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Building with earth

Realization: work in progress

1. The Auroville experience

Different trials in earth building have been attempted in Auroville with varying success. In 1989, with the creation of the Auroville Earth Institute and the construction of the Visitors' Centre, a new era in earthen architecture started. This Visitors' Centre, of 1200 m, used Compressed Earth Blocks (CEB) and demonstrated the possibilities of earth as a quality building material.

After that, many more projects blossomed: individual houses, clusters of houses, apartments, schools, and the Solar Community Kitchen designed for 1,000 people. The earthen buildings presently amount to 20 to 40% of the total number of buildings constructed in Auroville.

The diversity and quality of techniques and know-how has increased; and thus the demand for and general recognition of the value of this natural building material has risen. Its economic advantage, comfort quality and flexibility is now well established. The Auroville red soil makes for aesthetically pleasing buildings. It gets its colour from iron oxides, the properties of which enhance the already rich composition of this remarkable building material.

Some may say, "Using soils for building will lead to the destruction of nature..." True, if it is done unconsciously, without knowledge; but wrong if one is alert to proper management of resources and the natural balance thereof.

The Auroville Building Centre / Earth Unit lays emphasis on the management of resources, where the quarry is planned first, so as to be integrated in the processing of every development. First of all, one should scrape away and put aside the topsoil, which can be re-used later for agriculture or gardens. Two types of quarries may be developed: deep ones which can be used later on for water harvesting, pools, percolation systems, or shallow ones which can be used for landscape design, work or play areas, gardens and also percolation features, etc.

2. Compressed Earth Block (CEB)

Today, Compressed Earth Block technology is the widest one used worldwide, as well as in Auroville, because it represents a synthesis of traditional practice and modern technology. It is also benefitting from scientific input.

In Auroville, the average results obtained with CEB at 5% cement are () 50 kg/cm2 (5 Mpa) for the dry compressive strength, and () 9% for the water absorption. Local fired country bricks are at () 35kg/cm and () 12%). The Auroville Building Centre has designed a press for CEBs, which is manufactured by Aureka, and sold in India, Africa and even Europe.

3. Rammed earth (PISE)

This technology was used traditionally in countries like France, Morocco, northern India and Tibet, and is today used with stabilisers in USA and Australia. Pis is rammed in forms either manually or pneumatically. Until 1995, Auroville had only one house in raw rammed earth. AV-BC / Earth Unit designed slipping forms adapted to Indian conditions for building the 600m of Mirramukhi School with stabilised rammed earth. Since then, the demand has risen for houses, workshops and other developments using this technique.

4. Roads

AV-BC / Earth Unit is conducting research on soil stabilisation adapted to tropical climate. The aim is to implement roads, where the sub-grade courses and the wearing course are done in a single course, so as to reduce the construction process and cost. The challenge for Auroville is how to implement a quality road with little means and without the usual, incredibly heavy machinery.

5. Buildings, from foundation to roof

Vikas community

From the very beginning of the Vikas settlement in Auroville's residential zone, earth was used in all parts of the buildings, from foundations to roof. The proper management of earth resources has always been the first priority. The quarries where the soil was taken from were planned first. This procedure allowed a perfect integration of the excavations with the buildings and landscape.

Alongside the construction of Vikas, the Auroville Building Centre/Earth Unit researched and developed many appropriate building technologies which used stabilised earth. The first and second developments of the collective kitchen and the ten apartments on two floors could integrate the quarries as garden reservoir and wastewater treatment sites. The soil needed for these developments was already exceeding the volume of excavations, and some soil had to be supplied from elsewhere.

The soil requirement for the third building, which had four floors, was tremendous, and it was not possible to integrate the earth excavation required for the project. This building was planned with a basement floor, which was half underground (1.20m below the original ground level). The volume of this basement floor was equivalent to the volume of soil which was needed to produce the blocks and all the various works of the third building.
Thus, the amount of soil generated by the basement was enough to build 819 m2 (carpet area) on 4 floors.

To protect the basement from the overflow of rainwater, a particular landscape was designed: the immediate surrounding was shaped like a shallow crater to drain rainwater into a percolation pit.

This landscape design generated even more soil than needed. This was used for other projects, which could not implement the concept of a basement floor.

The third building used stabilised earth on four floors, from foundations to roof, and implemented various appropriate building technologies with earth and ferrocement. Some of these technologies were already implemented, on R&D level, for the first two buildings. They were all based on stabilised earth, with 5% of cement by weight. The structure is entirely load-bearing and the walls are 24cm thick from the plinth level to the parapet wall, which is 13.40m higher. Floors and roof used ferrocement channels for the service rooms (bathrooms and kitchenettes) and very flat vaults and domes for the living rooms. These vaults and domes were built with the "free-spanning" technique (without formwork). They were levelled flat with stone slabs that provided a cavity which was used for ventilation.

Training centre of Auroville Building Centre

Since its inception in 1989, the Auroville Building Centre / Earth Unit has been focusing its research & development entirely on building with stabilised raw earth for complete structures. Over the years, various techniques and equipment have been researched, developed and implemented: presses for CEB with 15 different moulds, stabilised rammed earth foundations, composite beams (RCC with U shape CEB), composite pillars (RCC with round hollow CEB), alternative soil stabilisation with homeopathic milk of lime & alum and cement, etc.

The research conducted over the past few years has given interesting results with this alternative stabilisation (combination of lime, alum and cement). The last experiment in this field dealt with waterproofing roofs, and was implemented for the new premises of the training centre.

This Training Centre has been built entirely with stabilised raw earth, from foundation to roof, and even up to waterproofing. It has stabilised rammed earth foundations and walls, plinths with CEB, flooring with CEB tiles, composite beams and pillars, paints and plasters with stabilised earth, vaults with CEB and waterproofing with alternative stabilised earth. A recent and exceptional rainfall, in February 2000, showed the effectiveness of this stabilised earth waterproofing: 402mm rainfall in five days, and no leakage and no dampness inside the vaults!

The moisture measured with an electronic hygrometer gave these results.

MOISTURE

After 402mm rainfall in 5 days

2 weeks after rainfall, under sun

Outside

Inside

Outside

Inside

Vault

100 %

31. 6 %

19. 4%

22 %

Window sill 

59. 8 %

27. 8 %

20 %

21. 8%

 

6. Comparison of building materials in Auroville

It's sometimes said that building with earth is more expensive than building with conventional fired bricks. Probably people are confusing the cost of masonry with the final cost of building, which implies so many variations in design and finish, and which includes the quality of the site management as well as the skill of the builders.

The following tables give interesting information on this issue.

 

Wire Cut Bricks (WCB)

Country Fired Bricks (CFB)

Compressed Earth Block (CEB)

Rammed Earth (RE)

Size of brick (cm) + Volume

23x11x7.3 = 1.95 lt.

20.5x 10x 6.3 = 1.29 lt.

24 x 24 x 9 = 5.18 lt.

(Cast in situ)

Weight of brick

3.4 kg = 1750 kg/m

2.2 kg = 1700 kg/m

9.6 kg = 1850 kg/m

1850 kg/m

Stabilisation

Fire

Fire

5% Cement

5% Cement

Cost per unit on site

Rs. 1.50

Rs. 1.25

Rs. 4.00

-

Wastage

4%

15%

5%

4%

Units per m (raw material)

541

774

193

-

 

Mortar used

1 Cement 6 Sand

1 Cement 6 Sand

1 Cement 6 Sand 6 Soil

-

Qty. of Mortar / m of Wall

61 lt./ m

72 lt./ m

36 lt./ m

-

Units per m of wall

87 (1.5 cm mortar)

112 (1.5 cm mortar)

40 (1 cm mortar)

-

Daily output per team

350 B = 3.65 m

500 B = 4.46 m

170 B = 4.25 m

8 m

Pointing output (m / day)

4 m

4 m

5 m

-

 

Cost of 1 m of raw material

(Including the waste )

Rs. 845 / m

Rs. 1115 / m

Rs. 810 / m

Rs. 810/ m

Cost of mortar per m

Rs. 1135 / m

Rs. 1135/ m

Rs. 610/ m

-

Cost of wall per m

Rs. 1520/ m

Rs. 1700 / m

Rs. 1215 / m

Rs. 810 / m

Cost of wall per m

Rs. 345 / m

(23 cm. thick)

Rs. 348 / m

(20.5 cm. thick)

Rs. 295/ m

(24 cm. thick)

Rs. 195 / m

(24 cm. Thick)

 

Pollution emission (CO)*

39 Kg / m

126 Kg / m

16 kg / m

16 Kg / m

Energy consumption (wall)*

539 MJ / m

1657 MJ / m

110 MJ / m

110 MJ / m

Dry Crushing Strength

() 90-120 kg/cm

() 30-40 kg/cm

() 40-60 kg/cm

() 40-60 kg/cm

Water absorption

9 11%

10 14%

9 - 11%

8 10%

 
Notes

* Source: Development alternatives, New Delhi 1998

 Value October 2000: 1 US $ = 42.5 Rs.

Country fired brick is also called village brick

  Wire cut brick is also called kiln-fired brick.

The material cost includes the delivery on site.   The CEB price is the production cost on site. All costs are cost price.

DATA

Sand  = 700 Rs./ 4.5m3 lorry

        200 Rs./ m sieved

Mason

= 120 Rs./ day

Team for bricklaying

= 1 mason, 2 helpers (M +F)

Male helper

=   65 Rs./ day

Team for rammed earth

= 5 labourers

Soil    = 50 m dug & sieved

Female helper

=   40 Rs./ day

Team for CEB making

= 9 block makers

Cement = 155 Rs./ bag

(L & T 53 grades)

Labourer

=   67 Rs./ day

Team for pointing

= 1 male helper

RE labourer

Block maker

=   75 Rs./ day

=   75 Rs./ day

 

 

 

 

SUMMARY

MONETARY COST

STRENGTH

ENVIRONMENTAL COSTS

Per m3, a finished CEB wall is

28.5 % cheaper than country fired bricks.

20 % cheaper than wire cut bricks.

Per m3, a rammed earth wall is

33.3 % cheaper than a CEB wall.

52.3 % cheaper than country fired bricks.

46.7 % cheaper than wire cut bricks.

CEB and rammed earth are:

42 % stronger than country bricks.

52 % weaker than wire cut bricks.

CEB and rammed earth present:

Pollution emission

2.4 times less than wire cut bricks.

7.8 times less than country fired bricks.

Energy consumption

5 times less than wire cut bricks.

15 times less than country fired bricks.

             

7. A material for the future

Building with earth is definitely an appropriate and cost & energy efficient technology that has a great future. However, one has to master the disadvantages of the material. These are usually caused by variations in the soil quality, and hence the block quality may suffer. Bad quality soil can give relatively poor characteristics (when compared to concrete) and shrinkage cracks may occur.

Among the advantages of earth as a building material, one observes:

  • Earth is a local material, contributing to sustainable development.

  • Production of the building components utilises a lot of semi-skilled manpower.

  • The technology is easily adaptable and transferable.

  • The energy & monetary costs are much lower than with most other materials.

  • The thermal comfort and 'vibratory' atmosphere are very positive.

Obviously, one has to master the materials and techniques so as to obtain the optimum possibilities with a harmonious, durable, agreeable and efficient architecture!

Nevertheless, the following drawbacks have to be considered:

  • Mechanical qualities less regular.

  • Sensible building details.

  • Constraint to organise and manage the production of one's own building material on the site.

Challenge

Building with earth has a great past, but also a promising future, especially in Auroville. It is a true challenge to realise an architecture full of light, suppleness, simplicity, imagination and beauty with a dark, heavy and formless mud. In Auroville we're working on it.

For further details, please contact:
the Auroville Earth Institute, eamil:   earthinstitute@auroville.org.in 

Website: http://earth-auroville.com

 

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