Concrete Technology Questions

• Aggregates for concrete — which statements about common rock/brick aggregates are correct? Consider the following statements: (a) Sandstones may be classified as calcareous, siliceous, or ferruginous sandstones. (b) Concrete made with sandstone aggregates tends to crack more due to relatively higher drying shrinkage. (c) Very hard, close-grained crystalline limestones are suitable aggregates but provide low concrete strength. (d) Concrete made with broken bricks can exhibit good fire-resistant qualities. Which option identifies the correct statements?
• Aggregate surface texture — which texture makes an aggregate most unsuitable for concrete? Considering bond, paste demand, and durability, which surface texture generally makes an aggregate the most unsuitable for quality concrete?
• Cement chemistry — primary cause of efflorescence on cement-based surfaces Efflorescence on cement surfaces is mainly caused by an excess of which constituent leading to soluble salts that migrate and crystallize on drying?
• Concrete shrinkage — key dependencies and time effect Which of the following general statements about drying shrinkage of concrete are true?
• Vicat apparatus — standard plunger dimensions used for consistency test In the Vicat apparatus used for standard consistency of cement paste, the plunger has a diameter of 10 mm. What is its standard length (approximate)?
• Design basis — allowable shear strength of concrete depends primarily on which property? In reinforced concrete design, the allowable (nominal) shear strength assigned to concrete sections is primarily related to the concrete’s:
• Air-entrained concrete — design adjustments and property changes When proportioning an air-entrained concrete mix, which of the following are generally true?
• Thermal expansion of concrete — effect of aggregate type How does the coefficient of thermal expansion (CTE) of concrete vary with the predominant aggregate type?
• Water–cement ratio law — what does concrete strength primarily depend on? According to the (Abrams) Water–Cement Ratio Law for workable, plastic concrete, which statement best describes the primary determinant of compressive strength?
• Concrete workability — factors that significantly influence it Which of the following factors affect the workability (ease of mixing, placing, compacting, and finishing) of concrete?
• Water required for hydration only — compute for 500 kg of cement Assume chemically bound (hydration) water demand is 0.23 times the weight of cement. For 500 kg of cement, how much water is required for hydration only (excluding water to fill gel pores)?
• Compressive strength test of cement mortar — identify the incorrect statement (IS practice) Which ONE of the following statements is incorrect for the standard compressive strength test of cement mortar cubes as per Indian practice?
• Aggregates for very high-strength concrete — preferred rock type To obtain very high-strength concrete, which aggregate type from the list below is generally preferred because of its high strength and low porosity?
• Fresh concrete defects — name the separation of water from the mix What is the term for the tendency of freshly placed concrete to expel water that rises to the surface, sometimes carrying fine cement/sand with it?
• Fineness limit for OPC by sieve residue — IS 90-µm (IS Sieve No. 9) An Ordinary Portland Cement, when tested for fineness by dry sieving, should not leave more than what percentage residue on the 90-µm IS sieve (IS Sieve No. 9)?
• Measuring workability of low w/c concrete — suitable field test For concrete mixes with a low water–cement ratio (stiff mixes) where slump may be near zero, which test is more appropriate to assess workability?
• Definition of water–cement ratio — choose the correct expression In concrete technology, how is the water–cement ratio (w/c) defined?
• Mass concrete for dams — maximum nominal size of coarse aggregate In constructing cement-concrete dams (large mass concrete placements), what is the typical maximum permissible nominal size of coarse aggregate used under standard practice and handling?
• Concrete Materials – Permissible compressive strength for Grade M150 (legacy designation) In traditional building materials nomenclature used in some older Indian texts, the concrete grade “M150” corresponds to a characteristic compressive strength of 150 kg/cm² at 28 days. What is the permissible (nominal) compressive strength associated with M150?
• Concrete Technology – Correct combined statement about workability and influencing factors Which of the following statements about water content, aggregate characteristics, temperature, and slump/workability of concrete is generally correct in site practice?