VITA - Volunteers in Technical Assistance

Understanding Small-Scale Brick Making - 01 جنوری 1990

Sun-dried earthen blocks (adobe) have been used as a building material for thousands of years, especially in very dry areas. Clay is mixed with water, and sometimes straw to keep the finished blocks from cracking, and formed by hand into blocks. The blocks are placed in the sun until they are thoroughly dry. The dried blocks are hard, but they soften and come apart in heavy rains.

The invention of more durable "fired" or baked brick was an event of enormous importance. Nearly 7,000 years ago people discovered that exposing clay to high heat would convert it to a hard, glassy material (called ceramic, from the Greek word for earthenware pottery). The first ceramic materials were cooking vessels and figurines; eventually, about 3,500 years ago, the technology was applied to building blocks.

Like sun-dried blocks, fired bricks were modular and easily handled. But fired bricks were very hard, as well as resistant to attack by weather and fire. They were usually cheaper than stone and often could be manufactured close to building sites. Firedbrick technology made it much easier for people to make durable buildings, walls, roads, and bridges. The Romans combined brick with concrete and developed new kinds of buildings. New kinds of cities, political institutions, and arts flourished. Today, extended and refined ceramic technology produces not only building materials, but special porcelains, glasses, and even such electronic devices as radio transistors and computer chips. Although bricks are flat and rectangular, their relatively small size and irregular surfaces require the use of mortar for assembly into walls and other structures. Mortar is an adhesive made of cement, lime, and sand, to which water is added at the time of use to make a paste. It hardens in a few hours.

Today, 65 percent of the bricks made in the world are used for dwellings; 35 percent are used for walls, public buildings, and other non-dwelling structures. In addition to common or ordinary building bricks, there are glazed and other decorative bricks and special "firebrick," designed to protect surfaces from intense heat. Bricks can be manufactured by large automated factories; they can also be made on a small scale by one or two families working together in a rural setting. This paper describes the small-scale manufacture of ordinary bricks.

Building bricks are made with clay and water, and fired with locally available fuels. Strenuous physical work is involved. The rewards, on the other hand, are enormous. Durable housing that resists the elements generates a feeling of purposefulness and security to those so sheltered. The comfort and improved health that comes with living in a dry house, one that holds warmth in cool weather or remains cool in the hot sun, reward the hard work involved.

Understanding Stabilized Earth Construction - 01 جنوری 1984

Soil is one of the oldest building materials. It has been used for centuries in all parts of the world. Ancient temples, fortifications, and pyramids as well as part of the Great Wall of China were built with soil.

The three traditional methods of soil construction are:

1. adobe block or lumps built up into walls; adobe is sun-dried soil mixed with stabilizers such as straw or rice husks to strengthen the soil;
2. wattle and daub: interwoven timber, saplings, or bamboo daubed with mud; and
3. rammed earth: soil mixed with stabilizers and subjected to high pressure.

Pure soil--whether molded into a block, i.e., adobe brick, or cut as a slab, i.e., sod--is technologically suitable for home and commercial construction. It can be used in combination with timber frames or stone. No soil additives are used in this process.

Stabilized soil, a product of scientific research, offers medium- and high-technology soil options. Unfortunately, local conditions will determine its applicability to your situation. Stabilized earth may not be appropriate unless stabilizing additives, technical assistance, and machinery are available and affordable. Simple adobe or rammed-earth may be preferable.

Medium technology can produce soils usable for road beds, airport runways, shoulders, road surfaces, and storage and parking areas. Higher technology options include: sub-bases for concrete pavings, drainage ditches, canals, dike surfaces, reservoir linings, and multi-story foundations.

Depending on the level of technology available, soil can serve as a basic resource. It is suitable as a universal building material. Many types of soil are relatively accessible, removable, and mixable. High technology increases its uses.

Stabilized Earth Construction - 01 جنوری 1987

Soil is a universal building material and is one of the oldest known to humanity. Simple soils (without additives), or soils improved by adding stabilizing materials such as bitumen or cement, are suitable for homes, schools, roads, and other construction.

For construction purposes, soil is usually formed into blocks. Two general types of blocks are described here: adobe block and stabilized earth block formed under great pressure. Adobe blocks are made from moistened soil that may be mixed with straw or other stabilizers. They are formed without pressure and usually cured in the sun. Stabilized earth blocks (sometimes called rammed earth blocks) are made from soil mixed with stabilizing material such as Portland cement, formed into blocks under high pressure, and cured in the shade.

Low cost is a primary advantage of soil block construction. An overall cost reduction of about 50 percent over conventional construction can be realized. Other advantages are that building materials are usually readily available and little skill and training are required for their use. The material is culturally acceptable in nearly all countries, including the United States.

Making Building Blocks with the CINVA-Ram Block Press - 01 جنوری 1977

This manual combines the experience of four men who used the CINVA-Ram Block Press and figured out answers, bit by bit, to the inevitable problems of detail as they came up day after day. That was the hard way to learn how to use the press; this handbook is intended to make it easier.

Understanding Ferrocement Construction - 01 جنوری 1988

Ferrocement is a building material composed of a relatively thin layer of concrete, covering such reinforcing material as steel wire mesh. Because the building techniques are simple enough to be done by unskilled labor, ferrocement is an attractive construction method in areas where labor costs are low. Sand, cement, and water usually can be obtained locally, and the cost of the reinforcing material (steel rods, mesh, pipe, chicken wire, or expanded metal) can be kept to a minimum. There is no need for the complicated formwork of reinforced cement concrete (RCC) construction, or for the welding needed for steel construction. Virtually everything can be done by hand, and no expensive machinery is needed.

1-Kw RIVER GENERATOR - 01 جنوری 1980

The plan presented here is a detailed description of a 1-kilowatt (1-kW) generator unit, which was prepared in 1971. The plan is scheduled to be revised and updated in the near future in order to incorporate additional data. At the time, this plan was prepared, the generator had not been built on the scale shown here. Therefore, until such time as testing results can be integrated into the plan, VITA offers this material as an idea paper.

Small Michell (Banki) Turbine - 01 جنوری 1980

The Michell or Banki turbine is a relatively easy to build and highly efficient means of harnessing a small stream to provide enough power to generate electricity or drive different types of mechanical devices.

The turbine consists of two main parts - the runner, or wheel, and the nozzle. Curved horizontal blades are fixed between the circular end plates of the runner (see page 17). Water passes from the nozzle through the runner twice in a narrow jet before it is discharged.

Once the flow and head of the water site have been calculated, the blades of the 30cm diameter wheel presented here can be lengthened as necessary to obtain optimum power output from the available water source.

The efficiency of the Michell turbine is 80 percent or greater. This, along with its adaptability to a variety of water sites and power needs, and its simplicity and low cost, make it very suitable for small power development. The turbine itself provides power for direct current (DC); a governing device is necessary to provide alternating current (AC).

Understanding Hydropower - 01 جنوری 1984

Once it is understood that gravity and water can be harnessed to produce energy, a study of methods to extract this energy efficiently can be undertaken. The purpose of this paper is to discuss several such methods in general terms. The paper provides a basic introduction to the science of water power (hydropower), along with an overview of state-of-the-art technology. It also discusses the sequence of events from initial surveys to end results to provide a well-rounded understanding of the use of hydropower. Although there are other methods, this paper focuses on turbines and waterwheels.

Understanding Mini-Hydroelectric Generation - 01 جنوری 1985

Electricity can be generated from the power of flowing water. This is called hydroelectric generation, and it can be done anywhere that there is water and a hill or drop for it to run down--in an irrigation canal, where a river runs through rapids or over a waterfall, or where a dam has backed up water above the level of the river. Hydroelectric generating plants come in many sizes --from huge plants that produce more electricity than most countries can use, to very small plants that supply electricity for a single house. Hydroelectric plants which supply electric power in the range from about 15 kilowatts to 15,000 kilowatts are called mini-hydroelectric or mini-hydro. Other phrases that mean the same thing are "small-scale hydro" and "small hydro."(*)

Fifteen kilowatts is about the amount of power used by seven or eight houses in the industrial countries, or by a very small manufacturing plant, or it can provide lighting and other basic services for a village of 50-80 houses. Fifteen-thousand kilowatts is enough for a medium-sized town. Hydro plants which are larger than 15,000 kilowatts are usually called "large hydro" or "conventional hydro" plants, but there is no sharp line dividing "mini-hydro" from "large hydro." All mini-hydro and large hydroelectric plants use similar machinery, and work in the same way. Plants of either type need specially manufactured machinery, and must be designed by trained engineers. Both types of plants are also fairly expensive. Because of this, mini-hydro plants are not well-suited to village-level development in most cases--a larger organization such as a town, a collection of villages, or an industrial plant is usually needed.

Understanding Micro-Hydroelectric Generation - 01 جنوری 1985

The power of flowing water can be used to generate electricity, or to do other kinds of useful work. Generating electricity in this way is called hydroelectric generation. It can be done anywhere that there is water and a hill or drop for it to run down, such as a drop in an irrigation canal, a place where a river runs through rapids or over a waterfall, or where a dam has backed up water above the level of the river, to name just a few examples. Hydroelectric generating plants come in all sizes--from huge plants that produce more electricity than most nations can use to very small plants that supply electricity for a single house. The smallest hydroelectric plants are often called micro-hydroelectric plants, or micro-hydro for short. Larger plants are usually called mini-hydro plants. Other names for this size of plant are "small-scale hydro" and "small hydro."

This report deals only with micro-hydroelectric plants. Microhydro is usually defined as having a generating capacity of up to about 15 kilowatts (KW). This is about enough power for 6 or 8 houses in a developed country, or it can provide basic lighting and other services to a village of 50 to 80 houses. Micro-hydro generation is best suited to providing small amounts of power to individual houses, farms, or small villages in isolated areas. Mini-hydro systems are larger. They can range from about 15 KW up to 15,000 KW, which is enough electric power for a medium-sized town, or for a whole rural region. However, the difference between mini-hydro and micro-hydro plants is not just size.