Shuttering Oil or formwork oil is high-quality mineral oil that is applied to the inner surface of formwork before concreting. Shuttering oil is also known as a form or mould release agent.
Uses of Formwork Oil
Shuttering Oil is used for the following reasons:
- Application of shuttering oil prevents sticking of formwork to the concrete surface thereby permitting easy stripping of formwork after the concrete has hardened.
- Shuttering oil protects the formwork and hence the formwork can be reused several times.
- Shuttering oil helps provide good finishing surface of the concrete with minimum defects.
- In the case of wooden formwork, shuttering oil prevents water absorption from concrete by the wooden formwork.
- Shuttering oil reduces leakage of water during the curing process.
- Shuttering oil prevents steel formwork from corrosion.
The performance of shuttering oil is largely dependent on the type of formwork that is being used. For wooden formwork, straight refined, pale, paraffin-based mineral oil and oil-phase emulsion have been successfully used. The oil that is chosen should be capable of penetrating the wood to some extent while leaving the surface slightly greasy to touch.
There should not be any free oil on the wood surface. The form release agents that are good for wooden formwork are not always suitable for steel formwork. And hence the shuttering oil or form release agents should be chosen based on the type of formwork that is to be used for construction.
The shuttering oil for steel formwork should be free of water and should contain rust inhibitor.
Types of Shuttering oil:
1. De-Shuttering Oil (DSO)
This is a water-based mould releasing agent which gives clean and stain free high-quality concrete. It is available in a sprayable form and ready to use as a direct application on required places. It should be applied in light film either by brush or mould oil sprayer. If it is over applied, excess oil should be drained before it dries. Pools of DSO cannot be allowed to dry as it causes surface retardation of concrete.
Advantages of De-Shuttering Oil are as follows:
- DSO is economical to use.
- It is non-toxic and non-hazardous.
- It can be used for all types of concrete formworks.
- It helps reduce the cleaning efforts before reusing of the formwork.
- DSO provides a damp proof interface that protects the formwork and ensures even texture and colour of concrete.
2. De-Shuttering Oil Emulsion (DSOE)
This oil does not require any dilution and can be used instantly.
3. De-Shuttering Oil Concentrate (DSOC)
This is dilutable and used as a mould release agent.
Before the application of shuttering oil on the formwork, it is important to make sure that the surface of the formwork is clean of previous impurities. The shuttering oil is applied by spraying guns, rollers or by brushes. It is important to remove any excess oil on the surface of the formwork.
The use of barrier paints extends the life of the formwork by producing a hard-wearing surface on the formwork. If barrier paints are not used, it is advised to use three coats of shuttering oil before the shuttering is used for the first time.
To avoid contamination of the reinforcement, it is advised that the shuttering oil is applied on the formwork before it is erected.