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Ferrocement

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Mindmap.pngConcept Map

Archerytarget.pngObjectives

This OER enables you to;

  • Explain that some products can have properties whose values are different from the sum of their constituent's properties.
  • Identify common measures of strength of a material.
  • Recognize the ingredients of ferrocement.
  • Describe essential steps in making ferrocement structure.
  • Identify structures that are made from ferrocement.
  • Explain economic aspects such structures.
  • Locate resources for building of ferrocement articles.
  • Make a ferrocement sheet

Writing.pngIntroduction

You are right to wonder how something can have strength different from those of its parts. Our everyday experience is that a final product is simply the sum of parts that make it. If you add water into milk it simply becomes a little watery milk. Nothing changes, but if you mix water in soil it become a mud. Using mud and bricks we can construct a house. Today we are going to learn the similar technique of construction called ferrocement technique.

Ferrocement – a wonderful material Ferrocement is an engineered material whose strength is very high more than that of its ingredients. The word ‘engineered’ means that it is a manmade material and is not found in nature. It also means that some of its properties, namely strength, have been built into it.

History of ferrocement:

About 150 years ago a Frenchman combined chicken wire mesh, a material that any child can bend, with cement that is really not very strong. But he could make very strong shapes and structures with the combined material. ‘Ferro’ indicates that the material is made up of iron. ‘Cement’ means joins together to become strong.

What is ferrocement?

It is a strong, versatile, low-cost, long-lasting building material made from a wire reinforced mixture of sand, water, and cement.

Properties of ferrocement

Our everyday experience is that big bulky things are more strong than thin things. Ferrocement is a special material called ‘thin membrane’ that is quite strong despite being thin. It's strong under both stress and strain, because it is both strong and thin in nature, many things can be constructed at low cost. Making of ferrocement articles uses more manpower than machines. This makes it especially suitable for India where manpower is relatively cheap. However, for long life, certain precautions must be taken during ferrocement construction.
Ferrocement image-1.png

Tools.gifActivity 1

List the materials that satisfy following criteria:

  • Found in nature
  • Is man-made
  • Manufactured in a factory

2. Highlight properties listed below that are built into ferrocement?

  • Length
  • Thinness
  • Strength

Materials use for making ferrocement

  1. Cement
  2. Sand
  3. Weld mesh/ Bar mesh
  4. Chicken mesh
  5. Water

Steps involved in building ferrocement structures

There are five steps in making a ferrocement structure.

Step-1

An outline of the structure is made from thin mild steel / iron rods.
Ferrocement image-2.png

Step-2

Weld Mesh / Bar mesh attached to this out line
Ferrocement image-3.png

Step-3

A chicken wire mesh layer is attached to this outline.
Ferrocement image-4.png

Step-4

Tie Jute cloth inside the structure with wire / trait
Ferrocement image-5.png

Step-5

Together they are plastered over with a rich cement mortar (mixture of cement, sand and water).
Ferrocement image-6.png

The cement: sand ratio

Firstly the cement sand ratio should be about 1: 3 by volume and not higher. Secondly the cement water ratio should be about 1 : 0.4 Precautions about mortar

  • A bucket can be used to accurately measure out the proportions of sand and cement to get the right ratio.
  • Plastering must be tight and not leave be behind tiny holes from where moisture can creep in.
  • Jute cloth Shattering base is used for a short time to allow wet mortar to be plastered.
  • Too much water must not be mixed.
  • This ensures that the mortar is rich in cement.

Cement consists of three different molecules.

  • When water is added to cement, the three molecules trap water molecules within themselves.
  • This causes the molecules to swell and push against each other.
  • They interlock and that gives cement its strength.

What is Curing?

The slow process of trapping of water molecules inside the other molecules of cement is called curing. Just like all other cement structures, ferrocement also requires curing. Curing is the name used for the process of making water available for cement molecules to absorb them.

Precautions about curing

  1. Though ferrocement structures gain sufficient strength in about one weeks time, curing should be done for about 26 days.
  2. The structure can be covered with jute cloth and periodically the jute wetted with water
  3. Curing the structure 3 times in a day.

Uses of ferrocement

Slabs for safety tank / sock pit, Boats, kitchen cabinets, compound walls, tanks for rain water harvesting, waste management/ vermi composting, fish culture etc. are some of other things being built in India out of ferrocement.

Giftbox.pngSummary

In this OER we learnt about ferrocement technique, history of ferrocement, stapes of ferrocement construction, material use for ferrocement construction what is curing, precaution of curing, uses of ferrocement construction.

Inkpot.png Assignments

Make a ferrocement sheet of given dimension – length – 24” Breadth- 24” thickness- 2”

Book.pngReferences

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