10.8 Precast v/s Cast in Situ Construction:
To a d o pt Precast concrete or site cast concrete for a specific building is an important
decision. This is a crucial question for anyone moving forward with a commercial
building project. Depending on project specific needs, we may choose to go with
one over the other. Because on site concrete pouring is custom to the build, it is
incredibly versatile. However, it is also far costlier, labor intensive and time intensive.
While precast concrete does have to be hauled to location, its unparalleled quality,
affordability, and longevity make it stand out against its on-site competitors. Given
below is a comparison of precast and cast – in- situ construction.
- It is poured and molded over rebar or wire and then cured offsite. This involves
pouring concrete into pre-made molds and then cured under ideal conditions
within the manufacturing plant itself. Once hardened and ready for use, those
preformed concrete products are shipped to the job site where they are
assembled into the desired structure. As opposed to precast, site cast, some
times known as in-situ concrete, is poured, molded and cured on site. Like precast
concrete, on site concrete is formed in a mold and then lifted in place. - 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. - 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, there
by saves time. Weather condition has no effect on casting work. In the cast-
in-situ concrete, column, slab etc. elements are cast on site in the open
environment and hence it is difficult to control mix, placement and curing.
Elements cannot be casted in advance. Weather conditions can delay the
casting work. - It is a cheaper form of construction if large structures are to be constructed. In
situ concrete is cheaper form of construction for small structures. - Precast concrete requires heavy machinery and cranes for handling i.e. lifting
and installation of heavy elements. Skilled and technical contractor is required
for construction of the precast concrete structure. Cast-in-situ concrete does
not require such handling equipment; more labor is required for this at the
construction site. - 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. In situ concrete construction is slow as gaining of
strength requires time. Increase in strength at situ by accelerated curing is a
difficult task.