How to Calculate Bearing Capacity of Concrete

Placing a load on standard concrete causes it to break when the applied stress exceeds 3000 lbs / in^2. This knowledge allows you to calculate whether a given slab of concrete will fracture under a specific load. According to the Portland Cement Association, concrete roughly has a composition of air (6 percent), cement (11 percent), gravel (41 percent), sand (26 percent), and water (16 percent). The cement is composed mostly of lime and silica (85 percent) and other ingredients which include calcium, silicon, aluminum, iron and gypsum.

Things You'll Need

• tape measure
• pencil
• paper

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Instructions

1. • 1

     Measure the length and the width in inches of the rectangular area on the concrete's surface to which the load will be applied. As an example, say that the length equals 10 inches and the width equals 20 inches.

   • 2

     Calculate the area of the section of concrete in in^2 by multiplying length times width. In the example, you have 10 inches x 20 inches = 200 in^2.

   • 3

     Determine the weight of the load in pounds by utilizing a scale. For the example, say you have a 3,000-pound block of steel.

   • 4

     Calculate the stress on the concrete by dividing the weight by the area. The stress for the example problem is 3000 lb / 200 in^2 which equals a stress of 15 lbs / in^2. This stress is well under the limit of 3000 lb / in^2, so the concrete will not break.