IET is based on the specimen resonance frequencies and, unlike static tests, takes just a few minutes, has low uncertainty and high reproducibility. To determine the E d, the Impulse Excitation Technique (IET) can be used. A practical, accurate and low-cost alternative is the estimation of E c from the dynamic elasticity modulus ( E d) using the Popovics model. However, there are two important sources of uncertainty that must be taken into account: the first one is the model employed validity and limitations, which depends on the concrete classification, the second one is the high dispersion of compressive strength test results. It is usual to estimate the concrete chord modulus of elasticity from the axial compressive strength using empirical models. Built in São Paulo (Brazil), this building applied concrete with a chord modulus of elasticity of 48 GPa developed by PhD Engenharia, Engemix and Nortis.įigure 1 - Leopoldo 1201 building construction, which used concrete with a modulus of elasticity of 48 GPa (2021). Figure 1 shows an example of high strength concrete application, the Leopoldo 1201 building. Ĭoncretes can be classified according to their characteristic axial compressive strength ( f ck): those with f ck up to 20 MPa are named low strength concretes, with f ck between 20 MPa and 40 MPa, medium strength concretes, and with f ck greater than 40 MPa, high strength concretes. However, concrete does not present such linearity due to the presence and development of cracks and microcracks at the interface between the matrix and the aggregates. When the matrix or the aggregates are loaded individually, both present a linear stress-strain curve and the modulus of elasticity determination is straightforward. Additionally, they allow the non-destructive measurement of these properties in the same specimens to be tested for compressive strength.Ĭoncrete is a composite material, in which aggregate particles or fragments are bonded by a matrix. The methods based on resonance frequencies, in particular the Impulse Excitation Technique (IET), are more accurate, practical and accessible than static methods for elastic moduli determination. However, these properties are not often measured, instead, they are frequently estimated from the compressive strength with considerable uncertainty. IntroductionĮlastic moduli are fundamental properties and, increasingly, designers specify minimum values to be met due to the evolution of the concrete compressive strength. This website section goals are to present the theory and methodology for non-destructive determination of the dynamic elasticity modulus of concrete ( E d) by Impulse Excitation Technique, a resonance frequencies method, for the estimation of the chord modulus of elasticity ( E c) from E d. Determination of elastic moduli of concrete by Impulse Excitation Technique
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