🔶 Concrete Technology
Answer: Common grades are M10, M15, M20, M25, M30, M35, M40. "M" stands for Mix and the number indicates the characteristic compressive strength in MPa at 28 days (e.g., M20 = 20 MPa).
2.Define Workability of concrete and name two tests to measure it.
Answer: Workability is the ease with which concrete can be mixed, placed, compacted, and finished without segregation. Tests: Slump Test and Compaction Factor Test.
3.What is the purpose of Reinforcement in concrete?
Answer: To resist tensile stresses, improve ductility, and control cracking since concrete is weak in tension.
4.Explain Curing and why it is vital for concrete strength.
Answer: Curing is the process of maintaining moisture and temperature in concrete to allow proper hydration. It is vital because it increases strength, durability, and prevents cracks.
5.What is the standard size of a concrete cube for testing?
Answer: 150 mm × 150 mm × 150 mm.
6.What is Creep in concrete?
Answer: Creep is the slow, time-dependent deformation of concrete under sustained load.
7.Define Segregation and Bleeding in fresh concrete.
Answer: Segregation is the separation of coarse aggregates from the mix. Bleeding is the upward movement of water to the surface.
8.What is the difference between Pre-tensioning and Post-tensioning?
Answer: In pre-tensioning, steel is stressed before concrete casting. In post-tensioning, steel is stressed after concrete has hardened.
9.Why is Water-Cement Ratio the most important factor in concrete mix design?
Answer: It directly affects strength and durability; lower water-cement ratio increases strength.
10.What is the initial and final setting time of Ordinary Portland Cement (OPC)?
Answer: Initial setting time = 30 minutes, Final setting time = 10 hours.
🌍 Geotechnical Engineering (Soil Mechanics)
1.Define Void Ratio and Porosity.
Answer: Void ratio = Volume of voids / Volume of solids. Porosity = Volume of voids / Total volume.
2.What is the difference between Compaction and Consolidation?
Answer: Compaction is immediate densification by removing air. Consolidation is gradual volume reduction due to water expulsion under load.
3.What is Bearing Capacity of soil?
Answer: The maximum load per unit area that soil can safely support without failure.
4.Explain the Liquid Limit and Plastic Limit.
Answer: Liquid limit is the water content at which soil behaves like liquid. Plastic limit is the water content at which soil begins to crumble when rolled.
5.What is a Plate Load Test used for?
Answer: To determine the bearing capacity and settlement characteristics of soil.
6.Define Specific Gravity of soil.
Answer: Ratio of density of soil solids to density of water (approximately 2.65).
7.What are the different types of Foundations (Shallow vs. Deep)?
Answer: Shallow foundations include footings and raft. Deep foundations include piles and caissons.
8.When do we use a Pile Foundation?
Answer: When surface soil is weak or loads are heavy.
9.What is Shear Strength of soil?
Answer: Resistance of soil to shear stress or sliding failure.
10.Explain Active and Passive earth pressure.
Answer: Active pressure occurs when soil pushes the retaining wall. Passive pressure occurs when the wall pushes into the soil.
🪵 Fundamentals of Shuttering
1. What is the primary difference between Formwork, Shuttering, and Centering?
Answer: Formwork is the overall mold. Shuttering is vertical formwork. Centering supports horizontal members.
2. What are the three main requirements of a good shuttering system?
Answer: Strength, stability, and watertightness.
3. Name the common materials used for shuttering (e.g., Timber, Steel, Aluminum).
Answer: Timber, steel, aluminum, plywood.
4. What is Staging in the context of formwork?
Answer: Temporary support system to hold formwork in position.
5. Define Deshuttering (Stripping).
Answer: Removal of formwork after concrete gains sufficient strength.
6. What is the role of Shuttering Oil (Release Agents), and why is it used?
Answer: Prevents sticking of concrete to formwork and ensures smooth finish.
7. How does the Water-Cement Ratio of concrete affect the pressure on shuttering?
Answer: Higher water-cement ratio increases fluidity and lateral pressure.
8. What is Mivan Shuttering, and why is it popular in high-rise construction?
Answer: Aluminum formwork system used for fast, repetitive construction with smooth finish.
9. Explain the term Soffit in formwork.
Answer: Bottom surface of slab or beam formwork.
10. What are Props and Jacks?
Answer: Vertical supports used to carry load of formwork.
🔧 Technical Design & Pressure
11. What factors determine the Lateral Pressure exerted by fresh concrete on vertical shuttering?
Answer: Density of concrete, rate of pouring, temperature, vibration.
12. How does the Rate of Pour affect the stability of the formwork?
Answer: Faster pouring increases lateral pressure and risk of failure.
13. What is the effect of Temperature on the time required for deshuttering?
Answer: Higher temperature reduces setting time; lower temperature increases it.
14. Why is Vibration of concrete a risk factor for shuttering failure?
Answer: It increases fluid pressure temporarily on formwork.
15. What is Camber, and why is it provided in shuttering of long-span beams?
Answer: Upward curve to compensate for deflection.
16. Explain the importance of Hydrostatic Pressure in tall column casting.
Answer: Fresh concrete behaves like liquid and exerts full pressure on formwork.
17. What are Tie-Rods and PVC Cones?
Answer: Tie rods hold formwork together; PVC cones maintain spacing and allow removal.
18. Define Dead Load and Live Load acting on formwork.
Answer: Dead load is self-weight; live load includes workers and materials.
19. What is the maximum allowable Deflection in formwork according to standard codes?
Answer: Generally span/270.
20. Why should shuttering be "watertight"?
Answer: To prevent leakage of cement slurry.
⏱️ Removal Times
21. Stripping time for Vertical Formwork?
Answer: 16–24 hours.
22. Props removal for Slabs (≤4.5m)?
Answer: 7 days.
23. Props removal for Slabs (>4.5m)?
Answer: 10 days.
24. Removal time for Beam Soffits?
Answer: 7 days.
25. Props removal for Beams/Arches (≤6m)?
Answer: 14 days.
26. Props removal for Beams/Arches (>9m)?
Answer: 21 days.
27. Effect of Rapid Hardening Cement?
Answer: Reduces stripping time.
28. Why re-propping is needed?
Answer: To support structure until full strength is achieved.
29. What happens if shuttering is removed too early?
Answer: Cracks or collapse may occur.
30. What happens if shuttering is left too long?
Answer: No harm structurally but delays work.
🔩 Steel Reinforcement
1. What does the grade of steel (Fe415, Fe500) signify?
Answer: Yield strength in MPa.
2. Difference between Mild Steel and Tor Steel?
Answer: Mild steel is plain; Tor steel is deformed with better bond.
3. What are TMT Bars?
Answer: Thermo-mechanically treated bars with high strength and ductility.
4. Define Yield Strength.
Answer: Stress at which steel starts permanent deformation.
5. Why steel is used in concrete?
Answer: Similar thermal expansion and high tensile strength.
6. Modulus of Elasticity of steel?
Answer: 200 GPa.
7. Density of steel?
Answer: 7850 kg/m³.
8. Define Ductility.
Answer: Ability to deform without breaking.
9. What are CRS bars?
Answer: Corrosion-resistant steel bars.
10. Maximum Carbon content?
Answer: About 0.25%.
🔗 Lapping & Cutting
21. What is Lap Length?
Answer: Length required to transfer stress between bars.
22. Why not lap at beam center?
Answer: Maximum stress zone.
23. Lap length values?
Answer: Tension = 50D, Compression = 40D.
24. Mechanical Couplers?
Answer: Devices to join bars without overlap.
25. Different diameters in lap?
Answer: Use smaller diameter.
26. Max diameter in slab?
Answer: Generally slab thickness/8.
27. Why stagger laps?
Answer: Avoid weak section.
28. What is BBS?
Answer: Bar Bending Schedule.
29. Steel weight formula?
Answer: D²/162.
30. Standard bar length?
Answer: 12 meters.
