## 2 Materials and Methods
### Experimental Testing System and Procedure
#### 2.4.2 Non-Destructive Tests  
The UPV tests collected the propagation velocities of the compression and shear waves by inducing the specimen to repetitive pulses with a pulse generator. The tests were carried out according to ASTM D 2845-05 [30] recommendations, and Pundit Lab equipment was used. The IEV tests were carried out using PICO equipment according to ASTM E 1876-01 [31] standard recommendations.  
The experimental test involved inducing manual excitation by a singular strike by an impulse (in this case, a steel sphere glued to the end of a flexible polymer rod) to obtain the specimens' mechanical resonant frequencies. Both tests had the same objective: to determine the specimens' dynamic properties. The properties were calculated through normalised equations defined in both standards.  
The elastic constants determined by the UPV test method are ultrasonic since the pulse frequencies are above the audible range. Therefore, they may differ from those determined by other dynamic methods. These two different dynamic tests were carried out redundantly for more accurate results.  
Ultrasonic Pulse Velocity Test  
Under the aforementioned standard recommendations, the experimental testing system setup is represented in Figure 1.  
It consisted of a 160 mm \(\times\) 40 mm \(\times\) 40 mm specimen (a); a pulse generator (b) to apply pulses with variable widths repeatedly on the specimen; two types of transducers, a 54 kHz capacity (c) for determining the P waves (longitudinal or primary waves, \(V_{p}\)) and a 1 MHz capacity (d) to determine the S waves (shear or secondary waves, \(V_{s}\)), both consisting of a transmitter that converts electrical pulses into mechanical pulses and a receiver that converts mechanical pulses into electrical pulses; a  
Figure 1: UPV test setup: (**a**) specimen, (**b**) pulse generator and display unit, (**c**) longitudinal wave transducer, (**d**) shear wave transducer, (**e**) computer and (**f**) support system.  
the equipment's software which displays the on-time readings, the graph and its parameters; and supports (f) to accommodate the specimen in the correct position. It is important to note that the energy transmission between the transducer element and test specimen was improved by lapping the surfaces of the face plates to make them smooth, flat, and parallel, and by coupling the transducer element to the face plate using a thin layer of Vaseline gel and a coupling medium.  
Impulse Excitation of Vibration Test  
The IEV test method is appropriate for determining the moduli of elastic, homogeneous, and isotropic materials. The specimen's dimensions differ from those of the other tests due to its standard recommendation, which indicates a minimum ratio of width to thickness of five. This ratio minimises experimental difficulties during shear modulus measurement. The experimental testing system consisted of a 200 mm \(\times\) 100 mm \(\times\) 20 mm mortar specimen, an impuser, a piezoelectric transducer with an 8 kHz frequency range to detect and transport the frequency waves, an electronic system to amplify, read and analyse signals received, a computer to display the waves that determine the frequencies and two supports: support for the longitudinal frequency measurement and the torsional frequency measurement. The first support system consisted of two supports spaced by 0.224\(L\) (\(L\) being the specimen's length) from the borders. The second support system consisted of a cross-shaped support at the specimen's length and width midpoint. The transducer location was set appropriately to measure the desired vibration mode following the standard recommendation. Special care was taken to ensure that the transducer's location remained similar within multiple readings as well as the force used on the impuser.