What Causes Expansive Demolition Grouts to Blowout?
Background
All brands of expansive demolition grouts are susceptible to “blowouts” if the wrong temperature version of product is used or other user errors occur.
Avoiding blowouts is of utmost importance to:
ensure safety of personnel
complete projects safely and successfully
avoid costs and legal liability for any injuries or property damage
prevent reputational damage
What is a Blowout?
A demolition grout blowout is a dangerous and sudden geyser-like ejection of demolition grout and debris fragments into the surrounding area (see pictures and video below).
The chemical reactions occur too quickly before the:
heat can be transferred to the surrounding material
grout mixture has a chance to cure and harden
The heat of hydration can exceed 125°C, boiling any free water within the mixture. The resulting steam pressure, confined within the drilled hole, is suddenly released, launching powder and rock/concrete fragments with a loud “pop” and great force into the air posing a risk of personal injury and property damage.
What Factors can Cause Expansive Grout to Blowout
1. Using the wrong temperature version of demolition grout.
2. Demolition grouts are temperature sensitive. Select the correct product based on the core temperature INSIDE the rock or concrete NOT based on the air temperature or weather forecast.
3. Pouring grout mixture into hot holes.
4. Boxes or bags of grout sitting in sunlight or warm conditions before being mixed with water.
5. Hole diameter is too large. Possibility of blowouts increases when hole diameter is greater than 1-3/4” (44 mm).
6. Leaving unused product sitting in mixing bucket. (see the video below)
7. Water temperature is too warm.
8. Not measuring water = wrong water to Dexpan ratio.
9. No open face or insufficient expansion room for material to expand, crack and break apart.
10. Water in the drilled holes.
11. Dexpan and water is not fully mixed. Be sure to scrape bottom and sides of bucket.
12. Mixing more than 1 bag of expansive grout at a time resulting in #14 below.
13. Mixing expansive grout by hand vs. using electric hand drill with mixing paddle attachment resulting in #14 below.
14. 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.
15. Adding expansive grout and water to leftover mixture remaining from previously mixed batch.
16. Filled holes exposed to hot direct sunshine.
17. 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.
See the videos below for two examples of Dexpan expanding demolition grout blowouts:
1. wrong product version was used for the conditions
2. surplus mixture is left sitting in mixing bucket / pitcher
