## 3 Materials and Methods
### Impact of Transport Scenarios on LCA Results  
As described in Section 2.3, in this phase of the study, the LCA performed for the \"local\" scenario is expanded, to calculate the impacts considering different transport scenarios entailing increasing distances between natural/recycled aggregates industries and mortar factories (module A2): 0 km, 100 km, 200 km, 300 km, 400 km and 500 km. This section reports the GWP-total results for all mortars and transport scenarios, while results related to the other impact categories are included in SI-2 (Supplementary information S2). Figure 4(a) shows GWP-total for REF1 and DELTA mortars, while Figure 4(b) for REF2 and HP mortars, through graphs in which the environmental impact (\(Y\)-axis) is a function of the delivery distance of aggregates (\(X\)-axis). The impact of the \"local\" scenario case (Section 4.1) is also reported in the graphs as a diamond shaped indicator, corresponding to the distances considered in that specific scenario. As a general trend, as expected, the environmental impact increases with the increase of the delivery distance of aggregate transports. As previously stated, within the same transport scenario (A or B), and at the same distance of the natural/recycled aggregate to the mortar production factory (value in the \(X\)-axis), mortars with recycled aggregates (DELTA and HP) are always those with the lowest impact. Consequently, the lines slope of reference mortars (REF1 and REF2) is always higher than that of mortars with recycled aggregates. The reason is mainly in the weight of the aggregates themselves, being transports calculated in kg \(\times\) km: In REF1 and REF2 mortars, natural aggregate weighs 1.35 kg, while in DELTA mortar there is only 0.90 kg of recycled aggregate, and in HP mortar the recycled carbon dust weighs only 0.974 kg. From Figure 4(a), it is also apparent that, for a same delivery distance, DELTA mortar always has a lower impact than REF1 mortar in both scenarios A and B: Actually, the impact of DELTA, scenario B, is even lower than that of REF1, scenario A. In contrast, from Figure 4(b), at the same distance, the HP mortar in scenario A always has the lowest impact and REF2 mortar in scenario B always has the highest; however, the \"impact lines\" of the HP mortar scenario B and REF2 mortar scenario A intersect. Figure 4: Sensitivity analysis of all the processes involved in the life cycle of (**a**) mortar REF2; (**b**) mortar HP. Graphs in Figure 5a also report solid and dashed black lines, representing the limit in conditions where reference mortars, produced in the same place as natural aggregates (0 km scenarios), have the same impact as mortars with recycled aggregates delivered at higher distances. In other words, they represent the conditions where mortars with recycled aggregates are not convenient from an environmental point of view, as aggregates transports have high impacts (compared to the situation of natural aggregates produced in the same factories together with reference mortars). This convenience evaluation is only possible for DELTA mortar, which consists entirely of recycled aggregates, while it is unfeasible for HP mortar, which always half consists of natural aggregate. In the case of GWP, it is convenient to use natural aggregates rather than recycled ones from the DELTA factory, only if the distance between mortar factories and the recycled aggregate factory is more than 978 km in scenario A (black solid line, Figure 5a) and more than 1203 km in scenario B (black dotted line, Figure 5a). These distance values are obtained by extrapolation, as higher than in the last computed 500 km distance scenario. Concerning the other analyzed impact categories, detailed results are reported in S2. In general, for almost all of them (ODP, POCP, AP, EP-freshwater, EP-terrestrial, ADP-fossil, PE-NRe), the use of natural aggregate is convenient from an environmental point of view only with recycled aggregates distances over 172-276 km (DELTA, scenario A), 397-501 km (DELTA, scenario B).