Concrete Technology Questions

• Concrete grade designation — permissible compressive strength for M 200 In the traditional kg/cm² notation, what is the permissible (characteristic) compressive strength associated with concrete grade M 200?
• Mass concrete for gravity dams — expected 28-day cube strength range For mass concrete in gravity dams using aggregates with maximum size about 5 cm, what is the typical 28-day cube strength range adopted in practice?
• Strength development of concrete with time — general trend under proper curing Under normal curing conditions, how does the compressive strength of concrete change with the passage of time after casting?
• Setting control of cement — identify the admixture that increases setting time Which addition is commonly used during cement manufacture to control and increase the initial setting time, preventing flash set during mixing and placing?
• Workability requirement — select the case demanding higher workability In which of the following structural situations is higher workability of concrete especially necessary to ensure full compaction and proper cover?
• Expansion joints in concrete structures — typical spacing trigger In general building practice, expansion (movement) joints are introduced if the overall length of a concrete structure exceeds approximately which value?
• Concrete Aggregates – Key qualities per IS 383 (formerly IS: 383–1963) According to Indian Standard requirements for concrete aggregates, a good aggregate should be chemically inert in cement paste, sufficiently strong to resist loads, and hard as well as durable against weathering and abrasion. Which option best captures these requirements?
• Flakiness Limit – 25 mm passing and 20 mm retained fraction An aggregate that passes the 25 mm I.S. sieve and is retained on the 20 mm sieve is termed “flaky” if its least dimension (thickness) is less than 0.6 times the mean size. What is this threshold value (in mm) for the stated size fraction?
• Cement Testing – Primary use of the Vicat apparatus In cement testing laboratories, the Vicat apparatus is primarily used to determine the standard consistency of cement paste and (with needles) its setting times. For this single-correct question, identify the principal test most commonly associated with the Vicat apparatus.
• Fineness Modulus (FM) classification of sand A natural sand sample has a fineness modulus (FM) of 2.5. According to common grading classifications used in concrete mix design, this sand is graded as:
• Concrete Mix Selection for Retaining Structures For the construction of retaining structures (such as gravity or RCC retaining walls), which nominal concrete mix proportion is most commonly specified in traditional practice for structural work?
• Pozzolanic Materials – Identifying sources with pozzolanic properties Which of the following materials are known to exhibit pozzolanic properties and are used to partially replace cement in blended systems?
• Flakiness Limit – 75 mm passing and 60 mm retained fraction Aggregates passing a 75 mm sieve and retained on a 60 mm sieve are considered “flaky” if their least dimension (thickness) is less than 0.6 times the mean size of the fraction. What is that threshold (in mm)?
• Improving Workability – Effect of common mineral/chemical additions Which of the following additions most reliably improves the workability of concrete (for the same water content), considering typical behavior of each material?
• Volume Box for Aggregates – 35 litre (0.035 m³) measuring box A standard 35 litre measuring box (used for volumetric proportioning of aggregates) should have internal dimensions whose product equals 35,000 cm³. Which set of dimensions below best matches this requirement?
• Cement Choice for Thin RCC Members – which cement should be avoided? For the construction of thin reinforced concrete (RCC) sections where early formwork removal and adequate early strength are desired, which type of cement is generally avoided in standard practice?
• Concrete Fundamentals – identify the most comprehensive correct statement Which of the following statements about concrete behavior and curing is broadly correct under normal site practice?
• Concrete Strength Gain – primary cause Concrete gains strength primarily due to which process during and after setting?
• Workability Classification – slump value of 60 mm If the measured slump of a concrete mix is 60 mm using the standard cone, how would you classify its workability for normal (non-flowing) concrete?
• Water–Cement Ratio Expression – common site convention In many site references, the water–cement requirement is expressed as the volume/mass of water needed per one standard cement bag. This “bag-basis” convention is generally stated per how many kilograms of cement?