How Much Concrete to Fill 10-Inch Blocks?

Six Blocks

• The standard sized concrete bag seen in home and hardware stores is the 80-lb bag. This fits and mixes with water in a regular wheelbarrow. The amount of finished concrete may vary a little but the basic measurement is that the 80-lb bag will equal 6,221 cubic inches after mixing. A 10-by-10-by-10-inch mold for a concrete block holds 1,000 cubic inches. An 80-lb bag of concrete will fill six, 10-inch blocks with a little less than 1/4 block left over.

Water Ratio

• The amount of concrete from a bag varies because of the water added. Less water makes a thicker paste that takes up less cubic inches, while more water gives a thinner concrete and more cubic inches. The highest quality concrete uses the least amount of water necessary to achieve an appropriate paste consistency and workability. Excessive water leads to weak bonds and much more shrinkage after the concrete dries.

Same Brand

• Concrete manufactures have different ideas about the best way to mix the aggregates and cement together. Some may use more sand while others use more gravel. The cement may vary with different kinds of concrete. It's important to purchase all the cement you need at one time from the same brand and the same type. Otherwise you may find that your blocks do not match in quality, look or performance after the job is done.

Air Bubbles

• Pouring concrete into a 10-inch deep mold introduces the possibility of large air bubbles. It is important to stop every few inches and throughly mix the concrete in the mold so that the corners are covered and any air bubbles have a chance to escape. After the mold is poured you can hit each side several times with a rubber mallet to settle the concrete down into the mold.