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Evaporites were deposited in every saline lake in the western Qaidam Basin (QB) during the late Quaternary, but the role of the Quaternary glacial environment in the formation of evaporite deposits remains to be clarified. In this paper, five upper Quaternary evaporite-bearing profiles in the western QB are studied. Uranium-thorium (U–Th) dating was applied to obtain the depositional ages of these profiles, and X-ray powder diffraction (XRD) analysis was applied to identify the evaporite minerals. The U–Th dating results indicate that halite (NaCl)-dominated profile D08 and mirabilite (Na2SO4·10H2O)-dominated profile MXK were deposited between 146.1 ± 53.4 ka and 171.3 ± 27.2 ka, mainly corresponding to Marine Isotope Stage (MIS) 6; the bloedite (Na2Mg(SO4)2·4H2O)-dominated profiles WMX1 and WMX2 were deposited between 182.1 ± 2.5 ka and 206.7 ± 7.0 ka, mainly corresponding to the late period of MIS7; and the mirabilite and halite-dominated salt layers in profile D30 were deposited between 9.0 ± 0.7 ka and 14.3 ± 1.6 ka, with mirabilite deposit ages corresponding to MIS2 and early MIS1. The minerals in the profiles identified by XRD analyses are mirabilite, thenardite (Na2SO4), bloedite, gypsum (CaSO4·2H2O), starkeyite (MgSO4·4H2O), hexahydrite (MgSO4·6H2O) and halite. This study, combined with those of previously reported evaporite deposits in the western QB, indicates that MIS7, MIS6 and MIS2 were important evaporite deposition periods in the late Quaternary. Evaporite depositions in the QB during MIS6 and MIS2 were attributed to a decrease in temperature and shrinkage of the saline lake hydrosphere. The cold glacial climate during MIS6 and MIS2 was conducive to mirabilite deposition in the western QB, while the relatively warm climate of the late period MIS7 was conducive to bloedite deposition.

Two hundred years (1750–1950) of earthen architecture represents an important period of construction in the central region of Portugal. Earthen architecture is usually built close to the coast or to rivers and placed in sandy ground. The impact of rising damp is a general problem and efflorescences are a common cause of damage decay. This problem was studied in a building with two types of earthen construction, adobe masonry walls and formed masonry walls. The aim of this research was to characterise the conditions for the appearance and phase transitions of thénardite and mirabilite, and determine how to prevent progression of salt effects in the two types of wall to support future conservation measures. Laboratory capillarity and porosimetry tests with dolomitic air lime mortar and hygrothermal monitoring were pursued along with in situ tests. Visual assessment showed that the progression of salts depends on the composition of the earthen materials. To understand these differences, all crystalline solid phases were analysed by powder X-ray diffraction, and building interior hygrothermal conditions were monitored. An investigation into the influence of surface lime water painting and sacrificial mortar application on the crystallisation of sodium sulfates concluded that these also depend on the wall's composition. Data allowed us to conclude that inside the building the temperature and humidity [relative humidity (RH = 100 pw/p°w > 70)] conditions led to the adobe breakdown by the fast conversion from thénardite to mirabilite. Therefore, contact with wet atmospheres should be avoided and interior hygrothermal conditions should be controlled. Laboratory and in situ tests showed that the environmental conditions of the spaces had effects on the results. The results contribute to understanding of the salt progression and pattern of decay, as well as supporting future recommendations for building conservation, based on the identification of environmental conditions proper to their occurrence.

This work focuses on the formation of evaporite minerals through a progressive evaporation of water of Sebkha Oum El Khialate. The precipitated salt is variable along the evaporation path. Weights of evaporite before each phase of precipitation indicate a heterogeneous evaporation process with a final cumulative amount of 294 g L−1. With an increasing evaporation of Oum El Khialate brine, the number of precipitated mineral species is increased. The cumulative number of species along the evaporation process reaches eight in the following depositional sequence: calcite (CaCO3) (29%), Vaterite (CaCO3) (10%), Potassium Pentasulphate (K2S5O16) (9%), thenardite (Na2SO4) (33%), beryllium sulfate (BeSO4) (10%), brucite (Mg(OH)2) (4%), gypsum (CaSO4·2H2O) (2%) and mirabilite (Na2SO4·10 H2O) (3%). The sebkha can provide 86 kt of evaporite deposits per year at 100% evaporation. These evaporite minerals have variable industrial, medical and military uses. However, beryllium sulfate may cause a health risk to the population including lung cancer. The study shows that the use of a fractional crystallization may decrease the cost of salt extraction and the environmental risks by localizing the crystallization domains of valuable and hazardous minerals.

Scanning electron microscopy (SEM) was used to analyze and study micron-nanometer evaporite samples collected from Paleocene and Eocene drill cores in the Jiangling Depression. Accordingly, seven beds of potassium-bearing solid rocks were accurately identified. Sylvite, carnallite, syngenite, dolomite, thenardite, anhydrite, glauberite, halite, barite, celestite, and other solid salt minerals were found, and carnallite, syngenite, and thenardite were found for the first time in the Jiangling Depression. Sylvite, syngenite, and carnallite indicate that the Paleogene salt lakes in the Jiangling Depression had evolved to the sylvite stage and that prospecting for solid sylvite would be satisfactory. Micron-nanometer celestite is contained in the evaporites, from which we can infer that strontium may have been provided by deep formation water (or oil-field water). This finding is of great significance to studying the genesis of sylvite sediment in the Jiangling Depression. From the extensive development of primary glauberite beds typical of warm salt minerals in the Shashi Formation, it can be inferred that the late Paleogene paleoclimate in the Jiangling Depression of the Jianghan Basin was dry and hot. Based on the extensive distribution of micron-nanometer pyrite, siderite, iron and Fe2O3/FeO ratios in evaporite sediments and color analysis of mudstones, the evaporites in the study area formed in an underwater anoxic, reducing environment during sedimentation. Therefore, the evaporite sediments in the Paleocene–Eocene interval of the Jiangling Depression are proposed to have formed in a saltwater lake sedimentary environment, and the ancient lake was characterized by a deep-water salt lake sedimentary model.

In sulfate-rich soils with high sodium sulfate contents, sulfate heave can occur and then generate severe damages to engineering facilities such as pavement, airplane runway due to the hydration of thenardite or crystallization of mirabilite when the temperature is below 32.4 °C. Based on the significant effect of expanded polystyrene (EPS) geofoam in reducing the temperature variations, a comparative experimental investigation on the sulfate heave of subgrade generated by the artificial coarse-grained saline soil with and without EPS material is conducted. Parameters of swell displacement and temperature fluctuation obtained from this comparative experiment are further validated and analyzed. The X-Ray Diffraction (XRD) measurement result is used to demonstrate the performance of EPS in microstructure. Test results indicate that: (1) The presence of crystallized mirabilite is proved within subgrade with saline soil when the temperature drops below 32.4 °C; (2) sulfate heave of subgrade is dependent on temperature fluctuation, but more specifically, on the temperature drop that occurs below 32.4 °C; and (3) EPS thermal insulation can reduce sulfate heave in pavement subgrade by effectively reducing the temperature fluctuation within the subgrade. Ce database subject headings Heave; Hydration; Salinity; Subgrades; Sulfates; Temperature effects.

Based on principles of chemical thermodynamics, the relationship between temperature and the Gibbs free energy of erosion products generated during the sulfate attack on cement concrete was deduced. The orientation of chemical reactions of sulfate attack on cement concrete was theoretically determined as well as the critical sulfate ion concentration and the formation conditions of erosion products. The phase composition, microstructure, crystal form, and morphology of erosion products before and after sulfate attack were investigated by environmental scanning electron microscope and energy spectrum analysis (ESEM-EDS) and X-ray diffraction (XRD). The results show that the effects of sulfate ion concentration and temperature on cement concrete sulfate attack are significant, and different influencing factors correlate with each other. The crystal transition temperature between the anhydrite and dihydrate gypsum is 42°C, and the corresponding concentration of sulfate ion is about 2.3 × 10−3 mol/L. Simultaneously, the crystal transition temperature between the thenardite and mirabilite is 32.4°C. Moreover, the theoretical upper limit temperature and sulfate ion lower limit concentration of thaumasite are 44°C and 0.0023 mol/L, respectively. The ESEM-EDS and XRD results imply that the chemical thermodynamics can be used to reveal the erosion mechanism of sulfate attack on cement concrete. The major erosion products of sulfate attack on cement concrete are rod-like ettringite with a larger slenderness ratio, plate-like gypsum, granular sulfate salt, incompletely corroded calcium hydroxide, and residual skeleton of calcium silicate hydrate. The sulfate attack has double effects on mechanical properties of specimens, which can affect the microstructure, phase composition, type, and morphology of erosion products.

Terrestrial environments at Bunger Hills, East Antarctica, vary from vegetation-rich, little-weathered rock surfaces retaining glacial polish and striations near the glacier and ice-sheet margins to salty, vegetation-poor, extensively weathered regions near to and downwind of marine bays and inlets. Weathering forms include tafoni and orientated pits, which record former wind directions. Although salts are found all over Bunger Hills, the strongly weathered area is coincident with the distribution of halite (NaCl) and thenardite (Na2SO4), both of which are derived from seawater and marine salt spray. Salts elsewhere in Bunger Hills are either subglacial calcium carbonates or rock weathering products including gypsum (CaSO4⋅2H2O) and a range of rarer minerals. These other salt minerals do not weather rocks and sediment. The distribution of halite and thenardite acts as a major control on the geomorphology, sediment geochemistry and biogeography of Bunger Hills.

The US Department of Energy Office of Nuclear Energy is conducting a brine availability heater test to characterize the thermal, mechanical, hydrological and chemical response of salt at elevated temperatures. In the heater test, brines will be collected and analyzed for chemical compositions. In order to support the geochemical modeling of chemical evolutions of the brines during the heater test, we are recalibrating and validating the solubility models for the mineral constituents in salt formations up to 100oC, based on the solubility data in multiple component systems as well as simple systems from literature. In this work, we systematically compare the model-predicted values based on the various solubility models related to the constituents of salt formations, with the experimental data. As halite is the dominant constituent in salt formations, we first test the halite solubility model in the Na-Mg-Cl dominated brines. We find the existing halite solubility model systematically over-predict the solubility of halite. We recalibrate the halite model, which can reproduce halite solubilities in Na-Mg-Cl dominated brines well. As gypsum/anhydrite in salt formations controls the sulfate concentrations in associated brines, we test the gypsum solubility model in NaCl solutions up to 5.87 mol•kg–1 from 25°C to 50°C. The testing shows that the current gypsum solubility model reproduces the experimental data well when NaCl concentrations are less than 1 mol•kg–1. However, at NaCl concentrations higher than 1, the model systematically overpredicts the solubility of gypsum. In the Na+—Cl–—SO2-4—CO2-3 system, the validation tests up to 100oC demonstrate that the model excellently reproduces the experimental data for the solution compositions equilibrated with one single phase such as halite (NaCl) or thenardite (Na2SO4), with deviations equal to, or less than, 1.5 %. The model is much less ideal in reproducing the compositions in equilibrium with the assemblages of halite + thenardite, and of halite + thermonatrite (Na2CO3•H2O), with deviations up to 31 %. The high deviations from the experimental data for the multiple assemblages in this system at elevated temperatures may be attributed to the facts that the database has the Pitzer interaction parameters for Cl–—CO2-3 and SO2-4 - CO2-3 only at 25°C. In the Na+—Ca2+—SO2-4- HCO-3–system, the validation tests also demonstrate that the model reproduces the equilibrium compositions for one single phase such as gypsum better than the assemblages of more than one phase.

Within the cooperation of the Geological Survey of Serbia (former Geoinstitute, Belgrade, Serbia) with the Industrial Research Center (Tripoli, Libya), during the period from 2006 to 2010 many polymineral samples were obtained from central and southern parts of Libya whose exact mineral composition was unknown, and which were intended for analysis by X-ray diffraction method. With the X-ray diffraction method on powdered samples there were determined the presence of numerous mineral kinds, such as: quartz, gypsum, anhydrite, calcite, aragonite, halite, dolomite, celestine, bassanite, palygorskite, ankerite, thenardite, fluorite, hematite and goethite; as well as various mineral groups: clays (illite, kaolinite, montmorillonite), chlorites, micas, feldspars, serpentines, zeolites and amphiboles. In this paper, a more detailed crystallographic analysis of thenardite (Na2SO4) and ankerite [Ca(Fe2+,Mg)(CO3)2] was performed, given the fact that these minerals are quite rare in nature, as well as to indicate the possible way of their formation as marine evaporites. These minerals were identified as dominant in sample 1018/10/1 from southern Libya (Sheet Wādi Eghei, NF 34-1), along with secondary calcite, quartz, and clay minerals. Calculated unit-cell dimensions of thenardite (space group Fddd, No 70) of: a0=9.820(3) Å; b0=12.312(3) Å; c0=5.867(1) Å; α=β=γ=90o; and V0=709.3(2) Å3 are in a very good agreement with the reference data (ICDD-PDF 74-2036: a0=9.829 Å; b0=12.302 Å; c0=5.868 Å; α=β=γ=90o; and V0=709.54 Å3). Calculated unit-cell dimensions of ankerite (space group R-3, No 148) of: a0=b0=4.829(1) Å; c0=16.121(5) Å; α=β=90o; γ=120o; and V0=325.5(2) Å3 are also in a very good agreement with the reference data (ICDD-PDF 84-2066: a0=b0=4.823 Å; c0=16.122 Å; α=β=90o; γ=120o; and V0=324.78 Å3; ICDD-PDF 84-2067: a0=b0=4.831 Å; c0=16.166 Å; α=β=90o; γ=120o; and V0=326.77 Å3). Since ankerite is very similar to dolomite (space group R-3, No 148; ICDD-PDF 74-1687: a0=b0=4.815 Å; c0=16.119 Å; α=β=90o; γ=120o; and V0=323.64 Å3), significantly larger calculated unit-cell dimensions prove that there was a significant (over 60%) isomorphic exchange of smaller Mg 2+ ion with bigger Fe2+. U ovom radu je izvršena detaljnija kristalografska analiza tenardita (Na2SO4) i ankerita [Ca(Fe2+,Mg)(CO3)2], s obzirom na činjenicu da se ovi minerali prilično retko javljaju u prirodi, kao i da ukazuju na mogući način njihovog obrazovanja kao morskih evaporita. Ovi mineralisu identifikovani kao dominantni u uzorku 1018/10/1 iz južnog dela Libije (List Wādi Eghei, NF 34-1), zajedno sa sporednim kalcitom, kvarcom i mineralima glina.

In the present study, the salinization trends of different soil types from a small hydrographic basin situated in NE Romania (Roșior basin) are investigated. The climatic conditions are favorable for long dry summers and intensive evaporation. The soils are developed on immature evolved clay sediments, as revealed by geochemical analysis. The salinity varies among soil types, attaining maximum values for Solonetz with total dissolved salts (TDS) between 1165.75 to 1881.25 mg/L. The aqueous solutions are represented by natural water and soil solution. The hydrogeochemical facies of the natural waters change from HCO3−—Mg2+ in the upper basin to SO42−—Na+ in the middle or lower basin. The soil solution is moderately or strongly salinized and shows anionic variations from HCO3− to SO42− in the studied profiles, whereas Na+ is always the main cation. The concentrations of Na+ and SO42− evolve simultaneously. Raman spectroscopic exploration of the white efflorescences, which occur on topsoil, reveals the presence of thenardite as the dominant phase. The composition of soil solution results from both the ionic exchange and evaporation processes. The nature of soil solution mineralization and summer temperatures are two main factors that interact and promote the thenardite precipitation. The soil salinization induces negative effects on crop nutrition, impacting further the crop yields. The results of this study can be extrapolated to larger areas formed on Sarmatian sedimentary deposits affected by salinization processes.

The most favourable locations for the development of saline lakes are in the rain-shadow of mountain ranges, which provide large areas of precipitation catchment while the base of the basin is under arid climate and exposed to evaporation. These conditions are found in Extra-Andean Patagonia under the rain-shadow generated by the Andean cordillera. There, an endorheic basin with two shallow and saline lakes, Cari Laufquen Chica (CLC) and Cari Laufquen Grande (CLG), was studied with the aim of analysing the factors that condition the hydrochemical processes acting in the formation of evaporites associated with these environments. A monitoring network was installed and five surface and groundwater survey campaigns were carried out at different points in the basin to define groundwater flow and also to extract samples. In situ pH, electrical conductivity and temperature and laboratory physicochemical determinations of major ions and stable isotopes of the water were measured. SEM-EDS and XRD analyses of saline crusts from the edge of the lakes and adjacent sediments were carried out. The obtained results allowed identifying that CLC and CLG saline lakes have different surface water-groundwater configurations. CLC is a flow-through shallow lake, while CLG is a discharge shallow lake. The analysis of the saline precipitates and the chemical facies of the water allows identifying cycles of dissolution, evaporation and precipitation in both saline lakes. However, the different groundwater flow between the two lakes is reflected in their salinity as well as in the evolution and development of saline precipitates. CLC saline lake shows a dissolution-precipitation trend of thenardite and Ca-Mg carbonates, whereas CLG saline lake displays a trend of dissolution-precipitation of halite, thenardite and trona with strong dominance of halite. The present study identifies for the first time the main factors conditioning hydrochemical processes in these saline lakes of extra-Andean Patagonia. Our results indicate that the hydrological configuration with respect to the groundwater flow is the prevailing factor setting the hydrochemical processes that trigger the formation of salt crusts.

A new mineral majzlanite, ideally K2Na(ZnNa)Ca(SO4)4, was found in high-temperature exhalative mineral assemblages in the Yadovitaya fumarole, Second scoria cone of the Great Tolbachik Fissure Eruption (1975–1976), Tolbachik volcano, Kamchatka Peninsula, Russia. Majzlanite is associated closely with langbeinite and K-bearing thénardite. Majzlanite is grey with a bluish tint, has a white streak and vitreous lustre. The mineral is soluble in warm water. Majzlanite is monoclinic,C2/c,a= 16.007(2),b= 9.5239(11),c= 9.1182(10) Å, β = 94.828(7)°,V= 1385.2(3) Å3andZ= 16. The eight strongest lines of the X-ray powder diffraction pattern are [d, Å (I, %)(hkl)]: 3.3721(40)($\bar{3}$12), 3.1473(56)($\bar{4}$02), 3.1062(65)($\bar{2}$22), 2.9495(50)($\bar{1}$31), 2.8736(100)($\bar{1}$13), 2.8350(70)(421), 2.8031(45)(511) and 2.6162(41)($\bar{5}$12). The following structural formula was obtained: K2Na(Zn0.88Na0.60Cu0.36Mg0.16)(Ca0.76Na0.24)(S0.98Al0.015Si0.005O4)4. The chemical composition determined by electron-microprobe analysis is (wt.%): Na2O 9.73, K2O 15.27, ZnO 11.20, CaO 7.03, CuO 4.26, MgO 1.07, Al2O30.47, SO351.34, SiO20.12, total 100.49. The empirical formula calculated on the basis of 16 O apfu is K1.99Na1.93Zn0.84Ca0.77Cu0.33Mg0.16(S3.94Al0.06Si0.01)O16and the simplified formula is K2Na(Zn,Na,Cu,Mg)Σ2(Ca,Na)(SO4)4. No natural or synthetic compounds directly chemically and/or structurally related to majzlanite are known to date. The topology of the heteropolyhedral framework in majzlanite is complex. An interesting feature of the structure of majzlanite is an edge-sharing of ZnO6octahedra with SO4tetrahedra.

The new mineral lussierite (IMA2018-101), Na10[(UO2)(SO4)4](SO4)2(H2O)3, was found in the Blue Lizard mine, San Juan County, Utah, USA, where it occurs as pale green–yellow prisms or blades in a secondary assemblage with belakovskiite, ferrinatrite, halite, ivsite, metavoltine and thénardite. The streak is white and the fluorescence is bright cyan under 365 nm ultraviolet light. Crystals are transparent with vitreous lustre. The tenacity is brittle, the Mohs hardness is 2½, the fracture is irregular and no cleavage was observed. The mineral is easily soluble in H2O and has a measured density of 2.87(2) g cm–3. Lussierite is optically biaxial (+), with α = 1.493(1), β = 1.505(1) and γ = 1.518(1) (white light); 2Vmeas.= 88(1)°; dispersion isr>v, moderate; pleochroism:X= colourless,YandZ= green yellow (X 2σI) contains a [(UO2)(SO4)4]6–uranyl sulfate cluster in which one SO4tetrahedron shares an edge (bidentate linkage) with the UO7pentagonal bipyramid. The uranyl sulfate clusters occur in layers and are linked through a complex network of bonds involving Na+cations, isolated SO4tetrahedra and isolated H2O groups.

The water wells at Karnak temples made of red brick and belonging to different eras, (Graeco-Roman and Byzantine periods). These water wells suffer from several deterioration aspects such as exfoliation, hard crusts, disintegration, spalling, cracks, fractures, salts crystallization, micro-organisms colonization's and vegetation. The aim of this paper is to study the deterioration mechanisms affecting the brick units of these wells to prepare a conservation strategy. Different scientific methods such as Light Optical Microscope (LOM), Polarizing Microscope (PM), Scanning Electron Microscope coupled with an Energy Dispersive X-Ray Spectrometer (SEM-EDX) and X-Ray Powder Diffraction (XRD) have been used to determine the mineralogical composition and the deterioration products. The obtained results have proved that the water wells suffer from salts crystallization of sodium chloride and sodium sulfate (thenardite) due to the severe effects of deterioration factors particularly the dominated environmental conditions, water-soluble salts and mineralogical composition of the brick.

Cementitious materials can be damaged by external sulfate attack due to ingress of sulfate ions from external environment. This process causes loss of cohesion, increase in porosity, local expansion, spalling and cracking. The objectives of this work were to study the influence of the capillary absorption time and of the sulfate ions concentration on compressed stabilized earth blocks (CSEB) exposed to sulfate attack. The CSEB were submitted to cycles of capillary absorption of sodium sulfate solution and drying. Two sets of procedures were used to evaluate the wear of the samples. In the first set of procedures, the capillary absorption time was varied. In the second one, the sodium sulfate concentration was varied instead. The CSEB used had the same dosage of earth, cement and water and for each procedure 3 samples were tested. The masses were measured after taking the samples out of the solution and after a 2-week drying time, being that a cyclic process for each procedure. The room temperature and relative humidity allowed crystallization of thenardite and mirabilite. Granulometry, XRD, XRF and SEM tests were used to identify the materials. The results showed that capillary absorption time and sulfate concentration influences the wear of the CSEB.

Reshuitang is an important active hydrothermal area in the Tengchong geothermal field and is characterized by many hot springs and their associated deposits. Detailed mineralogical, crystal morphological, and stable isotopic investigations of the smooth slope fossil travertines at Reshuitang and hydrochemical studies of two active springs around the fossil travertines were conducted to study their genesis. The results show that 1) the modern springs discharge waters with high temperature (>70 °C), near-neutral pH (6.3–8.34), and high saturation indices of calcite and aragonite; 2) the fossil travertines contain calcite and small amounts of Mn-Fe oxides, halite, thenardite, and non‑carbonate debris; 3) the calcite include ray crystals, dendrite crystals, platy crystals, and spike crystals; and 4) δ13C and δ18O of the fossil travertines at Reshuitang range from −1.59‰ to −0.87‰ and 6.48‰ to 7.80‰, respectively. According to comparison between the travertines at Reshuitang and other travertines in Tengchong, all these travertines are thermogene travertines, with a large contribution of mantle degassing to their parent CO2, but are formed at different temperatures. The fossil travertines at Reshuitang, similar to those at Shuzhishi, are formed at high temperatures (near 100 °C), which results in weak microbial activities during the formation of the fossil travertines. Most of the calcite crystals at Reshuitang were non-equilibrium products precipitated directly from the spring waters during the deposition process, while the spike crystals originated from diagenetic dissolution of large calcite crystals. Comparison between the fossil travertines at Reshuitang and other smooth slope travertines from other areas shows these smooth slope travertines have different lithofacies and fabrics. In smooth slope environments, temperature may control the distribution and development of microbes and the intensity of CO2 degassing, and consequently cause the precipitation of contrasting fabrics and lithofacies.

An experimental study was carried out on the preparation of schoenite from carnallite and thenardite by the double-decomposition method. According to the metastable phase diagram for the qu...

This paper focuses on the investigation of the co-utilization of two major industrial waste materials, power station fly ash and red mud. Experimental studies were carried out to establish the correlation between the physical properties of a geopolymer product and a mixture composition. The effect of mechanical activation and the red mud dosage on the geopolymerisation was investigated. Geopolymerisation of mechanically activated fly ash has been carried out with various proportions of red mud ranging between 0–30 % by weight. The compressive strength of fly ash based geopolymer increased until 15% of red mud addition. The optimal red mud addition in fly ash geopolymer was determined. The influence of red mud on phase composition and chemical bonds of the resulted geopolymer were determined by XRD analysis and FTIR studies. Due to the geopolymerisation reactions, new phases like hydroxy-cancrinite, faujasite and thenardite appeared in the product., U radu je ispitana zajednička uporaba dvaju glavnih industrijskih otpada kod elektrana – lebdećega pepela i crvene isplake. Eksperimentalno je pokazano kako postoji korelacija između fizičkih svojstava dobivenih geopolimera te udjela takvih otpada. Stoga je ispitana uloga mehaničke aktivacije lebdećega pepela i udjela crvene isplake tijekom geopolimerizacije. Taj postupak načinjen je s različitim udjelima crvene isplake – od 0 do 30 težinskih postotaka. Tlačna čvrstoća geopolimera s lebdećim pepelom povećava se do 15 % nakon dodavanja crvene isplake. Također su određeni i optimalni omjeri. Utjecaj isplake na fazni sastav i kemijske veze unutar geopolimera određen je XRD analizom i FTIR studijama. U njima su prepoznati novi minerali naziva hydroxycancrinit, faujasit i tenardit.

Safa Dam Tunnel to Golzar makes it possible to transfer water from Dam Safa to Kerman City. The tunnel, which is approximately 40 km long, is located in the Kerman Cenozoic magmatic arc as a part of the Dehaj-Sarduiyeh belt. The aim of this study was to investigate and identify the source of water resources around the tunnel path as well as the source of water entering the northern and southern parts of the tunnel. In this study, isotopes of oxygen, hydrogen (deuterium and tritium), and sulfur have been used. The values of these isotopes are first interpreted analytically on the reference graphs displayed in the next step. As a whole, 13 samples were taken for isotopic analysis from different parts of water resources around the tunnel path. In all samples, $$ {}{}^{18}O $$ and $$ {}{}^2H $$ were measured, and in addition, in 5 samples of $$ {}{}^{34}S $$ isotope and in seven samples $$ {}{}^3H $$ isotope values were measured as well. According to the isotopic composition, age of the samples, and hydrogeological conditions of the region, four types of water sources have been identified, which include the following: (1) meteoric waters (water samples of Chari and Dizin Mah Rivers, Mubarak Shah salt spring, Sarzeh and Ashkan, BH5 and artesian Shirink well), (2) hydrothermal waters (sample of Shirink hot spring water), (3) ancient waters (sample of water in the northern part of the tunnel), (4) ancient waters of snowmelt origin (southern part of the tunnel and BH4). The BH9 water sample is the result of mixing ancient water with ancient water from the source of snowmelt. Sulfur originates from water samples in the northern part of the tunnel and in the southern part of Thenardite sulfate (Na2SO4) mineral. In the source of sulfur, the samples of Shirink hot spring water and BH9, in addition to the extraction of Thenardite, also have some oxidation and reduction processes. The source of water sulfur of Ashkan spring was mainly fossil fuels and air currents. The results stated that the age of water samples shows a direct relationship with their depth.

Determining aqueous sulfate sources in terrestrial cold environments can provide an insight into the surface hydrological conditions and sulfur cycle on Mars. In this study, we analyzed sulfur and oxygen isotope compositions of secondary sulfate salts (e.g., gypsum, thenardite) in the surficial sediments and soils of the McMurdo Dry Valleys (MDV), Antarctica to determine contributions of sulfate from bedrock chemical weathering and atmospheric deposition under persistent dry polar conditions. The sulfate showed wider variation of δ34S (+15.8‰ to +32.5‰) compared to smaller ranges of δ18O (−8.9‰ to −4.1‰). In contrast, the δ34S of bedrock sulfide showed significantly lower and consistent values across the studied area (−0.6‰ to +3.3‰). Based on the δ34S trends, sulfide weathering may contribute up to 20–50% of secondary sulfate salts in the MDV. While the remaining 50–80% of sulfate inputs may originate from atmospheric deposition (e.g., sea aerosols, dimethulsulfide oxidation), the subglacial brines derived by relicts of seawater and/or lake/pond water influenced by microbial sulfate reduction could also be important sulfate endmembers particularly in the Antarctic lowland thaw zones. Additional field observations of frost, ponding water, and thin gypsum crusts on the terrestrial gypsum dunes at White Sands supports reactivity of gypsum on the surface of these dunes during cold winter conditions. Combined with our improved geochemical model of the sulfur cycle for cold Antarctic settings, we propose that transient liquid water or frost was available in near-surface environments at the time of gypsum formation in the north polar region on Mars. Ice and/or water interaction with basaltic sand of the basal unit (paleo-erg) would have enhanced leaching of sulfate from both sulfide oxidation and atmospheric deposition and resulted in formation of secondary gypsum salts.

Many of the large number of underground works constructed or under construction in recent years are in unfavorable terrains facing unusual situations and construction conditions. This is the case of the subject under study in this paper: a tunnel excavated in evaporitic rocks that experienced significant karstification problems very quickly over time. As a result of this situation, the causes that may underlie this rapid karstification are investigated and a novel methodology is presented in civil engineering where the use of saturation indices for the different mineral specimens present has been crucial. The drainage of the rock massif of El Regajal (Madrid-Toledo, Spain, in the Madrid-Valencia high-speed train line) was studied and permitted the in-situ study of the hydrogeochemical evolution of water flow in the Miocene evaporitic materials of the Tajo Basin as a full-scale testing laboratory, that are conforms as a whole, a single aquifer. The work provides a novel methodology based on the calculation of activities through the hydrogeochemical study of water samples in different piezometers, estimating the saturation index of different saline materials and the dissolution capacity of the brine, which is surprisingly very high despite the high electrical conductivity. The circulating brine appears unsaturated with respect to thenardite, mirabilite, epsomite, glauberite, and halite. The alteration of the underground flow and the consequent renewal of the water of the aquifer by the infiltration water of rain and irrigation is the cause of the hydrogeochemical imbalance and the modification of the characteristics of the massif. These modifications include very important loss of material by dissolution, altering the resistance of the terrain and the increase of the porosity. Simultaneously, different expansive and recrystallization processes that decrease the porosity of the massif were identified in the present work. The hydrogeochemical study allows the evolution of these phenomena to be followed over time, and this, in turn, may facilitate the implementation of preventive works in civil engineering.

Salt weathering is one of the most damaging processes affecting stone conservation and represents an extensively debated topic in heritage science. The main subject of previous research is the built heritage, whereas other types of assets are often neglected, such as underground cultural heritage. This paper introduces an investigation of stone decay in the subterranean environment focused on salt weathering, its patterns, compositional features, and variability in time and space, aiming at finding its driving forces in the rock properties and environmental setting. Field explorations and the mineralogical analysis of salt efflorescences and crusts were integrated by the petrographic, geochemical, and petrophysical characterization of the rock substrates, a microclimate monitoring, and the chemical analysis of groundwater and rainwater. The subject of study is the underground archaeological-historical site of Yoshimi Hyaku Ana in Japan, a complex of Kofun tombs of the 6th–7th century and galleries of the WWII era. The site is affected by intense salt weathering, involving efflorescences and crusts composed of mixed soluble sulfates, mostly hydrated: gypsum, alunogen, alum-(Na), halotrichite, epsomite, polyhalite, tamarugite, thenardite, and mirabilite. They derive principally from the dissolution of rock-forming minerals and components (pyrite, glass, feldspars, etc.) from the Miocene volcanic tuffs into which the site is excavated. The tuffs show a certain lithological diversity (e.g., glass amount and chemico-mineralogical composition) that controls the space variability of salt composition. Another major influencing factor is the underground microclimate, which also affects the time variability and seasonality of salt weathering. The innermost underground areas have an extremely high relative humidity (~100%) and are essentially salt-free, whereas, nearby the site entrances, the wider fluctuations of air temperature and humidity create conditions for salt crystallization in the dry winter season and deliquescence in summer. Depending on the solubility of each salt phase, cycles of crystallization/dissolution and hydration/dehydration can occur both seasonally and in the short-term, causing severe stresses to the stone and damage.

The feasibility of transforming the residues of cultivation of two rocks into secondary raw materials through the alkali activation process has been assessed. Mixtures of a sulfate-bearing kaolinitic clay (L02-K) and a sludge derived by the sewing of Pietra Serena stone (sPS) have been investigated. These materials were preliminarily treated at high temperature to improve their reactivity (heat-treated samples are hereafter labelled as L02-MK and sPS-800). Pastes were prepared with mixtures of L02-MK and sPS-800 in different weight proportions by using 8 M NaOH solutions as alkaline activator and cured at 85 °C for 24 h. Mechanical strength was determined after 1, 7 and 28 days and the reaction products were characterized by XPRD, SEM/EDX and MAS-NMR. Sulfate solubility was quantified by leaching tests. The alkali activation of the sole sulfate-bearing clay gives a material with developed mechanical strength of 4(1) MPa. Some N-A-S-H gel forms together with gibbsite and thenardite, which can be easily leached. Better results are obtained by the activation of mixtures of the two precursors, and mixed alkali cements or hybrid cements are obtained. The presence of CaO from heat-treated Pietra Serena sludge improves the mechanical strength of the resulting pastes up to 11.8(9) MPa. In this case, a mixture of gels forms, specifically, a calcium-rich gel (C-A-S-H-type) co-exists with (N,C)-A-S-H-type gel. U-phase and CAN-type zeolites also form. They trap sulfate from the clay and considerably reduce sulfate solubility. In conclusion, L02-MK and sPS-800 are promising raw materials for alkaline cements, whose properties may suggest application in soil stabilization or in waste confinement., The authors wish to thank the suppliers of the materials utilized for the present work: Eurit s.r.l. (L02 clay) and Pietra Serena Group s.r.l. (Pietra Serena). Ministero dell’Istruzione, dell’Universit` a e della Ricerca is thanked for the scholarship “Fondo per il sostegno dei giovani”. This research was also funded by the Spanish Ministry of Science and Innovation under research project PID2019-111464RB-I00, and by the Italian Ministry of Economic Development (D.M. 5 March 2018—CHAPTER II—Call for Research and Development Projects within the application areas consistent with the National Strategy of Intelligent Specialization [SNSI]—Smart Factory), under the Project I.E.S.MAN. (Internet of Enterprise Sustainable Manufacturing) n. 211.