Answer: B) Calcium sulfate dihydrate

Gypsum is a mineral composed of calcium sulfate dihydrate (CaSO₄·2H₂O), widely used in construction for plaster, drywall, and cement additives. It consists of calcium sulfate combined with two water molecules, making it ideal for lightweight and fire-resistant applications.

Answer: C) 30 liters

The water-cement ratio is 0.6, meaning 0.6 kg of water is required per 1 kg of cement. For a 50 kg bag of cement: Water required = 0.6 × 50 = 30 kg. Since 1 kg of water equals approximately 1 liter, the answer is 30 liters.

Answer: B) Within the middle third of beams and slabs

Construction joints are placed in the middle third of beams and slabs to minimize shear stress and ensure structural integrity. This positioning reduces the impact of differential stresses during concrete pouring.

Answer: C) 105 kg/cm²

First-class bricks, as per Indian standards, must have a minimum compressive strength of 105 kg/cm² to ensure durability and load-bearing capacity in construction projects.

Answer: B) Prevent moisture ingress

Damp proofing is applied to walls and floors to prevent moisture penetration, which can cause structural damage and mold growth. Materials like bitumen or waterproof membranes are commonly used.

Answer: C) Both A and B

Both stone masonry and brick masonry are widely used for load-bearing walls due to their high compressive strength and durability. The choice depends on availability, cost, and design requirements.

Answer: A) 30 minutes

The initial setting time of ordinary Portland cement is approximately 30 minutes, as per IS 4031, allowing sufficient time for mixing, transporting, and placing concrete before it begins to harden.

Answer: B) Thin, lightweight structures

Ferro-cement, made of cement mortar reinforced with wire mesh, is ideal for thin, lightweight structures like water tanks, roofing panels, and boats due to its high tensile strength and flexibility.

Answer: B) Uniform color and texture

Good-quality timber should have a uniform color and texture, be free from defects like knots and cracks, and have low moisture content to ensure strength and durability.

Answer: B) Scheduling and time management

The Critical Path Method (CPM) is a project management tool used to identify the longest sequence of tasks in a construction project, ensuring timely completion by focusing on critical activities.

Answer: B) Sieve analysis

The fineness of cement is determined using sieve analysis, typically with a 90-micron sieve, as per IS 4031. Finer cement particles ensure better hydration and strength development.

Answer: B) Modify properties of concrete

Admixtures are chemicals added to concrete to modify its properties, such as workability (plasticizers), setting time (retarders or accelerators), or durability (air-entraining agents).

Answer: A) English bond

The English bond, consisting of alternating courses of headers and stretchers, is widely used in residential buildings due to its strength and stability for load-bearing walls.

Answer: B) Slump test

The slump test measures the workability of fresh concrete by assessing its consistency and flow. A higher slump indicates better workability, suitable for specific construction needs.

Answer: B) Resistance to volume changes

The soundness test, conducted using the Le Chatelier apparatus, ensures that cement does not undergo excessive expansion due to free lime or magnesia, which could cause cracking in structures.

Answer: C) Angular aggregates

Angular aggregates provide better interlocking and higher bond strength with cement paste, making them ideal for high-strength concrete used in structural applications.

Answer: B) Prevent loss of moisture

Curing maintains adequate moisture and temperature in concrete to ensure proper hydration of cement, enhancing strength and durability. Methods include water curing and membrane curing.

Answer: B) Cement plaster

Cement plaster, made from cement and sand, is durable and weather-resistant, making it suitable for exterior walls exposed to rain and temperature variations.

Answer: B) Moisture content

Bulking of sand occurs due to moisture content, which causes sand particles to stick together, increasing volume. This must be accounted for in concrete mix design.

Answer: B) Provide temporary support and shape

Shuttering (formwork) is a temporary mold that holds fresh concrete in place until it hardens, ensuring the desired shape and structural integrity.

Answer: B) M10

M10 concrete mix (1:3:6 ratio) is commonly used for plain cement concrete (PCC) in foundations due to its adequate strength for non-structural purposes.

Answer: C) Concrete

Concrete has excellent fire resistance due to its low thermal conductivity and ability to withstand high temperatures without significant structural damage.

Answer: B) Waterproofing and road construction

Bitumen is a viscous material used for waterproofing (e.g., in damp-proof courses) and as a binder in road construction for asphalt pavements.

Answer: C) Pile foundation

Pile foundations are ideal for black cotton soil due to its high expansiveness and low bearing capacity, as piles transfer loads to deeper, stable soil layers.

Answer: C) 20%

As per Indian standards, first-class bricks should not absorb more than 20% of their weight in water after 24 hours of immersion, ensuring durability and strength.

Answer: C) Sulphate Resisting Cement (SRC)

Sulphate Resisting Cement (SRC) is designed to resist sulphate attacks, making it ideal for marine structures exposed to seawater.

Answer: B) Soil type and compaction

The bearing capacity of soil depends on its type (e.g., clay, sand) and degree of compaction, which determine its ability to support structural loads.

Answer: B) Pitched roof

Pitched roofs have a sloping design that allows water to drain quickly, making them ideal for areas with heavy rainfall to prevent water accumulation.

Answer: B) Enhance tensile strength

Concrete is strong in compression but weak in tension. Reinforcement (e.g., steel bars) is added to enhance the tensile strength of concrete structures.

Answer: A) Excessive water content

Segregation occurs when coarse aggregates separate from the cement paste, often due to excessive water content, leading to non-uniform concrete.