Spectrosc. J., Volume 4, Issue 2 (June 2026) – 4 articles

Ultra-high-performance concrete (UHPC) formulated with alternative binders represents a promising pathway for reducing carbon emissions while enabling multifunctional material performance. This study investigates the mechanical and electrical evolution of two systems: a traditional Portland cement-based UHPC (REF) and a geopolymer counterpart (GEO) where cement is fully replaced by ground granulated blast furnace slag (GGBS) and silica fume. By evaluating both mixes with and without steel fibers, the research assesses how binder chemistry interacts with conductive pathways to influence strength, resistivity, and impedance. Mechanical testing revealed comparable 28-day compressive strengths for the reference and geopolymer mixes (123 MPa and 120 MPa, respectively), which increased to 139 MPa and 130 MPa upon fiber incorporation. Electrical characterization showed that the geopolymer binder significantly enhances conductivity; resistivity values dropped from 9645 Ω·m in the reference mix to 925 Ω·m in the geopolymer and further to 76 Ω·m with fiber reinforcement. Impedance spectroscopy supported these results, as the GEO mixes displayed smaller Nyquist arcs compared to the REF system, indicating greater ionic mobility associated with pore solution chemistry and the GGBS-rich gel structure. Ultimately, this study demonstrates that geopolymer UHPC matches the mechanical integrity of Portland-based systems while offering superior electrical conductivity, making it a strong candidate for low-carbon, self-sensing infrastructure. Full article

Beryllium (Be), a critical strategic metal element, is predominantly extracted from beryl, which serves as a key mineral combining significant strategic importance with essential industrial applications. Significant debate remains, however, regarding the mineralogical characteristics and color-causing mechanisms of beryl. In this study, we integrate Electron Probe Microanalysis (EPMA), Fourier transform infrared spectrometer (FTIR), laser Raman spectrometer (LRS), X-ray diffractometer (XRD), and ultraviolet–visible spectrophotometer (UV-VIS) to elucidate the mineralogy and spectral characteristics of pegmatitic beryl from Xinjiang, Northwest China. The results indicate that the beryl mainly presents a yellowish-green color, associated with minerals such as feldspar, quartz, and garnet. The EPMA results confirm the chemical composition of the typical beryl and indicate that the Al content is lower than the theoretical value, reflecting the substitution of Al³⁺. The FTIR shows characteristic vibrations of Si-O tetrahedral groups within the range of 1400~400 cm⁻¹, along with distinct bending and stretching vibration peaks of H₂O molecules observed in the range of 1700~1500 cm⁻¹ and 3500~3800 cm⁻¹, respectively. Combined with spectral analysis, it can be determined that both Type I water and Type II H₂O are present in the samples. Raman spectroscopy reveals that the two distinct peaks of beryl are located at approximately 685 cm⁻¹ (attributed to the stretching vibration of Be-O) and 1067 cm⁻¹ (corresponding to the bending vibration of Si-O), respectively. The XRD analysis shows that the ratio of unit cell parameters c/a of the samples ranges from 0.9950 to 1.0068, and the isomorphous substitution in its structure is mainly manifested as the replacement of octahedral coordination sites by Al³⁺. The UV-VIS shows that Fe³⁺ exhibits a broad absorption band in the range of 200~300 nm, while no obvious absorption peaks are observed in the range of 300~800 nm. The above characteristics indicate that Fe³⁺ has a significant impact on the color of beryl. For green beryl samples, a portion of Fe³⁺ occupies the structural channel sites and interacts with H₂O molecules within the channels, which contributes to the yellowish hue of beryl. Our study highlights crucial data for mineralogical identification, genetic tracing, as well as efficient utilization of beryl resources. Full article