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The suggestions offered herein are intended as an aid to help the operator identify some of the factors that need to be taken into consideration when mixing and pumping cementitious grouts. Because a wide variety of materials are available for many different applications, it is incumbent upon the operator to become familiar with the specific characteristics of the material he intends to use.

Among the commercially manufactured materials available in today’s market are materials for structural repairs, floor toppings, high strength non-shrink grouts, manhole and sewer lining mortars and other specialty materials. Each of these materials has unique characteristics, which must be well understood to insure a successful application.

In general, most materials need to be of a flowable or pourable consistency for successful pumping. This means that if the material can be poured out of a pail or bucket, it can likely be pumped. The exception to this requirement is repair mortars, which tend to be mixed in a thicker consistency and require special pumping techniques. Materials that contain aggregates pump best and perform best when the consistency is kept to the lower range of pourable; that is, not too wet.

Some materials contain accelerating admixtures to reduce the setting time. This is particularly true of repair mortars and other spray applied materials so that strength gain can be fairly rapid. It is important to keep moving when using these types of materials. Once the material is mixed, it must be pumped immediately and kept in motion and subsequent batches must be mixed and pumped as rapidly as possible. Any delays in the application process could result in plugged hoses and equipment. Temperature also has an effect upon these materials to the extent that exposure of the hose to the sun on a hot day will accelerate the set time even more; therefore this should be avoided. It may even be necessary in some cases to cool the material, the mix water, or even the hose itself.

Pumping distances should always be kept to a minimum, and hoses should run as straight as possible no matter what material is being used. Sometimes circumstances require longer than usual hose lengths; when this occurs, every effort should be made to use every advantage possible to insure a successful application. Some materials simply cannot be pumped for long distances, so it’s best to know the proposed material characteristics before attempting a production procedure.

Before attempting to mix and pump production materials, it is prudent to rinse the mixer and charge the pump hopper with sufficient water to thoroughly flush the pump and all grout lines. This is to purge the grouting system of any residual materials or scale that may exist. Once that is completed, remove the grout hose from the pump and drain out all water by elevating one end, or by progressively elevating the entire hose, starting at one end and proceeding to the other.

Next, mix a slurry composed of portland cement in approximate proportions of 6-1/2 to 7-1/2 gallons of water to one bag (94 lbs.) of cement, and pump this through the grouting system. This is to remove any residual water from the hose, lubricating it for the production material to follow. Now the production grout may be mixed and pumped immediately behind the slurry mix, which is thus evacuated from the hose, and may be retrieved in a bucket. Do not attempt to pump production material through a dry hose.

Finally, one last word about procedures. Occasionally, no matter how conscientious an operator may be, a hose will get plugged. Once this happens, the only sure way to remove the plug is to empty it of material. Beating on it with a hammer or running over it with a vehicle will not usually be successful. A prudent operator will be prepared for such eventuality by having readily available a sufficient length of small diameter stiff tubing, hose or plastic pipe to which he can rapidly connect a water source and flush the grout from the hose.

After disposing of excess production material, carefully wash out mixer tanks, paddles and baffles into the pump hopper and pump the resulting washout material through the grout hoses to a suitable disposal site.  Continue this operation until only clear water is discharged.  It is advisable to drain all residual wash water from the pump and all hoses when washout is complete.



Mixing Procedure:
Load approximately 80% of the water anticipated for the size batch to be mixed and with the mixer running, slowly add the required amount of cement.  Allow sufficient time for the slurry to mix to a creamy consistency, before pumping or adding filler materials (sand, fly ash, etc.)  Slowly add sand, if required, until the mix just begins to lose the cement color.  This should be the maximum amount of sand the mix can accommodate and it may be necessary to use slightly less sand for subsequent batches.  The water may be adjusted for the relative wetness or dryness of the sand to produce a grout that is just pourable.

Premix Grouts:
Many building material suppliers manufacture pre-blended portland cement based grouts, some of which are pumpable and some are not pumpable.   Before attempting to pump a pre-blended grout material, determine whether the material conforms to the criteria described above.  It is also necessary to determine whether the material has a short working time before set because there may be insufficient working time to pump.  ChemGrout has tested many of the major grout manufacturers products.  Before pumping any pre-blended cement-based grout mix, it is good practice to first coat the pump and lines with a cement and water slurry mix as previously described, prior to pumping the grout mix.

“Homemade” Grout
Sometimes commercially prepared grouts are not readily available, and in these cases it may be necessary to formulate and produce the material on site. This can be done quite successfully, but certain basic principles must be observed.

The resultant material should exhibit the following characteristics:

  1. A stable suspension of solids that does not separate while at rest.
  2. Color must be predominantly that of the cement used.
  3. Fluid enough to pour from a container, but not too wet. (Thick batter consistency)
There are several types of Portland cements manufactured to satisfy a variety of specific requirements, such as high early strength, sulfate resistance and other needs. The most common of these is Type I Portland, and is that which is most frequently used in the production of cementitious grout.

In most instances, the water to be used for the production of grout should be clean and free of sulfates or other dissolved chemicals. If available, potable water is ideal. Since the water to cement ratio is the most important factor in the quality of the material in its final state, the water content should be kept to the minimum that will produce materials with the characteristics listed above.

Admixtures are available to modify and enhance the grout mixture. These include plasticizers, water reducing agents, expansive agents, anti-washout ingredients and others. If used at all, they should be used only with a full understanding of their effects, and only according to the manufacturers’ recommendations.

In some parts of the country, flyash (a byproduct of coal burning power stations) is available. This material has often been used to enhance the properties of cementitious grouts or to reduce the cement fraction in some cases. Use of this material should be approached with CAUTION, since ash from some sources have been observed to cause FLASH SET in grout mixes. If the use of this product is anticipated, trial mixes should be made to prove their applicability.

If the use of sand is anticipated, several factors must be considered such as the shape, size and gradation of the sand to be used. In general, the sand should be clean, well graded and of rounded, natural shape. Angular particles such as manufactured sands should be avoided.    Larger amounts of well graded and round shaped sand particles may be used in the mix than sand which is poorly graded or has a significant number of flat, sharp or angular particles.  Concrete sand is usually not pumpable but masonry and plaster sands usually are pumpable.  In terms of gradation, the following sieve analysis is offered as an example of a various types of sand available:

CONCRETE SAND                                   MASONRY SAND                           PLASTER SAND
Sieve Size
% Passing
Sieve Size
% Passing
Sieve Size
% Passing
3/8" 100        
#8 95-100 #8 95-100
#16 70-100 #16 70-95
#30 40-75 #30 35-70
#50 10-35 #50 5-35
#100 2-15 #100 0-10
#200   #200  
Suggested Mixes:
Ingredient Structural Grout Mix A Structural Grout Mix B
94 lbs.
94 lbs.
Graded Masonry Sand
1½ to 2 C.F.
2½  to 3 C.F.
Fly Ash  
75 lbs.
5½ to 6 Gallons
11 to 12 Gallons
When properly graded sand is not available and more fines are required to “carry” the sand in suspension; use Mix B.
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ChemGrout ®  Inc.
805 E. 31st St. • LaGrange Park, IL 60526 • USA
Phone: (708) 354-7112 • Fax: (708) 354-3881
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