**d. To thicken a grout, the volume of the cement solids, in cubic feet**

**(one~half the number of sacks of cement in the grout) is subtracted from the**

**cubic feet of grout to obtain the volume of water in the grout. Enough cement**

**is added to have the desired water-cement ratio with this volume of water.**

**It is preferable to add only whole sacks of cement.**

**Examples:**

**e. Most chemical grouts are liquid grouts consisting of mixtures of liq-**

**uids, and the consistency is usually not changed. The application and pene-**

**tration of these grouts depend upon the gel or setting time, which can be**

**regulated as required. As previously noted, chemical grouts vary widely in**

**under the direction of personnel trained in the use of the particular chemi-**

**cals being used.**

**3.**

**PRESSURE OF GROUT COLUMN. As in changing grout from one mix to**

**another, the quickest way to determine the pressure exerted by a column of**

**grout is by using a chart. In case a chart similar to figure 4 (main text) is**

**not at hand, the pressure in pounds per square inch exerted by a 1-ft column**

**of any grout can be found by dividing the weight of a cubic foot of the grout**

**by 144 (the number of square inches in a square foot). For portland-cement**

**grout with no fillers or admixtures , it is necessary to know that a cubic foot**

**of water weighs 62.4 lb and a sack of cement weighs 94 lb. Thus, for 2:1**

**grout a one-sack batch of grout contains 124.8 lb of water and 94 lb of ce-**

**ment for a total weight of 218.8 lb. Since a one-sack batch of 2:1 grout**

**makes 2.5 cu ft, 218.8 lb must be divided by 2.5 to obtain the weight of 1 cu ft**

**of the grout. Then 1 cu ft of 2:1 grout weighs 87.5 lb and exerts a pressure**

**78**