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V1.4 March 15
7.4 Grouting contd…
Grout strength decreases with water-cement ratio and controlling this ratio is the most
important factor for grouting and it is therefore recommended that the water and cement is
mixed first. Water and cement ratios greater than 0.7 - 1.0 by weight will segregate without
the addition of Bentonite or other filler to keep the cement in suspension and it is
recommended that Bentonite normally be used as it is readily available.
The tables below provide guidelines for typical mixes that may be adopted for varying soil
types but are only a guideline and the installer should request the project specification from
the Engineer.
Other compounds can be added to the grout mixture to alter its characteristics:-
•
Expanding agents are added to introduce small bubbles into a cement and water mix
as it cures to prevent it from shrinking.
•
Plasticisers can be added to a mixture to allow it to flow more freely through small
bore pipe work.
•
Fillers are added to provide weight and / or bulk to the mixture for use where grout
may have a tendency to flow through the borehole walls.
Materials
Unit
Weight ratio
Unit
Cement (OPC)
50Kg
1
50 Kg
Bentonite
15 Kg
0.3
15 Kg
Water
125 Lit
2.5
225 Lit
Weight ratio
1
0.3
4.5
Unit
Weight ratio
50 Kg
1
20 Kg
0.4
325 Lit
6.5
HARD SOILS
MEDIUM SOILS
SOFT SOILS
