PACKAGE : I Bid Document VOLUME : II - Public Health Engineering

7.9 Inspection.
Concrete shall not be placed until the Engineer has inspected the formwork and the
reinforcing steel, and taken necessary measurements of the latter, and has approved
the surface upon which the concrete is to be placed.
Transporting:
Fresh concrete shall be transported from the mixer to its place in the works as
quickly and as efficiently as possible by methods, which will prevent pre-set or
segregation. If segregation has nevertheless occurred in any instance, the materials
shall be remixed or discarded at the opinion of the Engineer.
Placing:
Fresh concrete shall be placed and compacted before initial set has occurred and in
any event, not later than thirty minutes from the time of mixing. Concrete shall be
carefully placed in horizontal layers which shall not be allowed to slide or flow
down sloping surfaces but shall be placed in its final position from skips, or similar
devices. If this is impracticable, it shall be shoveled into position care being taken
to avoid segregation. No concrete shall be dropped more than 1.5m. If greater
drops are necessary approved chutes may be used. If the concrete abuts against
earth or any other material liable to become loose or to slip, care shall be taken to
avoid falls of materials on the surface of the wet concrete.
As far as possible concrete for any particular portion shall be done in one
continuous operation leaving construction joints, if specified by drawing.
Before commencing subsequent concrete on the one left incomplete, all the loose
particles, laitance etc. shall be removed and surface shall be covered with thick
cement slurry. The concrete compacted manually shall be laid in layers not more
than 15 to 20cm. The successive layer shall follow within 30 minutes or earlier.
7.10 Compaction.
All concrete placed in-situ shall be compacted with power driven or pneumatic
internal type vibrators unless otherwise approved by the Engineer in writing, and
shall be supplemented by hand spading and tamping where required. Vibrating by
screed type vibrators may be used for thin slabs. There shall be sufficient and spare
vibrators of adequate capacity to compact the work in hand.
GTS : General Technical Specification. Page 62