Mixing Of Concrete [3 Types] -The Ultimate Guide

Mixing Of Concrete


Concrete is the 2nd Most consumed material in this🌏 planate, according to statistics 25 billion tons of concrete produced each year. So controlling the quality of concrete is essentially important and to produce its best quality Mixing Of concrete is the most prime factor. Here in this post, you will go through step by step procedure of all different types of mixing of concrete.

Mixing-Of-Concrete


Things You Must Kow 

Before you start mixing concrete I am sharing some important factors you must know.

Concrete is a composite material that is made up of mainly Four important constituents. Cement, Fine aggregate ( Sand), Coarse aggregate ( Stone chips), and Water sometimes different admixtures are also required.

Types of Mixing Of Concrete ratio proportions

Grade of concrete for low strength ( for PCC filling)

Grade of concrete

Ratio Proportions

(Cement:Sand: Aggregate) 

 

Compressive Strength (N/mm2)

In Psi
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 Grades of Concrete 

Grade of concrete

Ratio Proportions

(Cement:Sand: Aggregate) 

 

Compressive Strength (N/mm2)

In Psi
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 Grades of Concrete

Grade of concrete

Ratio Proportions

(Cement:Sand: Aggregate) 

 

Compressive Strength (N/mm2)

In Psi
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

There are technically two types of the mixing process

  • Design mix
  • Nominal Mix

The design mix is adopted generally for special types of structures and to obtain high strength as per structural requirements. Used for megaprojects 🏗 like high rise buildings, underground structures (like metro tunnels) & heavy structures like dams. The design mix is generally done for grades above M25.

For M25 and below grades of the concrete, the nominal mix is done as per the standard ratio proportion mentioned on the above table. Nominal mixes are used in smaller household 🏚 constructions.

Importance Of Concrete Mixing 

The stability of a structure depends on the quality of concrete and to maintain the concrete quality it is an utmost important factor to mix it properly.

  • Concrete gives compressive strength to a structure hence, a well-mixed concrete gives better strength.
  • The workability of concrete depends on the mixing.
  • Well, mixed concrete remains cohesive, if not mixed properly it tends to segregate.

Quick- Field Test Of Concrete Mixing 

Here are some quick checks of well & homogeneous concrete mixes.

  • Concrete should be uniform in color ( traditional gray)
  • Cement pastes should presence all around the surfaces of the aggregates.
  • Make a ball of concrete about 75 mm diameter and toss it with hand about half a foot when its land band into the hand, it should not disintegrate. If disintegration occurs it indicates the presence of excessive stone.
  • Make another ball of the same size and toss it about a foot, now it should disintegrate and develop some cracks otherwise it has excessive sand.
  • Another quick test is the workability test by checking the slump.

Method Of Concrete Mixing 

There are generally three standardized procedures for mixing concrete. Actually choosing the right procedure or methodology depends upon the Enginer-in charge of the project, there are several factors upon which the type & the methodology of mixing is adopted.like

  • Cost of the project
  • Amount of manpower involved
  • The distance of the location of pouring from the location of batching/mixing yard
  • Acsesseabilty to the project site.
  • Clearance of approach
  • The volume of concrete needed
  • Desirable quality of the project owner

 

  1. Hand Mixing Concrete ( manual mixing without machine)
  2. Machine mixing Concrete( using mixture machine)
  3. Ready-mix concrete (produced in an automatic/semi-automatic batching plant )

Let’s dive deep into the desired topic and explore three different types of mixing procedures step by step including the pros & cons of each type.


Hand Mixing of concrete


Hand mixing of concrete is the process of mixing without using a concrete mixture machine. This process is generally adopted for a small amount of concreting works where the quality of concrete is not the prime concern. Concrete shall be mixed by hand only when the mixture machine cannot be used due to a low amount of requirements. It is recommended to add10 % extra cement by volume while concrete is mixed by hand.

Tools & Pant Required For Hand Mixing Of Concrete

  • Shovel
  • Spade
  • Steel Rake
  • Aluminum Float
  • Sieve
  • Forma/Batch box
  • Trowel
  • wooden mallet
  • Iron Pan

Procedure Of Hand Mixing Of Concrete 

⇒ The first step is to make a batch box/ forma box if not present at the site.

⇒ Hand mixing is recommended to do on a non-porous steel/aluminum base plate.

⇒ According to the desired mix proportion, sand is to be filled into the batch box using a spade to get the exact required volume ( For example: In case of 1:1.5:3 mix 1.5 part sand is to be filled into the box) Strongly recommended to use a batch box.

⇒ Spread the measured quantity of sand evenly over the steel base plate.

⇒ Cement is to be measured in the same way as sand to its required ratio.                  ( remember to add to extra 10% cement by its volume )

⇒ Then, that measured cement is to be dumped into the sand.

⇒ Next, the sand & cement is to be mixed properly by turning it repeatedly using a spade to prepare a homogenous mix until the color becomes uniform throughout the mix and free from streaks.

⇒ After evenly mixing of sand & cement, it is time now to put the coarse aggregate into it, measure it the same way using the batch box ( Further recommended strongly for hand mixing of concrete) now, spread the measured quantity of course aggregate over the mixture of sand and cement.

⇒ Then the whole mass of the mixture is to be turned & twisted repeatedly from the side of the mixture to the center and back to the center again and have to repeat it several times until the mixture becomes uniform & the coarse aggregate should fully be covered and mixed all around.

⇒ After entirely mixing the main three constituents (Cement, Sand & Aggregate) fourth item will come into the frame-Water. Depression is to be made at the center of the whole mix and then 75 % required amount of bis to be added. And again have to perform the above mixing procedure using a shovel, after 1 or 2-minute remaining amount of water is to be poured and continue the mixing process until it develops a uniform color & consistency throughout the mix. Remember The process of mixing is to be done for a minimum of 5 minutes in case of hand mixing concrete.

⇒ Finally, it is time to pour the mixed concrete into the formwork, and after mixing remember to clean & wash the non-porous base plate.

Advantages of Hand Mixing of concrete

  • Easy to transport, can be mixed near the concreting area.
  • Easy for a small amount of concrete.
  • PCC can be hand mixed.

Disadvantages of Hand Mixing of concrete

  • Good quality of concrete cannot be obtained.
  • Not recommend for structures like Column, beams & slabs.
  • The ratio is not maintained in a proper way.
  • The mix doesn’t become homogeneous.
  • Strength not developed as desired.
  • More manpower is required.
  • The time involved in concrete is more than a machine mix.

Precautions To Taken For Hand Mixing Of Concrete

There are certain precautions that are to be taken while hand mixing of concrete  as follows:

  • Should not mix a large amount of concrete at a shorter interval of time, the mix shall be poured as soon as possible after the completion of mixing.
  • The mix should perform on a good quality impervious steel base plate free from corrosion  & dust. this can also be performed on the smooth clean surface of brick or concrete floor. Never mix the concrete over mud or dust.
  • The mixing area has to have sufficient clear space to accommodate the ingredients at least the volume of one bag cement and its proportionate materials sand & aggregate.
  • The order of addition of materials should properly maintain its sequence and method ( i.e. Firstly sand has to be dumped then cement is to be added followed by mixing aggregate should be added finally mix them with water )
  • The platform over which it is to be mixed should be free from water.
  • The mixing should not perform in a hurry take at least 5 minutes of time.
  • Good clean & free from rust tools shall be used ( shovel & spade)
  • Water shall be mixed in intervals, not in one stretch.
  • The batch box is a must-use tool to produce good concrete and it should be measured to accommodate exactly the amount of one bag cement, not more or less. Do not forget to clean the box before using it.
  • Sand must be sieved
  • Coarse aggregates ( stones) must be thoroughly cleaned with water.
  • All laborers shall wear PPE’s  ( gloves, mask, shoes, helmet)
  • Try not to mix the concrete under direct sun, water might get evaporate thus leaving the mixture dry.
  • The iron pan used to lead the concrete must be free from rust.
  • Don’t forget to add an extra 10% cement.
  • The base platform must be cleaned after every use.

Machine Mixing of concrete


Machine mixing is the process of mixing concrete in the mixture machine. It is highly efficient to produce consistent quality of concrete in a shorter span of time. There are different types of mixture machines available in the market starting from diesel-operated machines to an electric machine and it is also categorized by its production capability. Remember the size of the mixture should accommodate the ingredient of at least one batch. 200 ltr or 7/10 is commonly used.

Tools & Plants Required For Machine Mixing Of Concrete

  • Ghamelas
  • Batch Box
  • Shovel
  • Spade
  • Mallet

Procedure Of Mixture Machine- Mixing Of Concrete 

⇒ At the very beginning clean the inner surface of the mixing drum & wash it with water properly.

⇒ Now, in the case of machine mixed concrete coarse aggregate is the first constituent which is to be dumped into the machine hopper, before you dump the stones into the hopper remember to wash and then measure it using forma box/batch box.

⇒ Coming to the next process, sand is to be filled over the dumped coarse aggregate followed by cement at last.

⇒ Add 1/4th of the required amount of water.

⇒ Then the machine shall be start & lever of the hopper is to be pulled to lift the hopper (in case of a manual hopper) after lifting the hopper all filled ingredients goes into the running drum of the machine.

⇒ Next, add the remaining amount of required water into the drum, and let it mix for two minutes.

⇒ Finally, remember to clean the hopper & the drum after using it.

Advantages of Mchine Mixing of concrete

  • It produces concrete fast as compared to all other processes.
  • Require less manpower than hand mixing.
  • The mix becomes more constant, homogeneous & uniform in color throughout the mix.
  • It is a cost-effective way to produce concrete.

Disadvantages of Hand Mixing of concrete

  • It is a fixed machine hence it takes time to transport the concrete near the concrete area.
  • Difficult to produce high-grade concrete. ( above M 30)

Precautions To Taken For Machine Mixing Of Concrete

  • The mixing drum should be cleaned & free from dust.
  • The alignment of the mixing blade inside the drum should be proper it should be checked before starting the mix.
  • Remember to use the forma box.
  • The drum should be wet before starting the mix.
  • The produced concrete should be sure within half an hour after discharge.

Ready Mix concrete


Ready Mix concrete is the most heard term in the construction field. Ready-mix concrete can be produced at the site by installing automatic or semi-automatic batching plants and one can also buy concrete from a dedicated RMC ( ready mixed concrete ) supplier.

It is the process of producing concrete in a batching plant based on the standard specifications desired and approved by the client or consultants. After producing the concrete the mixture is poured into the transit mixture and then transport to the construction site and the transit mixture is mounted over a Truck.

Tools & Plants Required For Machine Mixing Of Concrete

It is generally produced in large automatic or semi-automatic batching plants.

  • Batching Plant
  • Transit Mixture
  • Lab equipment
  • Concrete Pump

Production Of Ready Mixed Concrete 

⇒ As it is produced in factories or the large project sites it has a dedicated area of storing the raw materials.

⇒ Required all raw materials are quality tested before starting the batching.

⇒ All raw materials of the required amount (according to the mix design)are loaded automatically to the plant through a set of computer-aided instruction, then the report of batching is generated. the whole process is fully automatic.

⇒ After completing the mix the plant automatically discharges the concrete.

⇒ Concrete is loaded in specially designed truck mounted mixtures called transit mixture wherein the concrete is kept under continuous agitation until it is taken out for use.

⇒ In case of a high rise building construction, the concrete is lifted to the upper floors using a concrete pump. plasticizers are used to keep the fluidity of the concrete.

Advantages of Ready Mixed concrete

  • Optimum quality of concrete can be produced in plants under close supervision & quality control.
  • No hassles of procuring raw materials & no worry for required huge storage area.
  • Noise pollution can be avoided.
  • It saves lots of cement consumption
  • The bulk amount of concrete can be produced in a short amount of time.
  • It increases the life cycle cost of a project.

Disadvantages of Ready Mixed concrete

  • Cost of setting batching plant at is very high
  • A lot of time loss might happen during the transporting of concrete this can lead to workability loss of concrete.
  • Transit mixture might get stuck in the traffic jam hence it leads to the setting of concrete.

So Let’s Sum It Up, we have discussed the different process of mixing of concrete all the information given in this article is based on my 7 years of experience in working at the site and at management levels.

The type of process involved in the mixing concrete is different from site to site as per the requirement of the client/owner or the structural consultant. Out of my experience, I gained at the site the best suitable method mixing concrete for a small project is through using a mixture machine and for larger projects over a spread area or for a highrise building the most cost & time effective way to use ready mix concrete. Finally, from an engineer’s perspective, I will recommend not to use hand mixing of concrete for major or serious structures though can be used for small works & for PCC works.

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