First column or brickwork- which is correct in the construction? (Part-1) /Column casting before brick masonry or after?/Confined masonry structure.

 Let us discuss one of the FAQs -  Column first or brickwork -which is correct in the construction? 

OK. You might be knowing that we divide the structural construction as

1. Load bearing structure &

2. Framed structure.

In load-bearing structures obliviously you build the brick walls first to take loads of slabs.

The question arises in framed structures where some contractors build the wall first followed by the column casting or vice versa.

Since the olden days, columns were cast after completing the brickworks to have a good bond between the two structures. This practice was followed in seismic zones to resist the effect of earthquakes on the buildings. 

This type of construction is known as confined masonry structures. 

Now the question that comes to your mind is

Shall we go for the confined masonry structures for good building strength?

Let us observe the advantages & disadvantages of a confined structure to get a clear picture.

Advantages:

1. Provides a good bond between the masonry & RCC structures.

2. Cracks at the junctions & joints of masonry & RCC members are reduced due to the bondage.

3. Minimizes the use of formwork materials & hence saves in your budget.

4. No need to use bonding agents & chicken mesh at the joints & junctions.

5. Provides protection against earthquakes to a certain extent.

6. The external & internal surface of the column falls in alignment with the masonry walls. 

7. No offsets at the junctions & joints.

  Disadvantages:

1. Brick masonry absorbs the water from the poured concrete & thus reduces the column strength.

2. Gaps in between the brick masonry layers become the exit point for the cement slurry while casting.

3. The clear cover for the column reinforcement may get disturbed due to the protruded brick edges within the column.

4. The verticality of the column depends upon the constructed masonry walls. 

5. The original size of the column may get altered as it depends upon the width of the wall.

So, what next?

Certainly, we can reduce the disadvantages by following good constructional practices. Some of the rules or methods to be followed are,

1. Any protruded brick edges should be chipped off so that the dimension of the column is kept intact.

2.  The concrete cover should be placed within the reinforcement before the shuttering works as per the specification. This ensures a clear cover on all four sides of the column. 

3. The brick wall should be wetted with water, prior to the concreting work. All the brick surfaces that come in contact with concrete should be allowed to absorb water. 

4. The cement slurry of the required consistency should be sprayed or splashed over the inner brick surfaces before the casting work.

5. The openings at the bricklayer edges should be smeared with wet clay soils. Applying the clay soil at the formwork & brick wall junctions prevents the oozing of cement slurry up to a certain extent.

6. If the brick wall is not in the vertical plane, plastering at the brick edges should be done by using a plumb bob. This helps the casted column to be on the vertical axis.

Note:

A confined masonry structure can be built for ground & G +1 residential buildings. For multi-storeyed buildings, frames are the priority member followed by the masonry works.

      Continued 👉 Part-2

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Thank you for going through this article❤. Have a good day 😄.

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