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Version 1.4 May 09
5.6 GROUTING
Backfilling of boreholes and other excavations for piezometer installation often calls
for the preparation and installation of a grout.
Grout should be mixed in a purpose designed grout mixer so as to ensure a
complete mix. However, and only as a last resort, grout can be mixed in a large
container using a high volume pump for circulating, mixing and placing the liquid.
The grout is used as either a sealing compound, a void filling material, or as a
combination of both. Commonly the components and proportions of the mixture are
designed to reflect the characteristics of the material into which it is to be placed.
Where a specific design is not required, generalisations can be made with regard to
the mix proportions.
Since the materials also vary from batch to batch, it is important to use
representative samples of the material that will be used on site, when preparing
samples for lab testing and mix design.
Where the grout is to be used to backfill for a borehole, the commonly adopted mix
proportions, by weight, would be :-
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.
Grout Mix for Hard and Medium Soils
Materials
Weight
Ratio by Weight
Portland cement
50 Kg ( 2 bags )
1
Bentonite
15 Kg
0.33
Water
125 Litres
2.5
Materials
Weight
Ratio by Weight
Portland cement
50 Kg ( 2 bags )
1
Bentonite
20 Kg (as required)
0.4
Water
325 Litres
6.5
Grout Mix for Soft Soils
