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Aftercare
Protection and Curing
After the application of lime
renders, plasters or coverings, controlled curing and
protection will be needed to ensure maximum strength and
durability are achieved. The chemical reaction which gives
hydraulic lime its long-term performance is known as the
‘hydraulic set’. ‘Carbonation’, (the reabsorbtion of carbon
dioxide), also takes place. This process is best achieved in
warm and moist conditions, which allows the new works to dry
slowly. Therefore, during and after completion of the work,
it is essential to ensure ambient conditions.
Rapid drying by the sun, wind or artificial heat will all
have a detrimental effect on the final outcome of the lime
finishes.
Temperatures below 5șc will slow the carbonation and
hydraulic setting process and frost conditions will damage
un-carbonated areas, through the action of freeze-thaw
(expansion/contraction) resulting in feeble and crumbly
finishes.
Excessive shrinkage is a result of rapid drying, and this
can lead to separation between coats and background. Rapid
drying of the surface of new mortars, can also lead to the
pores of the mortar becoming blocked with fine material,
transported to the surface by the passage of water
evaporation too quickly from the mix, this will inhibit the
carbonation process taking place deeper into the new mortar.
The best way to control and protect the carbonation process
is to form a microclimate for the new work. Where the new
work is scaffolded, this can be a reasonably simple job.
Scaffold netting is very useful for reducing the effects of
wind. In addition to this in warm or hot conditions, damp
hessian can be placed against the new work and then covered
by sheeting to stop rapid drying.
New work should be damped down for a minimum period of 10
days after completion and longer if possible.
The emphasis should be on damping down as opposed to
saturating new work. Provision should be made for damping
down over weekends, holidays etc. In cold weather, the work
must be protected from frost attack, by using thermal
blankets e.g. polystyrene sheets. Hydraulic plasters/mortars
will stand up to cold conditions after 3-4 weeks of
hardening. It should be remembered that prolonged periods of
cold temperature will slow the overall hardening process and
extended periods of protection will be called for.
The Building Lime Company | Tel: 01980 611950 | Fax: 0845 658 7788 |