Guidance on installing refractory castables

However good the quality of a castable, it is essential to follow the installation guidance scrupulously to benefit fully from its performance.

Preparing the formwork:

Timber formwork:
The parts in contact with the castable must be fully waterproofed (oil, paraffin,
polyethylene sheet) to prevent the mixing water from being partly absorbed by the wood.
Steel formwork:
Oil the parts in contact with the castable to make striking the formwork easier.
CAUTION:
Refractory castable must not be reinforced. In some cases, metal fibres or
anchors may be used in the coldest parts of the structure. For this, preferably use
heat-resistant steel.

Preparing the refractory castable 

Use a concrete mixer or a high-intensity mixer.
Mix the dry product for 30 seconds.
Add the water, which must be clean and at room temperature. 15/17 litres per 100 kg of product, as
follows: 2/3 all at once, the rest gradually to adjust the consistency. Stop
mixing when the product becomes plastic and glossy.
CAUTION:
Excess water will make the product easier to place but will considerably reduce its
mechanical strength, especially after firing.

Placing the refractory castable:

Pour, rod or vibrate until a flat, glossy surface appears. Do not re-wet or
re-mix the remainder of an unused batch within half an hour of mixing.

Drying:

To prevent drying too quickly, keep the structure damp for 24 hours after initial setting
by leaving damp sacks in contact with the castable or by spraying it lightly.

Striking the formwork:

This can be done 12 hours after placing the castable at an ambient temperature of 15/20°

First firing:

After drying (48 hours minimum), raise the temperature in steps of 50°/h up to 600°