Decide which of the following situations is relevant and then follow the reasoning.

If it is a FAST TAKE

Indications

• The surface level in the agitator falls perceptibly when watched for about half a minute.
• There is lack of pressure sensitivity in the hole when the control valve setting is varied.

Reasoning

• Did the water test before grouting have a relatively high take (experience indicates the relative magnitudes of takes)?
• If it did, the fast grout take is reasonable. Thickening of the mix may be necessary after a few more runs.
• If the water test did not have a relatively high take, the fast take probably indicates that a thicker mix could be used successfully without choking the cracks. Therefore, thicken the mix by one step now and possibly thicken further soon.

If it is a MODERATE TAKE

Indications

• The surface level in the agitator falls so slowly that it has to be stared at for about a minute to notice a drop.
• There is a definite, though mild and possibly sluggish, response on the pressure gauge when settings of the control valve are changed.

Reasoning

• This is the usual situation if the starting mix has been suitable. A thicker mix might give premature refusal.
• Keep on this mix for the next few runs at least.

SLOW TAKE

Indications

• Surface level in agitator falls too slowly to be seen.
• Pressure very sensitive to control valve settings.

Reasoning

• Did the water test before grouting indicate fairly tight conditions?
• If it did, slow takes can be expected on relatively thin mixes such as 3 : 1 or 2 : 1.
• Is 1 : 1 or thicker in use? If so, it is too thick for this hole.

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For the observing of grout level in the agitator to be successful, the agitator should have approximately the proportions shown in the sketches.

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The information about thickening shown on a previous screen is repeated here for convenience.

STANDARD MIXES and THICKENING STEPS

There is no need to use any other mixes than

•       5 : 1 by volume
•       4 : 1
•       3 : 1
•       2 : 1
•       1 : 1
•   0.8 : 1
•   0.6 : 1
•   0.5 : 1

These mixes give adequate increments in viscosity. Mixes in between give negligible extra control over viscosity and are only a nuisance.

When thickening the mix during grouting, proceed down the list one mix at a time - never jump a mix. For instance, if thickening from 3 : 1, go to 2 : 1 for a while and then to 1 : 1 and perhaps on. Never go straight from 3 : 1 down to 1 : 1 or else the too sudden thickening is liable to prematurely block cracks in the job.