What is the primary function of cement in concrete?
Cement acts as a binder that hydrates and binds fine and coarse aggregates together to form a solid mass.
According to IS 456:2000, what is the standard cube compressive strength test age for concrete?
IS 456:2000 specifies 28 days as the standard curing age for determining the compressive strength of concrete cubes.
Which type of cement is used for underwater construction?
SRPC (Sulphate Resisting Portland Cement) is used for underwater and marine structures to resist sulphate attack.
What is the water-cement ratio for M20 grade concrete as per IS 456:2000?
For M20 concrete, the maximum water-cement ratio is 0.55 to achieve the specified 28-day compressive strength.
Which of the following is NOT a type of aggregate used in concrete?
Rigid aggregate is not a standard classification. Aggregates are classified as coarse, fine, and lightweight based on size and density.
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What is the recommended slump for RCC columns according to IS 456:2000?
For RCC columns, the recommended slump is 25-50 mm to ensure adequate compaction and workability.
Hydration of cement produces which of the following as main products?
CSH (Calcium Silicate Hydrate) and CH (Calcium Hydroxide) are the main hydration products that give strength to concrete.
What is the minimum concrete cover for reinforcement in foundations as per IS 456:2000?
IS 456:2000 specifies 50 mm minimum concrete cover for reinforcement in submerged/buried foundations.
Which of the following factors increases the compressive strength of concrete?
Pozzolanic materials like fly ash and silica fume react with calcium hydroxide to improve strength and durability.
What is the nominal maximum size of coarse aggregate for concrete beams?
For reinforced concrete beams, nominal maximum coarse aggregate size is typically 20 mm to ensure proper placement around reinforcement.
Which standard specifies the code of practice for plain and reinforced concrete in India?
IS 456:2000 is the Indian Standard for plain and reinforced concrete - Code of Practice.
What is the typical strength gain pattern of concrete in the first 28 days?
Concrete gains approximately 40-50% strength in 7 days due to rapid hydration, then strength gain slows down gradually.
Which chemical compound in cement causes flash setting when exposed to water?
C3A reacts rapidly with water and is responsible for flash setting. Gypsum is added to control this reaction.
For a M25 grade concrete, what is the approximate 28-day compressive strength?
M25 designation means the concrete will achieve 25 MPa minimum compressive strength at 28 days with 95% probability.
What is the effect of adding admixtures like retarders in concrete?
Retarders delay the setting time of concrete, allowing more time for placement and compaction in large structures.
According to Abrams' Law, the relationship between w/c ratio and compressive strength is:
Abrams' Law states that compressive strength decreases exponentially with increase in water-cement ratio.
What is the recommended curing period for concrete in normal conditions?
IS 456:2000 recommends minimum 14 days of moist curing for normal Portland cement in normal temperature conditions.
Which of the following is a measure of concrete workability?
Slump test is the most common field test to measure the workability and flow characteristics of fresh concrete.
Self-compacting concrete (SCC) must achieve a slump flow of:
SCC requires slump flow between 600-800 mm to flow and compact under its own weight without vibration.
