Generally, grout should be of a pourable or flowable consistency for moving it to where it's needed. What this means is when the material may be poured out of bucket or a pail it will flow to fill in any gaps. The exception for this demand is repair mortars, which have a tendency to be mixed in a consistency that is heavier and necessitate specific techniques for application. Substances which contain aggregates pump best and perform best when consistency is in the lesser range of pourable; in other words, not exceedingly wet.
Some materials have setting time reduced by accelerating admixtures. This is especially true of repair mortars to ensure the strength gain may be reasonably rapid. It is critical to keep moving when when working with these sorts of materials as it is important to keep the grout pumping consistently and promptly after being mixed to avoid setting. To assist this each batch must be mixed and pumped as swiftly as possible as any delays in the application process might result in blocked hoses and gear. Temperature may accelerate the set time even further so pumping grout in direct sun and hot conditions should be avoided. It may be unnecessary in hot conditions to cool the mixture with cool water or even the hose itself.
Grout pumping works best when the pumping distance is kept to a minimum, and hoses run as straight-as possible. Occasionally circumstances demand longer spans and every effort should be taken to use ensure a successful application when this occurs. Some grout cannot be pumped for long-distances, so its best to know the material specifications before attempting a production run.
Before attempting to combine and pump production mixtures, it is wise to rinse the machine and charge the hopper with adequate water to completely flush the pump and all grout hoses. This is to remove from the grouting system of any remaining materials or contaminants that may exist. Once that's completed, eliminate from the pump and drain all water out by elevating one end, or by progressively elevating the hose, beginning at one end and carrying on to the other.
Next, mix a slurry composed of portland cement and pump this through the grouting system. This is to eliminate any residual water from the hose, lubricating it for the production of grout to follow. Now the grout can be combined and pumped immediately behind the slurry mixture, which is hence evacuated from the hosepipe. Don't attempt to grout pump with a dry hose.
Sometimes, however painstaking an owner may be, a hose can get plugged. The only certain way to eliminate the stopper will be to empty it of material once this occurs. A wise operator will probably prepare for such contingency by having readily accessible an adequate span of small-diameter stiff tubing, hose or plastic conduit to which can quickly connect a water source and eliminate the grout from your hosepipe.
Read more about pressure grouting