what is the advantages and disadvantages of precast in construction?

Answer 1

Some of the advantages - cost - since it is made by a company and shipped to the site, there is no need for formwork for precast elements. Formwork is commonly quoted at 40-60% of the cost of concrete construction. Depth of the elements can also be an advantage since they can be roughly sized by the engineer, confirmed by the precast supplier.

Disadvantages - it is another thing that the engineer needs to review a submittal on, it needs a lead time to construct it, (it is still faster than cast in place with formwork design and construction)..
It is not available everywhere and isn't very economical to ship long distances. There isn't a lot of flexibility in depths, planks are commonly available in 4", 6", 8", 10", and 12". If your span or loads exceed the capacity of these modules, there isn't much chance a precaster will produce custom beds for your project. Precast concrete is viewed as a comodity and bidded as such.
Precast elements are solid, and openings in the plank/slab for piping, ducts, elevators, stairs, etc. need to be coordinated before the precast is made (smaller openings can be field cut, but the precast engineer should be consulted and made aware of the location of the openings so they can confirm the openings are ok).
Lastly, precast does not have the same level of connectivity that is present in a cast in place structure, to get around this, it is common to install embed or weld plates into the precast and then field welding is needed to connect the various parts together. Field welding is expensive compared to bolted connections (which aren't practical here but are a preferred method of connecting steel structures in the field). This is more critical in seismic zones, but remains an issue where a missing embed plate will cause a lot of trouble to create the required connection. Other precast elements (beams, columns), have similar issues, particularly with connections and field welding needed to provide continuity.
A disadvantage common to cast in place concrete is that precast and cast in place structures are heavier than steel structures resisting similar loads. Heavier concrete also means earthquake forces are higher than for a similar steel structure. These both add up to more expensive frames, and heavier (and thus more expensive) foundations.

Answer 2

I remember a commercial that showed a couple of eggs in a frying pan and the tag line said - this is your brain on drugs. Another one was the photo of an old wrinkled woman with a cigarette in her mouth with the tagline - Smoking is Glamorous. If you can do something like that visually, because most people will spend about 20 seconds reading and retaining what you say, but will look at photo and be able to tell you years later what was on it - how about a photo of a super skinny anorexic model who eats 8 grapes a day and ends up dying and a photo of an extremely obese person a the other end of the rung, and one with a person in reasonable shape, looks like exercises, eats good foods then ask the question - Healthy? Your Choice!! It has been said a picture is worth a 1000 words - think about it.

Answer 3

Advantage: greatly reduced construction time
Disadvantage : design limited by precast unit dimensions

Answer 4

Precast Concrete Advantages