Title: A Study of Static and Dynamic Modulus of Elasticity of Concrete

Author(s): John S. Popovics

Publication: CRC

Volume:

Issue:

Appears on pages(s):

Keywords: Static, dynamic, modulus, elasticity

DOI:

Date: 10/1/2008

Abstract:
The static Young’s modulus (E) is defined as the ratio of the axial stress to axial strain for a material subjected to uni-axial load [Neville 1997]. It is important that E of concrete be known because engineers increasingly use this value in the structural design process. Most often E is inferred from the compressive strength (fc) of companion cylinders, rather than being measured directly, through the application of established empirical relations. This approach often leads to overly conservative results because, in order to meet the minimum E requirement, concrete with much higher fc is used than the specification requires, which leads to unnecessarily high material costs. Enhanced understanding of the relation between static and dynamic E and compressive strength, with respect to different types of concrete, would improve the efficacy of the estimation of E. The research objectives of this study were to obtain a better understanding of dynamic tests (based on vibration and wave propagation) used to compute the dynamic Young’s Modulus (Ed) in order to improve application by establishing consistent and accurate formulas to compute Ed and to better understand the relationship between the static Young’s modulus (E) in concrete and Ed. The following conclusions were drawn: 1. The dynamic and static modulus tests carried out at the University of Illinois laboratories confirm that Ed values vary, depending on method of measurement 2. As expected, Ed is always greater than E for concrete; however, this behavior may be caused by the composite nature of concrete, rather than non-linear behavior of concrete exposed by varying strain levels. 3. The results show that the relation between Ed and E is affected by nature of Ed data: the best relation to apply depends on how Ed was obtained. Overall, a thorough understanding of the various factors affecting Ed and E in concrete should enable improved prediction of Ed. Once this is established, vibration measurements should offer an effective, non-destructive, inexpensive and rugged method to estimate E for concrete.