The dynamic modulus of elasticity of concrete is an important variable
. The dynamic modulus in itself is not used in design; however, its im
portance is derived from the fact that it can be measured quite accura
tely using non-destructive tests, and it has been successfully correla
ted with other strength variables. Measurement of the dynamic modulus
non-destructively allows the monitoring of the concrete strength in si
tu and in laboratory specimens with very small statistical variability
. In this study, the effect of drying in several environmental conditi
ons on the dynamic modulus of concrete containing superplasticizers (S
Ps) is investigated. SPs are used frequently in concrete casting, espe
cially in hot arid climates, to compensate for the loss of workability
due to water evaporation. In addition, after the concrete has been dr
ied for some time the effect of rewetting the specimens on the dynamic
modulus is investigated. Specimens with and without superplasticizers
are cast and cured then dried in temperatures ranging from room tempe
rature to 100-degrees-C grade, with the relative humidity kept at arou
nd 20%. The dynamic modulus of the concrete is monitored over time via
two non-destructive techniques. The first is the resonant frequency m
ethod which gives quite accurate results for the dynamic modulus, and
the second is the pulse velocity method which is popular but less accu
rate. A comparison is made between the values obtained by the two meth
ods.