Specifications

STANDARD SPECIFICATION - BUILDINGS
DPI REFERENCE TEXT - APRIL 2009
PAGE 10
CONCRETE CONSTRUCTION
Concrete Grade
Footings - N25
Exposed slabs on ground - N32
Internal slabs on ground - N25
Columns & suspended slabs - N40
Other concrete grades may be required as shown
on the drawings or in the Project Schedules.
Grout for blockwork cores
Standard: AS 3700 clause 10.7.
Grout: Class S12 (to AS 1379) 12 MPa with a
pourable slump, a minimum cement content of 300
kg/m
3
and maximum 6 mm aggregate.
Concrete placing
Depth: If concrete is deeper than 350 mm, place it in
layers so that each succeeding layer is blended into
the preceding one by the compaction process.
Slabs and pavements: Place concrete uniformly
over the width of the slab so that the face is generally
vertical and normal to the direction of placing.
Hot weather placing - Hold Point
The provisions of this clause apply to concreting
where the surrounding shade outdoor temperature
is greater than 32
o
C.
Hold Point: Mixing: Do not mix concrete when the
outdoor shade temperature on the site exceeds
38
o
C, unless otherwise approved and then only
subject to such conditions as may be imposed.
Handling: Take precautions to prevent premature
stiffening of the fresh mix and to reduce water
absorption and evaporation losses. Mix, transport,
place and compact the concrete as rapidly as
possible.
Placing
Before and during placing maintain the formwork
and reinforcement at a temperature not greater than
32
o
C by protection, cold water spraying, or other
effective means. When placed in the forms, the
temperature of the concrete shall not exceed 35
o
c.
Temperature control methods: Submit for approval
the proposed method or methods of maintaining the
specied temperature of the placed concrete, which
may include using chilled mixing water, spraying the
coarse aggregate with cold water or covering the
container transporting the concrete.
Evaporation Control: Erect barriers to protect freshly
laid concrete from drying winds.
Compaction
Vibrate concrete to remove entrapped air, but avoid
over-vibration that may cause segregation.
Curing:
Protection: Protect concrete from premature drying
and from excessive hot, cold and/or windy conditions
by a suitable approved method.
Minimum Curing Time:
• In-ground footings: 3 days.
• Exposed footings, beams and slabs: 7 days.
3.8 FORMWORK
Surface nish class
Use the applicable class from AS 3610, Table
3.3.1.
Dimensional Tolerances
To AS 3600 clause 19.5, except where the
requirements of this clause or AS 3610 clause 3.4
are more stringent.
Formwork removal
Remove all formwork, including formwork in
concealed locations.
Stripping times
Leave formwork for suspended structures in place
after pouring concrete for the following periods:
• Vertical surfaces: 2 days.
• Bottom surfaces: 7 days with shoring and
backprops left in position for 21 days.
3.9 JOINTS
Construction joints
Joint preparation: Roughen and clean the hardened
concrete joint surface, remove loose or soft material,
free water and foreign matter. Dampen the surface
before placing the concrete.
Slip joints
If concrete slabs are supported on masonry, provide
proprietary pre-lubricated slip joints.
Movement Joints
Insert 12mm thick Abelex closed cell compressible
ller strip in the joint.
Detach the removable top strip and ll with Fosroc
Thioex 600.
3.10 FINISHES TO UNFORMED
SURFACES
Screeding
Finish slab surfaces by approved means to nished
levels. Produce surfaces to tolerance Class B -
maximum deviation from a 3m straight edge of 6
mm.
Scored nish
After screeding, give the surface a course scored
texture in the required direction by drawing a stiff
brush or rake across the surface.
Machine oated nish
Finish the screeded surface with approved power
driven equipment to a uniform smooth texture. Hand
oat in locations inaccessible to the machine oat.
Finish: To a surface tolerance class A.
Steel trowelled nish
Use steel hand trowels to produce the nal nish
free of trowel marks and uniform in texture and
appearance.
Finish:To a surface tolerance class A.
Wood oat nish
Produce the nal nish with a wood oat.
Specifications March 2009.indd 10 11/03/2009 11:47:10 AM