Transporting and Placing Concrete

When transporting and placing concrete, avoid:
DELAY
SEGREGATION and
WASTAGE.
TRANSPORTATION The method used to
transport concrete depends on which one is the
lowest cost and easiest for the job size.
Some ways to transport concrete include: a
concrete truck, a concrete pump, a crane and
bucket, a chute, a conveyor or a hoist. On small
jobs a wheelbarrow is the easiest way to
transport concrete.
Always transport concrete as little as possible to
reduce problems of segregation and wastage.
PLACING When placing concrete be careful
not to damage or move the formwork and reinforcement.
Place concrete as near to its final position as possible.
Start placing from the corners of the formwork or,
in the case of a sloping site, from the lowest level.


IMPORTANT SAFETY INFORMATION
When handling and using cement or fresh concrete, avoid skin contact.
Wear suitable protective clothing.



DELAY Delay can cause the concrete to dry-out and stiffen.
Delay is more of a problem on a hot, and/or
windy, day when the concrete will dry-out
and stiffen more quickly.
To avoid delay plan ahead. Check that all
labour, tools and containers are ready and
that all preparations for placing have been
done before the concrete is
delivered.
Never just add water to the
concrete to make it more
workable, always use a mix
of cement paste (ie water
AND cement).




SEGREGATION Segregation is when the coarse and fine aggregate, and cement paste,
become separated. Segregation may happen when the concrete is mixed, transported,
placed or compacted.
Segregation makes the concrete:
WEAKER,
LESS DURABLE,
and will leave A POOR SURFACE FINISH.
To avoid segregation:
Check the concrete is not 'too wet' or 'too dry'.
Make sure the concrete is properly mixed.
It is important that the concrete is mixed at the
correct speed in a transit mixer for at least two
minutes immediately prior to discharge. The
concrete should be placed as soon as possible.
When transporting the mix, load carefully.
If placing concrete straight from a truck, pour
vertically and never let the concrete fall more than
one-and-a-half metres.
Always pour new concrete into the face of concrete
already in place.
When compacting with a poker vibrator
be sure to use it carefully.
See CHAPTER 8 Compacting Concrete
Never spread concrete sideways with a poker
vibrator as this may cause segregation of the mix.
Always be sure to vibrate concrete evenly.
WASTAGE Wastage can be costly, especially
on small jobs. To minimise wastage; mix, load,
transport and place carefully.