover interfered with my efforts of taking better pictures.

Orchid in front of the house

Closeup

Very wet conditions created by the monsoon bring up lot of hidden life to visibility. See some amazing fungi found in our farm and around house.

Near our home

White fungi on dead coconut tree in the farm

Red fungi on dead coconut tree in the farm

Monsoon brings in its share of misery too. Here is one example of it - a tree fell on a 11,000 V electricity line bringing down the poles and wires to the ground. Luckily nobody was hurt. Electric equipment in the nearby homes were burnt to charcoal when the 11,000 V line touched 230 V domestic supply lines. Building behind the fallen tree is a school. Kids were inside the school when the incident took place. You can imagine what kind of disaster it would have been if this happened when the kids were walking out of school.

Tree fallen on electric line

Bhoomi Hunnime - day of earth worship

Bhoomi Hunnime is a festival for worshiping mother earth, say sorry for the digging and troubling her all round the year, offer delicacies to her and pray for a good harvest. For western people and people in cities it may look like a meaningless celebration. It is a natural thing and their own extension for people connected with the soil. Mother earth gives birth to us and supports our life in every way. That is why Indian farmers in our villages treat her as mother. This is the time when the crops are about to start flowering and producing grain. Therefore people treat earth as a pregnant lady. They worship her and offer many delicacies to her like we do in case of a pregnant lady. Some of these delicacies are buried in the soil and spread in the soil with the belief that it will satisfy pregnant mother earth's food craving. Even today many Indians don't look at earth as a 50x60 plot or a commodity to sell and buy. Earth is treated with greatest respect as a living being - which it is and it deserves that respect and royal treatment. No wonder, this festival is celebrated in India, the land where every living thing is treated as God. We are not at war with the nature like today's industrial farming, we are one with the nature and treat nature as God.

Mr. Satyanarayana Bhat (foreground) and his wife (background)

This year I got an opportunity to attend some of these celebrations. Some pictures of earth worship are here. See how environment friendly they are - everything is bio-degradable or becomes food for some animal. Even the lamp is made up of coconut shell. This is how we all were few years back. Plastics and chemicals have invaded our lives only in recent years. There is urgent need to reverse the clock and go back few decades. Only then can we live happy and fulfilling life like our ancestors did.

Mr. Kiran (foreground) and his son Tejas (background)

After the worship we ate in the farm and came back. This experience will remain in our memory for a long time.

Environment friendly lamp made from coconut shell

An example of environment conscience our ancestors had. Even the lamp is made from used coconut shell. People use lot of coconut to cook the delicacies for the celebration. One of those shells becomes the lamp :-)