Quick-Revision Formula & Fact Capsules

This chapter condenses the most frequently tested formulas and one-line facts across Civil Engineering technical topics for last-minute revision.

10A.1 Building Materials

OPC heating temperature: ~1450°C. Initial setting time (min): ≥30 min. Final setting time (max): ≤600 min. Standard modular brick: 190×90×90mm nominal. Brick water absorption limit: ≤20% (24-hr immersion). Bulking of sand peak: ~5–8% moisture.

10A.2 Concrete & RCC

M20 = 20 N/mm² characteristic strength at 28 days. Normal RCC slump: 25–75mm. Minimum OPC curing: 7 days. Steel Modulus of Elasticity: ~2×10⁵ N/mm² (200 GPa). Concrete Modulus of Elasticity: ~25–35 GPa (grade-dependent).

10A.3 Surveying

Gunter's chain: 66 ft = 20.12 m, 100 links. Metric chain: 20m or 30m. WCB range: 0°–360°. QB range: 0°–90° per quadrant.

10A.4 Geotechnical Engineering

Gravel: >4.75mm. Sand: 0.075–4.75mm. Silt: 0.002–0.075mm. Clay: <0.002mm. Typical soil specific gravity: 2.65–2.80. Darcy's Law: v = k·i. PI = LL − PL.

10A.5 Hydraulics

Water density: 1000 kg/m³. Water specific weight: ~9.81 kN/m³. Laminar flow (pipes): Re < ~2000. Turbulent flow (pipes): Re > ~4000.

10A.6 Theory of Structures

Simply supported beam, central point load W, span L: Mmax = WL/4 (at centre). Simply supported beam, UDL w, span L: Mmax = wL²/8 (at centre). Cantilever, point load W at free end, length L: Mmax = WL (at fixed support).

10A.7 Transportation Engineering

Indian broad gauge: 1676 mm (5'6"). Typical camber slope: 1.5–3%. Culvert span: generally <6m.

10A.8 Environmental Engineering

BOD standard test: 5 days at 20°C (BOD5). COD is generally higher than BOD for the same sample. Ozone depletion cause: CFCs. Acid rain cause: SO2 and NOx.

10A.9 Exam Pattern Quick Reference

RRB JE negative marking: 1/3 mark per wrong answer. CBT 2 Technical Abilities (Civil): ~100 marks. CBT 2 General Awareness: ~15 marks. CBT 2 Physics & Chemistry: ~15 marks.

10A.10 Practice Set — Formula Capsules (14 MCQs)

1. Steel's Modulus of Elasticity is approximately:
   (a) 2×10⁵ N/mm² (b) 25 GPa (c) 2×10² N/mm² (d) 9.81 kN/m³
2. Indian Railways' broad gauge width is:
   (a) 1000 mm (b) 1435 mm (c) 1676 mm (d) 610 mm
3. For a simply supported beam under UDL w over span L, maximum bending moment is:
   (a) wL/4 (b) wL²/8 (c) wL²/4 (d) wL/2
4. For a cantilever with point load W at the free end, span L, maximum bending moment at the fixed support is:
   (a) WL/2 (b) WL/4 (c) WL (d) WL²/8
5. Standard modular brick nominal size is:
   (a) 190×90×90mm (b) 200×100×100mm (c) 230×110×75mm (d) 250×120×80mm
6. OPC's initial setting time should not be less than:
   (a) 10 minutes (b) 30 minutes (c) 60 minutes (d) 90 minutes
7. Clay particles are classified as those smaller than:
   (a) 0.075mm (b) 0.002mm (c) 4.75mm (d) 1mm
8. Darcy's Law for flow through soil is expressed as:
   (a) v = k·i (b) v = k/i (c) v = k + i (d) v = ki²
9. Laminar pipe flow is generally associated with Reynolds Numbers:
   (a) Below ~2000 (b) Above ~4000 (c) Exactly 3000 (d) Above 10,000
10. BOD is conventionally measured over:
    (a) 1 day at 20°C (b) 5 days at 20°C (c) 10 days at 20°C (d) 30 days at 20°C
11. A Gunter's chain has how many links?
    (a) 50 (b) 100 (c) 150 (d) 200
12. RRB JE applies negative marking of:
    (a) 1/4 mark (b) 1/3 mark (c) 1/2 mark (d) None
13. M25 concrete has a characteristic compressive strength (at 28 days) of:
    (a) 20 N/mm² (b) 25 N/mm² (c) 30 N/mm² (d) 35 N/mm²
14. Typical camber slope on a road surface is:
    (a) 0.1–0.5% (b) 1.5–3% (c) 10–15% (d) 25–30%

Answer Key

1.(a)

2.(c)

3.(b)

4.(c)

5.(a)

6.(b)

7.(b)

8.(a)

9.(a)

10.(b)

11.(b)

12.(b)

13.(b) 14.(b)