What Is Concrete Mix Ratio? | Type of Concrete Mix Ratio | Factor Affecting of Concrete Mix Ratio

What Is a Concrete Mix Ratio?

The concrete mix ratio is doing a selection of the right component of concrete and determining the specific strength and durability of the concrete as economically as possible.

There are four main components for making concrete. These four components are cement, sand, aggregate, and admixture, respectively. Durability can be achieved according to the design by mixing these four components in the right proportions.

All concrete costs are based on two factors the cost of materials and the cost of labor. For good concrete and bad concrete, labor costs for formwork, batching, mixing, transportation and curing are almost the same. So the focus is mainly on the cost of the material.

The cost of cement is many times higher than the cost of other components, so it is mainly focused on using as little cement as possible with strength and durability.

Thus the concrete mix ratio is based on the quality of the material used in concrete and its proportions. The two essential components of concrete are aggregate and paste. The relationship between the two will be worth remembering.

The workability of mass is provided by the effect of the paste. This affects workability by the amount of paste and the thinning. The strength of the concrete depends on the strength of the paste. With rare exceptions, the strength of the mineral aggregate is stronger than the strength of the paste.

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Type of Concrete Mix Ratio

The mix of concrete is the mixing of the components of concrete according to the strength of the structure. The types of concrete mix are given based on the requirement as follows.

1. Nominal Mix

In the past, the proportions of cement, fine and coarse aggregates for concrete were suggested. These mixtures of fixed cement-aggregate ratio were called trivial mixtures if they ensured sufficient strength.

The nominal mix is concrete that is prepared on the basis of experience without any quality. In this type of concrete, fine aggregate, coarse aggregate, and cement were prepared based on the weight of these three components.

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According to is IS CODE 456-2000, the nominal mix includes M-5, M-7.5, M-10, M15, M20, etc.

This type of mix is ​​used to build small houses in villages. In addition, the nominal mix is ​​used in the footing and footing base.

2. Standard Mix

The mixture of cement-aggregate ratio (by volume) is fixed, which varies according to the change in power. It can also be mixed with high strength. For this reason, specifications are involved in obtaining minimal compressive strength. This type of mixture is called a standard mixture.

The standard mix consists of  M25, M30, M40, M45, etc.

Standard Grade of Concrete

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3. Design Mix

Designing for concrete used in construction on site is done keeping in mind its workability, strength, durability, etc.

Its quality is also taken into consideration while designing concrete. For the design mix, the first different concrete mix is prepared and tested in the laboratory.

Design mix is done keeping in mind various factors. Such as aggregate content, grading, water content, cement content, etc., are taken into consideration.

The sample thus prepared is tested in the laboratory, and the result is modified into concrete as required. The strength of concrete obtained in the laboratory is compared to the strength of concrete found at the site by the following formula.

F’_{ck =} f_ck +tS 

where F’_{ck  =  Target mean strength}   

f_{ck  = characteristic  strength}

t = constant

S= standard deviation.

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The standard mix consists of  M50, M55, M60, M65, M70, etc.

High Strength Concrete Grades

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Factor Affecting of Concrete Mix Ratio

The factors affecting the mix of concrete are as follows

• Grade of Concrete
• Type of Cement
• Maximum Nominal Size of Aggregates
• Water cement ratio
• Workability
• Durability
• Quality Control

1. Grade of Concrete

The grade of concrete represents the characteristic compressive strength of concrete. Its compressive strength value is a value that does not exceed 5% of the test result of the strength of the concrete cube.

The value of the strength of concrete at the site is kept higher than the target mean strength.

F’_{ck =} f_ck +tS

2. Type of Cement

The strength of concrete depends on the cement. High strength portland cement should be used where high strength is required.

Rapid hardening cement should be used where strength is to be obtained soon. Where the heat of hydration is to be reduced, low heat cement should be used.

3. Maximum Nominal Size of Aggregates

The maximum aggregate size in concrete is determined from sieve analysis. The larger the size of the aggregate, the less they need for cement pest. In addition, as the size of the aggregate increases, so does the workability.

Thus, as the need for cement pest increases, the compressive strength of concrete increases. Generally, aggregates of 10mm and 20mm size should be used to obtain high-strength concrete.

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4. Water cement ratio

The water/cement ratio is directly related to the compressive strength of concrete.

As the water/cement ratio increases, the compressive strength of concrete decreases. Similarly, as the water/cement ratio decreases, the compressive strength of concrete increases.

5. Workability

The workability of concrete depends on the various processes of concrete. The main principle of concrete mix design is to achieve the workability of concrete.

Concrete should be completely compaction to get the workability of concrete

6. Durability

As the permeability of concrete increases, the durability of concrete decreases. In addition, the water/cement ratio in concrete directly affects the permeability of concrete Therefore the water/cement ratio of concrete should be limited to 0.45 to 0.55.

In addition, the durability of concrete should be according to the location of the concrete.

7. Quality Control

When making concrete, a slump test should be done at each batch of concrete. So that the workability of concrete is maintained.

The quality of concrete components should be good. Supervision of concrete is essential during concreting.

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