Concrete mix design is the act of defining the quantities of cement, sand, aggregates ,water to get the most competitive grades of concrete mix ratios.
The 5 different methods of concrete mix design are given below.
- Minimum voids methods.
- Maximum density method,
- Abram’s water-cement ratio.
- Experimental methods
- Arbitrary methods
1.Minimum voids method for concrete mix design
In this method, the quantity of sand should fill the voids of the coarse aggregates and the quantity of cement used should be such that it fills the voids of sand.
The quantity of sand used in the mix keep 10% more than the voids in coarse aggregates and
the quantity of cement is to take 15% more than the voids in the sand.
2.Maximum density method for concrete mix design
Method of voids was later developed by Fuller.
Given the subsequent representation for maximum density method concrete.
P= 100 x (d/D)1/2
where P = % by weight of matter finer than diameter d.
D = aggregates maximum size
3.Abram’s water-cement ratio for concrete mix design
For any given situations of a test, according to this law on the basis of water-cement ratio only the strength of workable concrete mix is reliant.
According to this law, for the compacted concrete,
the strength is not influenced by type or surface texture, aggregates shape and aggregates grading.
According to this law, the strength of a concrete mix rises with a reduction in water content.
4.An Experimental method for concrete mix design
The proportion of constituents of concrete is prepared based on conclusions drawn from a large number of experiments.
The achieved concrete is called Design mix concrete.
The design of this concrete mix ratio is done on the basis of volume.
5.Arbitrary methods for concrete mix design
If the proportions of aggregates, cement and water are selected based on arbitrary measures, the concrete thus produced is termed as Nominal mix concrete.
In works where design mixes are not possible due to quality issues, this Nominal mix concrete is used.
This concrete mix ratio is done on the basis of its weight.
Nominal mix concrete can be generated by utilising fine aggregate, cement and coarse aggregate in the mix ratio of 1: n: 2n, for regular concrete works.
Example: M 25 concrete grade – 1:1:2
Aggregates Sizes in concrete mix design
In RCC works the greatest size of aggregates is restricted to 20 mm to 25 mm, as per IS standards.
The particle shape is very crucial since the water-cement ratio rules considerably the strength of concrete.
For concrete of assigned workability, the rounded aggregates need less water-cement ratio.
Coarse aggregates > 4.75 mm size.
Fine aggregates < 4.75 mm size
Fineness modulus of aggregates
An index number which is approximately proportionate to the average size of the particles in the aggregates is termed as the fineness modulus of an aggregate.
The more granular the aggregates, the larger is the fineness modulus.
It is achieved by combining the % of the weight of the material retained on the total 10 number of IS sieves between 80 mm to 150 micrometres and dividing it by 100.
Given below fineness modulus of various aggregates
| S.No|| Aggregates || Fineness Modulus|
| 1|| Coarse aggregates|| 6 to 8.5|
| 2.|| Fine aggregates|| 2 to 3.5|
| 3.|| Fine sand|| 2.2 to 2.9|
| 4|| Mixed aggregates|| 4.7 to 7|
| 5|| Medium sand|| 2.6 to 2.9|
| 6.|| Coarse sand|| 2.9 to 3.2|
Grades of concrete mix ratio
For various grades , concrete mix ratios are given below.
- M 5 concrete ratio-1:5:10
- M 10 concrete ratio- 1:4:8
- M 15 concrete ratio-1:2:4
- M 20 concrete ratio – 1:1.5:3
- M 25 concrete ratio – 1:1:2
The following are the minimum grade of concrete to use for various types of construction.
| S.No|| construction type || Minimum Grades of concrete|
| 1|| Lean concrete|| M 5|
| 2|| Plain cement concrete|| M 10,M 15|
| 3|| RCC for general construction works|| M20|
| 4|| Water tanks, domes, shell roofs concreting|| M25|
Ready-mix concrete, RMC vehicles are used for transporting of this concrete mix.
RCC in construction details
concrete compressive strength
6 corrosive metals|corrosion of steel
Prestressed concrete materials