The ratio of concrete mix is important in construction as it is the ratio of water to cement (w/c) that largely determines the durability and strength of the building. A w/c ratio of 0.4 means for every 100lbs of cement, 40 lbs of water must be added. Read on to find out more about the concrete mix ratio, its different types, and the ratio table for different grades of concrete.
But First Things First, What is Concrete Mix Ratio?
The ratio of concrete mix is defined as the proportion of the components that make concrete such as water, aggregates, sand, and cement. How do we determine what ratio is to be used? IS 456-2000 has designated concrete mixes into grades such as M40, M35, M30, etc. here. M refers to the mix and the digit refers to the strength of the mix after its 28th day in N/㎟.
4 Types of Concrete Mix Ratio
Check out these different types of concrete mix ratio and their grades:
1. High Strength Concrete Mix Ratio
The mix design of high-strength concrete depends on the properties of w/c ratio, sand aggregates, and cement which must be above 40 MPa. It must have a low w/c ratio to obtain high workability and proper compaction. For compressive strength values for each grade refer to the table given below.
Concrete Mix Ratio Table for High Strength Concrete
Sl. No. | High Strength Concrete Grade | Mix Ratio | Compressive Strength | |
Mpa (N/㎟) | psi | |||
1 | M50 Concrete Mix Ratio | Design Mix | 50 | 7250 |
2 | M55 Concrete Mix Ratio | Design Mix | 55 | 7975 |
3 | M60 Concrete Mix Ratio | Design Mix | 60 | 8700 |
4 | M65 Concrete Mix Ratio | Design Mix | 65 | 9425 |
5 | M70 Concrete Mix Ratio | Design Mix | 70 | 10150 |
2. Designed Concrete Mix Ratio
In this type of concrete mix, the ratio of ingredients is mentioned by the producer while the performance of the concrete is mentioned by the designer. However, the minimum cement content is laid down. This type of mix ratio is economical and is a rational approach. There are several factors that determine the strength of the mix in a designed concrete such as
- Compressive strength
- Workability
- Durability
- Maximum nominal size of the aggregates
- Grading and type of aggregates
- Quality control
3. Nominal Concrete Mix Ratio
The specification of making concrete meant prescribed proportions of cement and coarse and fine aggregates which ensure adequate strength to the mix. These are termed nominal mixes and under normal circumstances, they have a margin of strength that is above the specified value. However, its workability varies significantly because of the variability of its ingredients. Here’s a table showing the mix ratio and compressive strength of different grades of nominal concrete:
Concrete Mix Ratio Table for Nominal Concrete
Sl. No. | Nominal Concrete Grade | Mix Ratio | Compressive Strength | |
MPa (N/㎟) | psi | |||
1 | M5 Concrete Mix Ratio | 1:5:10 | 5 | 725 |
2 | M7.5 Concrete Mix Ratio | 1:4:8 | 7.5 | 1087 |
3 | M10 Concrete Mix Ratio | 1:3:6 | 10 | 1450 |
4 | M15 Concrete Mix Ratio | 1:2:4 | 15 | 2175 |
5 | M20 Concrete Mix Ratio | 1:1.5:3 | 20 | 2900 |
4. Standard Concrete Mix Ratio
The nominal mixes of cement and aggregate vary widely in strength and might over or under-rich the mixes. This led to the code specifying the minimum compressive strength for concrete mixes called the standard mix ratio. IS 456-2000 specified concrete mix ratio to grades M40, M35, M30, M20, M15, and M10. Check out the table below to know more!
Concrete Mix Ratio Table for Standard Concrete
Sl. No. | Standard Concrete Grade | Mix Ratio | Compressive Strength | |
Mpa (N/㎟) | psi | |||
1 | M25 Concrete Mix Ratio | 1:1:2 | 25 | 3625 |
2 | M30 Concrete Mix Ratio | Design Mix | 30 | 4350 |
3 | M35 Concrete Mix Ratio | Design Mix | 35 | 5075 |
4 | M40 Concrete Mix Ratio | Design Mix | 40 | 5800 |
5 | M45 Concrete Mix Ratio | Design Mix | 45 | 6525 |
Takeaway
Concrete mixing needs to meet certain proportioning and selection factors concerning its ingredients. They must satisfy the following requirements:
- The minimum compressive strength
- Adequate workability to achieve full compaction along with compacting equipment
- Maximum cement content or maximum w/c ratio to achieve durability
- Maximum cement content to avoid cracking caused by temperature changes