What is expansive mortar?
Expansive Mortar is a kind of powder with amazing 18,000 PSI expansive strength when mixed with common water. Expansive cements are powdery materials which produce expansive stresses during the moist curing process. These cements are classified as shrinkage-compensated or self-stressing cements (Dessouki, 2011).
Employee training specific to expansive cements is not necessary for the shattering of rocks. Therefore, it is preferred to use expansive cement instead of dynamite to crush rock because it is safer and easier to utilise.
In mining and quarrying industry, it helps to achieve perfect slabs and blocks from limestone, onyx, marble, granite or any other type of stone you are working with. Compares to blasting, expansive mortar avoids waste of valuable stone, high insurance, costly storage and labor.
How to use expansive mortar?
Drilling
- Drill holes using an air hammer drill and appropriate drill bit specific to the rock type.
- Holes should be drilled no further than 30-60cm (1ft-2ft) apart. Note: In reinforced concrete recommended no more than 20cm (8″) apart.
- Recommended hole diameter 38mm – 50mm (1 ½” – 2.0″). Depth would be 70-90% of the way depending on the type of rock/material to be removed.
Mixing
- For regular safety reasons and mixing small amounts by hand, it is recommended to use rubber gloves.
- In a bucket, combine 1.5 Liters of water to one 5kgs bag of crack agent. Or pour water and mortar as a rate of 1:3 units by weight.
- Mix well, using a drill and paddle is recommended. If mixing with a stick or other method, make sure powder is completely dissolved into the water. Mix to a slurry.
Filling
- Clean holes before filling using air hose remove excess dust from drilling.
- Mortar slurry should be poured into holes within 10-15 min. after mixing. Do not fill to the top, only fill the holes about 15mm (½” to 1″) from the top.
- Mix well and pour into holes while agitating the hole to make sure no air gaps are in the hole. Example: Using a piece of rod or stick to poke holes.
- For Horizontal holes, a grouting pump would be most reliable to poor.
Cracking
The cracks appear in 40-60 min. after filling, depending on the weather, rocks, and concrete type. The cracks become wider within time (maximum 48 hours expanding time).
What are the benefits of this breaking approach?
The main benefits of this technique are:
- It is easy to use;
- Non-explosive and environmentally friendly;
- Works Efficiently and Cost Effectively
What are the drawbacks of this technique?
Drawbacks of Expansive Mortar Rock Breaking Technique:
- Time-Consuming Process
- Dependence on Environmental Conditions
- Limited Breaking Efficiency
- Need for Precise Application
- Potential for Structural Damage
In summary, while expansive mortar offers a safer and more environmentally friendly alternative to explosive rock breaking, its drawbacks, including longer processing times, environmental dependencies, and potential for inefficiency, must be carefully considered in planning rock excavation projects.
