Introduction

Schools provide the space to produce human resources which are required for betterment of the future of the world in all walks of life such as peace, safety, quality of living, technology, knowledge and philosophy. Activities in schools are the most contributing factors for children and their contributions are, in turn, reflected on the whole society. Schools facilities not only provide formal education or knowledge but also contribute to the social development, impartment of livelihood skills and nourishment of social norms. Schools should like the field laboratory where children can see, explore, learn and implement. School is not only a provider of safer places for learning, but it also can act as a center to disseminate culture of safety and how to make environment friendly physical facilities to the communities.

Nepal is planning to build 50000 classrooms by 2015 to meet the Million Development Goal- Education for All. The study shows most o the existing school buildings and construction technology in practice does not consider the indoor comfort level to make classroom child friendly- classrooms are very cold in winter, hot in summer and noisy during rainy season. One of the major factors behind the students’ absenteeism in schools is the extreme indoor climate- extreme hot in Terai and extreme cold in the mountains that ultimately results into permanent drop- out of children from schools.

To address issues of non child friendly classroom environment and to impart quality education to children through Green School, Center of Resilient Development, Actionaid International Nepal and Department of Education (DOE) have adopted Green and climate responsive building construction technology on construction of schools in Nepal. Thus the schools under construction/ constructed in Bardiya, Banke,Kapilvastu, Morang and Dolakha are designed to be climate responsive and environment friendly.

Green School Features:

 Climate Responsive

The school is designed to be relatively more comfortable in all seasons. This is expected to have effect not only on the comfort and health of the children but also on their attendance and academic performance.  International research has shown that classroom temperature directly influence  students academic performance. The classrooms have high ceilings with insulated  roof  prepared of low cost locally available insulation materials like a panel of straw sandwiched between bamboo mat (Chitra or Mandro). It is a thermal asset in the terai that the temperature a few meters below ground remains constant and comfortable at 25° C in all seasons. When it is 42° C in summer this is a source for coolness and yet during winters the same 25° C can also be a source of heat. Hence to benefit from this treasure, the building has a green earth skirt piled up around it in order to better connect it to the underground. This also protects it from the fluctuations of the outside temperature. Where there is no fear of flood the school building can even be built 2 feet below ground level, this also becomes a good source of all the earth needed for the block making etc. In addition to this, the building has most of its glass windows on the south facing wall, which gets all the sunrays in winter but none in summer, as the summer sun stays overhead except during mornings and evenings. Therefore there are no windows on the east and westwalls except ventilations in order to prevent overheating in summer. To protect the building from the autumn sun and rain there are shades over all the windows.

Figure : Direct gain of sun light in cold regions

The heavy thermal mass in the earth walls act like magic. The hot afternoon heat travels inwards and reaches inside the classroom with a time lag of some 12 hours i.e., after midnight when there are no children. Similarly it captures the cool of the night in its mass and makes the classroom cool and comfortable during the day. Earth is also said to have this magical capacity to absorb and release moisture. at night when the temperatures fall the moisture in the air condenses on the earth wall and gives of its heat thus saving it from getting too cold and yet during the day as the temperature rises the reverse happens and the moisture in the wall starts evaporating and thus cooling the walls.

 

Environment Friendly

Unlike conventional schools the CSEB schools need little transportation of material. The blocks need only curing in water and no firing. Hence in the process 8 times less carbon is emitted compared to country fired bricks.  Since the building is climate responsive it would reduce or eliminate the energy needed for cooling and heating. Very little (7%) cement is needed for stabilizing and even this can be replaced by lime which Nepal is said to have in plenty. Lime is carbon neutral and together with earth we get a very clean building material which is healthy for the environment and could earn a significant amount of money in Carbon Credit if this technique is employed at a large scale.

CSEB has these advantages compared to fired bricks:

Pollution emission(Kg of CO2/m2) 7.9 times less than country fired bricks
Energy consumption (MJ) 15.1 times less than country fired bricks

 

Ecological comparison of building materials
Product and thickness No of Units(per m2) Energy consumption(NJ per m2) CO2emission(Kg per m2) Dry compressivestrength (Kg/cm2)
CSEB-24 cm 40 110 16 40-60
Wire Cut Bricks-22 cm 87 539 39 75-100
Country Fired bricks-22cm 112 1657 126 30-100
Concrete blocks-20 cm 20 235 26 75-100

Note: Wire cut bricks are also called Kiln fired bricks. (Source: Development Alternatives 1998)

Earthquake Safe

Nepal is located in an area that is very vulnerable to earthquake hazard. The building is designed as per earthquake safety norms. It has five horizontal tie beams starting from the foundation level ring beam. The others are at plinth level, window sill level, lintel level and finally at roof level. These are made of Reinforced Cement Concrete (RCC) cast inside U shaped CSEB blocks. It also has numerous vertical reinforcements – one at every 1.5 meters length of wall and also on each side of all openings like doors and windows (see photo).

The five horizontal ring beams are tied together by the vertical ties. Together the horizontal and vertical ties make a skeleton like network of reinforcement. The idea is that the metal reinforcements bring ductility (flexibility) to the building and the building is able to absorb a lot of energy before a major damage. In the event of an earth quake it should get cracks but should not collapse and if it has to collapse then it should give enough time to the people to leave the building.

Cost Effective

The cost of a CSEB school building of 80 meter square plinth area comes to roughly NRs 9 lakhs at the end of 2008 (see Annexure), which is comparable to the DOE‘s cost for a conventional school. In fact a significant part of the cost of this building goes towards the steel and cement used for earthquake safety features, otherwise with lower earthquake safety features it would easily be cheaper than the older school design. What is notable is that thanks to its labour intensive nature, out of the NRs 9 lakh, it was possible for the villagers to contribute NRs 1.5 in the form of voluntary labour and some wood, thus the actual cash requirement might be less than in a conventional school.

According to Auroville Earth Institute

CSEB blocks are most of the time cheaper than fired bricks. This varies from place to place and specially according to the cost of cement and sand. The cost break up of a 5 % stabilized block would be roughly as follows, for manual production with an AURAM press 3000:

Labour: 20 – 25 % Soil & sand: 20 – 25% Cement: 40 – 60 % Equipment: 3 – 5 %

In the context of Auroville the following cost comparison was found – A finished meter cube of CSEB masonry is always cheaper than fired bricks: 19.4% less than country fired bricks and 47.2 % less than wire cut bricks (March 2004).

Community Participation, Empowerment, Employment

Being labour intensive technique it offers the possibility of creating employment for thousands of masons and skilled labour provided the project is implemented at a large scale. In this regard the school buildings later could inspire the local population to switch over from polluting and costly materials and that could generate thousands of green jobs for rural youth in their own regions. Due to the known material and technology, maintenance will not be a challenge to the local communities as in other type of construction.

From the educational point of view it could be a process of engaging the community to participate in education in the construction. The resulting sense of ownership is expected to encourage the community to participate in the management of the school thereby ensuring accountability in the education system itself.

Community contribution is encouraged mainly to make community to feel ownership and reduce the overall cost of construction. For this reason the process of this participatory school construction involved meetings, gatherings and orientation sessions with the community at various stages of construction.

Merits of CSEB

A Local Material

Ideally, the production is made on the site itself or in the nearby area. Thus, it will save the transportation, fuel, time and money.

A bio-degradable material

But let’s imagine a building fallen down and that a jungle grows on it: the bio-chemicals contained in the humus of the topsoil will destroy the soil cement mix in 10 or 20 years?

And CSEB will come back to our Mother Earth!

Limiting deforestation

Firewood is not needed to produce CSEB. It will save the forests, which are being depleted quickly in the world, due to short view developments and the mismanagement of resources.

Management of resources

Each quarry should be planned for various utilizations: water harvesting pond, wastewater treatment, reservoirs, landscaping, etc. It is crucial to be aware of this point: very profitable if well managed? Disastrous if unplanned!

Energy efficiency and eco friendliness

Requiring only a little stabilizer the energy consumption in a m3 can be from 5 to 15 times less than a m3of fired bricks. The pollution emission will also be 2.4 to 7.8 times less than fired bricks.

Cost efficiency

Produced locally, with a natural resource and semi skilled labour, almost without transport, it will be definitely cost effective! More or less according to each context and to ones knowledge!

An adaptable material

Being produced locally it is easily adapted to the various needs: technical, social, cultural habits.

A transferable technology

It is a simple technology requiring semi skills, easy to get. Simple villagers will be able to learn how to do it in few weeks. Efficient training centre will transfer the technology in a week‘s time.

A job creation opportunity

CSEB allows unskilled and unemployed people to learn a skill, get a job and rise in the social values.

Market opportunity

According to the local context (materials, labour, equipment, etc.) the final price will vary, but in most of the cases it will be cheaper than fired bricks.

Reducing imports

Produced locally by semi skilled people, no need to import from far away expensive materials or transport over long distances heavy and costly building materials.

Flexible production scale

Equipment for CSEB is available from manual to motorized tools ranging from village to semi industry scale. The selection of the equipment is crucial, but once done properly, it will be easy to use the most adapted equipment for each case.

Social acceptance

Demonstrated, since long, CSEB can adapt itself to various needs: from poor income to well off people or governments. Its quality, regularity and style allow a wide range of final house products.

 

The Raw Material

The basic materials required for the production of compressed stabilized earth building blocks are soil, stabilizer, and water.

Soil

Soil is the main ingredient of the CSEB. Soil characteristics and climatic conditions of an area must be evaluated before manufacturing soil building blocks.. All soils are not suitable for every building need particularly CSEB. The basic material, however, required to manufacture CSEB is a soil containing a minimum quantity of silt and clay so as to facilitate cohesion.It should be much more sandy than clayey.

Good soil for CSEB contains the following proportion of the four components : gravel, sand, silt and clay

 

Gravel Sand Silt Clay
15    % 50 % 15% 20 %

 

Percentage proportion in good soil

Soil Stabilizers

Modifying soil properties by adding another material to improve its durability is called soil stabilization. When a soil is successfully stabilized one or more of the following effects will be evident strength and cohesion of the soil will increase, permeability of the soil will be reduced, the soil will be made water repellent, the durability of the soil will increase, the soil will shrink and expand less in dry and wet conditions.

The chemical admixtures such as lime, cement, and/or fly ash are widely usd as a mean of chemically transforming unstable soils into structurally sound construction foundation. In clay-bearing soils, those stabilizers induce a textural change in greater ease of compaction and handling as well as moderate improvements in the resulting strength.

 

Suitability of stabilizers and their percentage

Stabilizer SUITABILITY MINIMUM % AVERAGE % MAXIMUM %
Cement Mostly for sandy soil 5% 7% No technical maximumEconomic maximum: 9 – 10 %
Lime Mostly for clayey soil 5% 8% 10%

 

Other stabilizers are: Fibers (natural or synthetic), fly ash, natural products (straw, fur, juice of plants, latex, etc.), resins, and synthetic products.

 

Water

Water is one of the important elements in CSEB production but people still ignore quality aspect of this element. The water is required for preparation of CSEB and damp curing during production work. The quality and quantity of water has much effect on the strength of CSEB.

The water used for mixing and curing should be clean and free from injurious quantities of alkalis, acid, oils, salt, sugar, organic materials, vegetable growth and other substances that may be deleterious to bricks, stone, concrete or steel. Potable water is generally considered satisfactory for mixing. The pHvalue of water should be not less than 6.

Production Cycle

 Production Steps

  1. Soil Identification, Selection and Material Collection
  2. Soil Testing
  3. Breaking up Soil
  4. Sieving
  5. Proportioning
  6. Mixing
  7. Moulding CSEB
  8. Curing

 Some Limitations of CSEB

Like all other techniques of construction CSEB also has its own limitations.

  1. Proper soil identification is required; some soils may not be suitable.
  2. Ignorance about the need to manage resources.
  3. Ignorance of the basics for production & use.
  4. Wide spans, high & long building are difficult to do.
  5. Low technical performances compared to concrete.
  6. Untrained teams producing bad quality products.
  7. Over-stabilization through fear or ignorance, implying outrageous costs.
  8. Under-stabilization resulting in low quality products.
  9. Bad quality or un-adapted production equipment.
  10. Low social acceptance due to counter examples (By unskilled people, or bad soil & equipment).

SUB-STRUCTURES/FOUNDATION

There are different types of foundation in practices. In green school project, only the following types of foundation are used.

  1. Rammed Earth,
  2. Stone foundation with soil mortar
  3. Stone foundation with cement mortar

Rammed Earth Foundation

A soil can be compared to an earth concrete. A cement concrete is composed of gravel and sand with cement, acting as a binder. Likewise a  soil is composed of Gravel, Sand, Silt and clay which acts as binder. The main difference between the both is the strength and the stability when wet. Hence to get a stable material when wet and lasting strength, one needs to stabilize the silt and clay. For a Stabilized Rammed Earth Foundation one must use only cement to stabilize the soil and not lime which needs air for the carbonation. Do not use bitumen, which decreases the strength.

 

Figure: Rammed earth foundation

Stone foundation in stabilized soil mortar

They were analyzed taking seven factors into consideration such as cost, cement requirement, possibility of unequal settlement, moisture penetration control, workmanship control, sturdy formwork on side and construction period. On these bases and also due to special consideration of the site being in doubt of water logged, it was decided to use stone work in Stabilized Soil. The foundation sized 70cm depth and75cm width, and the position, size and number of reinforcement are still to be detailed out.

 

Figure: Stone foundation

SUPER STRUCTURES

Basement

  • A RCC ring beamis embedded at the top of the foundation and a plinth beam at the floor level should always be cast.
  • At the top of the foundation is laid a first a reinforced concrete ring beam, 1cement: 1.5 sand: 3 gravel, in which are anchored the vertical ties.
  • It is essential to locate very accurately thevertical ties in the first reinforced concrete ring beam.
  • A plinth beam is laid on the basement and its top level will be the floor level. This plinth beam is cast inUblocks with 1cement: 1.5sand: 3gravel.

Figure : Plinth ring beam

Verandah

Verandah is independent structure that stands in front of class rooms. There is no tie beam below as no severity was realized from earthquake viewpoint. The pillars of the verandah are two-third CSEB and one-third bamboo or timber with strut that supports the roof verandah above. Ramp has been provided for differently-abled children to go to the class-rooms.

Walls

Masonry technology is Reinforced Masonry with Compressed Stabilized Earth blocks. The wall is constructed out of CSEBblocks applying Auroville’s technology. It consists of wall built out of 24cmX24cmX9cm. The wall system has vertical ties at every corner: L-joints and T-joints. Also these are provided on the sides of each fenestration. The continuous wall has vertical tie in every less than 1.5 meters. This is meant for avoiding lateral buckling due to long continuous wall.

There are ring beams in plinth level, sill level, lintel level and roof level. These are connected to the vertical ties to give rigid box effect during earthquake. The ring beams are cast in situ out of U-blocks. The lintels are precast before they are made continuous with the lintel band during actual construction.

All courses should be bound by cement stabilized earth mortar 1 cement: 1 soil: 3 sand. It should beplasticand not too liquid. The soil should not have more than 20-25 % of clay.

Note for all courses: The blocks must be soaked before being laid and a well-laid block isimpossible to remove with one hand because it sticks well to the cement sand mortar.

Doors and Windows

CSEB construction offers a secure and stable wall system. The blocks are stacked using the binding material for the construction of the wall. Provisions for the doors and windows are made as per the requirements in the room.

Types of roof

Three different options for the roofs are proposed. They are:-

  1. Ferrocement Channel
  2. Bamboo Mud Roof
  3. CGI Sheet truss Roof

Ferro cement Channel

Ferrocement is a versatile technology in which there is a more uniform distribution of reinforcement by use of chicken wire mesh and welded mesh encapsulated in rich cement mortar. This composite provides a more uniform distribution of strength properties as compared to RCC. This also enables drastic reduction in section thickness and reinforcement required. This technology does not require stone aggregates. It however uses rich cement: coarse sand (or equivalent material) mix.

What are Ferrocement Roofing Channels?

FerrocementCement (FC)  Channels are precast shell units made with rich cement mortar (1:2 to 1:3) reinforced with a`jali of chicken wire-mesh reinforcement and steel bars.Ferrocement elements are durable, versatile, light and waterproof These shell units are cast either manually on a masonry mould or mechanically on steel moulds mounted on table vibrator. A (FC) channel is a longitudinal element of a curved section (often semi-cylindrical). It is precast usingmoulds. It uses less cement and steel while having the same strength as the same RCC. It is  primarily designed for roofing purposes, either basic roof or intermediate floor.

Figure : Ferro Cement Channel as roofing material

Bamboo-mud roof

In this roofing technology all the materials and labor used are local except small quantities of cement and polythene sheet. Cement will be used for the soil stabilization which will be coated over the roof. The technology is labour intensive.

The roof built at IOE, Pulchowk spans to 5.5 meters without use of truss that would otherwise invite costly non-green steel truss or heavy timber-consuming wooden truss. The solution to this problem is proposed as Trussed Beam. The structural concept behind this is: the timber takes only compression and the steel takes tension. So small cross-section of rafter is sufficient; otherwise flexure beam has to take both compression and tension that demands large cross section.

Figure : Rafter layout plan

Roof Layers details

CGI Sheet Truss Roof

Lattice steel trusses are fabricated from tubular steel sections that are cut, mitred and welded. CGI sheet roof as we all know has advantages like maintenance free, leakage free, fire resistance etc. But it has many defects too. It is extremely hot during summer and scorching cold during winter. Hence false ceiling are provided to maintain indoor comfort level.

Roof Thermal Insulation

Most of the school buildings’ roof in the Nepal are a tin roof (galvanized iron).It is hotter inside the class rooms during summer than the outside and gets really cold in winter. Then in monsoon, when the raindrops clatter on the tin roof, it becomes very difficult to hear, let alone understand, what the teacher is saying.  To minimize the three problem of CGI sheet roofing, a false ceiling with locally available, affordable, natural/sustainable building materials and easy local technology is required. In the green school, CoRD has proposed a false ceiling panel of bamboo mat and straw. In the panel,  two layer of  straw – dry straw and straw with mud on the top are sandwiched between the two locally available bamboo mats called Chitra or Mandro.  Using straw as a insulated false ceiling is increasing used instrawbale Housing in Europe and USA. The details of the panel is as shown in the following figure and photos