The measurement of tensile strength of concrete has many factors in determining the breaking point.
Many factors play into the determination of tensile strength in concrete. The materials used, the blend of water, sand and rock, the thickness and drying method all combine to strengthen or weaken a particular blend of concrete. Once you know all of the factors involved, the tensile strength is determined by a set mathematical equation.
Instructions
1. Know the material composition of the concrete. Understanding what balance of sand, rock and water are used helps know the range for tensile strength and breaking points. Concrete made with thicker sand tends to have higher tensile strengths than fine sand concrete.
2. Measure the thickness of the concrete. The thicker the piece you are working with, the stronger the concrete becomes. Thickness can alter the way the results are used for construction projects with that particular blend of concrete.
3. Apply pressure to your sample. The materials used in the construction and the thickness may have tensile strengths of several hundred pounds per square inch. Be sure that your pressure loader can reach at least 1,000 psi. Pressure is applied slowly to one area of the concrete until the point where the concrete begins to crack or bend. Record this pressure as "f'c" for the formula to follow. The unit for f'c is pounds per square inch.
4. Using f'c as determined in the pressure test, plug the figure into this equation: fr = 7.5 √ f'c. Assuming f'c was 100, the formula would look like this: fr = 7.5 √100. Solved through, fr = 7.5 x 10, leaving the fr or tensile strength of the concrete at 75 pounds per square inch of tensile strength.
5. Repeat the steps above to find the optimal blend of concrete for your project. The formula remains the same regardless of the blend. The higher the pounds per square inch, the stronger the concrete is.
