Using Crackamite: Hole Design

Crackamite's effectiveness depends on the placement, diameter and depth of the holes drilled in the material. The drilling must be done in relation to the job to be performed. The design for breaking should be done according to the properties of rocks, joint, volume to be removed, secondary breaking, and work period, etc.

Effective Hole Design for Crackamite

The hole design refers to the hole diameter and hole spacing/distance. For hole diameter between 30 to 50 mm, the hole spacing (distance between holes) should be in accordance with the following formula:

A = K x D

where, A - hole spacing (in mm),
D - hole diameter (in mm) and
K - cracking coefficient.

K value of rocks and concrete
Material to be cracked	K value	Steel contained (Kg/m³)
Soft virgin rocks	10 - 16	n/a
Medium hardness virgin rocks	8 - 12	n/a
Hard virgin rocks	5 - 10	n/a
Plain concrete	10 - 16	0 - 30
Reinforced concrete	8 - 10	30 - 60
Reinforced concrete	6 - 8	60 - 100

K Value changes with the geometry and shape of rock or concrete

Lesser the free surface, smaller the K value

Greater the free surface, larger the K value

Cracking design reference chart
Material to be cracked	Hole design parameters				Crackamite Consumption (Kg/m³)
Material to be cracked	Diameter D (mm)	Hole Spacing A (cm)	Row Spacing R (cm)	Hole Depth H (%)	Crackamite Consumption (Kg/m³)
Soft stone	35 - 40	40 - 100	(0.6 - 0.9) A	100%	5 - 10
Medium hard rock	38 - 42	30 - 40	(0.6 - 0.9) A	105%	12 - 22
Hard granite	38 - 42	25 - 40	30 - 80	105%	18 - 25
Rock cutting	30 - 40	20 - 40	(0.6 - 0.9) A	75%	12 - 18
Plain concrete	38 - 42	20 - 30	(0.6 - 0.9) A	80% - 85%	12 - 18
Reinforced concrete	38 - 50	15 - 30	(0.6 - 0.9) A	90% - 95%	18 - 25

Note: Before experimenting with a test break, reference should be made to '**Hole Design for Rock**' or '**Hole Design for Concrete**' to assist in your special needs for successfully planning a break design.

Estimating Crackamite Quantity Required

Once the hole design is fixed, it is simple to figure out how much Crackamite you need. Crackamite consumption is calculated as the sum of the depths of all boreholes times the corresponding factor of the used borehole diameter. The formula is:

C = Kg/m³ x Number of Holes x Depth of Holes

General coverage: Normally one 44 lb (20 kilograms) box of Crackamite can fill up to 35 linear feet (about 10 meters) of 1½ inches (3.8 centimetres) diameter holes. You might not have to fill up every hole depending on application.
As a thumb rule: Each 5 kilo bag will fill 8 linear feet of 1½" hole or 11 feet of 1¼" hole.

Kg/m³ values for different hole sizes and depth of 1 meter
Hole Diameter	30 mm	32 mm	34 mm	36 mm	38 mm	40 mm	42 mm	44 mm	46 mm	48 mm	50 mm
Crackamite (Kg/m³)	1.2	1.3	1.5	1.7	1.9	2.1	2.3	2.5	2.8	3.0	3.2
Hole Depth	One Meter
Note:	You may get 3% to 6% less yield due to field conditions.

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