# Evaluation of Mechanical Properties of Recycled Material for Utilization in Asphalt Mixtures
## 3 Experimental Work
### Laboratory Tests
#### 3.2.4 Particle Density and Water Absorption Test  
The absorption is an indication of porosity in aggregate which demonstrates the pore structure of the aggregate. In asphalt mixtures, a porous aggregate increases the binder absorption, resulting in a dry and less cohesive asphalt mixture. In addition, the particle density of the aggregate is an essential property of the aggregate which plays an important role in the whole procedure of asphalt mix design. Therefore, in this research, the particle density and water absorption test is conducted on coarse aggregates (i.e., RCA, RAP and coarse basalt) based on the procedure described in AS 1141.6.1 (2000), as presented in Figure 6.  
In this test, the amount of water which a dried sample will absorb is measured. This test is performed on three trials and the related test results on RCA, RAP and basalt are given in Table 4, under apparent, dry, and saturated surface dry (SSD) conditions. Figure 5: Conducting Flakiness Index Test for Coarse Aggregate. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample Number**} & \multicolumn{3}{c}{**Flakiness Index (\%)**} & \multicolumn{1}{c}{**Australian Standards**} \\ \cline{2-5}  & **RCA** & **RAP** & **Basalt** & **Flakiness Index Limits (\%)** \\ \hline Sample 1 & 5.6 & 12.8 & 21.3 & \\ Sample 2 & 8.1 & 10.1 & 21.1 & 25\% (max) \\ Sample 3 & 7.1 & 8.4 & 14.7 & For heavy and very heavy traffic \\
**Average Flakiness Index (\%)** & **6.9** & **10.4** & **19.0** & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The Results of Flakiness Index Test for Coarse Aggregates and Flakiness Index Limits for Dense Graded Asphalt Based on Australian Standards. The results of the particle density and water absorption test on different coarse aggregates (i.e., RCA, RAP and basalt) and their average value, as presented in Table 4, indicate the high absorption of RCA in comparison with RAP and basalt. The RCA water absorption exceeds the limit set by the Australian Standard. As this research aims to investigate the feasibility of the application of RCA as a recycled material for potential partial replacement of coarse virgin aggregate (basalt) in asphalt mixtures, the particle density and water absorption test is also conducted on the mix of coarse aggregates (i.e., RCA, RAP and coarse basalt) considering different percentages of these materials. Such undertaking was needed in order to get a better understanding of an acceptable range of mix proportions in terms of water absorption. The results of Particle Density and Water Absorption test on six different mixes of RCA, RAP and basalt and the average water absorption and particle density for each mix are given in Table 5. Despite the fact that above mixes (except when there is no RCA) have water absorption of more than 2%, the use of RCA is still a viable option as discussed in Section 3.3. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample Name** & \begin{tabular}{c} **Apparent** \\ **Particle Density** \\ **(g/cm\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **Particle Density** \\ **on a Dry Basis** \\ **(g/cm\({}^{3}\))** \\ \end{tabular} & \
\begin{tabular}{c} **Particle Density** \\ **on a SSD Basis** \\ **(g/cm\({}^{3}\))** \\ \end{tabular} &
\begin{tabular}{c} **Water** \\ **Absorption** \\ **(\%)** \\ \end{tabular} \\ \hline RCA 1 & 2.375 & 2.211 & 2.352 & 6.39 & \\ RCA 2 & 2.375 & 2.211 & 2.352 & 6.39 & \\ RCA 3 & 2.361 & 2.214 & 2.349 & 6.12 & \\
**Average Values** & **2.370** & **2.212** & **2.351** & **6.30** & \\
**for RCA** & **2.539** & 2.422 & 2.468 & 1.89 & 2\% (max) \\ RAP 2 & 2.544 & 2.437 & 2.479 & 1.72 & For heavy and very heavy traffic \\ RAP 3 & 2.540 & 2.433 & 2.475 & 1.73 & heavy traffic \\
**Average Values** & **2.541** & **2.431** & **2.474** & **1.78** & \\
**for RAP** & **2.635** & 2.528 & 2.568 & 1.60 & \\ Basalt 2 & 2.630 & 2.521 & 2.562 & 1.64 & \\ Basalt 3 & 2.654 & 2.542 & 2.584 & 1.67 & \\
**Average Values** & **2.640** & **2.530** & **2.571** & **1.64** & \\ \hline \hline \end{tabular}
\end{table}