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Slump Test

Extensive tests have been performed by Warner to evaluate the effect of bentonite and slump on mobility. The tests concluded that the composition of the grout, the shape and gradation of the sand material, the amount and nature of the fines content and the inclusion of a lubricating agent such as bentonite or other clay materials tend to greatly increase grout mobility and improve the pumpability. It was also found that the grout slump was not directly related to mobility of the grout. Additionally, Warner indicates that the selection of an appropriate grout pump is important for constructing a successful project.

Figure 9 Slump Test

It has been found by these authors, that most compaction grout mixes generally are a combination of a well graded sand, type I Portland cement, class F flyash or other soil fines and water. Occasionally, bentonite has been added for pumpability or by design modification of the project. Other additives are occasionally used such as Calcium Chloride or type III Portland cement to produce an early set. Shrinkage control additives are also available but seldom used. The quantities of the constituents of a typical compaction grout mix per cubic yard are as follows:

Description	Quantity	Standard	Comment/Effect
Sand	1,800 - 2,200 lb.	ASTM C-33	Well graded, rounded edge, min. 15% passing #200 Sieve
Cement	250 - 500 lb.	ASTM C-150	Control strength of mix, increase density of mix
Flyash	400 - 750 lb.		Increase pumpability and provide a well graded grout mix.

(1) Depending on the fines available from the sand.

Although documented testing is not available at this time, another successful additive to the grout mixture is small diameter aggregate, or pea gravel. This material is typically minus 3/8 inch in diameter and has normally been added at rates between 100 - 200 pounds per cubic yard. The addition of course aggregate tends to knit the grout mix together and decrease the mobility of the grout by increasing the internal friction developed at the soil interface. Even though this has been successfully used in many applications, analytical testing should be performed and evaluated to better define optimum quantities and effects.