# What is the proper concrete mix ratio?

Concrete has irreplaceable value in the field of contemporary architecture, such as high-rise buildings, bridges, underground tunnels, etc., which can be seen everywhere in life. It can be said that concrete symbolizes the development of the city.

The concrete mixing ratio refers to the proportional relationship between various constituent materials in concrete. There are four basic components in concrete: cement, aggregate, sand, and water.

Concrete mix design is an important task in concrete engineering, which directly affects the smooth construction of concrete, the quality of concrete works and the cost of concrete works.

## Ingredients

**Cement**

An adhesive, the principal ingredient in cement is calcium oxide. Calcium oxide is a product of superheated limestone. Cement also has silicon, aluminum, iron, and a variety of other secondary ingredients. Cement is the bonding agent that holds the aggregate and sand of concrete together once it cures.

While very hard, the strength of cured cement does not compare to that of rock and sand. As such, cement is the reason concrete has the weak tensile strength and requires rebar. Torque can easily break concrete. That is because concrete relies on the strength of the cement to resist torque.

It is important to remember, more cement does not mean greater compressive strength, it means better adhesion. The two are not synonymous.

**Aggregate**

Washed, crushed rock — often mistakenly called gravel — aggregate is the component that gives concrete its compressive structural integrity. Concrete has tremendous compressive strength. The rocks and sand support the concrete when it is being compressed.

**Sand**

Not only the filling agent that eliminates air pockets and spaces between the individual crushed rocks, but sand also has a very high compressive strength.

**Water**

Water creates the chemical change in the quicklime of cement that makes it adhere to rock and sand, water also makes concrete workable. Without water, mixing, forming, and finishing concrete is not possible.

## Concrete strength grade

The strength grade of concrete refers to the compressive strength of concrete. The strength rating of concrete shall be based on the standard values of concrete cube compressive strength. It is expressed by the standard value of the symbol C and the cubic compressive strength (in N/mm^2; or MPa).

The compressive strength with a 95% guaranteed rate measured according to the standard experimental method is taken as the concrete strength grade.

According to GB50010-2010 “Concrete Structure Design Code”, ordinary concrete is divided into fourteen grades, namely: C15, C20, C25, C30, C35, C40, C45, C50, C55, C60, C65, C70, C75, C80 . For example, concrete with a strength class of C30 means 30 MPa ≤ fcu < 35 MPa.

The concrete mix ratio refers to the proportional relationship between the various constituent materials (cement, water, sand, stone) in concrete. There are two ways to express: one is the amount of various materials in 1 cubic meter of concrete, such as 300 kg of cement, 180 kg of water, 690 kg of sand, and 1,260 kg of stone; the other is the use of cement and various materials per unit mass. The ratio of the amount of use and the water-cement ratio of concrete are shown, for example, the previous example can be written as: C: S: G = 1: 2.3: 4.2, W / C = 0.6.

## Concrete mix ratio table

Here is the standard chart table showing various grades of concrete mix design along with their respective ratios of cement, sand, and aggregates required.

Grades of Concrete |
Ratios of Concrete mix design(Cement:Sand:Aggregate) |

C5 | 1:5:10 |

C7.5 | 1:4:8 |

C10 | 1:3:6 |

C15 | 1:2:4 |

C20 | 1:1.5:3 |

C25 | 1:1:2 |

C30 | 1:0.75:1.5 |

C35 | 1:0.5:1 |

C40 | 1:0.25:0.5 |

**Concrete Mix Proportions Notes to Remember**

The more rock, the greater the compressive strength of concrete. The more sand, the greater the workability.

Adhesion (cement) and compressive strength (rock) are two different factors in the quality of concrete. More cement does not mean more compressive strength; it means more tensile strength.

The less water, the stronger the adhesion of cement, but the more difficult it is to work with the concrete.