Concreting can be supplied on
intimation within 24 hrs. Tentative Schedule for 1 week will be given by site
in advance. Concreting will start at 8.00 a.m. & should get over by 9.00
p.m.
C)
General terms and conditions.
1) Labour - 6 Nos. for shifting Pipes, ghodas etc. also will have to be
supplied by RMC supplier.
2) RMC supplier to ensure that concrete Pump should not
fail. If concrete pump fails, there will be heavy penalty on RMC supplier.
3) Pipes, including bending radius pipes also to be sent
for Pouring concrete on slab. Proper arrangements for supporting pipes shall be
made by RMC in such a way that they do not disturb shuttering of slab.
4) Supervisor - 2 Nos. to be available at Concrete Pouring
Point and communication with Plant and pouring plant with Mobile
5) There should be no interruption in concreting supply,
for slab. Minimum pour - 50cum Maximum pour - 300cum.
6) RMC supplier shall submit Concrete Mix Design of concrete mix, at the
time of every pour.
7) Washing and cleaning of transit mixers shall be done by
RMC supplier, in such a way that sites cleanliness is not affected.
8) All transit mixers must have cleaner.
9) All basic safety norms like wearing helmet etc shall be
observed by RMC personels, supervisors and labours etc.
10) During rains, mouth of transit mixer shall be covered
to prevent rain water from getting inside transit mixer.
11) If due to any delay from the RMC side, if concrete is
not pumped for more than 3 hrs. after arrival on site, then same will be rejected.
Some
guidelines for slump adjustment and to avoid pump choke up.
Basically the collapse slump can
be avoided if the following points listed below are taken care :
1. Number of times RMC concrete
pumping is stopped, due to various reasons at site, including changing of
direction in pipes supplying concrete on top of slab being concreted. If pump
is stopped for any reasons, keep the pump working,
sucking backwards i.e. 2 strokes
back and 1 stroke forward,
again wait for 1 or 2 min. and if pumping does not start, again
repeat the same & so forth up to regular pumping starts. Cycle - Suck 2
push 1, suck 2 push 1, suck 2 push 2, up to the RMC concrete pumping restarts.
2. A operator observing at the
Pump hopper level should ensure that concrete level does not go below, the
blade level so that air is not sucked or place a mirror in position, so that
operator can see the level of concrete in hopper & ensure that concrete in
hopper does not go below the blade level.
3).
Slump for pumping should be 125mm.
4). Concrete will be sent on
site, with a slump of less than 125mm and if required, to adjust for making it
pumpable, we will add (1:4) super plasticizer: water, at site itself, thereby
ensuring that case of collapse
slump of RMC concrete does
not occur at all.
4.
The temperature of 34-degree centigrade will be allowed, for the concrete
supplied at site, when the transit mixer actually arrives & not at placing
the concrete, since there can be delays at placing point due, to site
conditions.
6. Wetted Hessian cloth, to be
placed on RMC concrete supply pipes & transit mixer, in order to control
the temperature of concrete.
Reasons for additional water in concrete, which makes the concrete with
Collapse Slump is:
a)
There can be fault with valve supplying water in the drum of transit
mixer, for cleaning the transit mixer drum, after concreting is completed .
b)
After every supply of concrete, the mixer drum is washed. This water may not be removed and fresh concrete is
loaded in the transit mixer, at the RMC plant.
Hence during
mixing of concrete in pan mixer at the RMC plant, in the first 2 mixes of 0.5
cu.m, the operator to see the workability of concrete. If required, then in the
balance 10 batches of 0.5 m3, water to be added in lesser quantities. (Assuming
one batch of concrete is 0.5 cu.m)
Hope the above process, will
solve the problems of collapse slump & we can work in more harmonious
manner, achieving Quality, Speed & Economy.
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