## What is concrete

Concrete is a main and important **structural material** in construction, it is a mixture of **cement**, fine aggregate (sand), **coarse aggregate** (stone), and **water**. Concrete consists of a hard, chemically inert particular substance.

## What is the design mix?

There are different types of design mixes used in concrete. design mix means, selecting the **suitable materials** (cement, fine aggregate, coarse aggregate) and the material determining their relative proportion to produce concrete having minimum **workability, durability, and strength** of the concrete as **economically **as possible.

### Example

M25 design mix of concrete The ratio of the mix = 1:1:2 (1 part of cement, 1 part of fine aggregate, 2 parts of coarse aggregate )

M25- the compressive strength of the concrete cube after 28 days of curing is 25kn/m3

**M** – mix and compressive strength of concrete cube after 28 days of curing

**25** – compressive value (25 N/mm3)Cube dimension = 150mm x 150mm x 150mm (or) 100mm x 100mm x 100mm

## Different types of design mixes and their ratio

**Nominal grade concrete**

Concrete grade | Concrete mix ratio | Compressive strength (n/mm2) |
---|---|---|

M5 | 1:5:10 | 5 |

M10 | 1:3:6 | 10 |

M15 | 1:2:4 | 15 |

M20 | 1:1.5:3 | 20 |

**Standard grade concrete**

Concrete grade | Concrete mix ratio | Compressive strength (n/mm2) |
---|---|---|

M25 | 1:1:2 | 25 |

M30 | Design mix | 30 |

M35 | Design mix | 35 |

M40 | Design mix | 40 |

M45 | Design mix | 45 |

**High strength concrete**

Concrete grade | Concrete mix ratio | Compressive strength (n/mm2) |
---|---|---|

M50 | Design mix | 50 |

M55 | Design mix | 55 |

M60 | Design mix | 60 |

M65 | Design mix | 65 |

M70 and above | Design mix | 70 and above |

## Materials required for 1m3 M20 nominal mix concrete

### M2O MIX

M20 = 1:1.5:3 (cement: fine aggregate: coarse aggregate )

#### Cement

= ((part of cement) / (sum of ratio)) x total volume required

Part of cement = 1

Sum of ratio = (1+1.5+3) = 5.5

The total volume required = Wet volume x dry volume

Wet volume = Actual required volume, Dry volume = 1.54 (for concrete)

**What is dry volume? why 1.54 in concrete? CLICK HERE**

Total volume = ( 1 x 1.54 )

= 1.54 m3so, = ( 1/5.5 ) x 1.54= 0.28 m3

Unit weight of cement = 1440 kg/m3

= 0.28 x 1440 = 403.2 kg

**What is the unit weight? 1440? CLICK HERE **

1 bag cement = 50kg = 403.2 / 50

= 8.064 ~ 8 bags or 8.1 bag

#### Fine aggregate

= ((part of fine aggregate) / (sum of ratio)) x total volume required

= ( 1.5/5.5 ) x 1.54= 0.42 m3 (or) 14.83 cubic feet

**Unit conversions? CLICK HERE**

**Unit weight of F.A** = 1600 to 1840 kg/m3 take 1600 kg/m3= 0.42 x 1600=672 kg of fine aggregate required

#### Coarse aggregate

= ((part of coarse aggregate) / (sum of ratio)) x total volume required= ( 3/5.5 ) x 1.54 = 0.84 m3

**Unit weight of C. A** = 1200 to 1750kg/m3 ( density of coarse aggregate may go **higher** if void spaces decrease. **5mm coarse aggregate** has more density when compared to **20mm size coarse aggregate** )

= 1450 to 1750kg/m3 ( ASTM ) **American society for testing and materials **

so, assume = 1560 kg/m3 = 0.84 x 1560= 1310.4 kg of coarse aggregate required

#### Water

Assume water-cement ratio = 0.50 ( 50% of cement )= 403.2 x 0.50 = 201.6 kg= 201.6 liter ~ 200 (or) 201 liter of water required

#### Summary

Materials required for 1m3 of M20 concrete

- Cement = 8 bags (1 bag = 50kg)
- Fine aggregate = 672 kg
- Coarse aggregate = 1310.4 kg
- water = 200 litre

**Concrete Materials Calculator ( Cement, Fine aggregate, Coarse aggregate, and Water ) – ” Click Here “**

## Materials required for other design mixes in 1m3

### M5

- Cement = 2.60bags
- Fine aggregate = 752 kg
- Coarse aggregate = 1466.4 kg
- water = 65 litre

### M7

- Cement = 3.40 bags
- Fine aggregate = 736 kg
- Coarse aggregate = 1419.6 kg
- Water = 85 litre

### M10

- Cement = 4.40 bags
- Fine aggregate = 720 kg
- Coarse aggregate = 1419.6 kg
- Water = 110 litre

### M15

- Cement = 6.40 bags
- Fine aggregate = 704 kg
- Coarse aggregate = 1357.2 kg
- Water = 160 litre

### M20

- Cement = 8 bags
- Fine aggregate = 672 kg
- Coarse aggregate = 1310.4 kg
- water = 200 litre

### M25

- Cement = 11.20
- Fine aggregate = 624 kg
- Coarse aggregate = 1216.8 kg
- Water = 280 litre

**Concrete Materials Calculator ( Cement, Fine aggregate, Coarse aggregate, and Water ) – ” Click Here “**

## Note

- The other design mix does not have a constant mix ratio the
**different mix proportions**are used for other design mixes, it all depends on the**requirement and site/structure condition** - The above values are
**changed**if the material quality and quantity change or unit weight change - The water-cement ratio depends on requirement, strength and workability. (
**Do not use 0.5 only**)