BCE Construction & Building Materials 2 — Questions and Answers
Question 1: Which admixture is added to concrete to significantly reduce the water-cement ratio without losing workability?
- Fly ash
- Superplasticizer (Correct answer)
- Accelerator
- Air-entraining agent
Correct answer: Superplasticizer
Superplasticizers (high-range water reducers) allow a 20-30% reduction in water content while maintaining workability.
Question 2: What is the primary purpose of curing concrete after placement?
- To increase aggregate bond
- To prevent carbonation
- To maintain moisture for continued hydration (Correct answer)
- To accelerate setting time
Correct answer: To maintain moisture for continued hydration
Curing keeps concrete moist and at a suitable temperature so that cement hydration continues, developing strength and durability.
Question 3: Structural steel used in US construction is most commonly specified under which ASTM standard?
- ASTM A36 (Correct answer)
- ASTM A500
- ASTM A615
- ASTM A706
Correct answer: ASTM A36
ASTM A36 is the most widely used structural carbon steel standard, with a minimum yield strength of 36 ksi.
Question 4: What does the term 'modulus of rupture' measure in timber or concrete beams?
- Compressive strength
- Shear strength
- Flexural tensile strength (Correct answer)
- Torsional stiffness
Correct answer: Flexural tensile strength
Modulus of rupture (MOR) is the maximum fiber stress at failure in a bending test, representing flexural tensile strength.
Question 5: Which type of brick is most resistant to efflorescence due to its low water absorption?
- Common brick
- Facing brick
- Fire brick
- SW (Severe Weathering) grade brick (Correct answer)
Correct answer: SW (Severe Weathering) grade brick
SW grade brick has the lowest water absorption (≤17%) and is designed for severe weathering conditions, reducing salt migration and efflorescence.
Question 6: In reinforced concrete design, what is the primary function of transverse (shear) reinforcement (stirrups)?
- Resist longitudinal compression
- Confine concrete core and resist diagonal tension (Correct answer)
- Increase flexural capacity
- Reduce shrinkage cracking
Correct answer: Confine concrete core and resist diagonal tension
Stirrups confine the concrete core, resist diagonal tension from shear forces, and prevent buckling of longitudinal bars.
Question 7: Which asphalt mixture design method is most commonly used for heavy-traffic pavements in the United States?
- Marshall Method
- Hveem Method
- Superpave Method (Correct answer)
- French LCPC Method
Correct answer: Superpave Method
The Superpave (Superior Performing Asphalt Pavements) method, developed under the SHRP program, is the current US standard for mix design.
BCE Construction & Building Materials 2
Which admixture is added to concrete to significantly reduce the water-cement ratio without losing workability?