1. Precast concrete is concrete that is cast and cured offsite then transported for installation, allowing for tighter quality control. Cast-in-place concrete is poured and cured onsite. 2. Floor and roof slab systems commonly use precast concrete slabs stacked atop columns. Flat plate slabs and flat slabs are suitable for spans up to 8-9m, while waffle slabs can span up to 15m. 3. Slab on beam and one-way joist floor systems are more economical for smaller spans of 3-9m, with joist floors suitable for heavier loads over longer 6-9m spans.

1. ARC 044
BUILDING TECHNOLOGY 05
Alternative Building Construction

2. PRECAST & CAST-IN-PLACE
LECTURE SERIES #1

3. WHAT IS PRECAST CONCRETE?
Precast concrete, sometimes called
“prefabricated”or “pre made”
concrete, is a concrete product that
is created offsite, then deliveredto its
project destinationfor final use.

4. Precast concrete products, such as Pole
Base, are created by pouring a cement
mixture into a mold that can contain
wire mesh, rebar or even prestressed
cable.
The filled mold is then cured in a
controlledenvironment to ensure
greater control overmaterial quality.
Because this all happens offsite, the
deliveredproduct is ready for use right
away, which can save crucial time on
construction projects.

5. Because precast concrete is so
customizable, it’s the ideal choice for
a variety of applications, both large
and small, including:
Light pole and sign bases
Pillars and columns
Parking structures
Culverts
Retaining walls
Building construction

6. WHAT IS CAST-IN-PLACE
CONCRETE?
Cast-in-place concrete, also known as
“site-cast”or “poured-in-place” concrete,
is poured and cured onsite in the
concrete’s finished position.
For specific applications, this type of
casting can be ideal. For example, some
foundations and other very large concrete
components would be difficult to transport
between a concrete plant and job site,
making cast-in-place concrete more
feasible.

7. Cast-in-place concrete is also commonly
used for small projects. Precast concrete
pricing scales with projects, so smaller projects
can actually cost more.
In these cases, cast-in-place concrete may
be preferred. But overall,precast concrete is
the best choice for building foundations with
structural integrity and dimensions built to your
precise specifications.

8. ADVANTAGES OF PRECAST CONCRETE
1. Simplified material inputsand cost
2. Less time needed to install
3. Cost-effective for large projects
4. Stronger than cast-in-place concrete
5. Higher-quality control

9. COMPOSITE CONSTRUCTION
Composite construction is widely
recognized nowadays an efficient way
of enhancing the structural
performance of steelwork by ensuring
that, when used in association with
concrete, the two materials act as a
unit.

10. FLOOR SYSTEM &
ROOF SLAB SYSTEM
LECTURE SERIES #2

11. WHAT IS FLOOR AND ROOF SLAB SYSTEM?
It normally requires fewerjoints than other types of
precast building systems.
Typically, columns are erected first, but not
necessarily for the full height of the building.
Near the base of the columns, floor slabs are cast
in succession, one atop another, with a parting
com-pound betweenthem to prevent bond. The
roof slab is cast last, on top.
Usually, the construction is flat plate, and the slabs
have uniform thickness.

12. TYPES OF ECONOMICAL FLOOR AND
ROOF SLAB SYSTEM
FLAT PLATE SLAB FLOOR SYSTEM
Flat plate systems are directly supported by
columns and suitable for span of 6-8m with life
load of 3-5KN/m2.
This type of floor system is adopted mainly for
hotels, hospitals, multifamily residential buildings.
The most outstanding advantages of flat plates
include fast construction, simple and low
formwork cost, flat ceiling that reduces finishing
cost.

15. FLAT SLAB SYSTEMS
Flat slabs are similar to flat plate apart from
thickening of flat slabs around columns
which are provided to improve shear
capacity of this floor system.
Flat slabs are economically viable for spans
range from 6 to 9m and live loads range
from 4 to 7 KN/m2.
This type of floor system is suitable for the
case where punching shear stress prevent
the use of flat plates especially when
relatively shallow slabs are intended. It
shouldbe known that thickening of floor
system around columns (drop panels)
increase the cost of formworks.

18. WAFFLE SLABS
It is consist of reinforcedconcrete slab
and evenly distributed waffle slab in two
directions. The slab around columns is
solidto provide shear resistance in
column area.
Waffle slabs are economically
appropriate for spans of 9 to 15m and live
load of 4 to 7KN/m2. The ultimate load
carrying capacity of this floor system is
greater than of flat slabs, but cost of its
formworks is substantially high.

22. SLABS ON BEAMS
This type of floor system is economically
viablefor spans ranges from 6 to 9m and
live load of 3 to 6KN/m2.
The beam increases the relative stiffness of
the floor system and hence the deflection
is declined, but the cost of formwork is
increaseddue to beam formwork.

25. ONE-WAY SLAB ON BEAMS
This type of floor system is suitable for
span of 3 to 6m and live load of 3 to
5KN/m2.
This span range can be increased at the
expense of slight increase of deflections
and cost of the floor system.

28. ONE-WAY JOIST FLOOR SYSTEM
It consists of uniformly spaced concrete ribs spanning in
one direction,reinforcedconcrete slab constructed
monolithically with ribs and beams which are spanning
between columns.
On way joist floor system is economically suitable for
spans of 6 to 9m and liveload of 4 to 6KN/m2.
There are several advantages offered by this floor
system such as it is cost effectivefor long spans with
heavy loads, the overall depth does not require to be
increasedfor utility installation because they can be
placed between joists and pan voids reduces self-
weight. It is reported that of cost of formworks constitute
about 51 percent of the total cost of the floor system.