Title: Uncoupling Modulus of Elasticity and Strength—Effect of Small Addition of Carbon Nanotubes on Concrete Properties

Author(s): Surendra P. Shah

Publication: Web Session

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Date: 11/20/2018

Abstract:
Our industry has made considerable progress in increasing the compressive strength of concrete. At the time of the first workshop on high-strength concrete, held in Chicago, IL, in 1979, the lower limit for high-strength concrete was defined as 6000 psi (42 MPa). Less than 30 years later, the maximum concrete cylinder strength specified for Chicago’s Trump Tower was 16,000 psi (110 MPa). While compressive strength is important for minimizing the sizes of compression elements, designers of tall buildings may also specify a high modulus of elasticity (MOE) to limit lateral deformations and ensure occupant comfort. For example, the high compressive strength specified for some elements in the Trump Tower was needed to ensure that the MOE was about 7,000,000 psi (48 GPa)—far greater than the 4,000,000 psi (28 GPa) value that’s now routinely possible. In these cases, high strength was not the objective—it was the means to the end. This article summarizes recent research on an alternative way to obtain a high MOE concrete without necessarily increasing the compressive strength.