Why this topic is important for ECET?
In ECET Civil, Building Materials is a direct scoring subject. Questions about cement types, properties, composition, brick quality tests appear regularly. These are memory + concept-based, so if you practice well, you can score easy marks quickly. Also, many practical site-related questions come from these basics.
📘 Concept Notes
1. Cement
Definition: Cement is a binding material used in construction that sets and hardens when mixed with water.
Types of Cement:
- Ordinary Portland Cement (OPC): Grades 33, 43, 53 (IS: 269, IS: 8112, IS: 12269).
- Rapid Hardening Cement: Gains strength faster than OPC.
- Portland Pozzolana Cement (PPC): Contains fly ash/pozzolana, good for durability.
- Low Heat Cement: For massive concrete works (dams).
- Sulphate Resistant Cement: Used where sulphate attack is possible (sewage works).
Composition of Cement:
- Lime (CaO) → 60–67%
- Silica (SiO₂) → 17–25%
- Alumina (Al₂O₃) → 3–8%
- Iron oxide (Fe₂O₃) → 0.5–6%
- Gypsum (CaSO₄·2H₂O) → 2–4%
Properties of Cement:
- Fineness → measured by sieve/air permeability.
- Setting time → Initial: 30 min, Final: 10 hrs (IS: 4031).
- Soundness → measured by Le-Chatelier test.
- Strength → tested by compressive strength of mortar cubes.
Example: A 53 grade cement means its 28-day compressive strength is at least 53 MPa.
2. Bricks
Definition: Bricks are building units made from clay, burnt in kilns.
Types of Bricks:
- First class → well burnt, sharp edges, uniform shape.
- Second class → slightly irregular.
- Third class → poor quality, used for temporary works.
- Fourth class → over burnt, used as aggregates.
Properties of Good Brick:
- Uniform color, rectangular shape.
- Should not absorb more than 20% of its dry weight when immersed in water for 24 hours.
- Crushing strength ≥ 3.5 N/mm² (as per IS 1077).
- Hard surface, no cracks.
Tests on Bricks:
- Water absorption test.
- Efflorescence test.
- Compressive strength test.
- Hardness test (scratch test with nails).
Example: A first-class brick immersed in water for 24 hours should not absorb more than 20% of its weight.
⚙️ Formulas
→ Crushing strength of brick
🔟 10 MCQs
Q1. The initial setting time of OPC should not be less than:
a) 10 min
b) 30 min
c) 60 min
d) 600 min
Q2. The main constituent of cement responsible for strength is:
a) Lime
b) Silica
c) Alumina
d) Gypsum
Q3. A 53 grade OPC should have minimum compressive strength (28 days):
a) 33 MPa
b) 43 MPa
c) 53 MPa
d) 63 MPa
Q4. For massive concrete works like dams, which cement is preferred?
a) Rapid hardening cement
b) Sulphate resistant cement
c) Low heat cement
d) Portland pozzolana cement
Q5. Water absorption of first-class brick should not exceed:
a) 10%
b) 15%
c) 20%
d) 25%
Q6. Crushing strength of a good brick is at least:
a) 2.5 N/mm²
b) 3.5 N/mm²
c) 5 N/mm²
d) 10 N/mm²
Q7. The test used to check the presence of soluble salts in bricks is:
a) Hardness test
b) Efflorescence test
c) Water absorption test
d) Soundness test
Q8. Puzzolanic material used in PPC is:
a) Gypsum
b) Clay
c) Fly ash
d) Iron oxide
Q9. The function of gypsum in cement is to:
a) Increase strength
b) Reduce setting time
c) Control setting time
d) Reduce heat of hydration
Q10. If dry weight of brick = 2.8 kg, and weight after water absorption = 3.2 kg, then water absorption % = ?
a) 12%
b) 14.2%
c) 20%
d) 25%
✅ Answer Key
| Q | Answer |
|---|---|
| 1 | b |
| 2 | a |
| 3 | c |
| 4 | c |
| 5 | c |
| 6 | b |
| 7 | b |
| 8 | c |
| 9 | c |
| 10 | b |
🧠 Explanations
- Q1: IS code specifies initial setting time ≥ 30 min → (b).
- Q2: Lime (CaO) is the strength-giving constituent → (a).
- Q3: 53 grade OPC = 53 MPa strength at 28 days → (c).
- Q4: Low heat cement prevents cracks in dams → (c).
- Q5: Max absorption = 20% for first-class → (c).
- Q6: Good brick strength ≥ 3.5 N/mm² → (b).
- Q7: Efflorescence test checks salts → (b).
- Q8: PPC uses fly ash as pozzolanic material → (c).
- Q9: Gypsum prevents flash setting, controls setting time → (c).
- Q10: % absorption = (3.2–2.8)/2.8 ×100 = 14.2% → (b).
🎯 Motivation / Why Practice Matters
In ECET 2026 Civil, questions on cement grades, setting times, brick properties are straightforward scoring. If you master these facts + formulas, you can solve them in 10–15 seconds during the exam. That gives you more time for tougher structural/numerical problems.
👉 Speed + accuracy in such direct theory questions = extra competitive edge.
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