Useful information civil engineering knowledge

📐 Civil Engineering Reference Data

📊 Concrete Grades 📏 Clear Cover ⚖️ Rod Weight 🧱 Design Mix

Site engineer — Quality control at RCC works

1. Concrete Grade & Mix Ratio (Volume batching)

Grade	Mix Ratio (Cement:Sand:Aggregate)
M5	1:4:8
M10	1:3:6
M15	1:2:4
M20	1:1.5:3
M25	1:1:2

2. Clear Cover to Main Reinforcement (Minimum)

Footings : 50 mm

Raft Foundation (Top) : 50 mm

Raft Foundation (Bottom/Sides) : 75 mm

Strap Beam : 50 mm

Grade Slab : 20 mm

Column : 40 mm

Shear Wall : 25 mm

Beams : 25 mm

Slabs : 15 mm

Flat Slab : 20 mm

Staircase : 15 mm

Retaining Wall (on earth) : 20/25 mm

Water Retaining Structures : 20/30 mm

3. Reinforcement Bar Weight per Meter Length

Diameter (mm)	Weight per meter (kg)
6 mm	0.222 kg
8 mm	0.395 kg
10 mm	0.616 kg
12 mm	0.888 kg
16 mm	1.578 kg
20 mm	2.466 kg
25 mm	3.853 kg
32 mm	6.313 kg
40 mm	9.865 kg

💡 Formula: Weight (kg/m) = d² / 162.27 (where d in mm)

4. Common Unit Conversions (Civil Engineering)

1 bag cement = 50 kg

1 feet = 0.3048 m

1 meter = 3.28 ft

1 sq.m = 10.76 sq.ft

1 cu.m = 35.28 cu.ft

1 acre = 43560 sq.ft

1 cent = 435.6 sq.ft

1 hectare = 2.47 acre

1 acre = 100 cent = 4046.724 sq.m

1 ground = 2400 sq.ft

1 unit = 100 cu.ft = 2.83 cu.m

1 square (construction) = 100 sq.ft

5. Design Mix Proportions (per cubic meter)

M10 (1 : 3.92 : 5.62)

Cement	210 kg
20 mm Jelly	708 kg
12.5 mm Jelly	472 kg
River sand	823 kg
Total water	185 kg
Fresh concrete density	2398 kg/m³

M20 (1 : 2.48 : 3.55)

Cement	320 kg
20 mm Jelly	683 kg
12.5 mm Jelly	455 kg
River sand	794 kg
Total water	176 kg
Admixture	0.7%
Fresh concrete density	2430 kg/m³

M25 (1 : 2.28 : 3.27)

Cement	340 kg
20 mm Jelly	667 kg
12.5 mm Jelly	445 kg
River sand	775 kg
Total water	185 kg (adjust for moisture)
Admixture	0.6%
Fresh density	2414 kg/m³

M30 (1 : 2 : 2.87)

Cement	380 kg
20 mm Jelly	654 kg
12.5 mm Jelly	436 kg
River sand	760 kg
Water	187 kg
Admixture	0.7%
Fresh density	2420 kg/m³

M35 (1 : 1.79 : 2.57)

Cement	410 kg
20 mm Jelly	632 kg
12.5 mm Jelly	421 kg
River sand	735 kg
Water	200 kg (adjust with moisture)
Admixture	0.7%
Fresh density	2400 kg/m³

M40 (1 : 1.67 : 2.39)

Cement	430 kg
20 mm Jelly	618 kg
12.5 mm Jelly	412 kg
River sand	718 kg
Water-Cement ratio	0.43
Admixture	0.7%

M45 (1 : 1.58 : 2.26)

Cement	450 kg
20 mm Jelly	626 kg
12.5 mm Jelly	417 kg
River sand	727 kg + bulk age 1%
Water-cement ratio	0.43
Admixture	0.7%

M50 (1 : 1.44 : 2.23)

Cement	450 kg
20 mm Jelly	590 kg
12.5 mm Jelly	483 kg
River sand	689 kg + bulk age 12%
Water-cement ratio	0.36 (188 kg water)
Admixture	1.20%
Micro silica	30 kg
Super flow	6.7% of cement

6. Brick Calculation (1st Class Brick)

Standard brick size: 190 mm × 90 mm × 90 mm
With mortar (10 mm joint): 200 mm × 100 mm × 100 mm
Volume of 1 brick with mortar: 0.2 × 0.1 × 0.1 = 0.002 m³
Number of bricks per 1 m³: 1 / 0.002 = 500 bricks

7. Standard Conversion Factors (Imperial to Metric)

INCH	= 25.4 MILLIMETRE
FOOT	= 0.3048 METRE
YARD	= 0.9144 METRE
MILE	= 1.6093 KILOMETER
ACRE	= 0.4047 HECTARE
POUND	= 0.4536 KILOGRAM
MILLIMETRE	= 0.0394 INCH
METRE	= 3.2808 FOOT
METRE	= 1.0936 YARD

8. Useful Engineering Facts

Rope shape max area: A rope of fixed length covers maximum area when formed into a circle.

Stress conversion: 20 N/mm² = 203.942 kg/cm² (Ratio ~ 1:10.197)

1 Newton = 0.101971 kg

1 mm² = 0.01 cm² | 1 cm² = 100 mm²

1 mm² = 20 N → 100 mm² = 2000 N → 1 cm² = 2000 N ≈ 203.94 kg

📌 Disclaimer: These values are standard references for civil engineering and construction. Always follow project-specific design drawings and codes (ACI, BNBC) for actual site implementation.

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