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The objective of this work is to evaluate the potential use of gold and silver tailings (GST) as Supplementary Cementitious Material (SCM). Physical, chemical, and mineralogical characteristics of GST were evaluated. Based on the initial characterization of GST, mechanical and thermal activation were proposed to improve GST reactivity. The effect of both activation processes in crystallite size and Full Width at Half Maximum (FWHM) were determined by X-Ray Diffraction (XRD). Mechanical activation at 140 min of milling and thermal activation at 1000 °C allowed the most significant reduction of crystallite size and particle size. The unconfined compressive strength (UCS) and the Strength Activity Index (SAI) were tested in mortar cubes partially substituted with activated tailings. Results showed that 10, 15, and 20 wt% substitution with activated tailings exceed the 75% SAI according to ASTM standards. Micrographs showed the presence of a calcium silicate hydrate (C-S-H) gel rich matrix in experimental mortars.

This study investigated the self-healing process in concrete using limestone coarse aggregate impregnated with sodium silicate solution and encapsulated with polyvinyl alcohol (PVA). It discussed the self-healing mechanism by sodium silicate solution and evaluated the effect and the efficiency of this healing agent. To do this, limestone coarse aggregate was vacuum impregnated with a sodium silicate solution, encapsulated with PVA, and mixed into the concrete paste. The compressive strength was improved up to 50% in the concrete samples with sodium silicate. It also evaluated the porosity, density, and absorption ranges. It found a reduction of 4% in the range of absorption. Using x-ray diffraction (XRD), the chemical elements of the healing products were determined and the presence of the crystalline phases Etringite, Calcite, Dolomite and Minrecordite. This agreed with the chemical composition of dolomitic limestone’s (CaMg (CO3)2). The self-healing process was observed in the concrete samples cured at 28 days and was attributed to the formation of calcite crystals and silica gel C-S-H. Using the Scanning Electron Microscopy (SEM), the hydration products like calcite and C-S-H were visualized. Self-healing in the concrete could be observed due to the impregnation of Sodium Silicate in the aggregates.

Phosphors composed of Gd 1-x RE x AlO 3 (0≤x ≤ 5 RE = Dy or Pr) stoichiometries were synthesized using the reverse coprecipitation pathway. The thermoluminescent responses of all phosphors were studied under beta radiation exposure. Doping the gadolinium aluminate host improved the thermoluminescent response of the phosphors, with the phosphors composed of Gd 0.99 Dy 0.01 AlO 3 and Gd 0.95 Pr 0.05 AlO 3 being the most sensitive. The Dy 3+ ions produced a higher improvement of the thermoluminescent signal than the Pr 3+ ions. Additionally, a proportional relationship between the similarity of the atomic numbers of the dopant and replaced ions and the sensitivity to thermoluminescence was confirmed. Besides, a slight shift of the thermoluminescent peaks toward lower temperatures was detected for doped phosphors. In the repeatability tests applied to the phosphor composed of Gd 0.99 Dy 0.01 AlO 3 , an anomalous increase in sensitization was observed. The observed sensitization was associated with the formation of electron trap clusters resulting from the continuous exposure to beta radiation. Furthermore, another sensitization phenomenon was detected in the phosphor with Gd 0.95 Pr 0.05 AlO 3 stoichiometry when it was heated at low temperatures. The aforementioned striking behavior was related to quasi-continuous distributions of electron traps and the tunneling effect. In regard to linearity, the phosphor composed of Gd 0.99 Dy 0.01 AlO 3 exhibited a linear response with the dose across the entire range of beta doses. However, the response of the Gd 0.95 Pr 0.05 AlO 3 phosphor lost linearity beyond 26.4 Gy of beta dose. The results obtained through the use of the T max -T stop method and deconvolutions suggested an enhancement in the efficiency of the thermoluminescent mechanisms due to the incorporation of activators., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Juan Zarate Medina reports financial support was provided by National Council on Science and Technology (CONACYT-MEXICO)., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The suitable choice of an activator and host combination is essential for synthesizing very sensitive thermoluminescence phosphors. In addition, conspicuous synthesis variables must be optimized to achieve the maximal response. The research presented herein shows that the most recommendable conditions to improve the thermoluminescence response of beta irradiated Gd 1-x Eu x AlO 3 phosphors were: x = 0.02 for europium stoichiometry and 1500 °C for the calcination temperature. The glow curve recorded for the most sensitive phosphor was partially erased by photo-bleaching, and thus, should yield optically stimulated luminescence., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Juan Zarate Medina reports was provided by National Council for Science and Technology. Juan Zarate Medina reports equipment, drugs, or supplies was provided by National Council for Science and Technology., (Copyright © 2022 Elsevier Ltd. All rights reserved.)