Which of the below is NOT a property of ferro-cement?
🔬 Understanding Ferrocement
Ferrocement is a type of thin-wall reinforced concrete. It is a composite material made of a rich cement mortar applied over layers of continuous and relatively small-diameter wire mesh. The mesh acts as reinforcement, distributing stress evenly throughout the structure. This unique composition gives it properties that are very different from conventional reinforced concrete. The question asks to identify which statement is NOT a true property of ferrocement.
📝 Detailed Analysis of Properties
(d) Strength per unit mass is low
This is the correct answer because the statement is false. A defining characteristic and major advantage of ferrocement is its exceptionally HIGH strength per unit mass (or high strength-to-weight ratio). Because it uses closely spaced layers of mesh in a rich mortar, it can be formed into very thin, lightweight sections that are remarkably strong and durable. This makes it much stronger for its weight compared to traditional concrete. Since the statement claims the strength per unit mass is "low," it is incorrect and therefore NOT a property of ferrocement.
(a) Impervious nature
This is a true property. The rich cement mortar and dense packing of the mesh create a material with very low porosity. This makes ferrocement highly impervious to water penetration, which is why it's excellent for building boats, water tanks, and roofing.
(b) Capacity to resist shock
This is a true property. The wire mesh reinforcement provides high ductility and allows the structure to bend and absorb impact or shock loads without shattering. This makes it very resilient against dynamic loads and earthquakes.
(c) No need of formwork
This is a true property. The wire mesh acts as a skeleton or armature onto which the mortar is plastered. For many shapes, especially curved ones, the mesh itself is stiff enough to hold the mortar, eliminating the need for traditional, expensive formwork.
📊 Key Properties of Ferrocement
| Property | Description |
|---|---|
| High Strength-to-Weight Ratio | Very strong for how little it weighs. (The opposite of option D). |
| Impervious to Water | Dense structure prevents water from passing through. |
| Impact & Shock Resistance | Ductile nature allows it to absorb impacts without failing. |
| Formwork Not Required | The mesh armature supports the mortar, saving time and cost. |
| Versatility | Can be molded into any shape, especially complex curves. |
💡 Study Tips
- Ferrocement = Strong & Light: The most important thing to remember about ferrocement is that it's both strong and lightweight. This means its strength per unit mass is HIGH.
- Think "Wire Mesh Boat": A classic example of ferrocement is a boat hull. A boat needs to be waterproof (impervious), able to handle waves (resist shock), lightweight, and have a curved shape (no formwork). This helps remember all its key properties.
- Look for the Negative: The question asks what is "NOT" a property. The statement that its strength-to-weight ratio is "low" is the direct opposite of its main advantage.