# Adhesion Performance between Solid Waste and Bitumen Based on Surface Energy Theory
## 2 Materials
### Physical Properties  
The physical properties of the three aggregates were assessed to determine three aspects: the apparent density, water absorption, and the content of needle and flake-shaped  
\begin{table}
\begin{tabular}{c c c c} \hline  & **Limestone** & **Glass** & **Ceramics** \\ \hline
**Na\({}_{2}\)O** & 0.09 & 12 & 1.31 \\
**MgO** & 6.16 & 3.31 & 0.38 \\
**Al\({}_{2}\)O\({}_{3}\)** & 2.18 & 1.09 & 16.1 \\
**SiO\({}_{2}\)** & 7.88 & 67.1 & 63.1 \\
**P\({}_{2}\)O\({}_{5}\)** & 0.05 & 0.02 & 0.02 \\
**SO\({}_{3}\)** & 0.02 & 0.54 & 0.11 \\
**Cl** & - & 0.09 & - \\
**K\({}_{2}\)O** & 0.15 & 0.35 & 1.58 \\
**CaO** & 60.3 & 9.23 & 1.79 \\
**TiO\({}_{2}\)** & 0.14 & 0.08 & 0.26 \\
**Cr\({}_{2}\)O\({}_{3}\)** & 0.01 & - & - \\
**MnO** & 0.08 & 0.01 & 0.03 \\
**Fe\({}_{2}\)O\({}_{3}\)** & 1.23 & 0.32 & 0.77 \\
**NiO** & 0.01 & - & - \\
**CuO** & 0.01 & - & 0.01 \\
**ZnO** & - & - & 0.26 \\
**SrO** & 0.02 & - & 0.02 \\
**ZrO\({}_{2}\)** & - & 0.03 & 0.01 \\
**Pt** & 0.06 & - & 0.06 \\
**Total** & 78.39 & 94.17 & 85.81 \\ \hline \end{tabular}
\end{table}
Table 1: Chemical composition of aggregates (%).  
particles. The apparent density of an aggregate has a direct relationship with the porosity of its mixture, and a considerable amount of data prove that the porosity of a mixture containing low-density aggregate will be high. The water absorption of an aggregates lies in its water content under a saturated state. Aggregates with high water absorption have a poor adhesion performance to bitumen under normal circumstances. The research data of NCHRP show that compacting the aggregate on site becomes difficult as the content of needle and flake-shaped particles in the aggregate increases. Aggregates, assessed with the apparent density and water absorption tests, were passed through a 2.36 mm standard sieve during the test process to remove fine aggregates; aggregates in the content of needle and flake-shaped particles test were passed through a 4.75 mm standard sieve. Each physical index test was conducted twice, and the final result was equal to the average value of the sum of data of two tests. Namely, the D-value of the data of two apparent density measurements did not exceed 2%, the D-value of the data of two water absorption measurements did not exceed 0.2%, and the D-value of the data of two content of needle and flake-shaped particles measurements did not exceed  
Considering the apparent density, limestone has the highest, followed by ceramics and then glass. Therefore, limestone and ceramics can be used in all grades of roads. Considering water absorption, the order of the three aggregates is the same as above, and all three aggregates can be used in all grades of roads. Considering the content of needle and flake-shaped particles, glass becomes the maximum and limestone becomes the minimum; thus, the three aggregates far exceed the specification requirements. Waste glass and waste ceramics are not recommended for application in highways and first-grade highways during actual use based on the three indicators. Simultaneously, waste glass and waste ceramics should be processed by suitable crushing machinery to ensure that sufficiently small particle sizes are achieved. Excessively large particle sizes will markedly increase the content of needle and flake-shaped particles.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Physical Properties** & **High-Grade Highway** & **Low-Grade Highway** \\ \hline Apparent density & \(\geq\)2.60 & \(\geq\)2.45 \\ Water absorption (\%) & \(\leq\)2.0 & \(\leq\)3.0 \\ Content of needle and & & \\ flake-shaped particles (\%) & \(\leq\)12 & \(\leq\)20 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Local standards of physical properties.  
Figure 4: Physical properties of aggregates.  
Figure 3: XRD results of ceramics.