Do you know why curing required for castables?
You know very well that castable powder reacts with water and hardens.While hardening some quantity of heat evolves from the mortar.This heat evaporates the moisture present in the castable mortar quickly.
This affects the castable powder and water reaction due to lack of enough water resulting castable with poor strength and life.
So to avoid this problem,curing was required for castables.
When can be the shuttering and form works can be removed?
They can be removed from 5 hrs to 7 hrs from the completion of the work.
When curing can be started for castable work?
A general rule is : Just you touch the form/shuttering/cardboard work of the castable work by hand.If you sense heat, then it means the castable is ready for curing. 
What are the ways for curing a castable work?
You can select your own convenient ways for curing.But there are only two standard ways for curing.They are:

1.Water spraying on castable work on regular time intervals.

2.Cover the castable area with sac bags/gunny bags and spray water on that sac/gunny bags regular time intervals.

The following tips will be very useful for you regarding curing process:

·         Curing must be started immediately after the removal of shuttering works.

·     Never spray water on shuttering/form work for curing purpose as it was mere waste.

·         Never pour water.Just use water sprays.

·         Ice water can also be used for curing.

·   At areas where direct water curing was not possible due to low strength of castable or at areas where water addition on castable surface causes castable work collapsing,you can wrap a sac bag on castable surface and you can cure on sac bag.

·         Never remove any form work before the castable setting.

·         Never do this job in a hurry.Give enough time for castable setting and curing.

Note: Its safer to follow refractory supplier instructions and procedures for curing and for other refractory related works. 
How much time curing to be done?
Curing for 24 hrs to 30 hrs advisable to get enough strength.