# Pore Structure and Water Transfer in _Pietra d'Aspra_ Limestone: A Neutronographic Study
## 2 Materials and Methods
### Neutron Radiography Analysis  
One test specimen for seven samples (see Table 1) was used for neutron radiography analysis. Neutron radiographs were collected at the cold neutron imaging spectrometer IMAGINE of the Laboratoire Leon Brillouin (LLB) at the Orphee Reactor, in Saclay (F). By increasing the \(L/D\) ratio (with \(L\) equal to the distance between the entrance aperture of the neutron beam and the image plane (400 cm) and \(D\) equal to the diameter of the collimator aperture (1 cm)) up to 400, absorption contrast values with high resolution (\(\sim\)0.1%) were achieved, providing a spatial resolution of about 250 \(\upmu\)m. The incoming beam, characterized by a wide spectrum of neutrons having wavelength between 3 and 20 A, was of \(\sim\)2 \(\times\) 10\({}^{7}\) neutrons-cm\({}^{-2}\)-s\({}^{-1}\). Finally, for our measurements, the sample-detector distance was 10 cm. A sCMOS (scientific Complementary Metal-Oxide-Semiconductor) ANDOR NEO camera coupled to a Canon EFS 60 mm F/2.8 Macro USM (Ultrasonic Motor) was used to collect the transmitted beam coming from the sample. The key elemental composition of the investigated limestones, mostly characterized by C, O, Ca, etc., whose neutron cross-sections are typically two order of magnitudes lower than that of hydrogens (H) in liquid media, allows easily following the water motion by \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample Code** & **Products** & **Experimentation Tests** & \begin{tabular}{c} **Preliminary Characterization** \\ **(YL, MIP)** \\ \end{tabular} & \begin{tabular}{c} **Weight Loss** \\ **Measurements** \\ \end{tabular} & \begin{tabular}{c} **Neutron Radiography** \\ **Analysis** \\ \end{tabular} \\ \hline \hline PA1 & Nano Estel® & \begin{tabular}{c} Climatic chamber (T/RH) after 3 \\ cycles of salt crystallization \\ \end{tabular} & - & \(\times\) (3) & \(\times\) (1) \\ \hline PA2 & Nano Estel® & Salt weathering (15 cycles) & - & \(\times\) (3) & \(\times\) (1) \\ \hline PA3 & Nano Estel® & No wethered & - & - & \(\times\) (1) \\ \hline PA4 & CaLoSIL® & \
\begin{tabular}{c} Climatic chamber (T/RH) after 3 \\ cycles of salt crystallization \\ \end{tabular} & - & \(\times\) (3) & \(\times\) (1) \\ \hline PA5 & CaLoSIL® & Salt weathering (15 cycles) & - & \(\times\) (3) & \(\times\) (1) \\ \hline PA6 & CaLoSIL® & Not weathered & - & - & \(\times\) (1) \\ \hline PA-TQ & Untreated & No wethered & \(\times\) (1) & - & \(\times\) (1) \\ \hline PA-TQ1 & Untreated &
\begin{tabular}{c} Climatic chamber (T/RH) after 3 \\ cycles of salt crystallization \\ \end{tabular} & - & \(\times\) (3) & - \\ \hline PA-TQ2 & Untreated & Salt weathering (15 cycles) & - & \(\times\) (3) & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of all the investigated specimens together with details about products and experimentation tests. PLM, polarized light microscopy; MIP, mercury intrusion porosimetry; T, temperature; RH, relative humidity. spontaneous imbibition. As a result, even for a low quantity of penetrated water, a good contrast between the solid and liquid phase can be observed. The obtained raw images were corrected using dark-field (\(I_{(df)}\)) and open-beam (\(I_{(ob)}\)) images taken prior to the sample measurements. Investigated limestones were contained one by one within an aluminum holder and placed onto a 10 mm thickness filter paper pack (Kaltek S.r.l. Padova Italy), in order to scan the entire volume. The dynamics of water suction by capillarity was recorded by stepwise manual addition of water into the aluminum basement, which ensured the saturation of the filter paper pack (Scheme 1). For each sample, images were recorded with an exposure time of 40 s, until full saturation, except for PA4, for which an exposure time of 10 s was used. In those cases, in which the saturated condition was not completely reached, measurements were collected for no longer than \(\sim\)20 h.  
A homemade macro of the IMAGINE beamline was used to pre- and post-process raw images.