The Constructor

Pre-Concrete Checks for Formwork and Release Agents

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Pre-Concrete Checks for Formwork

Before the concrete is poured into the formwork, it must be checked by someone who has been trained to inspect formwork. Depending on how big or complicated the pour is, the inspection may just take few minutes or it could take hours. Only when the formwork has been approved, may the pour take place. Formwork pressures are function of height (including the height from which concrete is dropped into the forms) and are affected by concrete workability, rate of stiffening and rate of placing. One task of the temporary works co-ordinator is to consider such factors as ambient temperatures and concrete composition, when calculating maximum permissible rate of concrete placing. Exceeding this limit may lead to unacceptable formwork deflections, loss of grout / concrete at joints, or even collapse. The cost of remedial work due to formwork deflection will usually exceed the original cost of doing the job properly. Below are the checks that should be verified before pouring begins:

Release Agents for Formwork:

Formwork needs to be treated with a release agent so that it can be removed easily after the concrete has set. Failure to use a release agent can result in the formwork sticking to the concrete, which may lead to damage of the concrete surface when it is prised off. A single application of release agent is all that is required when forms are then used. Care must be taken to cover all the surface that will come in contact with the surface of concrete. However, if there is an excess of release agent, it may cause staining or retardation of the concrete. There are different release agents depending on what material is used for the formwork. The three most common release agents for formwork are:
  1. Neat oils with surfactants: used mainly on steel surfaces, but also suitable for timber and plywood.
  2. Mould cream emulsions: good general purpose release agents for use on timber and plywood.
  3. Chemical release agents: recommended for high quality work, applied by spray to all types of form face.
Read More: Types of Formwork (Shuttering) for Concrete Construction Plastic Formworks for Concrete – Applications and Advantages in Construction Concrete Formwork Design Considerations – Basis for Concrete Formwork Design Wooden Concrete Formwork Design Criteria with Calculation Formulas Concrete Formwork Loads and Pressure Calculations Concrete Formwork Removal Time, Specifications and Calculations Formwork (Shuttering) for Different Structural Members -Beams, Slabs etc Measurement of Concrete Formworks for Payment Calculation Formwork Safe Practices Checklist during Design and Construction
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