# Effect of Metallic Waste Addition on the Physical and Mechanical Properties of Cement-Based Mortars
## 3 Results and Discussion
### Influence of Metallic Waste on the Elastic Modulus of the Test Specimens
This behaviour was due to the random distribution of metallic waste inside the test specimens [37], which can be interpreted as the scattering of the data in Figure 11.  
Moreover, by analysing the error bars in Figure 9, it can be observed that the specimens with metallic waste did not present an increase in the elastic modulus with respect to the specimens without waste, in both elastic modulus types. With the purpose of evaluating the effect of the type and content of metallic waste on the elastic modulus measured by compressive and ultrasonic tests, the Modulus Influence Ratio (_MIR_) was defined in this study. This Ratio was determined as the quotient between an i-th value of the elastic modulus of a specimen with metallic waste (\(E_{i-with\ waste}\)) and the average value of the elastic modulus of the specimens without waste (\(\overline{E}_{without\ waste}\)), evaluated for the same type of waste, curing age, and test method (compressive or ultrasonic test):  
\[MIR=\frac{E_{i-with\ waste}}{\overline{E}_{without\ waste}}, \tag{2}\]  
Table 5 presents the average values of the Modulus Influence Ratios (_MIRs_) obtained for the compressive and ultrasonic elastic moduli, considering the different types of waste, contents, and curing ages. In this Table, it can be observed that the addition of metallic waste has greater influence on the compressive elastic modulus than on the ultrasonic modulus. The greatest influence was obtained in the case of the elastic modulus measured by compressive tests at a curing age of 7 days, reaching _MIR_ values of 1.122 and 1.105 in specimens with 16% of shavings and fibres, respectively. Likewise, it can be seen in Table 5 that _MIRs_ obtained in the case of the ultrasonic elastic modulus decreased with the increase of the metallic waste content. This was due to the fact that the ultrasonic pulses are affected by the porosity of the specimens, as was previously discussed. Finally, analysing the _MIR_ values of the elastic modulus obtained by compressive and ultrasonic tests, shown in Table 5, it can be observed that, in general, all data are close to 1. This suggests that both the type and amount of waste and the curing time do not have a noticeable influence on the increase of the elastic modulus of reinforced mortars with respect to reference mortars without waste. To prove this, Figure 12 shows the probability-probability plots of all _MIRs_ data, represented using a Weibull probability distribution function. The Weibull function has been chosen considering that the elastic modulus of mortars can be modelled as a mechanical process of fracture [10], because the fracture produced by compressive efforts is caused due to the multiple cracks that are produced during the mechanical load cycle. These data were plotted regardless of the amount of metallic waste and the curing time. In this Figure, it was observed that all the data, for both the compressive and ultrasonic modulus, can be aligned to a straight line with a slope 1:1, which indicates that neither the type and amount of waste, nor the curing time, presented a significant influence on the elastic modulus of mortars measured using the two different test methods: destructive (\(E_{c}\)) and non-destructive (\(E_{u}\)). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{3}{*}{ \begin{tabular}{c} **Metallic Waste** \\ **Content** \\ \end{tabular}  } & \multicolumn{3}{c}{**Compressive Modulus \(Ec\)**} & \multicolumn{3}{c}{**Ultrasonic Modulus \(Eu\)**} \\ \cline{2-9}  & \multicolumn{2}{c}{**7 Days**} & \multicolumn{2}{c}{**28 Days**} & \multicolumn{2}{c}{**7 Days**} & \multicolumn{2}{c}{**28 Days**} \\ \cline{2-9}  & **Shavings** & **Fibres** & **Shavings** & **Fibres** & **Shavings** & **Fibres** & **Shavings** & **Fibres** \\ \hline
4\% & 1.083 & 1.068 & 0.930 & 0.861 & 0.953 & 1.010 & 0.971 & 0.920 \\
8\% & 1.064 & 1.071 & 0.941 & 0.928 & 0.928 & 0.975 & 0.981 & 0.894 \\
12\% & 1.077 & 1.085 & 0.958 & 0.957 & 0.923 & 0.948 & 0.930 & 0.86