# Mechanical Strength Characterization of Plastic Fiber Reinforced Cement Concrete Composites
## 3 Results  
### Compressive Strength Evaluation  
The compressive strength test results for the fiber incorporated mixes with homogeneous fiber addition is presented to compare the effects of plastic fiber substituted concrete mixes to that of the reference concrete mix. Since the concrete is subjected to pure compressive force throughout the concrete specimen; the mechanism of fiber reinforcements in homogenously substituted concrete mixes is of importance. Hence, a reference concrete and three concrete mixes (PFC-05H, PFC-10H, PFC-15H) containing plastic fibers were tested for compressive performance. On the other hand, the concrete mixes PFC-05T, PFC-10T, and PFC-15T were not evaluated due to the non-significance of the confined tensioned plastic fibers in compressive performance. A maximum compressive strength up to 33.25 N/mm\({}^{2}\) with a 10% increase was noted with 0.15% V\({}_{\text{f}}\) substituted plastic fiber concrete mixes (PFC-15T) compared to the reference concrete (RCM-30). This increase in trend was noted in another study [25] where a maximum strength attainment up to 42.67 N/mm\({}^{2}\) was achieved for a high grade concrete. However, studies revealed that mortar strength enhancement with the addition of fibers derived from waste PET was optimal up to a maximum volume fraction and decreased with further increase in plastic fiber volume [26]. In order to assess the mechanistic action of plastic fibers in the compressive failure mode of concrete, various parameters were carefully evaluated as provided in Table 6. The wide range of compressive properties with the influence of plastic fibers to enhance the crack arresting properties is collectively provided in Table 6. The influence of plastic fibers on the compressive strength variations of various concretes mixes are provided in Figure 7. Graphical trends clearly represent the influence of plastic fibers in the matrix as it controls the progress of compressive failure. Initially, the reference plain concrete (RC-30) without fibers showed a sudden failure without post peak controlled yielding, resulting in a sudden drop in load carrying capacity exhibiting brittle failure. This behavior was completely absent in the plastic fiber incorporated concrete mixes (PFC-05H) as the pre-peak strain hardening and post peak strain softening were well controlled by the presence of fibers during matrix cracking. This was clearly interpreted for all the fiber substituted concrete mixes and the post peak characteristics were well improved during the progress of strain energy released during the failure process. However, the presence of fibers had a greater role during the post-peak crack propagationas the crack growth is well controlled by the presence of plastic fibers. In the case of high fiber incorporated concrete mixes (PFC-15H), the increased fiber availability at the crack-opening mode envisages effective stress redistribution in the nearby crack vicinity. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Mix ID**} & **Ultimate Strength** & **Residual Strength** & **Elastic Modulus (N/mm\({}^{2}\))** & **Elastic Modulus (\(\times\)10\({}^{3}\) N/mm\({}^{2}\))** & **Prede-Peak Strain** & **Absolute** & **Post** & **Ultimate** & **Strength** & **Toughness** & **Fiber Perme** \\  & **(N/mm\({}^{2}\))** & **(N/mm\({}^{2}\))** & **Modulus (\(\times\)10\({}^{3}\) N/mm\({}^{2}\))** & **Toughness (N-m)** & **Toughness (N-m)** & **Toughness (N-m)** & **Toughness** & **Toughness** & **Toughness** & **Fiber Perme** \\ \hline RCM-30 & 30.21 & 2.34 & 26.16 & 122.51 & 122.51 & 0 & - & - & - \\ \hline PFC-05H & 31.53 & 15.61 & 28.05 & 192.38 & 378.02 & 185.29 & 4.37 & 208.56 & 220.26 \\ \hline PFC-10H & 33.12 & 17.23 & 28.78 & 159.3 & 516.38 & 357.75 & 9.63 & 321.5 & 338.95 \\ \hline PFC-15H & 33.25 & 18.16 & 28.91 & 158.63 & 509.63 & 351 & 10.06 & 315.99 & 333.72 \\ \hline \hline \end{tabular} Note: Test results denote the average of five concrete specimens tested for each concrete mix type.  
\end{table}