Cement Sand Aggregate Ratio in Concrete Mix | How to calculate?

Concrete is a mixture of cement, sand, and aggregates. It is essential to blend these concrete mix components in the right proportions to achieve desired compressive strength. From constructing bridges and dams to building commercial and residential spaces, the correct quantity of concrete mix components is imperative to creating durable and economic structures. To calculate the amount of Cement Sand Aggregate Ratio, one needs to understand the different grades of concrete.

 

Different Grades of Concrete

There are various grades of concrete mixes such as M5, M10, M15, M25, etc. In these, ‘M’ denotes mix, and the number after M denotes the characteristic compressive strength of the concrete. This compressive strength is the minimum strength of concrete after 28 days of construction.

 

Concrete Grade Types

Concrete grades can be classified into three categories. These include:

 

Normal Grade of Concrete

It comprises M25, M20, M15, M10, M7.5 & M5 grades of concrete. These concrete mixes have lower compressive strength than the standard grade of concrete.

Standard Grade of Concrete

It includes M25, M30, M35, M40, & M45 grades of concrete. These have higher compressive strength as compared to standard grades. However, their compressive strength is lower than the high strength grade of concrete.

High Strength Grade of Concrete

It includes M50, M55, M60, M65, & M70 grades of concrete. These have much higher compressive strength than standard grades of concrete.

 

Cement Sand Aggregate Ratio in Concrete Mix

Under every grade of concrete, there are two kinds of mix ratios – nominal mix and design mix.

Nominal Mix

These are usually lower and normal grade concrete mixes with fixed cement, sand, and aggregate ratios. For example, in M20, the quantity of cement, sand, and aggregates are mixed in fixed proportion (1:1.5:3). These mixed designs are primarily used for small-scale constructions. These include grades such as M5, M7.5, M10, M15, M20, & M25.

Design Mix Concrete

These are unique concrete mixes designed for standard and high strength purposes that enable the construction of high-rise buildings, load-bearing structures, bending moment of columns, earthquake resistance, etc. In these, the mix ratios are decided by civil engineers based on the usage and application of concrete. Concrete grades higher than M25 belong to the Design Mix category.

 

Cement Sand Aggregate Ratio According to Different Grades

 

Type of Concrete	Concrete Grade	Mix Ratio	Characteristic Compressive strength of Concrete @28Days in N/mm2
Ordinary concrete	M5	1:5:10	5 N/mm2
	M7.5	1:4:8	7.5 N/mm2
	M10	1:3:6	10 N/mm2
	M15	1:2:4	15 N/mm2
	M20	1:1.5:3	20 N/mm2
Standard Concrete	M25	1:1:2	25 N/mm2
	M30	Design Mix	30 N/mm2
	M35	Design Mix	35 N/mm2
	M40	Design Mix	40 N/mm2
	M45	Design Mix	45 N/mm2
	M50	Design Mix	50 N/mm2
High Strength Concrete	M55	Design Mix	55 N/mm2
	M60	Design Mix	60 N/mm2
	M65	Design Mix	65 N/mm2
	M70	Design Mix	70 N/mm2

 

Source: Civilread.com

 

Calculating the Cement Sand Aggregate Ratio in the concrete mix

 

Let’s see how to calculate the quantities of sand cement aggregates ratio in different grades of concrete. For this, assume an M20 nominal mix of 1 m^3 concrete. This method can help arrive at the right quantities for any grade of concrete.

The proportion of cement, sand, and aggregate in M20 nominal mix concrete = 1: 1.5: 3

Total volume of concrete mixture will be = 1 + 1.5 + 3 = 5.5

Since the concrete hardens after some time, we need to arrive at the wet volumes of the components. For this, a factor of safety ranging from 1.54 to 1.57 is considered to counter the volume shrinkage.

 

Therefore, the Volume of dry concrete is 1.54 to 1.57 times the volume of wet concrete.

 

Now, assuming the factor of safety to be 1.57 for our calculations.

The volume of dry concrete (equivalent to 1 m^3 of wet concrete) = 1.57 m^3

 

Calculation of volume of cement in 1m^3 of concrete

 

Volume of cement = Ratio of Cement / (Cement+Sand+Aggregate)           x 1.57

= 1 / 5.5           x 1.57

= 0.28 m ^3

 

Now, 1 cubic meter of cement = 1440 kgs (approx.)

Hence, 0.28m^3 of cement = 1440 x 0.28 = 403 kgs

So, 1 m^3 of Concrete requires 403 kgs of Cement.

Number of Cement Bags required for 1m^3 of Concrete  = 403/50 = 8.06  = 8 bags (aaprox.)              

  So, 1 m^3 of Concrete requires 8 bags of Cement.

 

 Calculation of volume of sand in 1m^3 of concrete

 

Volume of sand = Ratio of sand / (Cement+Sand+Aggregate)         x 1.57

= 1.5 / 5.5        x 1.57

= 0.43 m ^3

 

Now, 1 cubic meter of sand = 1620 kgs (approx.)

Hence, 0.28m^3 of sand = 1620 x 0.43 = 696.6 kgs

So, 1 m^3 of Concrete requires 697 kgs of sand.

Number of sand Bags required for 1m^3 of Concrete  = 697/50 = 13.94  = 14 bags (aaprox.)

 So, 1 m^3 of Concrete requires 14 bags of sand.

 

Calculation of volume of aggregate in 1m^3 of concrete

 

Volume of aggregate = Ratio of aggregate / (Cement+Sand+Aggregate)     x 1.57

= 3 / 5.5           x 1.57

= 0.86 m ^3

Now, assuming 1 cubic meter of aggregate = 1500 kgs (because the bulk density of every type of aggregate is different)

Hence, 0.86m^3 of aggregate = 1500 x 0.86 = 1290 kgs

So, 1 m^3 of Concrete requires 1290 kg of aggregate.

Number of aggregate Bags required for 1m^3 of Concrete = 1290/50 = 25.8 = 26 bags (aaprox.)

So, 1 m^3 of Concrete requires 26 bags of aggregate.

 

Conclusion

We’ve done our best to explain the Cement Sand Aggregate Ratio in the concrete mix in this post. Hopefully, it will be helpful to have some ideas when constructing any structure. Please visit our website for more construction-related topics.