- We're pumping a grout that's made with 1 cubic foot of cement and 5 gallons of water. There's no sand or gravel in the grout. What will the volume be?
- You can calculate the volume if you know the specific gravity of the cement. Specific gravity is the weight of the cement divided by the weight of an equal volume of water. If you're using portland cement, 1 cubic foot loose volume weights 94 pounds and has a specific gravity of 3.15. Dividing the weight, 94 pounds, by the specific gravity times the unit weight of water (62.4 pounds per cubic foot) gives a volume of cement of 0.478 cubic feet. A gallon of water weighs 8.33 pounds. Dividing the weight of 5 gallons of water (8.33 x 5) by 62.4 pounds per cubic foot (pcf) gives 0.667 cubic foot of water. The volume of the grout is the sum of the volume of cement and water or 1.145 cubic feet. This assumes that there's no air entrapped in the paste. If air is entrapped, the volume will be greater. You can also calculate volume without knowing cement specific gravity if you first measure the unit weight of the grout. To do this, fill a quart jar with the grout, using a small glass plate over the jar mouth to ensure that the jar is exactly full. Weigh the jar, grout, and glass plate on a postal package scale or other scale that can weight to 0.01 pound. Then clean out the jar and weigh the jar and plate alone. Calculate the weight of the grout and divide it by the volume of the jar to get the unit weight. Then divide the weight of a grout batch by the grout unit weight to find the batch volume. Here's an example calculation: Weight of grout, glass jar, and plate 5.01 pounds Weight of glass jar and plate 1.15 pounds Weight of grout 3.86 pounds Volume of quart jar 0.033 cubic foot Unit weight of grout (3.86/0.033) 117 pcf If you use 41.7 pounds of water (5 gallons) and 94 pounds of cement per batch, the grout volume will be: (41.7 + 94)/117 = 1.16 cu. ft. Quart canning jars may not hold exactly a quart. If you want a more precise test for unit weight, calibrate the jar first by weighing it filled with water. Divide the weight of the water in pounds by 62.4 pcf to calculate the exact volume of the jar.