## 5 Conclusions  
The paper presents an experimental program aimed at assessing the long-term material properties of rubberized Portland cement concrete. Based on the obtained results, the following conclusions can be drawn: \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{5}{c}{**Reference Mix (Ref)**} \\ \hline Density & Modulus of Elasticity & Dynamic Modulus of Elasticity & Compressive Strength & Tensile Splitting Strength \\ \cline{2-6}  & [kg/m\({}^{3}\)] & [MPa] & [MPa] & [MPa] & [MPa] \\ \hline Value & 2227 & 28,210 & 35,863 & 43.61 & 3.89 \\ \hline Standard deviation & 8.558 & 456.54 & 937.57 & 1.865 & 0.12 \\ \hline Coefficient of Variation [\%] & 0.38 & 1.62 & 2.61 & 4.28 & 3.09 \\ \hline \multicolumn{6}{c}{**RuC00**} \\ \hline  & Density & Modulus of Elasticity & Dynamic Modulus of Elasticity & Compressive Strength & Tensile Splitting Strength \\ \cline{2-6}  & [kg/m\({}^{3}\)] & [MPa] & [MPa] & [MPa] & [MPa] \\ \hline Value & 2061 & 17,361 & 22,381 & 22.68 & 2.78 \\ \hline Standard deviation & 5.376 & 240.92 & 948.37 & 0.71 & 0.086 \\ \hline Coefficient of Variation [\%] & 0.26 & 1.39 & 4.24 & 3.13 & 3.09 \\ \hline \multicolumn{6}{c}{**RuC00**} \\ \hline  & Density & Modulus of Elasticity & Dynamic Modulus of Elasticity & Compressive Strength & Tensile Splitting Strength \\ \cline{2-6}  & [kg/m\({}^{3}\)] & [MPa] & [MPa] & [MPa] & [MPa] \\ \hline Value & 1986 & 13,395 & 17,128 & 17.98 & 2.25 \\ \hline Standard deviation & 13.539 & 1047.3 & 371.54 & 0.305 & 0.091 \\ \hline Coefficient of Variation [\%] & 0.68 & 7.82 & 2.17 & 1.69 & 4.06 \\ \hline \multicolumn{6}{c}{**RuC00**} \\ \hline  & Density & Modulus of Elasticity & Dynamic Modulus of Elasticity & Compressive Strength & Tensile Splitting Strength \\ \cline{2-6}  & [kg/m\({}^{3}\)] & [MPa] & [MPa] & [MPa] & [MPa] \\ \hline Value & 1909 & 9809 & 12,298 & 13.68 & 1.43 \\ \hline Standard deviation & 10.748 & 590.94 & 305.26 & 0.968 & 0.083 \\ \hline Coefficient of Variation [\%] & 0.56 & 6.02 & 2.48 & 7.08 & 5.76 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Characterization of the experimentally obtained data at the age of 5 years. A significant drop in the values of density after 5 years is observed for specimens made with rubberized concrete, whereas the density of the reference mix changes by a very small amount. The values of the static modulus of elasticity decrease after 5 years compared to the standard value obtained at 28 days, mainly due to the fact that the specimens were kept indoors, in laboratory conditions and in a relatively dry environment. Therefore, the excess water slowly evaporated during the 5 years. Since the presence of rubber creates a larger amount of excess water, its evaporation left behind voids in the concrete specimens that ultimately leads to lower values of the modulus of elasticity. Since the dynamic modulus of elasticity is influenced both by the mass of the specimen and by its fundamental longitudinal frequency of vibration, any trend observed for the two parameters is reflected in the evolution in time for this material property. The voids inside the RuC specimens lead to lighter concrete and to lower values for the frequency of vibration. The conversion equations from dynamic modulus to static modulus of elasticity cannot be directly applied to rubberized concrete. Further investigations are deemed necessary in this direction. Material damping is strongly influenced by the rubber content in concrete. A 40% replacement of sand by rubber aggregates leads to a three-fold increase in the value of the material damping. However, further increase of the replacement percentage has an opposite effect on the damping properties due, primarily, to the occurrence of voids at the ITZ level between rubber particles and cement matrix. Both compressive and tensile splitting strength are adversely affected by the presence of rubber aggregates.