Recent discoveries have demonstrated that the surfaces of Mars, Ceres and other celestial bodies, as well as asteroids and comets, are characterized by the presence of ammonium-bearing minerals. A careful study of remote data compared with the analyses of more accurate laboratory data might allow a better remote characterization of planetary bodies. In this paper, the reflectance spectra of some ammoniated hydrous and anhydrous salts, namely sal-ammoniac NH₄Cl, larderellite (NH₄)B₅O₇(OH)₂·H₂O, mascagnite (NH₄)SO₄, struvite (NH₄)MgPO₄·6H₂O and tschermigite (NH₄)Al(SO₄)₂·12H₂O, were collected at 293 and at 193 K. The aim is to detect how the NH₄ vibrational features are affected by the chemical and structural environment. All samples were recovered after cooling cycles and were characterized by X-ray powder diffraction. Reflectance spectra of the studied minerals show absorption features around 1.3, 1.6, 2.06, 2.14, 3.23, 5.8 and 7.27 μm, related to the ammonium group. Between them, the 2ν₃ at ~1.56 μm and the ν₃ + ν₄ at ~2.13 μm are the most affected modes by crystal structure type, with their position being strictly related to both anionic group and the strength of the hydrogen bonds. The reflectance spectra of water-rich samples [struvite (NH₄)MgPO₄·6(H₂O) and tschermigite (NH₄)Al(SO₄)₂·12(H₂O)] show only H₂O fundamental absorption features in the area from 2 to 2.8 μm and a band from hygroscopic water at 3 μm. Thermal analyses (TA), thermal gravimetry (TG) and differential scanning calorimetry (DSC) allowed to evaluate the dehydration temperatures and the occurring phase transitions and decompositions in the analyzed samples. In almost all samples, endothermic peaks at distinct temperatures were registered associated to loss of water molecules, differently linked to the structures. Moreover, an endothermic peak at 465 K in sal-ammoniac was associated to the phase transition from CsCl to NaCl structure type.

Recent satellite observations and the deconvolution of remote sensing data have shown the existence of various carbonate minerals in different solar system bodies. Emissivity, from 403 to 803 K, and reflectance spectra at 300 and 193 K of selected carbonates minerals with different ratios of Na:Ca and water amounts were respectively collected at 3–20 μm and at 1–16 μm. All reflectance spectra show absorption features in the 1.9–2.5 and 3.4–4.0 μm areas due to overtone and a combination of CO₃²⁻ and fundamental vibrational models at ≈9.09, 11.35, 7.06, and 14.7 μm. The increase of the Na:Ca ratio in anhydrous samples produces a shift of the absorption features in the 3.4–4.0 μm area toward shorter wavelengths, and the peak at 3.9 μm doubles in the presence of a CO₃²⁻ oxygen group shared with two cations in minerals having more complex structures. The comparison of the bands at ≈669 and ≈794 cm⁻¹ in the emissivity spectra collected at high temperatures indicates that around 600 K, phase transitions occurred in natrite and thermonatrite. The reflectance spectra measured at 193 K reveal a fine structure compared to spectra collected at room temperature. The comparison of laboratory results with the spectrum of Ceres’s brightest crater Occator from the Dawn mission, taken as a case study, showed how the anhydrous samples, shortite and nyerereite, studied in this work can also be hypothesized for Ceres’s surface beyond that already suggested (trona, natrite, thermonatrite).

Clayey soils are treated with binding agents to improve their mechanical properties, as these soils are widely used in construction. The production of binding agents is an energy-intensive process and emits significant amounts of CO₂. In addition, the interest in recycling industry waste materials has increased, and the management of significant waste from biomass power plants remains an issue. We used three biomass ashes derived from pellet, olive, and grapevine combustion as stabilizing agents of a clayey soil. The mechanical effects of the treatment on clay-ash mixtures were evaluated using confined compressive tests. The mixtures’ chemo-mineralogical evolution was evaluated through X-ray powder diffraction and quantitative Rietveld analysis, Fourier transform infrared spectroscopy (FT-IR), and energy-dispersive X-ray spectroscopy coupled with scanning electron microscopy (EDS-SEM). The FT-IR spectra showed an evolution of the Si-O-Si/Al features, with shifting band positions due to polymerization of the tetrahedral units. The EDS-SEM analysis showed an evolution of the Ca/Si distribution and the growth of pozzolanic reaction products, such as C-S-H nanocrystals and gels. This evidence confirms that the pozzolanic reaction occurs by dissolution of clay minerals and/or the amorphous phase of the ash, which affects the macroscopic behavior of clayey soils in terms of stiffening and strengthening, as confirmed by mechanical tests, albeit these effects are non-homogenous and continuous.

High-pressure synchrotron X-ray diffraction was carried out on a single crystal of mascagnite, compressed in a diamond anvil cell. The sample maintained its crystal structure up to ~18 GPa. The volume–pressure data were fitted by a third-order Birch–Murnaghan equation of state (BM3-EOS) yielding K₀ = 20.4(7) GPa, K’₀ = 6.1(2), and V₀ = 499(1) ų, as suggested by the F-f plot. The axial compressibilities, calculated with BM3-EOS, were K_0a = 35(3), K’_0a = 7.7(7), K_0b = 10(3), K’_0b = 7(1), K_0c = 25(1), and K’_0c = 4.3(2) The axial moduli measured using a BM2-EOS and fixing K’₀ equal to 4, were K_0a = 52(2), K_0b = 20 (1), and K_0c = 29.6(4) GPa, and the anisotropic ratio of K_0a:K_0b:K_0c = 1:0.4:0.5. The evolution of crystal lattice and geometrical parameters indicated no phase transition until 17.6 GPa. Sulphate polyhedra were incompressible and the density increase of 30% compared to investigated pressure should be attributed to the reduction of weaker hydrogen bonds. In contrast, some of them, directed along [100], were very short at room temperature, below 2 Å, and showed a very low compressibility. This configuration explains the anisotropic compressional behavior and the lowest compressibility of the a axis.

Enhancing the durability of cement paste through the incorporation of appropriate additives represents a promising approach to improving the sustainability of cement production. In particular, the inclusion of layered double hydroxides (LDHs) in cementitious systems has been shown to enhance their corrosion resistance to Cl ⁻ and SO ₄ ²⁻ anions. However, LDHs, due to their anionic exchange capability, significantly affect the initial kinetics. In this work, two types of nanometric LDHs, MgAl-NO ₃ and MgAl-HCOO, were added to cement paste in different proportions (1, 3, and 5 wt% of the binder) to investigate early hydration kinetics and to quantitatively evaluate the effect of anion exchange on cement hydration products and clinker phase consumption by in situ X-Ray diffraction (XRD). In addition, the chloride binding capacity of selected LDHs was tested by means of XRD and thermogravimetric analyses. The results show that, in the early hydration stage, LDHs can capture SO ₄ ² ⁻ ions, thereby inhibiting early ettringite precipitation and enhancing the production of hydration products (portlandite) after the first 24 h. LDHs containing formate decrease the availability of Ca ² ⁺ in solution, thereby limiting the precipitation of calcium-rich phases, slowing down the dissolution of alite (C ₃ S). Geochemical modelling supports these findings. Finally, both MgAl-NO ₃ and MgAl-HCOO improved the chloride binding capacity of the cement paste due to their excellent anion exchangeability.