# Limitations on the Use of Recycled Asphalt Pavement in Structural Concrete
## 3 Quality and Homogeneity of RAP Aggregates
### Definition and Origin/Production of RAP Aggregates
\begin{table}
\begin{tabular}{c c c c} \hline
**European** & **Title** & **RAP Use** & **Possible Limitations** \\
**Standard** & **Title** & **[Y/N]** & **for RAP Aggregates** \\ \hline EN 12620 & Aggregates for concrete & Y & See Section 3.3 of this paper \\  & Lightweight aggregates & & \\ EN 13055-1 & Part 1: Lightweight aggregates for & N & Not applicable \\  & concrete, mortar and grout & & (RAP density higher than that foreseen in the Scope) \\  & Lightweight aggregates—Part 2: & & \\ EN 13055-2 & lightweight aggregates for & & \\ EN 13055-2 & bituminous mixtures and surface & N & Not applicable \\  & treatments and for unbound and & & (RAP density higher than that foreseen in the Scope) \\  & bound applications & & \\  & & & \\  & & & \\  & & & \\ EN 13139 & Aggregates for mortar & Y & Setting speed should not exceed 120 min. \\  & & & \\  & & & \\  & & & \\  & & & 28 days. \\  & Aggregates for bituminous & & \\  & mixtures and surface treatments & & \\ EN 13043 & for roads, airfields and other & N & Aggregates’ affinity with bituminous binder. \\  & trafficked areas & & \\  & & & \\  & & & \\  & Aggregates for unbound and & & \\ EN 13242 & hydraulically bound materials for & Y & Setting speed should not exceed 120 min. \\  & use in civil engineering work and & & \\  & road construction & & \\ EN 13450 & Aggregates for railway ballast & Y & No limitations \\ EN 13383-1 & Armourstone—Part 1: & & No limitations \\  & Specification & Y & No limitations \\ \hline \end{tabular}
\end{table} 
Table 3: Harmonised European standards and possible limitations for RAP aggregates. 12620 [58] or EN 13055-1 [69] for the characterization of aggregates for structural concrete. If RAP aggregates do not fall in the scope of one of the two standards, it is not possible to apply them in structural concrete. Both standards give a description of the most important characteristics of the natural aggregate and, in particular, EN 12620 [58] covers aggregates having an oven-dried particle density greater than 2.00 Mg/m\({}^{3}\) for all types of concrete, including concrete in conformity with EN 206 [71], concrete used in roads and in other pavements and for precast concrete products. Furthermore, regarding the recycled aggregate, EN allows wider range with densities higher than 1.50 Mg/m\({}^{3}\). The European standard EN 13055-1 [69] covers, instead, lightweight aggregates for concrete, i.e., aggregates having particle densities not exceeding 2.00 Mg/m\({}^{3}\). According to [PERSON] et al. [33], the bulk density of RAP aggregate falls between 1.94 Mg/m\({}^{3}\) and 2.30 Mg/m\({}^{3}\), which therefore excludes the use of EN 13055-1 [69]. More details on EN 12620 are discussed later on in Section 3.3. As seen, the cited standards, although they do not fully cover the RAP, give harmonised methods for the assessment of the properties of the aggregate that can serve as a basis for the characterisation of RAP aggregates. Generally, the majority of these standards include geometrical, physical and chemical properties and, specifically, specific gravity, water absorption, bulk density, abrasion resistance, crushing strength and impact resistance. Studies have demonstrated that RAP aggregate has a lower specific gravity and water absorption [4]. A low specific gravity indicates a high porosity, which results in poor durability and a lower strength of concrete. Based on several research studies [1; 6; 38; 72], impurities negatively influence RAP aggregates, especially in terms of water absorption. Moreover, a differentiation in fine and coarse aggregate is highly recommended to define the characteristics [23; 73]. Shape and dimensions are also important to design the mix and fix the w/c ratios for both asphalt mix and concrete for buildings. In terms of shape, for a higher workability, it is generally recommended to use rounded aggregates [6; 74; 75]. Flaky and elongated aggregates could lead to the production of concrete with segregation and a poor surface finish, which will require a high cement and sand demand [6; 74; 75].