Concrete Mixing
Concrete mixing combines all its ingredients as required following the mix proportions of the relevant grade of concrete.
Let’s what are the mix proportions?
When concrete is made for different purposes, we consider different grades of concrete. The grade of the concrete represents its strength.
The strength of the concrete is achieved by different combinations of cement, water, and aggregate(fine and coarse). The leading ratio that we consider in categorizing strength classes is the water-cement ratio.
Types of Concrete Mixing Methods
Mainly, there are three methods for concrete mixing
- Hand Mixing
- Machine Mixing (Mixer Machine)
- Ready Mix Concrete
Hand Mixing
This is also called manual mixing in construction.
All the work is done manually without using any machinery. Mixing and quantifying the required material will be done as per the standard practices.
This is very common in small-scale projects. Construction of single-story buildings and two-story buildings is mostly done with manual mixing.
If we follow the correct practices that make sure the quantities of each material are correct, no need to worry about this method.
However, wrong practices would lead to strength and durability issues in the concrete. Therefore, we have to be careful when hand mixing is done to produce the concrete.
In addition, workers get tired when concrete mixing is done for a longer duration. It could lead to a loss of consistency of the concrete.
The following table indicates the typical mix proportions for a 50kg Cement bag.
| Specified mix | Equivalent Concrete Grade | Fine Aggregate | Coarse Aggregate | Approximate Water content in liters |
| 1:1:2 | C30 | 0.035 m3 | 0.07 m3 | 20 |
| 1:1.5:3 | C25 | 0.053 m3 | 0.105 m3 | 22.5 |
| 1:2:4 | C20 | 0.07 m3 | 0.14 m3 | 25 |
| 1:3:6 | C10 | 0.105 m3 | 0.210 m3 | 35 |
| 1:4:8 | 0.14 m3 | 0.28 m3 | 40 |
Practically, the quantities except for the water, would be difficult to measure by the column easily.
Therefore, people tend to use boxes made tally with the above quantities.
The internal size of the box will be 400x350x250 mm and it is quat to 0.035m3.
Thus, the above table can be written as follows.
| Specified mix | Equivalent Concrete Grade | Fine Aggregate Boxes | Coarse Aggregate | Approximate Water content in liters |
| 1:1:2 | C30 | 1 box | 2 box | 20 |
| 1:1.5:3 | C25 | 1.5 boxes | 3 boxes | 22.5 |
| 1:2:4 | C20 | 2 boxes | 4 boxes | 25 |
| 1:3:6 | C10 | 3 boxes | 6 boxes | 35 |
| 1:4:8 | 4 boxes | 8 boxes | 40 |
It is commonly observed that the quantity measurements are not done accurately and not following the method discussed above when concrete mixing is done.
As a result, low grade concretes can be observed. Inconsistency of adding the water to the mix also reduces strength with the increase of the water-cement ratio.
Machine Mixing (Mixer Machine)
Machine mixing is more advance than hand mixing in terms of the mixing method and having a mixture with equal consistency each time.
However, the amounts of materials that are poured into the bin could be the same if not control it correctly.
A proper mechanism shall be established to make sure the quantities are in accordance with the mix design.
For example, the water-cement ratio plays a major role in strength development. If we add more and more water it leads to reduces the strength of the concrete.
As indicated in the above table, we may use standard boxes to measure the quantities. Wate also can be measure and pure into the bin much easily. With that, concrete having the required strength can be produced.
This is a machine that works with the help of a motor. The number of rotations will depend on the mixing concrete. This can be moved easily from site to site.
The concrete mix can then get out and be poured into the place.
Readymix Concrete
The ready mix concrete is the type of concrete most widely used in the work in construction work.
The two types of concrete which are based on the mixing method, are using in small-scale projects.
Readymix concrete projection is a more complicated process that is connected with modern technology. All the measurements are done electronically and with a single button push, we can get the concrete into the truck mixture.
Fine aggregates, coarse aggregates, cement, water, and other additive are added to the mixing bin electronically. Initially, we need to provide the quantities required based on the mix design. Thereafter all things can be done by pressing a button.
The following figure indicates the whole process of ready mix concrete projection.
Though this required some pre-planning, this is the easiest method to produce the concrete.
The article written as Ready Mix Concrete could be referred for further information.
