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TECHNICAL PAPER

DeteRminAtion of

DynAmic moDULUs

of eLAsticity of

concRete PRIYARANJAN PAL

Abstract 1. INtRODUCtION
An experimental investigation was carried out to determine The elastic modulus is an important parameter used in the
the dynamic modulus of elasticity of pozzolana Portland analysis and design of structures. For concrete structures, now
cement concrete. Large numbers of concrete cubes were a day, several changes have been made to the regulation of
prepared in the laboratory for investigation. The destructive construction from the view point of minimum values of the
[1]
and non-destructive tests were conducted on concrete cubes modulus of elasticity. According to IS 456 , the concretes are
at different ages. The destructive test was conducted to obtain classified into three groups, i.e., low, medium and high strength
the compressive strength of concrete cubes. Ultrasonic pulse concretes. Today, low and medium strength concretes are
velocity of cubes was measured according to IS 13311 (Part the most commonly used concrete in the construction of civil
1). The recorded values are used to determine the dynamic engineering structures. The static modulus of elasticity can
modulus of elasticity of concretes. Based on experimentally be estimated from the standard design code rather than on
obtained data and analysis, a few relationships are proposed direct measurement. However, this practice underestimates the
to correlate the water/cement ratio, compressive strength, and demand of higher compressive strength to achieve a desired
[2]
elastic moduli of concretes. Several interesting findings are value that is actually required in the structural design . Hence,
observed from the correlations of the coefficients while analyzed the dynamic modulus of elasticity values should be ensured in
by regression analysis. This study helps to determine the static addition to the concrete compressive strength. Further, using
properties of concrete from the dynamic ones. non destructive testing in concretes the static modulus can be
predicted from the dynamic modulus. For an existing structure,
Keywords: Compressive strength; Mix proportion; dynamic modulus of elasticity can be determined by the non-
Modulus of elasticity; Pozzolana Portland cement; destructive testing method. The dynamic values obtained by
Ultrasonic pulse velocity NDT cannot match with the static values, but their relationships
can be established. In order to establish their relationships,
Abbreviations and symbols regression technique may be considered to correlate the
coefficients.
PPC Pozzolana Portland cement

UPV Ultrasonic pulse velocity The properties determined by NDT are the density, moduli of
NDT Non-destructive test elasticity, Poisson’s ratio, strength, surface hardness and surface
absorption of concrete. In addition to that, the NDT has the
FA Fine aggregate
ability to detect the voids and cracks in concrete. One of the
CA Coarse aggregate most effective NDT is the UPV test, which is applied to assess
W/C Water/cement ratio the structural integrity without causing any damage. In UPV test
method , two transducers are used to produce and receive the
[3]
μ d Dynamic Poisson’s ratio
ultrasonic pulse (electrical signal). While the receiving transducer
E d Dynamic modulus of elasticity, GPa is positioned exactly on the opposite face of the test sample
E c Static modulus of elasticity, GPa (direct method or cross probing), and qualitative results are
obtained. The quality of concrete can be characterized in terms
V p Longitudinal pulse velocity, km/s
of pulse wave velocity. UPV test can be adopted to determine
ρ Unit weight of concrete, kg/m 3 the properties of concrete. The dynamic modulus of elasticity
f ck Characteristics compressive strength of concrete, MPa can be estimated using the following equation if the density and
[3]
Poisson’s ratio of concretes are known .
f cm Mean compressive strength of concrete at 28 days, MPa (1+μ d)(1-2μ d)
2 (1)
E d = ρV p
R Coefficient of determination in regression analysis (1-μ d)
The IndIan ConCreTe Journal | november 2019 7