Cement in Building Materials – Complete JE Exam Guide | SSC & RRB JE Civil

Building Materials – Cement (JE Exam Complete Guide)

(Chemical Composition, Manufacturing, Types & Tests)

🔹 1. Concept Explanation (Exam-Focused)

1.1 Cement – Basic Definition

Cement is a binding material which sets and hardens by hydration reaction when mixed with water.

JE Focus: Portland cement is hydraulic cement.

1.2 Chemical Composition of Ordinary Portland Cement (OPC)

Gypsum (CaSO₄·2H₂O): Added 3–5% to control setting time.

🔑 Revision Key
👉 C₃S = Early strength
👉 C₂S = Long-term strength
👉 C₃A = Flash set

1.3 Manufacturing of Cement (Dry Process – JE Favourite)

Steps:

1. Crushing & Grinding of limestone + clay
2. Proportioning & Mixing
3. Preheating
4. Burning in Rotary Kiln (1450°C) → Clinker formation
5. Grinding clinker + gypsum
6. Storage & Packing

🧠 Mnemonic: C-M-P-P-B-G-P

1.4 Types of Cement (JE Syllabus Based)

1.5 Tests on Cement

Field Tests

• Color → Uniform grey
  • Touch → Smooth
  • Float test → Should sink
  • Hand insertion → Cool feeling

Laboratory Tests

🔹 2. Important Formulas (Most Repeated)

Standard Consistency

Compressive Strength

📌 JE Repeated Unit: N/mm²

🧠 Short Trick:
👉 Strength = Load ÷ Area

🔹 3. Short Notes / One-Liners

• Initial setting time of OPC ≥ 30 min
  • Final setting time ≤ 600 min (10 hrs)
  • Soundness test → Le-Chatelier / Autoclave
  • Higher C₃A → Faster setting
  • Finer cement → Higher strength
  • Excess gypsum → Delayed setting

🔹 4. PYQ Patterns (SSC / RRB JE)

✅ Most Asked Areas
• Compound responsible for early strength
• Temperature of kiln
• Standard consistency range (26–33%)
• Setting time limits
• OPC grades comparison

⚠️ Traps
• Confusing C₃S & C₂S
• Unit mismatch in strength
• Gypsum % error

🔹 5. Solved Examples

Numerical

A cement cube (70.6 mm) fails at 200 kN. Find strength.

✅ Answer: 40 N/mm²

Conceptual

Q: Which compound causes flash setting?
Ans: C₃A (Without gypsum)

🔹 6. MCQs (Exam Level – 30 Questions)

1. Early strength of cement is due to:
   A) C₂S B) C₃S C) C₄AF D) Gypsum
   ✅ Ans: B – C₃S hydrates fast
2. Gypsum is added to:
   A) Increase strength
   B) Control setting
   C) Reduce heat
   D) Improve color
   ✅ Ans: B – Prevents flash set
3. Kiln temperature is:
   A) 900°C B) 1200°C C) 1450°C D) 1600°C
   ✅ Ans: C
4. Soundness test checks:
   A) Strength B) Fineness C) Setting D) Volume stability
   ✅ Ans: D
5. The compound responsible for long-term strength in cement is:
6. A) C₃S
   B) C₃A
   C) C₂S
   D) C₄AF
   ✅ Ans: C
   📝 C₂S hydrates slowly and contributes to strength after 7 days.
7. Standard consistency of cement generally lies between:
8. A) 15–20%
   B) 26–33%
   C) 35–40%
   D) 40–50%
   ✅ Ans: B
   📝 Most repeated factual question in SSC JE.
9. Which test determines the volume stability of cement?
10. A) Fineness
    B) Strength
    C) Soundness
    D) Consistency
    ✅ Ans: C
    📝 Soundness ensures no excessive expansion.
11. Initial setting time of OPC should NOT be less than:
12. A) 10 min
    B) 20 min
    C) 30 min
    D) 45 min
    ✅ Ans: C
    📝 IS code requirement.
13. Final setting time of OPC should NOT exceed:
14. A) 300 min
    B) 480 min
    C) 600 min
    D) 720 min
    ✅ Ans: C
15. Cement suitable for mass concrete works is:
16. A) OPC
    B) Rapid hardening
    C) Low heat cement
    D) White cement
    ✅ Ans: C
    📝 Reduces thermal cracking.
17. Which cement has maximum C₃A content?
18. A) OPC
    B) PPC
    C) Rapid hardening cement
    D) Sulphate resisting cement
    ✅ Ans: C
19. Fineness of cement is tested by:
20. A) Vicat apparatus
    B) Le-Chatelier
    C) Compression testing machine
    D) Sieve / Blaine method
    ✅ Ans: D
21. The purpose of adding gypsum to cement is to:
22. A) Increase strength
    B) Improve color
    C) Reduce heat
    D) Control setting time
    ✅ Ans: D
23. Which cement is best for marine structures?
24. A) OPC
    B) PPC
    C) Sulphate resisting cement
    D) White cement
    ✅ Ans: C
25. Soundness test is conducted using:
26. A) Vicat apparatus
    B) Le-Chatelier apparatus
    C) Blaine apparatus
    D) Compression machine
    ✅ Ans: B
27. Cement becomes hard due to:
28. A) Evaporation
    B) Oxidation
    C) Hydration
    D) Carbonation
    ✅ Ans: C
29. Heat of hydration is maximum for:
30. A) C₂S
    B) C₄AF
    C) C₃A
    D) Gypsum
    ✅ Ans: C
31. Which of the following increases early strength?
32. A) Higher C₂S
    B) Coarser cement
    C) Higher fineness
    D) Excess gypsum
    ✅ Ans: C
33. OPC 53 grade cement achieves compressive strength of 53 MPa at:
34. A) 3 days
    B) 7 days
    C) 28 days
    D) 90 days
    ✅ Ans: C
35. The standard size of cement cube for strength test is:
36. A) 100 mm
    B) 6 mm
    C) 150 mm
    D) 50 mm
    ✅ Ans: B
37. Which test determines the amount of water required for hydration?
38. A) Setting time
    B) Strength test
    C) Soundness
    D) Consistency test
    ✅ Ans: D
39. Which cement is used for architectural finishes?
40. A) PPC
    B) OPC
    C) White cement
    D) Rapid hardening
    ✅ Ans: C
41. Increase in fineness of cement results in:
42. A) Lower strength
    B) Higher early strength
    C) Delayed setting
    D) Less heat of hydration
    ✅ Ans: B
43. Which is NOT a field test of cement?
44. A) Color test
    B) Float test
    C) Hand insertion test
    D) Soundness test
    ✅ Ans: D
    📝 Soundness is a lab test.
45. The chemical formula of gypsum is:
46. A) CaO
    B) CaCO₃
    C) CaSO₄·2H₂O
    D) Ca(OH)₂
    ✅ Ans: C
47. Rapid hardening cement gains strength equivalent to OPC at:
48. A) 1 day
    B) 3 days
    C) 7 days
    D) 28 days
    ✅ Ans: B
49. Which statement is TRUE?
50. A) C₂S gives early strength
    B) C₃S gives early strength
    C) C₄AF causes flash set
    D) Gypsum increases strength
    ✅ Ans: B
51. If cement shows excessive expansion, it indicates:
52. A) Proper hydration
    B) Unsound cement
    C) Low fineness
    D) Excess water
    ✅ Ans: B
53. Match the following:

1. C₃S → ( )
2. C₂S → ( )
3. C₃A → ( )

1. a) Flash setting
   b) Long-term strength
   c) Early strength

Correct Match:
1–c, 2–b, 3–a
✅ Ans: Correct

30. A cement cube of area 5000 mm² fails at 250 kN. Strength is:
31. A) 40 MPa
    B) 50 MPa
    C) 60 MPa
    D) 25 MPa

✅ Ans: B

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