CIT Construction

1. Place and Fix
Reinforcement
Materials.
In this subject you will learn
the basic materials and
methods of placing and
fixing steel reinforcement in
the building industry.

2. Reinforcement in Concrete
Steel Reinforcement for concrete is provided by placing & fixing deformed steel bars or
welded wire fabric mesh inside excavations or formwork prior to placing the wet concrete,
combined this makes a composite material, versatile and strong.
Steel reinforcements job is to provide additional strength to concrete .
Concrete is strong in Compression so reinforcement steel is installed when pouring concrete
to add strength where Tensile and Shear strength is required. This helps prevent the
concrete from cracking and breaking.
Steel Reinforcement helps prevents the concrete from cracking, buckling and caving in
when a load is placed on it by improving the tensile and shear strength of the concrete.
For example, Fabric mesh in a simple slab on ground provides tensile strength to the slab
helping to resist loads bowing the slab vertically up or down and reinforcement in a
concrete beam helps resist shear forces where the beam is connected to their vertically
supporting structure.

3. Tensile vs Compressive vs Shear Strength
+ Tensile strength is the maximum pulling force
that a material can withstand without breaking.
+ Compressive strength is the maximum load force
that a material can withstand without breaking.
+ Shear strength of a material is its ability to resist
forces that cause the material's internal structure
to slide against itself.

4. Tools used in Placing Reinforcement
+ Bolt Cutters
+ Wire ties
+ Wire spool
+ End cutters/steel fixers Pliers
+ Portable hydraulic benders
+ Tie wire reel
+ Tie wire puller/ used with Acro ties
+ Rebar bender/cutter
+ Battery operated rebar cutter
+ Battery operated tie wire gun

5. Types of Steel Reinforcement
+ Round Plain Bar is a cylindrical steel rod that has a smooth
finish
+ Deformed Bar/ N-bar. is a cylindrical steel rod that has a
ribbed texture to its surface
+ Trench Mesh is a mesh reinforcement and is a series of 3 , 4
and 5 deformed bars connected with welded wire bars.
+ Fabric Mesh is a series of small diameter cylindrical steel rods
with a ribbed surface welded together to form a grid pattern.

6. Round Plain
Bar
+ Round Plain Bar is a cylindrical
steel rod that has a smooth
finish.
+ Normally used when
movement needs to occur for
engineering purposes

7. Deformed Bars
+ Deformed Bar/ N-bar is a cylindrical steel rod that
has a ribbed texture to its surface.
+ This helps the concrete bond to the deformed bar
and provides better adhesion results
+ Originally straight bar was twisted to make
deformed bar but has developed over the years to
the N-bar we use today
+ Lots of different deformed designs, usually based
on manufacturer

8. Fabric Mesh
+ Fabric Mesh is a series of small diameter
cylindrical steel rods with a ribbed
surface welded together to form a grid
pattern
+ Most fabric mesh sheets have bars with
a deformed texture to help the concrete
bond to the surface
+ A very versatile product used in
commercial and residential applications

9. Fabric Mesh Configurations and Terms
Two common configurations of fabric mesh;
SL - “S” means Square and L is the grade of steel used in the ribbed wires.
RL – “R” means Rectangle and L is the grade of steel used in the ribbed wires.
Mesh terminology example:
SL41 RL718
S = Square mesh R = Rectangular mesh
L = Grade of steel L = grade of steel
4 = wire diameter (in mm) 7 = Longitudinal Wire diameter (in mm)
1 = mesh spacing size (100x100mm) 1 = Mesh spacing size (100x100mm)
8 = Cross wire diameter (in mm)

10. Trench Mesh
+ Trench Mesh is a type of fabric mesh
reinforcement typically used in residential and
commercial builds to reinforce concrete
footings, beams columns and slabs.
+ Trench Mesh comes in 8, 11 and 12mm
diameter bars in 6.000m lengths.
+ Trench Mesh comes in different widths.
+ 3 bars wide or 200mm wide
+ 4 bars wide or 300mm wide
+ 5 bars wide or 400 mm wide

11. Trench Mesh
+ When ordering Trench mesh we
need to understand the
terminology.
+ L is the grade of steel used in
the Trench Mesh.
+ The first number (i.e. 8) is the
diameter of each longitudinal
bar that make up the Trench
Mesh.
+ TM is an acronym or means
Trench Mesh.
+ The last number represents the
number of longitudinal bars.
+ L8TM4
+ L8TM5
+ L11TM3
+ L11TM4
+ L11TM5
+ L12TM3
+ L12TM4

12. Trench Mesh Spacers
+ Can also be known as Bogar clips and
Trench Mesh Clips.
+ The Spacers are used to join the top
and bottom mesh.
+ Joining the top and bottom mesh
forms a footing cage.
+ The spacers come in different heights
from 150 mm to 500 mm for different
depths of footings or beams.
+ Spacers are spaced at max 900mm
centres or 3 bays between spacers.
+ When ordering spacers you need to
order spacers for the correct size
longitudinal bar in the trench mesh.

13. Trench Mesh Supports
+ Are specifically designed to work with trench mesh applications.
+ Trench mesh supports are used to support the trench mesh
when pouring, pumping or vibrating concrete.
+ Trench mesh supports are typically used for bar diameter of
8mm to 16 mm.
+ Typically the supports are made from plastic & clip to the
bottom layer of trench mesh.
+ Trench mesh supports have a flat base to help protect moisture
barrier membrane (Plastic sheeting )
+ The bottom of a footing should be kept flat where possible so
the Trench mesh support sits flat and level.
+ The spacers provide minimum cover from reinforcement to
external surfaces of the concrete (see NCC or AS/NZS)
+ The supports when placed to engineers specifications locate
the reinforcement with correct minimum cover from the bottom,
sides and top of footings, slabs and beams.

14. Ligatures in
Reinforcement
+ Ligatures or Stirrups are steel reinforcing bar bent to
shapes and tied to rebar, trench mesh and fabric mesh used
in concrete construction.
+ Ligatures are used in some of the following applications;
- To separate top and bottom layers of trench mesh or rebar
into a cage for footings.
- For cages used in bored or drilled piers, or formed columns
- Stiffening beams in ground or suspended concrete slabs.
- Engineers details will typically specify ligature spacings
specific to the application

15. Typical footing cage with trench mesh and
ligatures.

16. Bar Chairs
+ Bar Chairs are used to support reinforcement bar, fabric mesh
and trench mesh.
+ Bar chairs are also used to keep mesh in place when pouring,
pumping and vibrating concrete.
+ The bar chairs also provide correct minimum cover from
reinforcement to external and internal surfaces of the concrete.
+ Bar chairs when placed to engineers specifications locate the
reinforcement with correct minimum cover from the bottom,
sides and top of footings, slabs and beams.
+ Positioning of reinforcement with correct minimum cover limits
exposure to the elements minimising the risk of corrosion.
+ Bar chairs come in different heights and designs but all
achieve the same effect

17. Metal Bar Chairs
+ Typically made with 4 legs and are plastic
tipped to prevent corrosion.
+ Metal bar chairs can be used in slabs on ground,
suspended slabs, concrete beams and concrete
walls.
+ Metal bar chairs can be used directly on
formwork, or structural formwork (Bondek )
+ Base plates for the chairs provide support for
metal bar chairs, this stops them sinking into
soft surfaces & piercing the moisture barrier
membrane below.
+ Base plates are also known as pizza plates, or
tin plates.

18. Plastic Bar Chairs
Come in a variety of styles and sizes
Features slotted or clipped sections for typical
heights for slab-on-ground construction
The two listed heights are the low and high
sides of the chairs themselves
Typical Availability;
25/40mm
50/65mm
75/90mm
85/100mm

19. Bending Reinforcement into Shapes
Many engineer details will specify the use of
various bent reinforcement bars to increase load
strength, shore up weak points of the
reinforcement, or to tie pieces together.
The main varieties are the Cog, Crank and Hook
Crank

20. Cogs
A Cog is a simple 90-degree bend in a piece of
reinforcement.
This is normally used on corners to tie pieces of
trench mesh together, among other uses.
Cogs provide effective anchorage because they
make use of bearing pressure inside the bend
to resist strain.
If a Cog is not the required length, it is simply
considered a straight bar for strength, failing its
task.

21. Cranks
A Crank is a Z-shaped bent piece that acts as a tie
between layers of mesh.
This is typically the trench mesh to the main fabric mesh
layer, but can also be used to join other pieces of
reinforcement together that might not perfectly align.
Crank bars are generally provided;
- To resist negative bending movement (hogging)
- To resist shear force which is greater at supports and
intersections
- To reduce the risk of a failure of slab-footing or slab-
column connection

22. Hooks
A Hook is a piece bent with a 180-degree
curve at the end.
This is used for anchorage, to prevent other
pieces of reinforcement from slipping, moving
and failing.
Like the Cog, Hooks use bearing pressure to
resist strain. As such, it’s very important to
follow the engineers details for hook design,
shape and size.

23. Vapor Barriers
Vapor Barriers are required to be installed for
all Class 1 and 10 buildings under
reinforcement components and are an
important part of concrete preparation.
‘Vapor Barrier’ refers to 0.2mm thick
polyethylene membrane, usually black.
It is used for a variety of reasons;
- Stops water from the concrete escaping into
the ground when poured, increasing strength
- Prevents moisture from the soil permeating
the slab and into the house (known as rising
damp)

24. Vapor Barrier
Installation
The AS2870 and NCC (Part 3.2) specify how
Vapor Barriers must be installed. These
include;
+ A lap not less than 200mm at all joints;
+ Tape or seal with a close fitting sleeve
around all service penetrations; and
+ Fully seal where punctured (unless for
service penetrations) with additional
polyethylene film and tape.
Additionally, most engineers details will
specify if the vapor barrier requires additional
details outside of the regular application

25. Australian Standards.
Below are some of the applicable standards for Steel
reinforcement and associated use of steel reinforcement.
+AS/NZS 4671 : 2001 Steel Reinforcing Materials.
+AS 2870 : 2011 Residential Slabs and Concrete Footings.
+AS 3600 : 2009 Concrete Structures.
+AS 3727 : 1993 Guide to Residential Pavements.
+NCC: Part 3.2 Footings and Slabs