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Rockcreter C70 grout mixing and pumping suggestions

NOTE
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 wide varieties 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.


MATERIALS

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

FLOW

In general, most materials need to be 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.

SETTING TIME

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 DISTANCE

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 its's best to know the proposed material characteristics before attempting a production procedure.

GENERAL PROCEDURES

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, at one end and proceeding to the other. Next mix a slurry composed of portland cement in approximate proportions of 25 liters of water to ½ a bag 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.

GROUT PUMPING TIPS SET- UP

  • In general, the most important factors in setting up are proximity to the work and access to materials and water supply, consideration should be given to the disposal of waste materials and wash-out residue.
  • It is always best to keep grout lines as short as possible to reduce pumping distances. This is particularly important when pumping hard-to-pump materials, such as sanded grouts and pre-blended materials.
  • The source of solid materials (cement, fly ash, sand, etc.) should be readily accessible and adequate supply water should be available for mixing and clean up.
  • When planning a project for high production rates, it is well to remember that the greatest consumption of time occurs when charging the mixers. A proper set-up can reduce this to a minimum.

START-UP

  • After set up, visually inspect that there are no foreign objects or old set up materials in either the pump or the mixer, then make all necessary connections.
  • With operating levers, valves, or handles in"NEUTRAL" or "OFF" position and the primary power source turned OFF, fill the pump hopper with clear water.
  • Turn on the primary power source and observe that conditions are normal and machine is ready to run.
  • Check the mixer for proper operation by running the mixer and pump in the right direction.
  • Next, start the delivery pump to discharge the water that was previously introduced into the pump hopper. This ideal opportunity to check the grouting system to determine that all lines and hoses are clear and unobstructed. Pump condition may also be checked at this time by testing discharge pressure.
  • When it is determined that all systems are normal, shut off the pump and drain the water from the pump and all lines.
  • NOTE Some pre-blended materials and some on-site mixes of sand and cement tend to separate and clog the hoses upon contact with residual water in the hose, so it is a good procedure to mix and pump the production material, to lubricate the pump and hoses.

PRODUCTION

  • During the production phase of work, monitor pump and mixer performance continuously, being alert to any signs of abnormality.
  • Keep mixers free of material build-up, keep the outside of the machine clean.

CLEAN-UP

NEVER RUN PUMP WITHOUT FLUID, AS IT WILL CAUSE SERVER DAMAGE!
After disposing of excess production material, carefully wash out mixer paddles, screen 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

SAFETY USE

SAFETY STRAPS ON ALL GROUT HOSE CONNECTIONS. KEEP ARMS, HANDS, FINGERS ETC AWAY FROM MOVING PARTS. DISCONNECT POWER/AIR BEFORE ATTEMPTING TO CLEAN OR REPAIR EQUIPMENT MIXING PROCEDURE
Load approximately 80% of the water or liquid anticipated for the size batch to be mixed and with the mixer running add the required amount of cement. Allow sufficient time for the slurry to mix to a creamy consistency, before pumping or adding filler material (sands, fly ash, etc) Slowly add sand, if required, until the the mix just begins to lose the 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 sand to produce a grout that is just pourable. Never switch the mixer off during mixing batches. This will cause excessive load and will damage the motor and gearbox.

PREMIX GROUTS

Many building material suppliers manufacture pre-blended cement based grouts, 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. Before pumping any pre-blended cement-based grout mix, it is good practice to first coat the pump and lines with cement 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:

  • A stable suspension of solids that does not separate while at rest.
  • Color must be predominantly that of the cement used.
  • Fluid enough to pour from a container, but not too wet. (Thick batter consistency)

CEMENT

There are several types of Portland cements manufactured to satisfy a variety of specific requirements, such a 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.

WATER

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 important factor in the quality of the material in its final state, the water content should be kept to the minimum that will produce material with the characteristics listed above.

ADMIXTURES

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.
View the Rockcrete Admix Products page

FLY ASH

In some parts of the country, fly ash (a by-product of coal burning power stations) is available. This material has often been used to enhance the properties of cementitious grouts or reduce them 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.

SAND

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. Regular particles such as manufactured sands should be avoided. Larger amounts of well graded and rounded, natural shape. Angular 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.

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