What Is Mix Design | Types of Concrete Mix Design | Advantages & Disadvantages of Mix Design | Application of Mix Design
Important Point
What Is Mix Design?
Concrete mix design is a procedure of manufacture of concrete with an ideal proportion of ingredients to fulfill the desired strength & sturdiness of the concrete structure.
Concrete is generally a blend of cement, sand & aggregates. Bridges, dams require an oversized amount of concrete, utilizing it incorrect quantity makes the structure economical.
Hence, to find the proper quantity of cement, sand & aggregate construction mix design is required.
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Types of Concrete Mix Design
Three different types of concrete mix design are as follows.
1. Nominal Concrete Mix:
Nominal concrete blend are low quality concrete blends utilized for bijou & unimportant jobs. Superior aggregate quantity is fixed regardless of cement & coarse aggregate proportions.
Therefore, the standard of concrete blend are varied in range & required brawn might not be achieved. However, the nominal concrete for given workability ranges in brawn on account of the discrete combination of design materials.
2. Designed Concrete Mix:
Designed concrete blends doesn’t possess any specified ranges in proportions. Planning is done in terms of the necessities of concrete brawn. So, it is possible to achieve the desirable features of concrete.
Fresh concrete properties like workability, setting time & hardened concrete properties like compressive strength, durability, etc. are achieved by this procedure.
Utilization of additives like admixtures, retarders, etc. are done to ameliorate the properties of blend. The range of grades of concrete can be designed from as low as M10 grade to loftier grades like M80, M100.
Workability requirements of every blend can be attained utilizing this procedure from 0 to 150 mm slump. The performance of the concrete is marked by the designer & combination ratio is set by the manufacturer.
This is the principal rational strategy for the selection of blending ratios with specific substances, considering discrete features.
The strategy ultimately ends up in manufacturing concrete at a low-cost price. There is no control test required according to the mass of the substance.
3. Standard Mix:
Nominal blends of constant cement– aggregate proportion range in sturdiness & will lead to fewer or over-content blends. That’s why, minimal compressive sturdiness obtained in many features & therefore these blends are referred to as standard mixtures.
Letter M denotes the amount which is specified by 28-day cubic energy of the mixture in N/mm2. The mixture grades M10, M15, M20 & M25 approximately correspond to mixing ratios (1: 3: 6), (1: 2: 4), (1: 1.5: 3) and (1: 1: 2).
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Advantages of Mix Design
1. Desired Proportions of Every Ingredient:
Main goal of the concrete blend design is to search the specified proportion of every module like cement, coarse aggregate, fine aggregate, water, etc.
2. Quality Concrete Mix:
Every module utilized in the concrete blend design is examined for its superior quality. The aggregates with good brawn, shape, relative density & free from organic content are utilized.
Superior concrete ameliorates its features like brawn, durability, etc. the design blend which is ready from ideal modules in definite proportions itself ameliorates the concrete features.
Concrete blend generated is examined utilizing compressive strength machines, tensile strength machines within concrete cubes & cylinders.
3. Economical Concrete Mix:
For generating concrete in nominal mix, cement is employed in place of other materials to inflict more brawn which affects the price of the project.
It additionally surges the warmth of hydration & causes cracks in concrete. But by utilizing a mix design, concrete of required sturdiness is designed with the precise quantity of cement.
It saves the value of the project & an economical concrete blend is derived & it also shields the formation cracks by lowering heat of hydration.
4. Best Use of Locally Available Material:
Mix design permits the employment of locally achievable materials like coarse aggregates, fine aggregates, etc. as long as it’s of eximious quality. This may diminish the value of the project.
5. Desired Properties of Mix:
The concrete thus achieved possesses features like workability, sturdiness, setting time, strength, impermeability, etc. Design is done by keeping in mind a few vital factors like water-cement ratio, gradation of aggregates, etc.
According to the development conditions, admixtures are utilized to ameliorate the features of concrete. Designed concrete blend fulfills the brawn requirement of a structure against several tyrannical environmental effects.
Also, Read: Difference Between Beam and Column | What Is Beam | What Is Column
Disadvantages of Mix Design
- It requires a high initial cost.
- Also, require skilled labor.
- Also, requires specific attention.
Application of Mix Design
- Find out the mean target brawn ft from compressive brawn at 28-day fck & quality control level. ft= fck + 1.65 S, where S = standard deviation.
- Derive water-cement ratio for the target utilizing the relationship between compressive strength & water-cement proportion.
- Evaluate air quantity which is entrapped for optimum nominal size of the blend.
- Select the water content, for the specified workability & optimum size of blends.
- Derive the share of fine mixture in total combination by absolute volume for the concrete utilizing coarse aggregate.
- Regulate values of water & percentage of sand supplied for difference in workability & water-cement proportion.
- Evaluate cement content from the water-cement proportion & additionally the final water content.
- From water & cement per unit volume of concrete & percentage of sand already calculated, derive the quantity of coarse & fine aggregates per unit volume of concrete:
V =[W + (C/Sc)+{(1/p) x (fa/Sfa)}] x [1/1000]
V =[W + (C/Sc)+{(1/1-p) x (ca/Sca)}] x [1/1000]
-
- V = Absolute volume of concrete = Gross vol (1m3) – entrapped air vol
- Sc= Relative density of cement
- W = Mass of water/m3 concrete determined in kg
- C = Mass of cement/m3 concrete evaluated in kg
- p = Fine aggregate: total aggregate by absolute volume
- fa, Ca= Total masses of fine & coarse aggregates/m3 of concrete, respectively evaluated in kg
- Sfa, Sca= Specific gravities of saturated surface dry fine & coarse aggregates, respectively
Also, Read: Difference Between Plinth Level, Sill Level, and Lintel Level.
Uses of Mix Design
Various area uses of mix design are as follows
- Designed to achieve the desired functionality within the plastic phase.
- Determine the minimal energy within the rigid phase.
- Supply concrete at a low cost.
Purpose of Mix Design
- Superior concrete mix design generates the foundation of a sound infrastructure.
- It is actually is a combination of modules which generates desired strength & sturdiness for the concrete structure.
- Because every ingredient within the mixture possesses a range of features, it’s not effortless to prepare a good concrete blend.
- Every one ingredient needs to be tested to note their features & therefore additionally the bearing capacity of the project location is also required to be examined.
- Water, fine sand, coarse aggregate, cement, chemicals, reinforcement, & soil needs to be checked.
- Values derived after testing are utilized for all mix designs. This makes sure that the structure is able to resist failure.
Conclusion
The rules & blended proportions ought to be done attentively as a bijou blunder may result in an adverse effect on the structure. Select the suited ratios of water, cement, fine aggregate, coarse aggregate, admixture for concrete.
Also, Read: How to Load Calculation on Column, Beam, Wall & Slab
Mix Design
Design mix concrete is adopted for high rise constructions. In this type of mix, the mix ratios are decided by an Engineer after analysing the properties of individual ingredients of concrete. Like, cement is tested for Fineness modulus and Specific gravity of cement in the lab while deciding the Design mix ratio.
What Is Mix Design?
Mix design can be defined as the process of selecting suitable ingredients of concrete and determining their relative proportions with the object of producing concrete of certain minimum strength and durability as economically as possible.
Types of Concrete Mix Design
Concrete Grade | Mix Ratio (Cement : Sand : Aggregates) | Compressive Strength | |
MPa (N/mm2) | psi | ||
Grades 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 Mix Design
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.
Disadvantages of Mix Design
- It requires a high initial cost.
- Also, require skilled labor.
- Also, requires specific attention.
Application of Mix Design
The object of mix design is to decide the proportions of materials which will produce concrete of required properties. The mix proportions should be selected in such a way that the resulting concrete is of desired workability while fresh and it could be placed and compacted easily for the intended purpose.
Uses of Mix Design
The object of mix design is to decide the proportions of materials which will produce concrete of required properties. The mix proportions should be selected in such a way that the resulting concrete is of desired workability while fresh and it could be placed and compacted easily for the intended purpose.
Purpose of Mix Design
The object of mix design is to decide the proportions of materials which will produce concrete of required properties. The mix proportions should be selected in such a way that the resulting concrete is of desired workability while fresh and it could be placed and compacted easily for the intended purpose.
Shotcrete Mix Design
Shotcrete typically consists of one part cement and four parts sand by weight with approximately 7% water by mass of dry ingredients. It can also include coarse aggregate and admixtures. Dry mix shotcrete involves the premixing of dry ingredients with water added at the nozzle.
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