1) FORWARD FLOWING METHOD OF CONCRETING
Never put concrete directly over a densely
reinforced section. At such a section it is impossible to vibrate and this
results in honeycomb.
At a beam column junction, place concrete in the
beam (at the junction) and then push the concrete towards the column by
vibrating the same.
This prevents mortar from sticking to the column
steel and thereby preventing honeycombing.
2) CONSTRUCTION JOINT
Construction joint is the joint between the
hardened concrete and the fresh concrete.
A. HOW TO MAKE A SLAB CONSTRUCTION JOINT STOPPER ?
Fold an empty cement bag along its width for around
3 to 4 times so that a strip of the bag is formed.
Tie the bag at both the ends in the form of a
sausage.
Place such bags along the length of the slab along
the construction joint below the bottom bars. Place 'stopper chavis' over the
bags. This prevents any slurry or concrete from moving beyond the joint.
Remove the stopper with the bags just before the
concrete hardens.
B. WHAT ABOUT A BEAM STOPPER ?
Cover wooden chavi with empty cement bag.
Insert such chavis, in the beam where the stopper
is desired so as to cover the entire width of the beam.
The number of chavis depends on the width of the
beam in question.
After the concrete is placed, remove the stopper
chavis before the concrete gets hardened.
.
C. WHAT CARE SHOULD BE TAKEN DURING CONCRETING OF THE
CONSTRUCTION JOINT?
Clean the hardened concrete at the joint face.
Remove all the loose material.
Put 'Policemen Grout' over the joint.
Place the fresh concrete at around 300 mm from the
hardened concrete and than vibrate the fresh concrete towards the joint.
In case of a slab, let the concrete flow beyond and
over the joint by around 50 mm. (To be leveled by the mason at the later
stage.) This will guarantee that all the voids are filled and a leak proof
joint is obtained.
D. WHAT IS A POLICEMEN GROUT?
Cement Grout = Cement + Water = (Glue) with
controlled water/cement ratio.
1 litre of cement (loose) weighs 1.2 Kg. approx..
So we require 0.6 litres of water,
for maintaining a water/cement ratio of 0.5.
For easy understanding,
For every 5 litres of cement add 3 litres of water.
Use 1 litre measure for the same.
