Comparison between Different Methods of Determining Apparent Elasticity Modulus of Cementitious Materials

This study aims to compare four different techniques for determining the apparent elasticity modulus of cementitious materials: Impact Resonance Testing (IRT), Ultrasonic Testing (UT), Static Modulus Testing (SM), and Dynamic Modulus Testing (DM). Tests were conducted on twelve cylindrical specimens comprising three conventional concretes (with and without superplasticizer), a high-performance concrete (HPC), and a cement mortar. The experimental campaign followed a sequential protocol: (i) initial characterization using UT; (ii) characterization using RM; (iii) after, evaluating the CM testing under sinusoidal loading; (iv) evaluating RM again, to check for microdamage associated with the tests and (v) final evaluating SM. All specimens were tested using the four techniques under the same conditions, allowing for direct comparison of the results. The IRT showed excellent agreement with the DM method, with differences of less than 1 GPa across all materials. The UT also presented good consistency, particularly for stiffer concretes, while the SM yielded lower average values and higher variability. Strong linear correlations were found (near-1 R² values) between IRT and the other testing methods analyzed. The findings confirm the potential of IRT as a reliable, fast, and non-destructive technique for evaluating the stiffness of cement-based materials. The methodology also proved effective in detecting modulus reductions caused by repeated loading cycles, especially in mortar specimens.