Concrete Mix Ratio | What Is Concrete Mix Ratio or Concrete Grade Ratio | Type of Concrete Mix Ratio | Different types of Standard Concrete Mixes Ratio
Concrete mix ratios are the proportions of concrete components such as cement, sand, aggregates and water. These mix ratios are decided based on type of construction and mix designs.
In this article we are discussing about concrete mix ratio and ideal mix concrete. Making concrete, it is important to use the correct concrete mixing ratios to produce a tough, long life, durable concrete mix.
To make concrete, four basic materials you need: Cement, sand, aggregate, water, and add-mixture.
Different types of Concrete Mix Ratio
There are different mix ratios of Concrete. Mix ratios are decided based upon the type of construction structures and mix designs.
- Nominal Concrete Mix Ratios
- Standard Mixes Ratio
- High Strength Concrete Mix Ratio
Different Grades of Concrete denotes its strength for required construction. The “M” denotes mix. For example if the concrete mix is of M20 Grade then the compressive strength will be 20 MPa.
So, What is 20 MPa here ?? 20 MPa is expression or Unit to show Compressive Strength of CMR (Concrete Mix Ratio).
Different types of Concrete Grade Ratio
Concrete mix design is process of preparation of concrete with suitable proportion of ingredients to meet the required strength and durability of concrete structure. Every ingredient of concrete consists different properties so, it is not an easy task to get economical and good concrete mix. The types and advantages of concrete mix design are discussed below.
Nominal Concrete Mix Ratios
Previously the specification for concrete was proportion of Cement, Sand and Course Aggregates. The fixed ratio of these was to ensure the strength to the structure. Nominal concrete mix are low grade concrete mixes which are used for small and unimportant works. In this method, fine aggregate quantity is fixed irrespective of cement and coarse aggregate proportions. Hence, the quality of concrete mix will be varied and required strength may not be obtained.
In Nominal mix design water-cement ratio also not specified. Grades of concrete M20 and below are prepared by the Nominal mix design. For higher grade designed concrete mix is preferred.
Standard Concrete Mix/Ratio
As per Indian Standards (IS 456–2000) concrete mixes are segregated into different grades. It starts from M5 and goes up to M40. M refers to Mix and the numbers are to signify the strength of Mix N/mm2.
The material proportion for each Grade is different.
M10 = 1:3:6
M15 = 1:2:4
M20 = 1:1.5:3
M25 = 1:1:2
Designed Concrete Mix/Ratio
The proportion of the material is determined by the concrete mix expert in this method. In design mix the concrete production is with appropriate properties. In Design mix there is no guide for right mix proportions it follows the economical method as per the requirement.
It is followed by standard mixes — quantities of dry materials per cubic meter and by plunge. This method is may use for small construction purpose where the strength is required on 28 day strength 30 N/mm2. Testing for this grade is not necessary the mix is placed on the bulk ingredients.
The designed concrete mix does not contain any specified ranges in proportions. The design is done according to the requirements of concrete strength. So, we can achieve the desirable properties of concrete either it is in fresh stage or in hardened stage.
The fresh concrete properties like workability, setting time and hardened concrete properties like compressive strength, durability etc. are attained surely by this method. Use of additives like admixtures, retarders etc. other than basic ingredients are used to improve the properties of mix.
Here is the list of different types of concrete mix ratios and their strengths.
For Mix proportions
First one = Cement
Second one = Sand
Third one = Coarse Aggregate
Based on the weight of materials the strength is measured with concrete cube by civil engineers.
|
Concrete Grade |
Mix Ratio |
Compressive Strength | |
| MPa (N/mm2) | psi | ||
Normal Grade of Concrete | |||
| M5 | 1 : 5 : 10 | 5 MPa | 725 psi |
| M7.5 | 1 : 4 : 8 | 7.5 MPa | 1087 psi |
| M10 | 1 : 3 : 6 | 10 MPa | 1450 psi |
| M15 | 1 : 2 : 4 | 15 MPa | 2175 psi |
| M20 | 1 : 1.5 : 3 | 20 MPa | 2900 psi |
Standard Grade of Concrete | |||
| M25 | 1 : 1 : 2 | 25 MPa | 3625 psi |
| M30 | Design Mix | 30 MPa | 4350 psi |
| M35 | Design Mix | 35 MPa | 5075 psi |
| M40 | Design Mix | 40 MPa | 5800 psi |
| M45 | Design Mix | 45 MPa | 6525 psi |
High Strength Concrete Grades | |||
| M50 | Design Mix | 50 MPa | 7250 psi |
| M55 | Design Mix | 55 MPa | 7975 psi |
| M60 | Design Mix | 60 MPa | 8700 psi |
| M65 | Design Mix | 65 MPa | 9425 psi |
| M70 | Design Mix | 70 MPa | 10150 psi |
Advantages of Concrete Mix Design
The advantages of concrete mix design are as follows-
1. Desired Proportions of Each ingredient
The main aim of the concrete mix design is to find out the desired proportion of each ingredients which are cement, coarse aggregate, fine aggregate, water etc. to obtain the required properties of resulting mix.
2. Quality Concrete Mix
Each ingredient used in the concrete mix design is tested for its quality. The aggregates with good strength, shape, specific gravity and free from organic content are used. The water used also is of good quality generally potable water is used.
Concrete with good quality improves its properties such as strength, durability etc. The design mix which is prepared from suitable ingredients in respective proportions itself improves the concrete properties.
The concrete mix prepared is tested using compressive strength machines, tensile strength machines in the form of concrete cubes and cylinders. Hence, recommended grade of concrete can be obtained using concrete mix design.
3. Economical Concrete Mix
Normally For making concrete in nominal mix, cement is used more than the other materials to get more strength which effects the cost of the project. It also increases the heat of hydration and causes shrinkage cracks in concrete.
But using concrete mix design, concrete of required strength can be designed with accurate quantity of cement. It saves the cost of the project and economical concrete mix will be obtained and also prevents the formation shrinkage cracks by lowering heat of hydration.
4. Best Use of Locally Available Material
Concrete mix design allow the use of locally available material such as coarse aggregates, fine aggregates etc. only if it is of good quality. This will reduce the cost of project and will also encourage rapid construction.
5. Desired Properties of Mix
The concrete obtained through mix design contain desired properties like workability, durability, setting time, strength, impermeability etc. The design is processed by considering some important factors like water cement ratio, gradation of aggregates etc.
British Standard Concrete Mixes
The British method of concrete mix design, popularly referred to as the “DOE method”, is used in the United Kingdom and other parts of the world and has a long established record.
- The DOE method was first published in 1975 and then revised in 1988.
- While Road Note No 4 or Grading Curve Method was specifically developed for concrete pavements, the DOE method is applicable to concrete for most purposes, including roads.
- Since DOE method presently is the standard British method of concrete mix design, the procedure involved in this method is described instead of out dated Road Note No 4 method.
The method originates from the “Road Note No 4” which was published in Great Britain in 1950. In 1975 the note was replaced by the “Design of Normal Concrete Mixes”, published by the British Department of the Environment (DOE).
In 1988 the “Design of Normal Concrete Mixes” was issued in a revised and updated edition to allow for changes in various British Standards.
DOE mix design generally involves the following stages.
- Step #1. Determine the target strength
- Step #2. Determine the water/cement (W/C) ratio according to the target strength, types of cement and aggregate.
- Step #3. Determine the water content, W, from required workability, size and type of aggregate.
- Step #4. Determine cement content, C, from W/C ratio and water content.
- Step #5. Estimate the density of wet fresh concrete, D, based on relative density of combined aggregate and water content.
- Step #6. Determine the total aggregate content from D, C, and W.
- Step #7. Determine the proportion of fine aggregate according to the fineness of fine aggregate, maximum aggregate size, slump/Vebe time and W/C.
- Step #8. Determine coarse aggregate.