All About Concrete Mix Ratio: A Full Explanation
Construction and concrete come in the same bracket. When you think of one, the other automatically comes to mind. However, concrete must be used selectively for the best result in construction. Concrete has different grades, differentiated by different concrete mix ratios.
Concrete mixing is the science of determining which materials to use and in what ratios to produce concrete that fits the technical standards for a certain construction project. The required properties vary according to the project. Apartments, roads, underground pipes, bridges, or walls all require concrete with varying qualities.
Cement, water, and aggregates like gravel or sand are the ingredients of concrete. The workability, strength, and other properties of the concrete are determined by the ratio of each of these ingredients. This article covers the types of concrete mixes and their ratios in detail.
What is the Concrete Mix ratio?
The concrete mix ratio is the proportion in which the various ingredients are used to create a certain grade of concrete mix. The process of choosing the right materials and using them in the right ratios is important to create a concrete mix that will be strong, durable, and easy to work with.
Concrete with a predetermined ratio can be used, or an expert can determine the ratio based on the construction needs. There are many grades of concrete with different composition ratios and strengths. While cement, water, and aggregates are the constituents of concrete, their ratios differ from grade to derive the expected characteristics of the concrete mix.
Cement, being the binding agent, creates a paste that binds the aggregates to form a concrete mix. The following elements need to be taken into account for the perfect concrete mix:
- Cement paste to aggregate ratio,
- Water to cement ratio in cement paste
- Coarse aggregate to fine aggregate (sand) ratio
- What admixtures to use to achieve the required quality
Concrete Mixes explained
Depending on the proportion of its constituents, the concrete mix ratio can be of the following types:
- Nominal Mix Concrete
- Standard Mix Concrete
- Design Mix Concrete
Nominal Mix Concrete
There are various grades of concrete mixes, and the proportions of concrete ingredients in each grade are predetermined. In the case of M15 grade concrete, for example, the set ratio of cement to sand to aggregate is 1:2:4.
The nominal mix is typically used in small buildings. Nominal mix concrete includes grades M5 through M20 of concrete.
If the amount of water in the mix needs to be raised, the cement content of any nominal mix must be increased correspondingly. Compaction problems or improper placement of the concrete might cause an increase in water content.
Standard Mix Concrete
Standard mix concrete mixes typically contain cement, sand, and aggregates in 1:2:4 ratios. The standard concrete mix includes grades M25 through M50 of concrete.
Design Mix Concrete
The design mix of concrete uses a variety of additives to match the required properties of concrete more economically. A qualified civil engineer analyses the qualities of each ingredient to determine the mix ratios for designed mix concrete. The ratio is established based on the required specifications for the strength and quality of the concrete.
The below concrete mix ratio table provides the specific mix ratios and compressive strengths for the different grades of concrete.
| Concrete Grade | 1: 5: 10 | Compressive Strength after 28 days | |
| MPa (N/mm2) | |||
| Grades of Concrete | |||
| M5 | 1: 1.5 : 3 | 5 MPa | |
| M7.5 | 1 : 4 : 8 | 7.5 MPa | |
| M10 | 1 : 3 : 6 | 10 MPa | |
| M15 | 1 : 2 : 4 | 15 MPa | |
| M20 | 1: 1 : 2 | 20 MPa | |
| Standard Grade of Concrete | |||
| M25 | 1: 1: 2 | 25 MPa | |
| M30 | Design Mix | 30 MPa | |
| M35 | Design Mix | 35 MPa | |
| M40 | Design Mix | 40 MPa | |
| M45 | Design Mix | 45 MPa | |
| High Strength Concrete Grades | |||
| M50 | Design Mix | 50 MPa | |
| M55 | Design Mix | 55 MPa | |
| M60 | Design Mix | 60 MPa | |
| M65 | Design Mix | 65 MPa | |
| M70 | Design Mix | 70 MPa | |
This table helps the engineers get the relevant data at a glance. For example, what should be the M40 concrete mix ratio, or M25 concrete mix design?
How are Concrete Mixes Graded?
Concrete grades are determined by composition and minimum strength of the mix required after 28 days of initial application. Concrete grades are expressed in MPa units.
The maximum pressure that may be applied to concrete before it fails or cracks is indicated by the MPa, a measure of the concrete’s compressive strength. 1 MPa is equivalent to 1 megapascal or a million pascal. One megapascal is equal to one million newtons per square meter.
For example, a concrete mix of M20 grade should have a compressive strength of 20 million newton/m2 i.e. 20 MPa after 28 days.
Different grades of concrete mixes are denoted by the letter M and a number in ascending order of 5, starting with the lowest grade, M5.
Importance of Water Content Ratio in Concrete Mix
Apart from cement and aggregators, water content has a significant impact on the strength and workability of concrete. The more water there is in the concrete, the more workable it will be (more fluid), but its strength will be compromised.
On the other hand, if you maintain the water level too low, the water’s usefulness will suffer. As a result, such concrete will be difficult to place in the building. The amount of water required for the same volume of concrete can vary depending on the grade of the concrete. As a result, a balance must be found on the construction site while mixing concrete.