•We assessed the influence of the chemical composition of aggregates on moisture damage in HMA.•Three lithologies with an ample mineralogical and chemical spectrum were selected.•Asphalt-aggregate ...samples were tested in dry and in three moisture-related conditions.•Results show that mafic rocks were more resistant to moisture damage than felsic rocks.•Al2O3, Fe2O3, MnO, MgO oxides in rocks prevent moisture damage while SiO2 promotes this phenomenom.
Rock mineralogy is critical in determining the adhesion quality and moisture susceptibility of asphalt-aggregate systems in asphalt mixtures. This work aims at identifying the chemical properties of aggregates that influence the quality and durability of these systems. To accomplish this goal, three lithologies with an ample mineralogical and chemical spectrum (i.e. quartzite, granodiorite and serpentinite) were selected. Asphalt-aggregate specimens fabricated with these lithologies were tested using a new pull-off experiment in dry condition, and after 1, 3 and 7 days of being submerged in water. The results show that rocks of mafic composition (e.g. serpentinite) have better resistance to moisture damage than felsic rocks (e.g. quartzite and granodiorite), and that certain specific aggregate oxides promote or prevent moisture degradation in these systems.
Recurring discoveries of abiotic methane in gas seeps and springs in ophiolites and peridotite massifs worldwide raised the question of where, in which rocks, methane was generated. Answers will ...impact the theories on life origin related to serpentinization of ultramafic rocks, and the origin of methane on rocky planets. Here we document, through molecular and isotopic analyses of gas liberated by rock crushing, that among the several mafic and ultramafic rocks composing classic ophiolites in Greece, i.e., serpentinite, peridotite, chromitite, gabbro, rodingite and basalt, only chromitites, characterized by high concentrations of chromium and ruthenium, host considerable amounts of
C-enriched methane, hydrogen and heavier hydrocarbons with inverse isotopic trend, which is typical of abiotic gas origin. Raman analyses are consistent with methane being occluded in widespread microfractures and porous serpentine- or chlorite-filled veins. Chromium and ruthenium may be key metal catalysts for methane production via Sabatier reaction. Chromitites may represent source rocks of abiotic methane on Earth and, potentially, on Mars.
Hydrogen produced during water-rock serpentinization reactions can drive the synthesis of organic compounds both biotically and abiotically. We investigated abiotic carbon production and microbial ...metabolic pathways at the high energy but low diversity serpentinite-hosted Lost City hydrothermal field. Compound-specific
C data demonstrates that formate is mantle-derived and abiotic in some locations and has an additional, seawater-derived component in others. Lipids produced by the dominant member of the archaeal community, the Lost City Methanosarcinales, largely lack
C, but metagenomic evidence suggests they cannot use formate for methanogenesis. Instead, sulfate-reducing bacteria may be the primary consumers of formate in Lost City chimneys. Paradoxically, the archaeal phylotype that numerically dominates the chimney microbial communities appears ill suited to live in pure hydrothermal fluids without the co-occurrence of organisms that can liberate CO
. Considering the lack of dissolved inorganic carbon in such systems, the ability to utilize formate may be a key trait for survival in pristine serpentinite-hosted environments.
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This work has focused on adsorption of both biosurfactants and sodium dodecyl sulfate (SDS) anionic surfactant onto mineral surfaces activated by nickel(II) ions. Surfactants of ...biological origin produced by a new strain of Streptomyces sp. S4 isolated from the environment are analogues of surfactin. They adsorb on the magnesite, serpentinite and silica surface according to the Somasundaran-Fuerstenau isotherm model, changing the electrokinetic properties and hydrophobicity of these minerals. The culture broth was stable at pH 8. The critical micelle concentration for surfactin was 9.6 μM and for biosurfactants – 100 μM. The adsorption of anionic surfactants and biosurfactants decreased the measured value of the electrokinetic potential of the mineral particles. It was found that the adsorption of biosurfactants produced by Streptomyces sp. S4 may be a useful tool for mineral surface modifications that can be used for selective separation of minerals in flotation.
Vast reserves of peridotite and serpentinite rocks can be utilised for the safe and permanent sequestration of global CO2 emissions via aqueous mineral carbonation. These, and indeed most feedstocks ...used in mineral carbonation require ultrafine grinding and/or heat-activation, to engender significantly enhanced reactivity in the rock such that it can then be carbonated. Both activation processes are energy intensive and present significant obstacles to the commercial application of mineral carbonation. Here we show that these limitations can be addressed, at least in part, through the application of a concurrent or in operando grinding technique which does not require feedstocks which have been subjected to prior ultrafine grinding nor heat-activation.
Concurrent grinding is shown to result in a significant increase in magnesite yields for non-heat activated feedstock, prepared such that fines (<20 μm particles) were excluded from the feed. We assert that concurrent grinding may be a suitable technique for the processing of feedstocks such as those containing significant proportions of forsterite and pyroxene, minerals which are unresponsive to thermal activation for use in aqueous mineral carbonation. This study also investigates the effect of different grinding media particle size on reducing the particle size distribution (PSD) of the feed. Optimum ratio of grinding media size to feed particle size, optimum grinding media and slurry concentrations, optimum time for grinding and optimum impeller designs are determined for the system under study. The quantitative effect of grinding media concentration, slurry concentration, pressure and temperature on magnesite yield has been investigated.
•Feedstocks can be carbonated using concurrent grinding without prior pre-treatment.•Different grinding medias and media mixtures were investigated.•Different impeller designs were investigated.•Quantitative effect of operating variables was determined.•62% magnesite yield was obtained using raw dunite rock.
In this study, modelling the carbon footprints of magnesium oxide and magnesium hydroxide (>99% purity) production based on technologies treating bischofite brines (e.g. Aman process) and ...serpentinite ores (e.g. Magnifin process) was performed. The two technologies have been utilised by many producers around the world to deliver specialty magnesium products. Using theoretical values of heat of reaction obtained from HSC (H-enthalpy, S-entropy and Cp-heat capacity) software simulations and the practical thermal efficiency of roasting and pyrohydrolysis equipment, greenhouse gas (GHG) emissions of 2.7–5.6 kg CO2eq/kg MgO and 1.6–3.3 kg CO2eq/kg Mg(OH)2 were estimated for the process treating a bischofite brine. The corresponding figures calculated for the process recovering magnesium values from a serpentinite ore were determined as 3.8–7.5 kg CO2eq/kg MgO and 2.6–5.2 kg CO2eq/kg Mg(OH)2. They are somewhat comparable to MgO's carbon footprint of 3.1–4.5 kg CO2eq/kg MgO from Chinese producers using one-stage magnesite calcination to produce caustic calcined magnesia (∼92% purity). From a carbon footprint perspective, it is apparent that the brine process provides the lowest environmental burdens compared to the serpentinite and magnesite routes.
•2.7–5.6 kg CO2eq/kg MgO and 1.6–3.3 kg CO2eq/kg Mg(OH)2 were estimated for a brine process.•3.8–7.5 kg CO2eq/kg MgO and 2.6–5.2 kg CO2eq/kg Mg(OH)2 were determined for a serpentinite route.•HSC software was used for simulations to calculate energy requirements and CO2 emissions.•The brine route provides the lowest environmental burdens compared to other schemes.
We present a model to describe carbon dioxide (CO2) capture using reactive silicate-based mineral slurries exposed to a gas flow containing CO2. The model is validated through experimentation using ...thermally conditioned or heat-activated serpentinite (hydrous metamorphic ultramafic rock) in a laboratory-scale bubble column reactor. The kinetic model developed advocates a holistic modeling approach, offering an expanded view of the dissolution of heat-activated serpentinite under lean CO2 conditions, in which the gas–liquid–solid system and its influence on CO2 dissolution and the coupled dissolution behavior of the material are considered in their entirety. Modeling incorporates the characteristics of the gas to liquid phase interaction, such as CO2 composition of the gas phase and interfacial area, the composition of the aqueous phase and its temperature, and compositional and morphological features of the solid. We demonstrate that such an approach is essential when considering proton-limiting conditions that are especially relevant to mineral dissolution under dilute CO2 conditions in short reaction timeframes. The model is of particular relevance to the use of reactive silicate-based minerals for the aqueous capture of CO2 from dilute CO2 gas streams. The model as developed can be used to predict CO2 capture using heat-activated serpentinite slurries for a given set of operating conditions and should be adaptable for use with other alkaline materials of defined reactivity in similar or varying reaction settings by adequately specifying reaction conditions.
Positively identifying serpentine mineral types is important for a wide range of disciplines in the Earth sciences and health sciences. Although Raman spectroscopy has been widely applied as a tool ...to distinguish four of the main serpentine minerals (i.e., antigorite, lizardite, chrysotile, and polygonal serpentine), some uncertainty remains as to whether all four varieties have unique Raman spectra. In this paper, submicron Raman spectroscopy mapping was performed directly on electron‐transparent regions of serpentine samples that were unambiguously identified by transmission electron microscopy (TEM). The increased spatial resolution of the Raman mapping technique (~370 nm), combined with the detailed characterization provided by TEM, indicates that polygonal serpentine has the same Raman spectrum as lizardite and therefore cannot be spectrally distinguished from lizardite. Furthermore, the Raman spectral profile that has previously been reported as unique to polygonal serpentine is likely to represent a mixture of chrysotile and polygonal serpentine/lizardite. To positively discriminate between lizardite and polygonal serpentine requires TEM investigation.
Submicron Raman spectroscopy mapping was performed directly on electron‐transparent regions of serpentinite samples that were characterised by transmission electron microscopy (TEM). The unambiguous identification of serpentine mineral types provided by TEM, combined with the spatial resolution of the Raman mapping technique (approximately 370‐nm resolution), indicates that polygonal serpentine has the same Raman spectrum as lizardite and therefore they cannot be spectrally distinguished.
Serpentine soils have long fascinated biologists for the specialized floras they support and the challenges they pose to plant survival and growth. This volume focuses on what scientists have learned ...about major questions in earth history, evolution, ecology, conservation, and restoration from the study of serpentine areas, especially in California. Results from molecular studies offer insight into evolutionary patterns, while new ecological research examines both species and communities. Serpentine highlights research whose breadth provides context and fresh insights into the evolution and ecology of stressful environments.
We chose two glass compositions suitable for the synthesis of foam glass. The influence of additive at the amorphous silica charge in the amount of 20% and 100%, a by-product in the leaching of ...serpentinite, was studied. By the method of stable temperature drop, the crystallization ability of the welded glass compositions was studied. The surface tension was measured by the sessile drop method.
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