Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

900 FORMWORK AND SURFACE FINISH FOR STRUCTURES
A Methodology
A 1 Design and Erection
151
Quality Assurance Handbook for Rural Roads
1. Examine all materials and components used for formwork, for damage or excessive deterioration
before use and reuse only if found suitable after repairs.
2. For timber formwork, inspect for physical damages, besides signs of attack by decay, rot or insect
attack or development of splits.
3. Use familiar materials like timber, steel, plywood, concrete and masonry for false work. For metal
forms, the thickness should be adequate to keep them true to shape. Use counter sunk bolts and
permit use of approved internal steel ties or steel or plastic spacers.
4. Ensure false work (formwork + temporary support system) is designed to meet the requirements
of permanent structure including ease of erection and dismantling and is approved by the Engineer.
5. Provide proper and safe access to all parts of formwork for inspection.
6. Make the formwork robust and use ballies of 100 mm dia of heights not more than 4 m. Provide
cross and diagonal bracings of 75 mm dia (ballies) in both directions. For metal forms, the diagonal
bracings shall be of the same size of angles used for columns.
7. Check for design deficiencies such as shoring or reshoring, insufficient allowance for unsymmetrical
or eccentric loading due to placement sequence of concrete.
8. Pay attention to detailing which otherwise may cause instability, local failure or progressive
collapse. Lay emphasis on attention to details.
9. In case of false work erected on normal ground, ensure distribution of loading to the ground,
through timber or base plates to avoid differential settlement.
10. Control the alignment of the distribution members, so that shores of the falsework system are
centrally placed on the member.
11. Make the forms tight and sufficiently rigid by the use of ties and bracings to prevent any
displacement or sagging between the supports.
A 2 Preparation before concreting
1. Apply a coat of oil or grease as release agent, inside the surfaces of forms to prevent adhesion of
concrete to formwork.
2. Make the formwork leak proof to prevent escape of cement slurry during compaction with vibrators.
Clean the forms thoroughly just before concreting.
3. Line formwork with a proven material to provide smooth finish of uniform texture and appearance,
without leaving stain on concrete.
A 3 Removal of Formwork
1. Plan removal of formwork (deshuttering and decentering) in advance. Give due consideration to
the local conditions viz. character of structure, weather and materials used in mix.