Removal of formwork – Some useful tips

Formwork belongs to temporary moulds where concrete is poured, and condensed to cast concrete with adherence to the design.

Formwork is built up in the exact location to cast concrete structural members. The formwork is retained in its position unless the concrete gets solidified and starts attaining strength.

When the concrete attains adequate strength to bear its dead weight devoid of using formwork or any props furthermore, formwork can be eliminated. The preventive measures should be undertaken throughout the elimination of formwork or props. It is also required to identify the exact time of formwork elimination.

The formwork should be eliminated once the required strength is obtained by the concrete structural components which are supported inside the formwork.

Supporting period means the time from which the concrete is set in formwork up to the time the formwork is eliminated is called as. The fluctuation in time period is dependent on the following factors :-

• Type and grade of concrete
• Admixtures applied in concrete mix
• The formwork designs
• Temperature
• The type of structural element (Columns/beams/slabs)
• Material quality

Curing conditions:

The formwork removal method after the concrete is casted and attained adequate strength is known striking of formwork. For this reason, the stresses will occur in the structural element because of the loss of supports either on sides or below, now the structure has to take the liability to support itself. A concrete element that is perfectly hardened can withstand these external stresses throughout the elimination of formwork. Formwork is retained for prolonged time for simplifying the curing method of concrete elements.

Given below, the normal time period for eliminating the formwork according IS:456-2000, Clause 11:

The above conditions are suitable for normal conditions; the normal temperature should remain under 15 degrees Celsius and the ordinary portland cement should be applied. For lower temperatures and other types of cement, the suggested time can be modified accordingly. Under such situation, one should firmly abide by the instructions of the structural engineer.

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