How Much Concrete to Pour for Block Cores

Written by nathan fisher
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How Much Concrete to Pour for Block Cores
Filling the cores of concrete blocks will increase their strength. (Jupiterimages/Comstock/Getty Images)

To save on weight, concrete breeze blocks have hollow chambers, or cores. For some applications, you may want to fill the block's cores once the blocks are set in place. Filling the cores will provide almost the same level of strength and support as solid "poured" concrete. Because of the large volume of concrete needed for most construction projects, concrete is usually measured in cubic yards. To calculate how much concrete to pour for block cores, you will need to calculate the cubic area of the cores in inches and convert the cubic inches to cubic yards.

Skill level:

Things you need

  • Tape measure
  • Calculator

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  1. 1

    Measure and multiply the width, height and depth of one of the bock's core. As an example, if a single core is 5 inches wide by 5 inches high by 5 inches deep, it would have a total cubic area of 125 cubic inches (5 x 5 x 5 = 125).

  2. 2

    Calculate the total number of block cores. If the structure contains 100 single-core blocks, it would equal a total of 100 cores. A structure with 400 double-core blocks would equal 800 cores (400 x 2 = 800). If the structure consists of 400 double-core blocks and 200 single-core blocks, there would be a total of 1,000 block cores (800 + 200 = 1000).

  3. 3

    Multiply the area of one core, assuming that all blocks have a uniform core area, by the total number of cores. A structure with a total of 1,000 block cores, with uniform cores of 125 cubic inches, would equal 125,000 cubic inches of concrete (1,000 x 125 = 125,000).

  4. 4

    Convert cubic inches into cubic yards by dividing 125,000 (cubic inches) by 46,656 (cubic inches in a cubic yard) to obtain 2.67918 cubic yards of concrete to fill 1,000 block cores (125,000 / 46,656 = 2.67918).

Tips and warnings

  • Always order extra concrete (figure 5 to 10 per cent, deepening on the size of the project) as it is better to have a little left over then to run just a little short. But extra if you are mixing it yourself by the bag.

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