Requirement for Good formwork (Shuttering)

A good formwork should satisfy the followings requirements:

The material of the formwork should be cheap and it should be suitable for reuse several times.

The form should be practically waterproof so that it does not leak and absorb water from concrete.  Also, its shrinkage and swelling should be minimal.

It should easily carry the load of concrete and live load of pouring, vibration, compaction, and curing.

It should have enough stiffness and rigidity so that deflection is minimum.

As soon as possible it should be light in weight, smooth and should be easily stoppable.

All the joints in formwork should be leakproof.

The formwork should rest on non-movable supports.

CODE PROVISION FOR STANDARD FORMWORKS (SHUTTERING)

General requirement:

The formwork shall conform to the orientation, lines, and dimensions, as shown the plans and be so constructed on remain sufficiently rigid during the placing and compacting of the concrete, and shall be sufficiently tight to stop loss of liquid from the concrete.

2. Cleaning and treatment of forms:

All rubbish, particularly chippings, shavings, and sawdust, shall be faraway from the inside of the forms before the concrete is placed and therefore the formwork in touch with the concrete shall be cleaned and thoroughly wetted or reacted with an approved composition. Keep in mind that that approved composition should be kept not be touching the reinforcement.

3. Stripping time:

In no circumstances, forms shall be struck until the concrete reaches a strength of a minimum of twice the strain to which the concrete could even be subjected at the time of striking.

As soon as possible for a longer time, the formwork should be kept in contact, because it might withstand the curing. In normal condition, generally when the temperature is above 20 ⁰C and where ordinary cement is used, forms can be stripped after the following periods:

4. Procedure when removing the formwork:

At the time of removal of formwork keep in mind that there is no shock or vibration as that would damage the reinforced concrete. Before the soffit and struts are removed, the concrete surface shall be watched out, where necessary so as to determine that the concrete has sufficient strength and hardened. Proper precaution shall be taken to permit for the decrease within the rate of hardening that happens with all cement in, the cold water not be done unless allowed for in design calculations of the beams.

5. Camber:

It is generally desirable to offer forms an upward camber to make sure that the beams don’t have a sag once they have kept up their deflection, but this could not be done unless recommended by the calculated design of the beams.