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How to Mix Expansive Mortar Correctly: Step-by-Step Guide
Incorrect mixing is the #1 reason for project failure in non-explosive demolition. A contractor recently reported that 40% of their boreholes failed to crack rock because they estimated the water by "feel" rather than weight. The resulting slurry was too thin, expansion pressure was lost, and the product was wasted. Success in rock breaking starts in the mixing bucket.
Direct Answer (Quick Summary)
The Problem: Weak cracking or blowout caused by incorrect preparation.
The Answer: Mix the soundless cracking agent with exactly 28–30% clean water by weight.
The Data: Use 1.4–1.5 liters of water for every 5kg of expansive powder.
Note: Always pour powder into water (not the other way around) and stir for 2–3 minutes.
Conclusion: Filling boreholes within 5 minutes of mixing ensures 120MPa expansion pressure and reliable crack propagation.
How to Mix Soundless Cracking Agent: The Process
Step 1 — Verify Temperature and Grade Selection
Before mixing your expansive grout, check the actual rock and ambient temperature. Match the formulation: HSCA-1 for summer/desert heat (25°C–40°C), HSCA-2 for mild weather (10°C–25°C), and HSCA-3 for cold conditions. Grade selection is the first step to preventing blowout.
Step 2 — Weigh Water by Mass (Crucial)
The expansive mortar water ratio must be 28–30% of the total powder weight.
For 5kg of powder: 1.4–1.5 Liters of water
For 10kg of powder: 2.8–3.0 Liters of water
Step 3 — Control Water Temperature
In standard environments, use room temperature water. However, if the ambient temperature is above 35°C, you must use chilled water (below 15°C) to slow the initial reaction and prevent steam discharge (blowout). Always measure water temperature with a thermometer.
Step 4 — Add Powder into Water (The Sequence)
Always pour the rock cracking powder into the water. If you pour water onto powder, dry lumps will form at the bottom of the bucket, preventing the calcium oxide from hydrating properly. Stir continuously while adding the powder. Mix for 2–3 minutes until the slurry is uniform and smooth.
Step 5 — Filling Boreholes Immediately
The chemical reaction begins the second the powder touches water. You must pour the mixed slurry into the boreholes within 5 minutes. Do not mix more than can be filled in this window. Fill the holes to within 5cm of the opening and do not plug or seal the holes.
Expansive Mortar Mixing Parameters at a Glance
| Parameter | Target Specification | Risk if Incorrect |
|---|---|---|
| Water Ratio | 28–30% by Weight | Low pressure / Incomplete cracks |
| Mixing Order | Powder into Water | Lumps and uneven reaction |
| Mixing Time | 2–3 Minutes | Incomplete hydration |
| Fill Time | Within 5 Minutes | Stiffening in the bucket |
| Water Temp (>35°C) | Below 15°C (Chilled) | High risk of blowout |
Expansive Mortar Mixing & FAQ
Q: How do you mix soundless cracking agent correctly?
Measure 1.5 liters of water for every 5kg of cracking agent. Pour the powder slowly into the water while stirring. Mix for 3 minutes until smooth and pour into boreholes within 5 minutes. This ensures you reach the full 120MPa expansion pressure needed for hard rock.
Q: What happens if the expansive mortar has too much water?
Exceeding the 30% water limit reduces the viscosity and the overall expansion force of the non-explosive demolition agent. If the slurry is too fluid, it cannot generate the necessary friction against the borehole walls, leading to weak or failed cracking. Always weigh water on a scale.
Q: Can I store the mixed slurry for later use?
No. Once mixed with water, the hydration reaction of the chemical rock splitter begins immediately. If the slurry starts to stiffen in the bucket, it must be discarded. Never add more water to "revive" old slurry, as this permanently destroys its expanding properties.
Q: Can I use tap water to mix expansive mortar?
Yes. Clean tap water is generally suitable. Avoid seawater, muddy water, or water contaminated with chemicals, as impurities may affect the hydration reaction and expansion performance.
