Difference between Precast & Cast-in-situ Concrete

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Nowadays, the construction industry is growing more and more with new technics. Various researches and development programs are held by researcher and national association to find economic and time-saving technics for construction. Precast concrete is one of them. Do you know precast concrete?

Precast concrete is the new construction technic that makes construction speedy and economical on the large construction projects. It has many advantages over the cast-in-situ concrete method for construction. Cast-in-situ concrete is the easy and conventional method that we have been seeing for past decades.

Precast & cast-in-situ concrete are the product produced by casting concrete in a mould or formwork cured to get the strength of RCC elements. The precast concrete is transported to the construction site, lifted and positioned at the predetermined place. The cast-in-situ concrete is a standard concrete which is poured into the specific formwork on the site and cured to get the strength of RCC elements.

Here, we will discuss the differences between the precast & cast-in-situ concrete.

Precast Concrete VS. Cast-in-situ Concrete

01. Definition

Precast Concrete

  • According to ‘Precast Concrete Institute, U.S.A’ (Published in: Designing with Precast and Prestressed Concrete), precast concrete is cast into a specific shape at a location other than building site like factories. The concrete is placed into a form, typically wood or steel, and is cured. These components are then transported to the construction site for erection into place. Precast concrete can be plant-cast or site-cast.

Cast-in-situ Concrete

  • According to ‘Edward Allen and Joseph Iano’ (Author of Fundamental of Building Construction Materials & Methods), cast-in-situ concrete is cast into forms on the building site. It offers unlimited possibilities to the designer for any shape formation with a limitless selection of surface textures.

02. Casting

Precast Concrete

  • In the precast concrete, elements are manufactured in a controlled casting environment and hence it is easier to control mix, placement and curing.
  • Elements can be cast in advance and held until the hour you need them, thereby saves time.
  • Weather condition has no effect on casting work.
Precast Concrete Elements

Precast Concrete Elements

Cast-in-situ Concrete

  • In the cast-in-situ concrete, column, slab etc. elements are casted on site in the open environment and hence it is difficult to control mix, placement and curing.
  • Elements cannot be casted in advance.
  • Weather condition can delay the casting work.
Cast-in-situ Concrete construction of Slab

Cast-in-situ Concrete Construction of Slab

03. Quality Control

Precast Concrete

  • Quality can be controlled and maintained easily.

Cast-in-situ Concrete

  • Quality control and maintenance is difficult.

04. Cost

Precast Concrete

  • Precast concrete is cheaper form of construction if large structures are to be constructed.
  • Maintenance cost of precast concrete structure is higher.

Cast-in-situ Concrete

  • In situ concrete is cheaper form of construction for small structures.
  • Maintenance cost of cast-in-situ concrete structure is less compared to the precast concrete structure.

05. Requirement of Worker & Machinery

Precast Concrete

  • Less labours are required.
  • Skilled labours are required at construction site.
  • Skilled and technical contractor is required for construction of the precast concrete structure.
  • Precast concrete requires heavy machinery and cranes for handling i.e. lifting and installation of heavy elements
Heavy Machinery Used for Precast Concrete Construction

Cast-in-situ Concrete

  • More labours are required.
  • Skilled labours are required at construction site.
  • Local contractors can also build the structure.
  • Cast-in-situ concrete does not require such handling equipment.

06. Strength

Precast Concrete

  • Precast concrete construction is quick as it can be installed immediately and there is no waiting for it to gain strength.
  • Increase in strength can be achieved by accelerated curing.
  • On site strength test is not required.
  • High strength concrete can be used because it is in controlled condition.

Cast-in-situ Concrete

  • In situ concrete construction is slow as gaining of strength requires time.
  • Increase in strength at situ by accelerated curing is a difficult task.
  • On site strength test is required.
  • It will difficult to use high strength concrete as it depends on site condition and resources available.

07. Time of Construction

Precast Concrete

  • Total construction time is less as compared to cast-in-situ.
  • Speedy construction is possible.

Cast-in-situ Concrete

  • Total construction time is more as compared to precast.
  • Speed is less as elements are casted at site.

08. Technical Points

Precast Concrete

  • Large number of joints in structural system.
  • Less resistant to Earthquake and wind forces not recommended where seismic loads are dominant.
  • In precast concrete construction, details at the joint become very critical and needs careful attention.
  • The elements have to be designed for handling stress or loads during handling, which may or may not increase steel.
  • Elements of varying lengths and shape can be developed.
  • Precast concrete does not offer a monolithic architectural character.

Cast-in-situ Concrete

  • Less number of joints present in structural system.
  • More resistant to earthquake and wind forces.
  • Elements cannot be casted in advance.
  • Elements are not to be designed for any such loads or stress.
  • There is constraint in length and shape of element.
  • In situ concrete offers a monolithic architectural character.

09. Surface Finishing

Precast Concrete

  • According to ‘Bulletin of American Concrete Institute‘ (1993), precast concrete gives smooth interior finish hence they need minimum preparation before paint, wallpaper etc. or the other wall coverings can be applied directly.

Cast-in-situ Concrete

  • In the cast-in-situ concrete construction, you have to do plaster for the smooth finish and also requires pre-preparation for a paint like wall putty etc.

10. Points to Be Taken Care of

Precast Concrete

  • One has to meticulous during work with precast concrete because the precast unit can be damaged during transportation and handling.

Cast-in-situ Concrete

  • In the cast-in-situ concrete construction, be careful about following points:

01. During the concreting process like mixing, transportation, placing, finishing etc.

02. Curing of concrete for certain time etc.

In the final note, precast & cast-in-situ concrete both are the easy construction technics. Both methods have their advances such as precast concrete construction gives cost benefits on a large project, quality assurance due to control casting condition, reduces the high supervision of concreting process like mixing, placing etc. at the construction site. On the other side, cast-in-situ concrete is the conventional method for concreting, it is very and largely used for construction, and any local contractor can adopt this method.

Also Read:

Difference between R.C.C. Frame & Load Bearing Structure
RCC bands in Load Bearing Structure (Masonry Building)
Difference between Reinforced Concrete & Steel Framed Structure

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