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1. Carbonation rate of alkali-activated concretes and high-volume SCM concretes: a literature data analysis by RILEM TC 281-CCC

   https://doi.org/10.1617/s11527-022-02041-4  

   Gluth, Gregor J.; Ke, Xinyuan; Vollpracht, Anya; Weiler, Lia; Bernal, Susan A.; Cyr, Martin; Dombrowski-Daube, Katja; Geddes, Daniel A.; Grengg, Cyrill; Le Galliard, Cassandre; et al (October 2022, Materials and Structures)

   Abstract The current understanding of the carbonation and the prediction of the carbonation rate of alkali-activated concretes is complicatedinter aliaby the wide range of binder chemistries used and testing conditions adopted. To overcome some of the limitations of individual studies and to identify general correlations between mix design parameters and carbonation resistance, the RILEM TC 281-CCC ‘Carbonation of Concrete with Supplementary Cementitious Materials’ Working Group 6 compiled and analysed carbonation data for alkali-activated concretes and mortars from the literature. For comparison purposes, data for blended Portland cement-based concretes with a high percentage of SCMs (≥ 66% of the binder) were also included in the database. The analysis indicates that water/CaO ratio and water/binder ratio exert an influence on the carbonation resistance of alkali-activated concretes; however, these parameters are not good indicators of the carbonation resistance when considered individually. A better indicator of the carbonation resistance of alkali-activated concretes under conditions approximating natural carbonation appears to be their water/(CaO + MgO_eq + Na₂O_eq + K₂O_eq) ratio, where the subscript ‘eq’ indicates an equivalent amount based on molar masses. Nevertheless, this ratio can serve as approximate indicator at best, as other parameters also affect the carbonation resistance of alkali-activated concretes. In addition, the analysis of the database points to peculiarities of accelerated tests using elevated CO₂concentrations for low-Ca alkali-activated concretes, indicating that even at the relatively modest concentration of 1% CO₂, accelerated testing may lead to inaccurate predictions of the carbonation resistance under natural exposure conditions. 

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2. Density of Sodium Aluminosilicate Melts Along the NaAlSiO ₄ ‐NaAlSi ₃ O ₈ Join at High Pressure: In‐Situ Measurements and Re‐Calibration of a Modified Hard‐Sphere Equation of State For Silicate Melts

   https://doi.org/10.1029/2025JB033223  

   Xu, Man; Jing, Zhicheng; Van_Orman, James A; Hu, Qingyang; Chen, Qi; Yu, Tony; Wang, Yanbin (February 2026, Journal of Geophysical Research: Solid Earth)

   Abstract Silicate melts play a crucial role in planetary differentiation. The density contrast between silicate melts and the surrounding solid residue exerts a primary control on many magmatic processes. However, direct measurements of the density of silicate melts at high pressure (P) and temperature (T) conditions remain challenging, particularly for the highly viscous and reactive silica‐ and alkali‐rich melts. Here we determined the highP‐Tdensities of three sodium aluminosilicate melts with nepheline (NaAlSiO₄), jadeite (NaAlSi₂O₆), and albite (NaAlSi₃O₈) compositions, using the high‐PX‐ray microtomography technique up to 4.1 GPa and 2020 K. Our results suggest that the substitution of (NaAl)⁴⁺for Si⁴⁺along the NaAlSiO₄‐NaAlSi₃O₈join leads to higher melt density and lower melt compressibility. In addition, our new data, combined with a wide range of literature data, were employed to re‐calibrate a modified hard‐sphere equation of state (HS‐EOS) for silicate melts, which provides a unified framework for calculating the density and other compressional properties of multi‐component silicate melts in the CaO‐MgO‐Al₂O₃‐SiO₂‐FeO‐Na₂O‐K₂O (CMASFNK) system up to ∼25 GPa. The calibration also reveals that SiO₂, alkalis, and CaO are the major components contributing to the compositional dependence of melt elastic properties. The HS‐EOS was then applied to alkali basaltic melts at cratonic mantle conditions and silica‐ and alkali‐rich melts at early planetesimal melting conditions, with implications for the gravitational stability and extraction of melts in Earth's mantle and planetesimal settings. 

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3. High-Temperature Oxidation and Thermal Expansion Behavior of NbTi–X (X = 5Co, 10Cr, 10Ni, 10CoCrNi) Refractory Medium Entropy Alloys

   https://doi.org/10.1007/s11661-025-07911-4  

   Ochieze, U P; Simpson, N; Jestude, Z; Steiner, M A; Payton, E J (October 2025, Metallurgical and Materials Transactions A)

   Abstract The formation of Nb₂O₅and other oxides in NbTi–X(X = 5Co, 10Cr, 10Ni, 10CoCrNi) after exposure to 800 °C accelerates oxidation kinetics, shifting from a parabolic rate law to a power-law exponent of two at 1200 °C. Subsequent oxidation at 800 °C for material initially exposed to oxidation at 1200 °C shows that the retained TiNb₂O₇and CrNbO₄oxide scale substantially improves oxidation kinetics, transitioning from linear to parabolic behavior at this temperature. The oxide scales were heterogeneous, exhibiting regions with thin oxide layers alongside areas of thick, porous scales due to the formation of discontinuous metal and complex oxide structures. Microstructural analysis using scanning electron microscopy (SEM) revealed that the formation of metal oxides and complex oxides plays a crucial role in oxidation resistance. In alloys containing Co and Ni, TiNb₂O₇and Nb₂O₅layers are observed. Additionally, NbTi–10(CoCrNi) exhibited significant internal corrosion zones composed of various oxides. Quantitative X-ray diffraction (XRD) analysis of the oxide scales formed after 16 hours of oxidation confirmed that Nb₂O₅and TiO₂were the predominant phases when oxidation resistance is relatively poor and TiNb₂O₇and CrNbO₄are present when oxidation weight gain rates are comparatively lower. Furthermore, it is found that these alloys exhibit low, stable thermal expansion, with hysteresis primarily in the as-cast state due to phase transitions and internal stresses, which largely disappear after homogenization due to single-phase stability and reduced partitioning effects. These findings may provide valuable insights into the oxidation behavior, structural evolution, and thermal stability of these alloys, particularly in environments involving thermal cycling between high and low temperatures. 

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4. Reactivity and reaction kinetics of calcium aluminosilicate glasses

   https://doi.org/10.1617/s11527-025-02905-5  

   Panda, Subhashree; Pestana, Luis Ruiz; Suraneni, Prannoy (December 2025, Materials and Structures)

   Optimizing the utilization of SCMs in concrete requires understanding their composition-structure–reactivity relationships, a task that remains challenging due to their inherent structural and chemical complexity. This study addresses this challenge by analyzing a diverse range of calcium aluminosilicate (CAS) glasses, serving as pure-phase model systems to better understand SCM reactivity. Sixteen CAS glasses were synthesized, with their amorphous nature confirmed by X-ray diffraction (XRD), and their reactivity assessed using heat release measurements from a modified R3 test. X-ray diffraction (XRD) was performed to study the glass structure. Although several structural parameters—non-bridging per tetrahedral oxygens (NBO/T), average Qn(Si) species, metal–oxygen bond strength (SM–O), the average number of topological constraints per atom (nr), and XRD hump maxima angle—correlated linearly with CaO (reflecting its depolymerizing effect), the 72-h heat release followed a non-linear trend with CaO. It increased initially, peaked at around 35–45 mol % CaO, then decreased. Consequently, high-CaO glasses reacted rapidly but did not sustain their reaction over time, whereas those with higher SiO2 content showed slower yet more prolonged reactivity. These findings demonstrate that reactivity cannot be directly predicted from existing structural descriptors alone. 

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5. Spontaneous passivation in a Rare-Earth-Free Mg4(TiZnSn)3 Multi-Principal element alloy

   https://doi.org/10.1007/s42247-025-01203-8  

   Helmer, Alexander T; Gupta, Rajeev K (August 2025, Emergent Materials)

   Abstract Mg₄(TiZnSn)₃, a rare-earth-free Mg-based multi-principal element alloy, was synthesized via high-energy ball milling and cold compaction. Potentiodynamic polarization in 0.1 M NaCl revealed spontaneous passivation with a corrosion current density of 8.96 ± 0.83 µA/cm²and a nobler than Mg corrosion potential of -1058.35 ± 15.91 mV_SCE. X-ray photoelectron spectroscopy confirmed the formation of a mixed oxide film containing ZnO, SnO₂, and TiO₂, contributing to the observed passivity. The alloy also exhibited improved mechanical performance, with a hardness of 5.06 ± 0.41 GPa and Young’s modulus of 109.24 ± 10 GPa. These results demonstrate that tailored multi-element alloying and powder metallurgy can synergistically enhance both corrosion resistance and mechanical properties in Mg alloys. 

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