Using Crackit: Cracking

Crack Formation

Upon filling of the pre-drilled holes with the mixed Crackit slurry, reaction immediately starts to occur in the Crackit. Upon reacting, the Crackit mortar starts hardening and expanding causing the material to develop cracks. The cracks generally appear within 3 to 20 hours after filling, depending on the temperature. These cracks spread further and become wider with time.

Time Required for Crack Formation

Reaction starts as soon as Crackit is mixed with water causing it to expand and harden. When the Crackit expansive mortar is packed into a hole in stone or concrete, it swells and exerts pressure on the hole-walls and thus fractures it.

The cracks appear within 45 minutes after filling, depending on weather, rock or concrete temperature. The cracks become wider with time. The ambient temperature in the material being cracked determines the reaction speed. The higher the temperature, the shorter the reaction time.

The time required for full crack formation in material at 30°C is about 6 - 8 hours. The lower the temperature, the longer the crack formation takes. The crack width for rock continues to increase with time and can become 10 - 30 mm (3/8" - 1 1/8") after several days, depending on free surface available. It is best to wait until Crackit has worked to full depth before removing the rock, as premature removal at the first sign of a crack can hamper the leverage effect of Crackit.

Some points to remember after filling, while waiting for the cracks to appear:

1. Tamping with mortar or sand is not required after filling Crackit. It is also not necessary to put any restrictive cap. Just leave it as it is and wait until cracks initiate.
2. Covering the filled hole with tarpaulin is desirable to avoid dilution of Crackit from external water source until cracking starts.
3. Spraying the surface with water, after the cracks initiate, tends to increase the width of cracks and speeds up the cracking process.
4. If only small cracks are found, you can pour more water into the crack line for further expansion.

Controlling Expansive Strength and Reaction Time

For Crackit, the higher the temperature, the quicker is the reaction. There are two ways to control the cracking agent's reaction time. For universal type, reaction inhibitors of 20 gram per bag are available for each 5 kg package in carton. 20 gm inhibitor can be added into water first and then the powder can be mixed to avoid the possibility of blow out shots. For quantity details refer to the following table:

Cutting and Secondary Breaking

When the cracking gap is around 3 - 5 cm, you can carry out the further demolition work. After cracks initiate, secondary breaking is carried out with a hand-breaker, a pick-hammer, a giant hydraulic breaker, a ripper, etc. It is best to wait until the Crackit has worked to full depth before removing rock or concrete since premature removal at the first sign of a crack hampers the leverage effect of Crackit.

Please Note:

1. Be sure to wear PROTECTIVE GLASSES when secondary breaking is carried out.
2. The crack width for rock or concrete continues to increase with time and can become 10-30 mm (3/8"-1 1/8") after several days, depending on free surfaces available.

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