What Is Concreting| Types & Processes| Step by Step

 Concreting

 Concrete is a product obtained artificially mixed, by hardening of a mixture of Cement, sand, gravels, and water in predetermined proportions. The process of mixing and pouring it into the desired location is called Concreting.

For a Fact!  Concrete is the second most consumed material in this planate after water”


What Is Concreting 


As from the definition, we knew the mixture of concrete requires the main three constituents Cement, Sand, Aggregate, and Water.

Concreting is the major and milestone activity in a construction project followed by reinforcement & formwork in construction. Concretes are used in major structural elements of a structure like foundations, beams, columns, walls, slabs, etc.


Technical Information Required Before Concreting 


  • Type and grade of concrete
  • Type of cement to be used
  • The maximum or minimum size of aggregates
  • Cost of concrete
  • Mix design of concrete
  • Process of mixing to be adopted
  • Type of tools and manpower used
  • Quality control during
  • Tests on concrete

What Are the Types of Concrete Used in Construction?


There are generally two types of concrete PCC (plain cement concrete) and RCC (reinforced cement concrete)

Types of concreting

PCC is the type of concrete that is done without and reinforcement steel, generally, it is done bellow the foundation rafts and footings to avoid the settlement and to strengthen the base over which steel reinforcements of the foundation are placed.

RCC is done using reinforcement steel hence, it is termed reinforced cement concrete. For information, concrete is used in structures to bear mainly the compressive loads and it is only able to withstand 10 % of its compressive strength in terms of tension, hence reinforcement steels are provided in concrete to impart tensile strength thereby making the structure strong in both terms.


Grades of Concrete Used in construction


Grade of concrete for low strength (for PCC filling)

Grade of concreteRatio Proportions (Cement: Sand: Aggregate) Compressive Strength (N/mm2)  In Psi
M51: 5: 105 MPa725 psi
M7.51:4:87.5 MPa1087 psi
M101:3: 610 MPa1450 psi
M151:2:415 MPa2175 psi
M201:1.5:320 MPa2900 psi

Standard Grades of Concrete 

Grade of concreteRatio Proportions (Cement: Sand: Aggregate) Compressive Strength (N/mm2)In Psi
M251: 1: 225 MPa3625 psi
M30Design Mix30 MPa4350 psi
M35Design Mix35 MPa5075 psi
M40Design Mix40 MPa5800 psi
M45Design Mix45 MPa6525 psi

High Strength Grades of Concrete

Grade of concreteRatio Proportions (Cement: Sand: Aggregate) Compressive Strength (N/mm2)In Psi
M50Design Mix50 MPa7250 psi
M55Design Mix55 MPa7975 psi
M60Design Mix60 MPa8700 psi
M65Design Mix65 MPa9425 psi
M70 Design Mix70 MPa10150 psi

Material Used in Concreting


As we have discussed three main required materials in concrete. Their types, for example, type of cement, size of aggregate to be used in construction for making concrete varies from project-to-project structure to structure depends on the suggestion and technical specification given by consultants or Engineer-In charge.


Cost Of Concreting


The cost of concrete also varies from place to place as the cost of available raw material is different from place to place. So, before determining the price of concrete per meter cube rate analysis is to be done. Here we are listing some factor that affects the rate of concrete.

  • Place of work
  • The volume of total concreting for the project.
  • Hight of the structure.
  • Availability of required raw material.
  • Type and the quality of cement to be used.
  • Methode of mixing of concrete.
  • Rate increases if any admixtures are used
  • Type of concrete to be used.

What Is Mix Design in Concreting


Mix design is the special process where concretes are mixed on the basis of results obtained from the performed trials mixes. This process is adopted to obtain the best and strong concretes on lower a cost, this process involves lots of calculations and laboratory experiments, it is generally done by mixing the all required materials into the calculated proportions to minimize the consumption of cement, after mixing the concrete specimens are taken and tested to finalize the design mix.


What is the process of Concreting?


The process of concreting involves many steps as it is a milestone activity there are many operations are involved before we actually start concreting.

Activities before concreting

As we know there are generally two types of PCC and RCC.

As the PCC is done just below the foundations, we have to excavate the earth first and then Brick soling is done for some cases and sometimes PCC is done directly over the soil.

In the case of RCC, making and laying of reinforcement is done as per the bar bending schedule then formwork is done to pour the concrete in the desired shape or size according to the design of the structure.

Here are some points to check before concreting is stated below:

Checks before concreting 

  • Ensure Construction Joint preparation as per procedure given in Procedure.
  • Prepare system formwork, shutters, and erect & check.
  • Transfer level reference on Shutter, and mark top of concrete levels.
  • Provide inserts, Pockets, block-outs and any other openings, service crossings, etc. as per Services Drawings shall be checked.
  • Fix Reinforcement as per drawings and bar bending schedules. Place cover blocks.
  • Close the shutters and check plumb, rigidity, etc.
  • Start concreting after getting clearance in Pour cards from Client.
  • Prepare the construction joint for the next pour as per the procedure.
  • Conduct inspection of Line, level dimensions and surface quality finish.
  • Close all tie rod holes & anchor cone holes and cure it with water.
  • Inspect and clean the starter bars continuing from this level

Batching or mixing of concrete

Batching and mixing of concrete are the prime activity in concreting works. The mixing of concrete can be done in many ways, there are generally three types of mixing done in terms of production method

  • Hand mixing,
  • Machine Mixing
  • Ready-mix concreting.

The process of mixing is of two types Nominal mix and Design mix. The nominal mix is done up to the M25 grade of concrete. Higher grades are generally done by design mix concrete.

Now all the ingredients are measured in the batch box one by one and they are dumped into a mixing plate or platform and they are being mixed by shovel and spade in case of hand mixing. 10 percent of cement is added extra if it is hand-mixed concrete then the process of mixing is to be done at least five minutes. Hand mixing should be recommended to avoid at the site, it can only be used for a very little amount of concreting where quality is not taken into consideration.

For machine mixed concrete aggregate stones are measured first and dumped into the hopper of the machine the sand is measured in format/batch box and dumped over the stones finally cement is added at the top and all the materials are poured into the running drum of the machine followed by adding some water into the drum and it is mixed about 2 minutes minimum before discharging the mixture.

Ready-mixed concrete is either produced in factories or in large automatic batching plants installed at large construction projects where a large volume of concrete is required and the quality of concrete is the foremost concern. In this type of mixing all the materials like cement, sand, aggregate, and water are laboratory tested individually. Say initial and final setting time tests and consistency tests are conducted for cement, for sand and aggregates fineness module tests are conducted and the PH value of water is checked and many other important tests are conducted before using them in the batching plants.

Checking Of Quality Before Concreting 

Quality tests for concreting

Image credit Ultratech

After mixing and discharging the concrete some quality checks are conducted at the site by taking the specimen of concrete. Generally, workability, cohesiveness, and compressive strength tests are conducted at the site. A cube test is performed to check the compressive strength. And workability of concrete is determined by conducting various tests like (1) Slump test (2) Compacting factor test (3) Vee-Bee test (4) Vibro-workability test.

The slump test is generally performed instantly just after the discharging of concrete. other tests are performed at later stages in the laboratory.

Transporting Of Concrete

Transporting concrete done in many ways by using different types of machines.

Concreting transportation

In the case of concrete mixed at the site, it is transported from one corner to another corner of the site using manual chute carts or mini dumpers or even using a shovel loader machine.

For the case of concrete is imported from outside of construction site from a batching plant and in case of large site transit mixtures are used it is a special type of mixing drum mounted on a truck to transport the concrete from place to place. And moreover, if the concrete is to be lifted at upper floors in case of a Highrise building construction concrete pumps are used and to execute large areas of concrete and conducting it faster boom-mounted pressure pumps are used.

Pouring of Concrete

Concreting work

The main objective is to pour the concrete into the proposed formworks after we receive the concrete, we should start pouring it into the desired location without any further delay, concrete work is to be completed within a certain amount of time before it gets sent. I am sharing some step-by-step procedure of concrete pouring:

Compaction Of Concrete

  • We shall take care to use a suitable type of immersion or surface vibrators.
  • We shall take care to avoid vibration and bleeding.
  • Insert Immersion vibrator minimum 100 mm away from the shuttering face vertically to the full depth, and withdraw vertically and slowly, do not drag.  Don’t allow the needle to touch the reinforcement.
  • We shall ensure Keeping of enough spare vibrators and needles.

Finishing Of Concrete

  • Finishing is carried out after a little stiffening of concrete has occurred with suitable tools.
  • We shall ensure providing green cut immediately after finishing a particular layer of concrete by using a wire brush and small brooms and cleaning it thoroughly.

Removal Of Formworks

After concreting is completed, formwork has to be released for further use and to proceed to the next stage of the project. There are some standardized periods of removing the formworks.

Curing Of Concrete

Curing is the process of keeping the concrete hydrated at least for seven days after removal of formwork, and maybe some more depending on the structure as per the requirement of Engineer-In-Charge of the project.

We shall use one or a combination of the following curing methods shall be adopted depending on site conditions, availability of curing materials, type of job, economy, etc.

Summing Up, in this article, I have shared the best knowledge available to me based on my 7 years of experience in the construction field. Concreting is the most common activity in a construction project.

 

 

You may also like...

Leave a Reply

Your email address will not be published. Required fields are marked *