Concrete Curing Method of Statement

The scope of this procedure covers methods of concrete curing to achieve specified strength and durability parameters of concrete.

Procedure for concrete curing on a project site will vary depending on the type, exposure, location and design mix.

It is advised to check the specification and obtain the approval of the Consultant prior to the adoption of any of the following methods.

Method one for Curing of Concrete – Keeping the surface of concrete moist:

Ponding:

This method is normally applied on horizontal surfaces, such as floor slabs.

Water for curing shall be of potable quality and free from undesirable levels of dissolved salts.

Spraying/Sprinkling Water:

Curing of horizontal and vertical surfaces can be done by sprinkling water.

This method can also be used for curing inaccessible areas.

Care shall be taken that temperature of water to be used for concrete curing shall be similar to the concrete itself.

Damp Sand or Hessian

Materials such as wet hessian or wet sand are used but they must be kept continually wet and not allowed to dry out.

Constant vigilance is necessary to guard against the protective material drying out and becoming useless.

Careful  supervision is required to see that the hessian  is kept properly Damp throughout the period of curing.

It may also cause staining. For these reasons it is a practice, best avoided.

Concrete Curing Method Two – Prevent loss of moisture from the concrete

Polythene Sheeting

A simple way of keeping moisture in the concrete is to cover it with polythene sheeting.

The polythene sheet shall be placed in position as soon as possible.

Wait until water sheen has evaporated but not so long that the concrete starts to dry out.

It must be in direct contact with the concrete.

It is important that the exposed edges and corners of the sheet shall be well fixed down.

Otherwise wind and draughts would get underneath and create a wind-tunnel effect that would dry the surface of the concrete.

Spraying Curing Compounds on a Curing Membrane

Curing compounds are sprayed on the surface with a hand held hose spray.

This can be used on both horizontal and vertical surfaces.

Special precautions shall be taken while using spray-on compounds (manufacturer’s instructions regarding use shall also be followed).

Surfaces that will not be exposed to bright daylight shall not be treated with a curing compound if they are to receive any additional finish viz. screeds, rendering, paint type finishes or a further layer of concrete.

The compounds shall never be applied to dry surfaces since these will absorb the compound and staining or discoloration may result.

If the surface has dried out, wet it down with clean water then spray while it is still moist.

Curing compounds do not work if sprayed on top of water.

Use safety precautions while handling these compounds.

Follow manufacturer’s  instructions.

Leaving the Formwork in Place

When it is in position, formwork protects concrete against loss of moisture and thus allows curing to proceed.

It is only after it has been struck that further curing of columns, walls and beams may be necessary.

Even where the formwork is left in place, exposed top surfaces must be cured in the normal way.

Curing of Exposed Concrete

All concrete surfaces that will be permanently exposed to the weather needs to be cured with extra care and at least for seven days.

Well cured concrete will be more impermeable and better able to withstand wetting and drying and will have a better long-term appearance, since dirt will not collect so easily.

Paving and Floor Slab Curing

Always start the curing soon after water sheen has disappeared.

For small paved areas, a curing membrane applied by a hand operated hose spray is most convenient.

Always use compounds which reflect the sun’s rays.

Care must be taken that a uniform coat of the membrane is applied, particularly in windy weather when stream of compound could easily be blown ‘off course’.

As a guide, requirements for general curing of in-situ concrete shall be as shown below.

The curing record will be documented in the approved format.