TIPS REGARDING GROUT MIXES

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)

CEMENT
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.

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 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
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.

FLYASH
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.

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. 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:

Suggested Mixes: