Civil war sep 25 LSGD

Fly ash obtained from electrostatic separator is

• Coarse
• Relatively fine
• Non-reactive

• none

Answer explanation

Fly ash collected from electrostatic precipitators is in very fine powder form. Its fineness makes it highly reactive (pozzolanic), which is why it is used in cement and concrete.

Homogeneous plastics contain chains of

• Only carbon atoms
• Carbon and oxygen
• Carbon and nitrogen
• Carbon and sulphur

Answer explanation

Homogeneous plastics (like polyethylene, polystyrene) consist of long chains made up of only carbon atoms, giving them uniform properties.

Example of air entraining admixture

• Synthetic detergents
• Calcium chloride
• Gypsum
• Asbestos

Answer explanation

Air entraining admixtures introduce microscopic air bubbles into concrete to improve workability, resistance to freeze-thaw, and durability. Synthetic detergents are common examples.

Accelerators are preferred in

• Hot weather
• Cold weather
• Normal weather
• Frost areas

Answer explanation

Accelerating admixtures are used in cold weather concreting to counteract delayed setting and slow strength gain due to low temperatures.

Pozzolans react with lime in presence of

• Acid
• Water
• Heat
• Sulphur

Answer explanation

Pozzolans are siliceous/aluminous materials that react chemically with calcium hydroxide (lime) in the presence of water, forming compounds with cementitious properties.

Which of the following is incorrect statement

• Steel sections are named according to their cross section shape
• Different categories of standard shape of steel is turned by hot rolling and cold rolling
• Rolled steel sections which are readily available in market due to frequent demand are called regular steel sections
• With increase in carbon content tensile strength reduces but ductility increases

Answer explanation

As carbon content increases, the tensile strength of steel increases but ductility decreases. Hence, the given statement is incorrect.

The specific gravity of mild steel is ?

• 10.5
• 5.6
• 8.1
• 7.8

Answer explanation

The specific gravity (relative density) of mild steel is about 7.8, meaning it is 7.8 times denser than water.

Steel produced by crucible steel process is called

• Blister steel
• Ingots
• Cast steel
• None of these

Answer explanation

In the crucible steel process, steel is melted in clay crucibles and then cast into molds. Hence, the steel obtained is known as cast steel.

Steel having carbon content of 0.25% to 0.6% is known as

• High carbon steel
• Mild steel
• Medium carbon steel
• Dead steel

Answer explanation

Medium carbon steel contains 0.25%–0.6% carbon, giving it a balance of strength and ductility. Mild steel has <0.25% carbon, while high carbon steel has >0.6%.

Which of the following sections are mostly used as columns

• ISHB
• ISLB
• ISJB
• All of the above

Answer explanation

• ISHB (Indian Standard Heavy Beams / H-sections):
  These have thicker flanges and greater load-carrying capacity, making them the most suitable choice for columns. Their geometry provides high moment of inertia and buckling resistance.