reinforced concrete floor systems can provide an economical solution to a wide variety of situations. Numerous types of nonprestressed and prestressed floor systems are available to satisfy virtually any span and loading condition

Cast-in-place reinforced concrete floor systems (a) flat plate, (b) flat slab, (c) oneway joist, (d) wide-module joist, and (e) two-way joist

pros – high-quality – eco-friendly and saving forest – lots of reinforcement needed for seismic resistance are arranged at the factory • cons – higher cost than cast-in-situ – unable to change member dimensions at the site – unable to make holes at the site – long, large and heavy members cannot be transported

(• Service load – carry service load – transfer service load to beams, walls and columns – deformation (< L/300) and vibration • Earthquake load – transfer horizontal load from upper floors to columns and walls in lower floors – rigid and strong enough to make assumption in structural calculation valid -> diaphram action • Other issues – fire resistance, noise and heat insulation, and durability)

Following are the advantages of precast concrete:

1. The concrete of superior quality is produced as it is possible to have better technical control on the production of concrete in factory.

2. It is not necessary to provide joints in the precast construction.3. The labour required in the manufacturing process of the precast units can

easily be trained.4. The moulds employed for preparing the precast units are of steel with exact

dimension in all directions. These moulds are more durable and they can be used several times.

5. The precast articles may be given the desired shape and finish with accuracy.

6. The precast structures can be dismantled, when required and they can then be suitably used elsewhere.

7. The transport and storage of various components of concrete for cast in situ work are eliminated when precast members are adopted.

8. The work can be completed in a short time, when precast units are adopted.9. When precast structures are to be installed, it is evident that the amount of

scaffolding and formwork is considerably reduced

Disadvantages of Precast Concrete

Following are the disadvantages of precast concrete:

1. If not properly handled, the precast units may be damaged during transport.2. It becomes difficult to produce satisfactory connections between the precast

members.3. It is necessary to arrange for special equipment for lifting and moving of the

precast units.4. The economy achieved in precast construction is partially balanced by the

amount to be spent in transport and handling of precast members. It becomes therefore necessary to locate the precast factory at such a place that transport and handling charges are brought down to the minimum possible extent.

Since precast is manufactured in a controlled casting environment it is easier to control the mix, placement, and

curing

Quality can be controlled and monitored much more easily

Since a precaster can buy materials for multiple projects, quantity discounts can lower costs

Weather is eliminated as a factor-you can cast in any weather and get the same results, which allows you to perfect

mixes and methods

Less labor is required and that labor can be less skilled

On site, precast can be installed immediately, there is no waiting for it to gain strength and the modularity of precast

products makes installation go quickly

Repeatability-it's easy to make many copies of the same precast product; by maximizing repetition, you can get

plenty of value from a mold and a set-up

Accelerated curing, by heating the precast parts, greatly increases strength gain, reducing the time between casting

the part and putting it into service

With the ability to so tightly control the process, from materials to consolidation to curing, you can get extremely

durable concrete

Advantages • Easy transportation of wet concrete • Flexible when it comes to geometric shapes • Relatively easy to do late changes to structure • Structure becomes monolithic

27. Disadvantages • Produced in an unprotected environment • Additional time required for drying out process • Requires more temporary work • Complex process with many inputs and flows

Cast-in-place provides benefits to builders and building owners alike.

Owners appreciate:

strong walls safety and disaster resistance mold, rot, mildew, and insect resistance sound-blocking ability for insulated systems, energy efficiency and resultant cost savings

Contractors and builders like:

familiarity expands business to include more than basements

Concrete sandwich panels are highly engineered to provide rugged, durable surfaces for walls and can be used for floors, as well. Precast concrete panels (and other items) are manufactured in factory settings. Not only is this conducive to improved quality control, it’s also possible to manufacture year round during any type of weather.

By designing buildings to have one predominant panel size, panel manufacturing becomes a repetitive process and gains efficiency. Following a two-step casting process, the resulting void between panels can be filled with insulation. 

The ability to quickly erect panels at the site is another advantage of precast. Once footings are prepared, panels can be placed quickly to form the enclosure. This requires some lead time to order the panels, but is an advantage at the site. It also means that construction can be completed within a relatively small footprint and may allow building in weather that would negatively affect other types of construction. Solid, high-quality concrete construction built with an efficient use of labor makes for cost effective structures. 

Precast, like all concrete construction, provides fire, rot, termite, and mold resistance. Exterior walls can withstand tornado-force winds. It is solid construction that protects occupants from weather and from natural disasters.

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