Building Materials MCQ Questions & Answers | Civil Engineering

Mild steel is a type of steel that is known for its ductility and weldability.
One of the key factors determining the properties of steel is its carbon content.
A higher carbon content makes steel harder and stronger but also more brittle.
Mild steel has a relatively low carbon content, making it a good choice for applications where toughness and formability are important.
The question asks about the percentage of carbon in mild steel.
Option A: Less than 0.25% is the correct answer because this range defines the carbon content of mild steel.
Option B, C, and D represent higher carbon content, leading to different types of steel with different properties (like medium carbon steel or high carbon steel).

Gneiss is a type of rock that forms through a process of metamorphism. Let’s look at the options:

Option A: Igneous rocks → Incorrect. Igneous rocks are formed from the cooling and solidification of molten material, such as magma or lava. Gneiss is not derived from igneous rocks.

Option B: Metamorphic rocks → Correct. Gneiss is a metamorphic rock that is formed when granite or other rocks undergo high pressure and temperature, leading to the formation of distinct bands.

Option C: Sedimentary rocks → Incorrect. Sedimentary rocks form from the deposition of materials over time, such as sand, silt, and clay. Gneiss does not come from sedimentary processes.

Option D: Sedimentary metamorphic rocks → Incorrect. Gneiss is specifically a metamorphic rock, not a combination of sedimentary and metamorphic types.

Therefore, the correct answer is Option B: Metamorphic rocks, as gneiss is derived from the metamorphism of other rocks, typically granite.