## 3 Results and Discussion
### Chemo-physical Characterization of Line-Treated Samples  
The X-ray diffraction patterns of OR soil treated with 5% by weight of Ca(OH)\({}_{2}\) is shown in Figure 5. The mineralogical evolution of the system was monitored over time, from 24 h to 90 days of curing. The main phases added through lime are portlandite and a small fraction of calcite. Calcite is steadily detected until 90 days of curing, meaning that it is not involved in the ongoing reactions. Portlandite actively promotes and participates to the reactions taking place in the system and it is quickly consumed. Signals ascribable to portlandite are never detected, thus suggesting that it is entirely consumed within 24 h after the addition.  
Figure 4: Soil water retention curve of OR raw material (SWRC).  
Figure 6 shows the DTG curves of raw and lime treated OR samples at increasing curing times. Orvieto DTG natural curve is mainly affected by Chabazite-Ca. The characteristic double peak of dehydration of Chabazite (between 50 \({}^{\circ}\)C and 250 \({}^{\circ}\)C) plausibly indicates the presence of molecular water absorbed in two different sites [18]. Immediately after lime addition, the two peaks of chabazite quickly smoothen. The main peak of portlandite dehydration at around 450\({}^{\circ}\), is just slightly visible after 1 day of curing. It completely vanishes for longer curing times. The signal of decarbonation CaCO\({}_{3}\)\(\rightarrow\) CaO+ CO\({}_{2}\)[19] decreases in time as well. After 90 days, there is still no sign of hydrates formation for temperature ranging around 300 \({}^{\circ}\)C, typical of C-S-H. Nevertheless, it is clearly detectable in the interval 1-90 days a constant increase of the % mass loss around 100 \({}^{\circ}\)C.  
MIP of raw OR soil samples allowed the identification of three main classes of pores (Figure 7). The first two classes are mainly composed of inter-particles voids while the main contribution to the smaller pore population is mainly given by the intrinsic porosity of the altered iron-enriched amorphous phase. Differently from soils formed by exchanging clay minerals, no microstructural reorganization is detected after the addition of lime. Treated samples show a bimodal distribution, with similar modal sizes. In the smallest pore range (entrance diameter \(<\) 0.1 \(\upmu\)m) an increase of frequency is observed in  
Figure 5: X-ray diffractograms obtained for raw and lime treated OR soil at increasing curing time (from [PERSON] et al. (2017) [10]).  
Figure 6: OR-soil: results of thermogravimetric analyses (DTG) on 5% lime treated samples for different increasing curing times (from [PERSON] et al. (2017) [10]).  
the very short term (24 h of curing), indicating the formation of a new pore class due to precipitation of secondary hydrates phases in form of gel. Increasing the curing time, a progressive filling of cavities and voids is due to the precipitation of secondary phases, with the progressive decrease of frequency of each class, even if the modal size of the two main classes of pores is not relevantly changed. This observation is evident for 0.3-3 \(\upmu\)m pore entrance diameters within the first 28 days of curing. The filling is less relevant for 3-12 \(\upmu\)m pore entrance diameters. The precipitation of hydrates is congruent with the formation of the smallest class of pores, particularly evident after 28 days of curing.