What Causes Expansive Demolition Grouts to Blowout?

Background

All brands of expansive demolition grouts are susceptible to blowouts if the wrong product is used or instructions are not followed. Expansive demolition grouts work on the principle of the powder being mixed with water and poured into pre-drilled holes where a chemical reaction occurs that generates heat and expansion.

If the reaction goes too quickly the temperature can be above the boiling point of water before all the water has chemically combined with the powder. This may result in a steam driven blowout where the expansive grout, under pressure within the confined holes, is ejected with sudden force. Avoiding blowouts is of utmost priority to ensure safety of personnel, projects are completed successfully (the first time, uneventfully, on-time & on-budget) and legal liability for any injuries or property damage is avoided.

Potential Causes of Expansive Grout Blowouts

1. Using wrong version of expansive grout given the core temperature of the rock or concrete.

2. Pouring grout mixture into warm or hot holes.

3. Hole diameter is too large.

4. Hole depth is too shallow. Drills hole to a minimum depth of 5 times the hole diameter.

5. Distance between holes is too large.

6. No open face or expansion room for material to expand, crack and break apart.

7. Mixing more than 1 bag of expansive grout at a time resulting in #9 below.

8. Mixing expansive grout by hand vs. using electric hand drill with mixing paddle attachment resulting in #9 below.

9. Too much time passing between beginning to mix and pouring into holes. Ensure mixed grout is poured into holes within 5-10 minutes of adding, mixing with water.

10. Adding expansive grout and water to leftover mixture remaining from previously mixed batch

11. Too much dust in holes.

12. Not measuring water. Using too little water.

13. Using warm water.

14. Grout sitting in sunlight or warm conditions before being mixed with water.

15. Filled holes exposed to hot direct sunshine.

16. Filling holes incorrectly.

Always fill row of holes closest to your open face first, pouring left to right; next row, back to the start, pour left to right.

IMPORTANT

Never stand directly above or look into filled holes. Use the correct version of expansive grout based on your material core temperature. Follow all product instructions and recommendations. Early or warning signs do not always precede blowouts. If filled holes start to smoke or steam, that could be a sign they may be about to blow out. Clear the area of people immediately.