Mix Design of Concrete
What is Mix Design of Concrete?
Mix design of concrete defined as the art of selecting suitable materials combination of concrete to achieve their relative required proportions of concrete for certain minimum required strength
Mix design of concrete is code is IS 456:2000, give the different numbers of grades of concrete mix are categorised into M5, M7.5, M10, M15 etc
Where M represent Mix and the number behind M represent for Characteristic compressive strength (fck) of concrete materials after 28 days in N/mm2
Objective of Concrete Mix Design
The main purpose of calculating the mix design of concrete ratio is to make sure the proportions of the materials with the optimum requirement to fulfil the requirement of the structure building
Mix design should ensure the following object
- To gain the designed Workability of concrete in the Plastic stage
- To gain the desired minimum strength of concrete in the hardened stage
- To gain the desired durability in the given environmental conditions
- To produce concrete as economically as possible
What is the code for the mix design of concrete?
The code for the design of concrete is IS 10262-2009
Basic considerations of mix design
- Cost
- Specifications
- Workability
- Strength and durability
1. Cost
The cost of a concrete mix design depends on material cost, Equipment cost, Labour cost etc
There are lots of variation in the cost of concrete materials like cement is costlier than aggregate So that our main aim is to reduce cement content as possible
But without sacrificing the desirable properties of concrete, such as strength and durability
Substitution of pozzolanic materials like fly ash or ground iron blast furnace slag, for portland cement, is likely to reduce the cost of materials
2. Specifications
The following points may be kept in mind while designing a concrete mix design procedure as per is code
- Minimum compressive strength required
- Maximum water/cement (w/c) ratio
- Maximum cement content to avoid shrinkage cracks
- Maximum aggregate/cement ratio
- Maximum density of concrete in case of gravity dams
3. Workability
Some key point related to Workability should be kept in mind while designing concrete mixes for any purpose
The consistency of concrete should be no more than that necessary for placing like Compacting and finishing
At the time of placing concrete mixes requiring high consistency so that the use of water reducing and set regarding admixtures should be used rather than the addition of more water
If possible, increase the sand/aggregate ratio instead by increasing the proportion of the fine particles in the sand to improve the cohesiveness and finish ability of concrete
4. Strength and durability
It is generally achieved not by increasing the cement content but achieved by decreasing the water demand at a given cement content
We can reduce Water demand by a thorough control of the aggregate grading and by using water-reducing admixtures
- Nominal Mix
- Design Mix
1. Nominal Mix
The nominal mix is that type of design mix in which specifies the fix proportion of the cement, sand and aggregate
- Nominal mix concrete design generally used in small quantity or also used when the amount of load is small
- Prepare on-site normally due to the small quantity
|
Mix design of concrete ratio for M5 |
1:5:10 |
|
Mix design of concrete ratio for M10 |
1:3:6 |
|
Mix design of concrete ratio for M15 |
1:2:4 |
|
Mix design of concrete ratio for M20 |
1:1.5:3 |
Where I take M20 example in M20 M denote to Mix and 20 denote to strength in N/mm2 and 1 part of cement, 1.5 part of sand and 3 part of aggregate
2. Design Mix
Design mix concrete is recommended for high rise building construction
In this type of design mix proposition of material is calculated by the engineer after all required test performed on materials like
Fineness, soundness, Setting time both initial & final time, Compressive strength, Consistency of standard cement paste watch video to full detail like which IS CODE required for which test and also for all materials
Used in heavy structure construction
|
M25 |
1:1:2 |
|
M30 |
1:0.75:1.5 |
|
M35 |
1:0.5:1 |
|
M40 |
1:0.25:0.5 |
But the above proposition is not fixed it varies depending on materials and conditions
FAQ 1: What is Mix Design of Concrete?
Mix design of concrete defined as the art of selecting suitable materials combination of concrete to achieve their relative required proportions of concrete for certain minimum required strength
FAQ 2: What is the Objective of Concrete Mix Design?
1. To gain the designed Workability of concrete in the Plastic stage 2. To gain the desired minimum strength of concrete in the hardened stage 3. To gain the desired durability in the given environmental conditions 4. To produce concrete as economically as possible
FAQ 3: What is the Basic considerations of mix design?
The following point must be considered while designing concrete mix design 1. calculations 2. Cost 3. Specifications 4. Workability 5. Strength and durability
FAQ 4: How many Types of mix design of concrete?
There are mainly two types of mix design types: 1. Nominal Mix 2. Design Mix
FAQ 5: What is the code for the mix design of concrete?
The code for the design of concrete is IS 10262-2009
