RCC slabs (Types of Reinforced cement concrete slabs)

A brief presentation about Reinforced cement concrete slabs including various types of RCC slabs used in general.

1. TYPES OF REINFORCED
CEMENT CONCRETE SLABS

ADA

Vamsi Putta

3rd
I AMITY
Bachelors in Civil engineering UNIVERSITY

DUBAI

2. What is RCC?

RCC is the combination
of ordinary concrete with
the reinforcement(steel,
fiber, etc.,) to increase its
compressive and tensile
strength to a great
extent.

a
Purpose of RCC? ¿TA Da f

Concrete has very high compressive
strength, but has low tensile strength.

But where tensile forces are also involved,
as in, beams and slabs, there is a very
high risk of its failure when plain concrete
is used.

Steel has very high tensile strength, so
then steel and concrete are added
together, resulting in a material that ‘s
capable of withstanding both tensile and
compressive forces acting upon the
structure.

3. Types of RCC

One way system slab aBubble deck slab
QJoist slab (Ribbed) uPrecast slab
OFlat slab Composite slab
Flat plates

aTwo way system slab

aWaffle slab

OHollow core slab

QHardy slab

4. One way slab

One way slab is
supported by beams
on the two opposite
sides to carry the load
along one direction.

Longer span
Shorter span —

Deflection usually governs the design, and steel
content is usually increased to reduce service stress
and increase capacity

These slabs bend in the direction along its shorter
span. Main reinforcement is provided in shorter span
and distribution reinforcement is provided in longer
span.

5. One way slab

Applications
Cantilever slabs

Office buildings (low
rise)

Shopping malls
Warehouses, Verandahs.

Economic span range:
4-7m

Economic slab thickness
range. 150 - 250mm

Live loads: 3 - 5KN/m2

Advantages
Simple construction

Penetrations in the slabs
are easily manageable

Ao À

Disadvantages

Associated down stand
beams may require
greater story height

Deter fast formwork
cycles.

Compromise flexibility
of partition location
and horizontal service
distribution

6. Joist slab
(Ribbed)

It consists of a floor
slab supported by
reinforced concrete
ribs. The ribs are
supported on
girders that rest on
columns.

Introducing voids to the soffit of a slab reduces dead
weight and increases the efficiency of the concrete
section.

A slightly deeper section is required, but these stiffer
floors facilitate longer spans and provision of holes.

7. Joist slab (Ribbed)

Applications
Parking structures

Office buildings
(low rise)

Warehouses

Economic span range:
8-12m

Economic slab thickness
range. 50 - 100mm

Live loads: 4 - 6KN/m2

Advantages
Medium to long spans
Lightweight

Holes in topping easily
accommodated

Large holes can be
accommodated

Profile may be expressed
architecturally

Ao À

Disadvantages

Higher formwork costs
than for other slab
systems

Slightly greater floor
thicknesses

Slower floor to floor
cycle

8. Flat plate

Flat plates can
be constructed
as one-way or
two-way slabs
and it is directly
supported by
columns or walls.

The main feature of the flat plate floor is a uniform
thickness with a flat soffit which requires only simple
formwork and is easy to construct.

The floor allows great flexibility for locating horizontal
services above a suspended ceiling or in a bulkhead.

9. Flat plate

Applications

Residential & Office
buildings (high rise, low
rise)

Parking, Hotels

Economic span range:
5 - 8m (Conventional)
6 - 10m (Post-tensioned)

Economic slab thickness
range. 230 - 350mm

Live loads: 3 - 5KN/m2

Advantages

Typically has the lowest
floor to floor cycle time
of the cast in-situ
options.

No beams - simplifying
under-floor services.
Minimum structural

depth and reduced
floor-to-floor height.

Disadvantages

Long-term deflection
may be a controlling
factor.

May not be suitable for
heavy loads.

High concentration of
reinforcement around
the columns in order to
ensure the slab has
adequate punching
shear capacity.

10. Flat slab

This is typically a
reinforced slab
supported directly
by columns or
caps, without the
use of beams.

Drop panels, formed by thickening the bottom of the
slab around columns, increase shear capacity and the
stiffness of the slab, allowing thinner slabs to be used.

A flat slab with prestressing tendons (PT) results in
longer spans and thinner slabs.

11. Flat slab

Applications

Residential & Office
buildings (high rise, low
rise)

Parking, Hotels

Economic span range:
6 - 9m (Conventional)
7 - 11m (Post-tensioned)

Economic slab thickness
range. 210 - 330mm

Live loads: 4 - 7KN/m2

Advantages

More efficient than flat
plate, typically with lower
stress concentration at
column locations.

Slabs are generally
thinner than flat plates.

Absence of beams allows
lower storey heights.

Flexibility of partition
location and horizontal
service distribution.

Disadvantages

More complicated formwork
which can increase floor to
floor cycle time.

Drop panels require a
higher level of coordination
with the services in the
ceiling space than flat
plates and may not be
architecturally acceptable
for areas where suspended
ceiling is not envisaged.

12. Two way slab

Two-way slabs
are supported on
all sides. More
stiffness of the
slabs, producing
low deflection.

Economical flooring system, costs less than flat plates
or flat slabs. In other words, when the loads or spans
or both become quite large, the slab thickness and
column sizes required for flat plates or flat slabs are of
large magnitude that it is more economical to use
two-way slabs with beams, despite the higher form
work costs.

13. Two way slab

Applications
Super markets

Residential & Office
buildings (high rise, low
rise)

Warehouses, Parking

Economic span range:
9-12m

Economic slab thickness
range: 210 - 300mm

Live loads: 3 - 6KN/m2

Advantages

Economical for longer
spans and high loads

Less column sizes

Ao À

Disadvantages

Presence of beams may
require greater storey
height.

Requires a regular
column layout

Slow floor cycle

Flexibility of partition
location and horizontal
service distribution

14. Waffle Slab

It is a type of
RCC slab that
contains square
grids with deep
Voids and thus
reducing the
deadweight.

Slab thickness is governed by deflection, punching
shear around columns and shear in ribs.

Waffle slab construction process includes fixing forms,
placement of pods on shuttering, installation of
reinforcement between pods, installation of steel
mesh on top of pods, and pouring of concrete.

15. Waffle slab

Applications
Roofing, Carparks
Office buildings
Economic span range:

8- 14m

Economic slab thickness
range: 85 - 100mm

Overall depth:
300 - 600mm

Live loads: 4 - 7KN/m2

Advantages

Slab soffit profile may
be expressed
architecturally.

Longer spans possible.

Lightweight in nature.

Ao À

Disadvantages

Higher formwork costs
than for other slab
systems.

Slightly greater floor
thicknesses.

Slower floor-to-floor
cycle.

Requires square or
rectangular column/grid
arrangements.

16. Hollow core
slab

It is a type of precast
slab through which
cores are run. Not only
do these cores decline
slab self-weight and
increase structural
efficiency but also act
as service ducts.

Pre-cast floor systems will typically consist of factory pre-
tensioned pre-cast planks, tied together with a structural
topping to provide a robust and efficient floor system to
resist the imposed vertical and horizontal loading.

The most commonly used pre-cast slabs in the UAE
market are the pre-stressed, pre-cast hollow core planks.

17. Hollow core slab

Applications

Residential, Office
buildings (Low rise)

Educational
Parking structures
Warehouses

Economic span range:
6- 16m

Typical plank thickness
range: 150 - 400mm

Live loads: 2.5 KN/m2
for 16m span

Advantages

Heavy load carrying
capacity.
Exceptional fire
resistance.

Lower self-weight.

Superior acoustic
insulation and thermal
properties.

Rapid speed of erection.

Factory made with
highest quality control.

Disadvantages

Irregular shaped hollow
cores are difficult to
cast and expensive.

The segments cannot
be cut on site, must be
carefully designed.

18. Hardy slab

It is constructed using
hardy bricks (hollow
concrete blocks)
which significantly
decline the amount of
concrete and
eventually the slab's
self-weight.

The construction of hardy slab involves formwork
installation, hardy block placement, placement of
reinforcement into gaps between blocks, placement of
steel mesh on the blocks, and finally pouring of
concrete.

Dimensions of Hardy brick is 40cm x 20cm x 20cm.

19. Hardy slab

Applications

Constructed at locations
with high temperatures,
generally seen in Dubai
and China.

Hospitals, office and
residential buildings.

Economic span range:
more than 5m

Economic slab thickness
range: around 270mm

Live loads: moderate

Advantages

Improved insulation for
sound and heat.

Reducing slab weight by
reducing the amount of
concrete below neutral
axis.

Ease of construction,
especially when all
beams are hidden
beams.

Disadvantages

If not properly handled,
the hollow core ribbed
brick units may be
damaged during
transport.

Not economic for small
spans.

Difficult to repair and
strengthen

20. E
el

ay

Bubble deck

slab

21. Bubble deck
slab

It is constructed by
placing plastic bubbles
which are prefabricated
and the reinforcement is
then placed between
and over plastic bubbles
and finally, fresh
concrete is poured

Consequently, not only does it decline the total cost of
construction but is also environmentally friendly since
it reduces amount of concrete.

The plastic bubbles replace the ineffective concrete at
the center of the slab.

22. Bubble deck slab

Applications
Residential, office
buildings

Utility and industrial
buildings

Schools, parking,
hospitals, laboratories
factories.

Economic span range:
5 - 24m

Economic slab thickness
range: 230 - 700mm

Advantages

Less weight, more
strength.

Larger spans can be
provided, fewer
columns needed.

No beams or ribs under
the ceiling are required.

Disadvantages
Skilled labor required.

Thickness of slab is
limited.

Punching shear capacity
is low.

Conventional slab is less
deflect than bubble
deck slab.

Load carrying capacity
hard than conventional
slab.

23. Precast slab

Precast concrete
slabs are casted
and cured in
manufacturing
plants, and then
delivered to the
construction site
to be erected.

Double-T's are most commonly used precast slabs for
long spans. They are relatively lightweight with a high
load capacity.

The units are pre-stressed and can be left exposed.
Units are intended for up to two hours fire resistance.

24. Precast slab

Applications
Carparks.
Office buildings.

Warehouses, roofing,
bridges and industrial
buildings.

Economic span range:
8 - 20m

Typical double-T depth
range : 500-1200mm

Advantages
Speed of construction.
Longer spans.

Elimination of formwork
or propping.
Preparation of slabs in
manufacturing plants
increases efficiency and
higher quality control.

Ao À

Disadvantages

Crane may prove
critical.

25. Composite slab

Composite
slabs consists
of profiled
steel decking
with an in-situ
RC topping.

The steel decking acts as a permanent formwork and
also provides sufficient shear bond with the concrete.

The decking acts as working area during the
construction phase, and it also acts as external
reinforcement during service life of the slab.

26. Composite slab

Applications

Residential, Office,
Educational buildings
(Low, high rise)

Hospitals, Cinemas &
Theatres, Hotels.

Economic span range:
2.5 - 4m

Steel decking of
thickness: 50-60mm

Advantages

Speed of construction.

Elimination of
formwork.

Safe method of
construction.

Saving in weight.
Shallower depth.
Sustainability.

Highly efficient,
lightweight design.

Ao À

Disadvantages

Limited spans and
capacities.

Propping may be
required.

Fire proofing.

27. References

Ohttps://civilread.com/16-different-types-slabs-construction/#2_Two_Way_Slab
Ohttps://civilshastra.com/2019/04/12/types-of-slabs/

QO https://bsbgroup.com/blog/one-way-concrete-flooring-system
Ohttps://bsbgroup.com/blog/guidelines-for-two-way-concrete-flooring-system
Ohttps://theconstructor.org/practical-guide/concrete-slab-construction-cost/28153/

28. sio

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THANK YOU

ARTE

“gs

Vamsi Putta
[email protected]
0544514874