How to Use Expansive Cracking Agents for Controlled Concrete Demolition

Expansive cracking agents use chemical force to break up concrete.

The use of an expansive cracking agent will allow you to break up concrete without the use of explosives or heavy equipment. A mixture of an expansive agent can apply more than 12,000 pounds per square inch of pressure to the concrete from the inside, forcing the block or slab to crack apart into pieces that can be picked up and hauled away.

Things You'll Need

• Electric or compressed air hammer or rock drill
• 1.5-inch or 1.75-inch concrete drill bit
• Air compressor
• Mixing bucket
• Drill-powered mixing paddle
• Thin rod or stick

Instructions

1. Drill an even pattern of 1.5- to 2-inch-diameter holes in the concrete to be demolished. For nonreinforced concrete, the holes should be 1 to 1.5 feet apart. For reinforced concrete, the holes should be 8 inches to 1 foot apart. The hole depth should be 90 percent of the concrete thickness -- almost but not all the way through.

2. Clean any debris and dust out of the drilled holes using a compressed air hose.

3. Mix the expansive cracking agent compound with water using the proportions listed on the cracking agent bag or box. Use a drill with paddle mixer to thoroughly and quickly mix the agent to a thick slurry consistency. The agent should be used within 10 minutes of being mixed with water.

4. Pour the slurry mix into the drilled holes, filling each hole to within about 1 inch of full. Use a thin rod or stick to stir the slurry in each hole to release any trapped air bubbles.

5. Wait 24 hours for the expansive agent to fully crack apart the concrete to be broken up. Cracks in the concrete should start appearing within a couple of hours, but the agent will continue to expand and break apart the concrete for a full 24 hours.

Tips & Warnings

• Expansive agents may be temperature dependent. Choose an agent appropriate to the current air temperature.

• Mix enough expansive agent slurry to fill your holes without any leftover. Slurry left in the bucket will start to expand with the possibility of a blowout.

• Expansive cracking agent in a drilled hole is subject to possible blowouts, sending material out of the hole with a significant amount of force. Do not look directly into filled holes while the agent is working.

• Wear goggles, safety gloves and a safety helmet during all steps when demolishing concrete with these products.

References

• Concrete Network: Expansive Demolition Agents
• Archer USA: Dexpan Non Explosive Controlled Expansion Demolition Agent
• Crackamite: How Does Crackamite Work?