...velocity method In this paper, a new approach easily implemented in practice is suggested to predict the compressive strength by the non-destructive ultra- sonic pulse velocity (UPV) method, regardless ofthe type of aggregate. For different concrete compositions produced with natural sand and ranging from about 30-80 MPa and density classes from D1.6-D2.0, it is found that structural lightweight concrete (LWC) and normal weight concrete (NWC) are affected differently by mix design parameters. No unique direct relation between UPV and compressive strength exists. Based on the dependence of the UPV on the density and elasticity of concrete, a simplified expression is proposed to estimate the com- pressive strength of concrete, regardless its composition. The high correlation attained for a wide range of concrete strength and density classes shows the validity of the method. This eliminates the need of a new UPV-compressive strength curve whenever the concrete com- position varies, as recommended in European standards.
