High Performance Concrete - High Modulus Concrete

The development of high performance concrete has been progressive over the years. Many decades ago, concrete with a compressive strength of 5000 psi was considered high strength. Currently, compressive strengths are approaching 20,000 psi. High-strength concrete is predominately used in the columns of high rise buildings. It is also used in bridge girders, offshore drilling structures, and dams.

The modulus of elasticity is a very important mechanical property of concrete. The higher the value of the modulus, the stiffer the material is. Thus, comparing a high performance concrete to a normal strength concrete, it is seen that the elastic modulus for high performance concrete will be higher, thereby making it a stiffer type of concrete. Stiffness is a desirable property for concrete to have because the deflection a structure may experience will be decreased. However, deformations, such as creep, increase in high strength concrete (Neville 608).

The modulus of elasticity of concrete is typically calculated from a compressive strength test of a concrete specimen. From these strength tests, stresses and strains are measured and plotted. The ratio between stress versus strain on these diagrams is called the modulus of elasticity, E. Since concrete typically does not act in a linearly elastic manner, there exists no portion on the stress versus strain diagram where Hooke’s law may be applied to find the modulus of elasticity.

s = Ee Hooke’s Law

(where s = stress, e = strain)

Therefore, several methods are used to determine a value for the elastic modulus from a stress versus strain diagram. There are also several equations that have been developed to compute a value for the modulus of elasticity once the compressive strength from a test cylinder has been determined.

The following parameters can affect the value obtained for the modulus of elasticity:

While all these properties affect the modulus of elasticity, not all of these properties are critical factors. Therefore, when dealing with high performance concrete with a high modulus of elasticity desired, it is most important to use a high strength coarse aggregate.

Information compiled by Deborah Sipics.