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SLAB

What is Slab???

“A flat piece of concrete, typically used as a

walking surface, but may also serve as a load

bearing device as in slab homes.”

FUNCTION

Provide a flat surface To support load Sound, heat and fire insulator Act as a divider (privacy) for the occupants Upper slab became the ceiling for the

storey below Space between slab and ceiling can be used

to place building facilities

Classification of Slab

GROUND FLOOR

UPPER FLOOR

SOLID FLOOR

SUSPENDED GROUND FLOOR

TIMBER FLOOR

REINFORCED CONCRETE FLOOR

PRECAST FLOOR

Classification of Slab

GROUND FLOOR

UPPER FLOOR

SOLID FLOOR

SUSPENDED GROUND FLOOR

TIMBER FLOOR

REINFORCED CONCRETE FLOOR

PRECAST FLOOR

Characteristic of Ground Floor

Simple design Load will be supported by the ground Less problem related to distance of span Choice to construct solid floor or

suspended ground floor will depends on nature of the building and site condition

DESIGN CONSIDERATION

Among the design function that need to be taken

in consideration for construction of ground floor

slab is

• The provision of a uniform, level surface

• Sufficient strength and stability

• Exclusion of dampness from inside of building

• Thermal insulation (max.0.45 W/square metreK

• Resistance to fire

Solid Floor

Solid Floor / Non Suspended Floor

Constructed using concrete Doesn’t use timber so there will be no

decay Solid floor need other finishing

Construction Of Solid Floor

1) Clear the construction area

2) Remove topsoil / unsuitable material (225 mm)

3) Compact and level the soil

4) Place hardcore and compact itHardcore plays the role to fill in any small pockets that have formed during oversite excavation in order to provide a firm base for placing concrete bed and to help spread any point loads over a greater area.

5) Place Damp Proof Membrane

6) Prepare formwork

7) Prepare lean concrete (50 – 75mm) in order to ensure the reinforcement didn’t touch the ground.

8) Place Reinforcement Bar to increase strength

9) Pour concrete (1:2:4) with thickness of (150mm) and level it.

10)Place concrete of (25-50mm ) thickness . (rendering process)

Topsoil Is Stripped

AFTER

BEFORE

Rebar Used For Slab Construction

Pouring concrete

Concrete Slab Finishing

Screeding is the process removes excess concrete and

brings the top surface of the concrete to proper grade.

SUSPENDED GROUND FLOOR

SUSPENDED GROUND FLOOR

A ground floor need to be suspended under the following condition:a) domestic buildings on sloping sites where more than 600mm depth of infill would be requiredb) where the bearing capacity and nature of the

ground different from one part to anotherc) where the ground is shrinkable clay, expansive material or unstable soil type.

Suspended floors / slab is fixed some distance above the ground.

There are 2 types of suspended ground floor such as a) Suspended timber ground floorsb) Suspended precast concrete floors

Suspended Timber Ground Floor

Suspended Timber Ground Floor

it has some flexibility and will accept nail fixing (solid ground floor can’t use nail)

Under side of ground floor must kept dry to prevent fungus attack

Susceptible to dry rot and draughts but it can be avoided if the floor is designed correctly.

Adequate ventilation under the floor and correct positioning of dampproof courses can keep the under floor area and timber dry.

Space beneath the suspended timber floor is ideal for running electric cables, water pipes and gas pipes

It’s more expensive form of construction than concrete floor

Cheaper than precast concrete flooring system

UPPER FLOOR

Timber Floor / Timber Slab

• Lantai Papan Tunggal

• Lantai Kayu Kembar

Precast Concrete Floor

PRECAST CONCRETE FLOOR

Advantages of Precast Concrete floor isa) Doesn’t need formwork

b) Time taken for concrete to cure in the formwork can be eliminatedc) Better quality control d) Doesn’t need many workers as in in-situ concrete constructione) fast completion of construction project

long spans available with precast concrete flooring systems reduce the number of secondary beam required and maximize the column free space.

Fire resistance ratings normally between 1 & 2 hours

Among the things that need to be considered before considering any system of precast concrete flooring are: a) maximum span f) Sound insulation b) nature of support g) Thermal insulation propertiesc) weight of units h) Fire resistance of unitsd) thickness of units i) Speed of constructione) Amount of temporary support required

There are many types of precast concrete floor such as :a) Precast Hollow Floorsb) Composite floors

Precast hollow floor units are available in a variety of sections such as box planks / beams, tee section, I beam sections and channel sections.

Composite floors are combination of precast units and insitu concrete.

Precast Hollow Slab

Precast Hollow Floors

more economic compared to in-situ floor due to reduction in volume of concrete used, weight of reinforcement and size of foundation.

cheaper than composite in-situ concrete is not required Units are self centering so, no need temporary

support Construction period is shorter

Composite Floors

Composite Floors

combination of precast units and in situ concrete.

precast units that are usually prestressed / reinforced with high yield bars are used to provide the strength of the floor with the smallest depth practicable

At the same time, act as permanent formwork to the in-situ topping that provides the compressive strength required.

Composite floors will act in the same manner as in-situ floor so it can be designed for more complex loadings

Reinforced Concrete Slab / Floor

In- Situ construction Flat Slab Flat Plate Slab Waffle Slab / Honeycomb Floors Beam Floor Slab

FLAT PLATE SLAB

FLAT PLATE SYSTEM

Simple construction Flat plate construction can minimize storey

height (piping, wall cladding, elevators etc) in areas with absolute height restrictions.

Low storey heights due to shallow floor Spans < 20ft (residential & light commercial) Flat ceilings (reduced finishing cost) Have the simplest formwork

Least labor costs Can be applied for short to medium spans

with light loadings Also reduce building weight and effective

area of wind loads

FLAT SLAB

FLAT SLAB

Reduce slab displacementIncreased slab shear resistanceThis system provide relatively a flat ceilings

(reduce finishing cost)Low storey heights due to shallow floorMedium span with light loadingSpans 20 to 40 ftLive load > 100psf (garage, warehouses)

WAFFLE SLAB

WAFFLE SLAB

Used as alternative to an in-site flat slab or a beam and slab suspended floor

This is because it requires less concrete, less reinforcement and can be used to reduce the number of beams and columns required with the resultant savings on foundations.

Moulds are very strong, lightweight & capable of supporting all the normal loads encountered in building works.

Spans >30 ft Use prefabricated standard forms special moulds are placed at certain distance skilled workers are needed & need less steel

SLAB DESIGN

One Way Slab Two Way Slab

- Require less steel

- Few two slabs built in the area of high labor costs

- Suitable for minimizing deflections

One Way Slab

BEAM

Two Way Slab

SLAB FAILURE : CAUSES & EFFECT

TYPES OF SLAB PROBLEM

Cracking Of The Slab

Cold Floor

Damp Or Wet Floor Slab

CRACKING OF THE SLAB : CAUSES

Poor construction techniques and practices Differential / Uneven settlement Inadequate structural strength of concrete Improper placement of reinforcing & mesh

Cracking Of The Slab

Damp or Wet Floor Slab : Causes

Moisture migration through the slab Poor site drainage

Life Is Very Short So Make It Meaningful

Love & Appreciate Your Parents Always