Comparative Study of Different Types of Waterproofing Screeds with a Focus on Cohesion with Selected Building Materials after the Freeze-Thaw Exposure

The aim of the research was focused on the functionality of three types of waterproofing screeds from the perspective of their use in building structures. Bitumen, polymer, silicate (mineral) were studied in terms of their cohesion with the substrate and their sealing ability, used in combination with different building materials—ceramics, concrete, lime-sand bricks and marl stone, the permeability properties of which were taken into consideration, too. The cohesion was also studied after the freeze-thaw exposure to take into account the aspects of durability. During the experimental program, the basic waterproofing ability of all types of tested screeds applied on building materials was confirmed. Comparing the overall tested screeds, despite the best adhesion of the polymer-based screed, this material exhibited the lowest durability after the freeze-thaw exposure. The bitumen and silicate (mineral) screed attained similar values of adhesion to the studied base materials. However, they differ in their ability to withstand freeze-thaw cycles over time. The modified water permeability test on model masonry specimens was performed. No leakage of water during the test was monitored for the specimens with all types of applied screeds over time, and, in addition, water had not penetrated through the bricks, nor through the joints. The waterproofing effect of the screed is not affected by the joints in masonry.

Strong Pyro-Electro-Chemical Coupling of Elbaite/H2O2 System for Pyrocatalysis Dye Wastewater

Elbaite is a natural silicate mineral with a spontaneous electric field. In the current study, it was selected as a pyroelectric catalyst to promote hydrogen peroxide (H2O2) for dye decomposition due to its pyro-electro-chemical coupling. The behaviors and efficiency of the elbaite/H2O2 system in rhodamine B (RhB) degradation were systematically investigated. The results indicate that the optimal effective degradability of RhB reaches 100.0% at 4.0 g/L elbaite, 7.0 mL/L H2O2, and pH = 2.0 in the elbaite/H2O2 system. The elbaite/H2O2 system exhibits high recyclability and stability after recycling three times, reaching 94.5% of the degradation rate. The mechanisms of RhB degradation clarified that the hydroxyl radical (·OH) is the main active specie involved in catalytic degradation in the elbaite/H2O2 system. Moreover, not only does elbaite act as a pyroelectric catalyst to activate H2O2 in order to generate the primary ·OH for subsequent advanced oxidation reactions, but it also has the role of a dye sorbent. The elbaite/H2O2 system shows excellent application potential for the degradation of RhB.

A Combination of Genomics, Transcriptomics, and Genetics Provides Insights into the Mineral Weathering Phenotype of Pseudomonas azotoformans F77

Silicate mineral weathering (dissolution) plays important roles in soil formation and global biogeochemical cycling. In this study, a combination of genomics, transcriptomics, and genetics was used to identify the molecular basis of mineral weathering activity and acid tolerance in Pseudomonas azotoformans F77. Biotite was chosen as a silicate mineral to investigate mineral weathering. The genome of strain F77 was sequenced, and the genes significantly upregulated when grown in the presence of biotite included mineral weathering-related genes associated with gluconic acid metabolism, flagellar assembly, and pilus biosynthesis and acid tolerance-related genes associated with neutralizing component production, reducing power, and proton efflux. Then, the biotite-weathering behaviors of strain F77 and its mutants that were created by deleting the tkt , tal , gntP , potF , nuoF , and gdtO genes, which are involved in gluconic acid metabolism and acid tolerance, respectively, were determined. The Fe and Al concentrations in the strain F77-inoculated medium increased 2.2- to 13.7-fold compared to the controls. The cell numbers of strain F77 increased over time, while the pH values in the medium ranged from 3.75 to 3.90 between 20 and 36 h of incubation. The release of Al and Fe was significantly reduced in the mutants F77Δ tal , F77Δ gntP , F77Δ potF , and F77Δ nuoF . Bacterial growth was significantly reduced in the presence of biotite in the mutants F77Δ potF and F77Δ nuoF . Our results demonstrated the acid tolerance of strain F77 and suggested that multiple genes and metabolic pathways in strain F77 are involved in biotite weathering and acid tolerance during the mineral weathering process. IMPORTANCE Acid production and tolerance play important roles in effective and persistent mineral weathering in bacteria, although the molecular mechanisms governing acid production and acid tolerance in bacteria have not been fully elucidated. In this study, the molecular mechanisms underlying biotite (as a silicate mineral) weathering (dissolution) and acid tolerance of P. azotoformans F77 were characterized using genomics, transcriptomics, and genetics analyses. Our results showed that the genes and metabolic pathways for gluconic acid metabolism, flagellar assembly, and pilus biosynthesis may play important roles in mineral weathering by strain F77. Notably, the genes associated with neutralizing component production, reducing power, and proton efflux may be related to acid tolerance in strain F77. The expression of these acid production- and acid tolerance-related genes was observed to be increased by biotite in strain F77. Our findings may help to elucidate the molecular mechanisms governing mineral weathering and, especially, acid tolerance in mineral-weathering bacteria.

Palaeo-environmental evolution of Central Asia during the Cenozoic: new insights from the continental sedimentary archive of the Valley of Lakes (Mongolia)

The Valley of Lakes basin (Mongolia) contains a unique continental sedimentary archive, suitable for constraining the influence of tectonics and climate change on the aridification of Central Asia in the Cenozoic. We identify the sedimentary provenance, the (post)depositional environment and the palaeo-climate based on sedimentological, petrographical, mineralogical, and (isotope) geochemical signatures recorded in authigenic and detrital silicates as well as soil carbonates in a sedimentary succession spanning from ∼34 to 21 Ma. The depositional setting was characterized by an ephemeral braided river system draining prograding alluvial fans, with episodes of lake, playa or open-steppe sedimentation. Metamorphics from the northern adjacent Neoarchean to late Proterozoic hinterlands provided a continuous influx of silicate detritus to the basin, as indicated by K–Ar ages of detrital muscovite (∼798–728 Ma) and discrimination function analysis. The authigenic clay fraction is dominated by illite–smectite and “hairy” illite (K–Ar ages of ∼34–25 Ma), which formed during coupled petrogenesis and precipitation from hydrothermal fluids originating from major basalt flow events (∼32–29 and ∼29–25 Ma). Changes in hydroclimate are recorded in δ18O and δ13C profiles of soil carbonates and in silicate mineral weathering patterns, indicating that comparatively humid to semi-arid conditions prevailed in the late(st) Eocene, changing into arid conditions in the Oligocene and back to humid to semi-arid conditions in the early Miocene. Aridification steps are indicated at ∼34–33, ∼31, ∼28 and ∼23 Ma and coincide with some episodes of high-latitude ice-sheet expansion inferred from marine deep-sea sedimentary records. This suggests that long-term variations in the ocean–atmosphere circulation patterns due to pCO2 fall, reconfiguration of ocean gateways and ice-sheet expansion in Antarctica could have impacted the hydroclimate and weathering regime in the basin. We conclude that the aridification in Central Asia was triggered by reduced moisture influx by westerly winds driven by Cenozoic climate forcing and the exhumation of the Tian Shan and Altai Mountains and modulated by global climate events.

Silicate Mineral Eutectics with Special Reference to Lithium

In this paper, the system of natural mineral alkali fluxes used in typical mineral industry technologies was analyzed. The main objective was to reduce the melting temperature of the flux systems. Particular attention was paid to the properties of lithium aluminium silicates in terms of simplifying and accelerating the heat treatment process. In this area, an alkaline flux system involving lithium was analyzed. A basic flux system based on sodium potassium lithium aluminosilicates was analyzed; using naturally occurring raw materials such as spodumene, albite and orthoclase, an attempt was made to obtain the eutectic with the lowest melting point. Studies have shown that there are two eutectics in these systems, with about 30% spodumene content. The active influence of sodium feldspar was found.

Mechanical Properties of Eco-Friendly and Energy-Saving Mortar with Porous Feldspar

ABSTRACTPorous feldspar is a silicate mineral that is made up of more than 80% of SiO2 and Al2O3 as components. It has a large specific surface area than sand. It has an excellent reactivity with cement as a pozzolanic component. A normal mortar as a construction material is composed of 75% of sand and 25% of cement. Carbon dioxide (CO2) is a cause of environmental pollution. It is often made when making cement contained in mortar. Therefore, it is necessary to study alternative materials that can reduce the amount of cement used. This study was conducted using feldspar as a fine aggregate instead of sand. First, feldspar was standardized through physical testing. Compressive strength tests were then carried out to compare feldspar mortar and sand-based mortar. Hydration products of mortars were confirmed using a scanning electron microscope (SEM). Result of these tests revealed that when feldspar was used, the compressive strength tended to be high. In this study, Case 3 consisting of feldspar 80% and cement 20% with reduced use of cement was found to be the most suitable one. Secondly, to confirm the appropriateness of using feldspar mortars as a floor material, thermal conductivity and thermal efficiency experiments were conducted using mortars with ingredients that differed from a normal mortar. Results of these experiments revealed that feldspar mortar was more effective as an insulating material than a normal mortar because it had lower thermal conductivity and longer heat retention time than a normal mortar. Therefore, the use of feldspar mortar could have an energy reduction effect compared to a normal mortar as a flooring material in an ondol (under-heating) type floor-heating system in Korea.

The best temperature range to acquire reliable thermal infrared spectra from orbit

Solar System bodies undergo to daily and periodical variations of temperature that mainly depend on their closeness to the Sun. It is known that mineral expansion and contraction due to such variations modify the thermal infrared spectra acquired on solid surfaces. Therefore, it becomes crucial to know the best temperature range at which the acquisition itself should be carried out to get reliable information on the mineralogy of such bodies. Here we provide the thermal expansion of olivine between 20 and 298 K determined by X-ray diffraction. Our data reveal the non-linear behaviour of silicates that undergo to low temperatures, where volume variations appear positively correlated with temperatures. Subtle bond-length variations occurring at low temperatures are then expected to minimally affect vibrational absorption positions. We suggest that thermal infrared spectra of those Solar-System surfaces that are not exceeding 300 K provide reliable information about not only the silicate mineral identification but also on their chemical composition, regardless of the instantaneous temperature.

Influence of the ore reduction method on the percolation leaching efficiency

This paper covers gold leaching from sulfide ores. The data on the silicate, mineral, and grain-size composition are presented for the ore studied. Agitation leaching studies were completed for the combined sample and direct cyanidation dynamics indicators are established for the material sample. For all material with the grain size class of 95 % passing –0.074 mm, the required agitation leaching duration is 9–10 hours; with the material sizes up to 2 mm, the leaching duration shall be at least 22 hours. In order to study the efficiency of using roller presses as an alternative to fine crushing, two percolation leaching tests were conducted for the ore size of –5 mm. The material for the first test was prepared by crushing in a standard jaw crusher and the material for the second test was prepared by crushing in a laboratory press with complex monolayer reduction. It has been found that ore reduction using high-pressure crushers, as compared to standard crushing equipment, allows increasing gold recovery during subsequent leaching by 13.52 %. At the same time, the consumption of sodium cyanide increases by 0.26 kg/t of ore.