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Formwork/Plasticisers/Retarders |
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What is the type of Formwork required for receiving concrete? |
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What is the rate of pour? |
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What is the average
time lapse expected between the time the concrete is mixed
and the time it is placed in position? |
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What are plasticisers?
Will the strength of concrete be affected by the addition
of these plasticisers? |
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What are retarders?
Will the final setting time be affected by the addition of
retarders; thus affecting the deshuttering cycles? |
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What is the back
up measure should the delivery of a particular batch of
concrete be delayed beyond the normal delivery period?
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What
is the type of Formwork is required for receiving concrete? |
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Most common formwork in India consists
of casuirina poles and steel plates. This can be used for
receiving L&T Concrete provided it is suitably strengthened
to withstand the pressure developed due to pumping of concrete.
However its preferable a system formwork is used. It may
be noted that as part of our service to our customers we
always advise them on the use of system formwork.
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What is the
rate of pour? |
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Rate of pour depends on type of pour.
However laying and finishing 12 cum per hour on a roof slab
is easily achievable.
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What
is the average time lapse expected between the time the concrete
is mixed and the time it is placed in position? |
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In general time lapse between the time
of mixing and the time of placing is in the order of about
two hours. However, by the addition of retarders/ plasticisers
the initial setting time of concrete can be delayed to suit
the time required for transporting the concrete to the place
of placing. The dosages of these chemicals have to be designed
to suit the need of the particular pour of concrete.
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What
are plasticisers? Will the strength of concrete be affected
by the addition of these plasticisers? |
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Plasticisers are chemical additives added
to concrete to increase the workability of concrete. This
is done without altering the water cement ratio. The strength
of the concrete will not be affected.
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What
are retarders? Will the final setting time be affected by
the addition of retarders; thus affecting the deshuttering
cycles? |
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Retarders are chemical additives added
to concrete in predetermined designed doses in order to
retard the initial setting time of the concrete. This will
not affect the final setting time of the concrete.
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In the event of inadvertent
overdosing of the retarders the final setting time of the
concrete will be delayed. |
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Even if the deshuttering period is delayed,
the strength of the concrete will not be affected.
In addition to plasticisers and retarders there are Retarder
plasticisers that have the effect of increasing the workability
(Slump) and retaining the same over a period of time.
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What is the back up measure should
the delivery of a particular batch of concrete be delayed
beyond the normal delivery period? |
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In such a rare eventuality the concrete
in transit can be redosed with the addition of predetermined
dosage of the retarders. This is to be strictly done under
the supervision of L&T Concrete Personnel
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