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Purpose: To evaluate the distortion probability in impressions of completely dentate arches when different impression materials are used in relation to operator experience. Materials and Methods: A total of 28 students (Group A) and 7 dentists (Group B) performed three maxillary impressions on 28 participants, each using vinyl siloxane ether (VSE), polyether (PE), and irreversible hydrocolloid (IHC). Gypsum master casts were fabricated and subsequently digitized. Intraoral scans were taken as a control. Differences between master casts and intraoral scans were visualized with heatmaps, and planar deviations were investigated. If planar deviations > 120 µm were found, the impression was rated as "distorted." An additional superimposition using the casts from VSE or PE was performed to confirm the presence of distortions. The relative number of surfaces with distortions in each impression was calculated. The procedure was repeated for a distortion threshold of 500 µm. The statistical analyses included repeated measures ANOVA (RMA) and post hoc tests (a < .05). Results: When 120 µm was considered as the threshold for distortions, IHC impressions showed higher distortion probability than PE impressions in Group A (P = .003) and Group B (P < .0001). In Group B, PE showed a lower distortion probability than VSE (P = .02). There was no significant difference between the study groups (P = .42). Considering 500 µm as a threshold for distortions, there was no difference between impression materials (P = .17) or study groups (P = .53). Conclusions: There were no statistically significant differences in relation to operator experience. Different impression materials had a significant impact on distortion probability. PE impressions showed the lowest distortion probability. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the in vitro accuracy of impressions obtained with two silicone and corresponding stone models using two laboratory scanners. Materials and Methods: A master model with synthe:c resin teeth with two single-unit crown prepara:ons was created and scanned using a 12-megapixel scanner. Five conven:onal impressions of the physical model were prepared with different silicone impression systems (Zhermack and Coltene) using the double-mix technique and poured with gypsum. The impressions and stone models obtained were scanned using two extraoral scanning systems (Iden:ca T500, Medit; S600 ARTI, Zirkonzahn). All best-fit superimposi:ons of the teeth areas were conducted between the master model and the scans of the impressions and models obtained with the two scanners. A P < .05 level was considered significant. Results: The Iden:ca T500 Medit scanner showed an accuracy of 102.34 (89.67, 115.01) µm for Coltene silicone and 79.51 (67.82, 91.21) µm for Zhermack silicone, while the S600 ARTI Zirkonzhan scanner presented 110.79 (98.24, 123.33) µm and 91.91 (81.29, 102.54) µm, respec:vely, with significant differences between scanners for Zhermack silicone (P = .008) and for the corresponding stone models (P = .002). Zhermack silicone presented overall discrepancies lower than Coltene silicone, with sta:s:cally significant differences in both scanners analyzed (P < .001; P = .017). However, the discrepancies found were within clinically acceptable values. With the Zirkonzahn scanner, discrepancies found in the Zhermack impressions were lower than in the corresponding stone models (P < .001). Conclusions: The direct digi:za:on of silicone impressions with laboratory scanners presented comparable results to conven:onal techniques with stone models. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South-Central Minzu University (Natural Science Edition) is the property of Journal of South-Central Minzu University (Natural Science Edition) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The World Bank study predicts that 4 °C warming will bring high temperatures, sea-level rise, and saltwater intrusion to coastal areas, damaging coastal concrete structures. Increased CO2 from industrialization exacerbates this, necessitating durable, low-carbon concrete. Combined use of fly ash (FA) and ground granulated blast furnace slag (GGBFS) as high-volume OPC replacements boosts performance while reducing concrete's carbon footprint. In this perspective current study examines the durability of concrete against aggressive agents (H2SO4, MgSO4, NaCl, and CO2) causing premature deterioration of concrete structures. Initially, three cost-effective sustainable concrete mix designs were developed, incorporating 50% replacement of OPC with locally available supplementary cementitious materials, specifically FA and GGBFS. These mixes were then evaluated for their mechanical and durability performances. The impact of aggressive ions (SO42−, Cl−, and CO32−) was studied by examining the changes in mechanical performance and phase assemblages. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) techniques were used to estimate the phase compositions. Ternary blended concrete having 50% OPC+ 30% GGBFS + 20% FA exhibited optimal synergistic performance, enhancing pozzolanic and hydraulic reactions for better resistance to harmful ions. The sorptivity test confirmed that as the GGBFS content increased, the sorption rate decreased, indicating the higher reactive nature of GGBFS to that of FA. Deleterious compounds formed due to the action of SO42-, Cl-, and CO32- were identified to be ettringite (Ca6Al2(SO4)3(OH)12.32H2O, AFt) and gypsum (CaSO4.2H2O, Gy), Friedel's salt (Ca4Al2(OH)12Cl2.4H2O, Fs) and polymorphs of calcium carbonate (CaCO3), respectively through TG mass loss curve. These results were corroborated by FTIR analysis, which showed predominant characteristic bands at 662 cm−1 for SO42−, 459 cm−1 for Mg–O stretching, 790 cm−1 for Al–OH bending, and 1431-1443 cm−1 for C–O, confirming the presence of the deleterious compounds. [ABSTRACT FROM AUTHOR]

Understanding the dynamics of rock mass behavior necessitates the study of seismic waves generated by various sources of vibration within rocks. Joints and fractures are prevalent in rock masses and substantially impact their dynamic response to seismic waves. The present study has identified natural rubber latex (NRL) as an effective energy-absorbing medium in the rock masses for limiting wave propagation across the joint. Gypsum plaster has been used to replicate the natural rocks as a model material for conducting this study. The damping properties of rock mass have been determined using split shear plate (SSP) and resonant column (RC) tests. The mechanical response of intact gypsum plaster and NRL has been examined using resonant column testing. The influence of the thickness of the NRL layer on the damping characteristics of the jointed rock mass was studied by varying the thickness of the NRL layer within the joints from 2 to 5 mm. Using RC testing, the variations of shear moduli and damping ratios with different thicknesses of NRL have been studied. The variations of transmission coefficient (T), absorption coefficient (A), and reflection coefficient (R) with variable NRL thickness have been investigated utilizing SSP testing. The findings of the present study can be applied to developing numerical models that can anticipate the behavior of rock masses under dynamic loading conditions and for utilizing the NRL as an effective energy-absorbing material in the rock mass to reduce the vibrations that are transmitted to the structures. Practical Applications: The utilization of natural rubber latex (NRL) as an infill material in rock masses presents promising practical applications across various engineering domains. Its application extends to tunneling, mining, and stabilizing rock slopes. In tunneling and mining, NRL aids in increasing ground stability and controlling water intrusion during excavation, thereby enhancing safety and efficiency. In addition, it proves beneficial in stabilizing roofs and walls and preventing water and gas infiltration in mining operations. NRL reinforces joints within rock masses, reducing permeability and enhancing structural integrity. NRL stands out for its environmentally friendly and sustainable nature compared to synthetic polymers. Research indicates that NRL-stabilized soil has a lower carbon footprint than traditional cement-stabilized soil, thus offering an ecofriendly solution. Moreover, NRL presents opportunities for repurposing waste materials and reducing the environmental impact of concrete production. This study pioneers the application of NRL for vibration damping in jointed rocks, expanding the understanding of its dynamic properties under shear wave propagation. Through resonant column and split shear plate tests, this research explores the influence of NRL thickness on wave propagation, providing valuable insights for engineering practices in rock-dominated environments. [ABSTRACT FROM AUTHOR]

Polyhalite-based POLY4, a multi-nutrient source containing potassium, calcium, magnesium, and sulphur, is increasingly recognised for its potential to improve crop yields and soil health in agricultural systems. It is also been considered as a feasible approach for addressing the deficiency in potassium, calcium, and sulphur within a single application source. The present study aimed to investigate the impact of polyhalite-based POLY4 application, either as a complete or partial substitute for traditional potassium fertiliser and gypsum supplement, on the improvement of peanut (Arachis hypogaea) growth and soil quality. An extensive field study was conducted from 2021 and 2022, employing ten distinct nutrient management treatments with three replications in a randomised complete block design. The findings of the study indicated that the application of polyhalite (POLY4) in conjunction with only NP fertilisers resulted in a higher yield advantage (approximately 150-200 kg ha-1) than in plots treated with NPK + gypsum (at 500 kg ha-1) and control plots. The application of polyhalite-based fertiliser (POLY4) at a rate that was 100% equivalent to K along with NP fertilisers resulted in a significant increase in pod yield (5.3-12.8%) over NPK + gypsum and control plots. Thus, the increased crop yield led to an increase in gross returns of 4.88% and in net returns of 4.28% with the application of POLY4 (100%) + NP fertilisers over other treatments. Likewise, variable rates of conventional fertilisers along with POLY4 (100% recommended) + NP + gypsumat 310 kg/ha significantly increased the linoleic acid content (38.5%), oleic acid content, and oil content (48.1%) by reducing palmitic acid (11.96%) content in the groundnut seed. Interestingly, POLY4 use at the 50% recommended rate also resulted in yields that were comparable with those obtained with 100% NPK. Therefore, applying POLY4, a polyhalite fertiliser, in either a 100% or 50% equivalent of essential K can be an effective way of increasing the production of peanut crops and promoting agricultural sustainability. [ABSTRACT FROM AUTHOR]

With the continuous development of underground engineering construction in China, it is particularly important to study the identification of structural plane characteristics of rock masses. In this study, three types of pseudo-rock specimens with structural plane interlayers were fabricated to analyze the patterns of drilling parameter changes in rock bodies with structural planes during the drilling process and to explore the characterization and identification methods of rock body structural planes. Gneiss, granite, and sandstone were used as rock materials, with gypsum mortar as the interlayer material for the structural planes in these three types of specimens. The indoor digital drilling equipment was utilized for conducting indoor digital drilling experiments. The variation patterns of drilling parameters in rock bodies with structural surfaces under different interlayer inclinations and thicknesses were analyzed. The relationship between the ratio of the change in rotational speed and drilling speed during the stable phase of the upper rock mass and the peak torque and peak drilling pressure has been established. The relationship between the structural plane inclination angle and the ratio of change in rotational speed and drilling speed has been determined. By utilizing the variation in these ratios, the impacts of the structural plane inclination angle and the thickness of the structural plane on the peak torque and peak drilling pressure have been elucidated. The research results provide a theoretical basis for the stability evaluation of rock masses with structural planes under drilling action. [ABSTRACT FROM AUTHOR]

Water film thickness (WFT) is a primary factor influencing the flowability of cement mortar and gypsum slurry. However, conventional WFT calculation models have overlooked the impact of fiber surface properties on flowability. This study addresses this issue by introducing a parameter called the residual moisture distribution coefficient into the residual moisture distribution coefficient (RMDC) and the WFT calculation model. Thirty-six groups of basalt fiber-Phosphogypsum composite slurry with varied mix proportions were designed and assessed for their flowability and packing density. The RMDC and WFT were derived from fitting with the improved model. Finally, a basalt fiber-Phosphogypsum composite slurry flowability prediction model based on WFT was established, laying a foundation for the design and further application of fiber-gypsum composite flowability. [ABSTRACT FROM AUTHOR]

Typical condensate reservoirs have been developed in the No.4 fault zone of the Shunbei area in the Tarim Basin. However, exploration expansion is restricted due to the unclear genetic mechanisms and main controlling factors of condensate accumulation. Through a comprehensive analysis of organic geochemical characteristics and the regional geological background, the genetic mechanisms and main controlling factors of condensate accumulation in the No.4 fault zone of the Shunbei area have been identified, and the following understandings are mainly obtained: (1) the condensate oil and gas reservoirs in the No.4 fault zone of the Shunbei area are mainly primary condensate reservoirs, and their formation is mainly affected by differential maturation of organic matter, multi-phase accumulation, and secondary alteration; (2) the overall secondary effects on the condensate oil and gas reservoirs in the Shunbei No.4 fault zone are relatively weak, however, the secondary effect experienced by the middle and southern sections is relatively stronger compared to the northern section; these secondary processes include oil cracking, gas invasion, and thermochemical sulfate reduction (TSR); and (3) the enrichment degree of condensate oil and gas reservoirs in the northern section of the Shunbei No.4 fault zone is significantly higher than in the middle and southern sections; the enrichment and high production of condensate oil and gas are mainly controlled by transport conditions and reservoir scale. Stronger fault activity, better transport conditions, larger reservoir size, and thinner gypsum-salt rock layers facilitate the upward migration of oil and gas along strike-slip faults, leading to higher production and enrichment of condensate. [ABSTRACT FROM AUTHOR]

Incorporating waste to produce new environmentally friendly construction products has become one of the great challenges of the industry nowadays. The aim of this research is to analyse the behaviour of novel gypsum composites against water action, incorporating recycled rubber aggregates (up to 8.5% vol.) and dissolved expanded polystyrene (up to 10.0% vol.). To this end, a total of 10 dosages have been proposed with the progressive substitution of natural resources by these secondary raw materials. The results show how it is possible to reduce the total water absorption of the gypsum composites by up to 8.3% compared to traditional gypsum material. In addition, it is also possible to reduce water absorption by capillary by up to 52.7%, resulting in lighter composites with good performance against water action. In all composites analysed, the mechanical strengths exceeded the minimum values of 1 MPa in bending and 2 MPa in compression, making them an optimal solution for the development of lightweight prefabricated products for damp rooms. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Petroleum Geology & Oilfield Development in Daqing is the property of Editorial Department of Petroleum Geology & Oilfield Development in Daqing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Complex underground conditions make it challenging to conduct extensive coring, and it is difficult for laboratories to carry out a large number of rock mechanics experiments due to the limited number of cores. Rock-like specimens are commonly used in the laboratory to replace coal-rock specimens. In this paper, rock-like specimens with different proportions are produced to study the mechanical properties, failure characteristics, and acoustic emission laws of rock-like specimens under uniaxial compression. The results show that when the rock-like specimen does not contain gypsum, the stress of the specimen decreases rapidly after reaching the peak stress, which is similar to the mechanical properties of hard brittle rock. When the rock-like specimen contains gypsum, the stress of the specimen decreases slowly after reaching the compressive limit, and the failure of the specimen is gentle, which is similar to the mechanical properties of soft rock. When the specimen lacks gypsum, the strength of the rock-like specimen is larger, and the strength of the specimen is positively correlated with the proportion of cement. When the specimen contains gypsum, the strength of the rock-like specimen decreases sharply, and the strength of the rock-like specimen is negatively correlated with the proportion of gypsum. The maximum acoustic emission ringing count increases with higher cement content but decreases with increased gypsum content. The cumulative count change of acoustic emissions approximately underwent four stages, aligning well with the four stages of uniaxial compression failure observed in typical rock. The research results have important reference value for the selection of rock-like materials to replace the original rock materials for laboratory research. [ABSTRACT FROM AUTHOR]

Steel structures are vulnerable to fire due to the degradation of their mechanical properties at high temperatures, making it necessary to protect them when exposed to high temperatures. This paper presents the results of an experimental research work to characterise the mechanical properties of gypsum-based fire-resistant mortars with and without nano and micro silica particles by destructive and non-destructive tests at ambient temperature. Five compositions were studied: one commercial composition was used as a reference and four were developed in the laboratory. Two were based on gypsum with perlite or vermiculite, and the other two included nano and micro silica particles. Twenty specimens underwent ultrasonic pulse velocity, flexural, and compression tests, while five specimens were tested by the impulse excitation of vibration. Young's modulus, shear modulus, and Poisson's ratio were assessed by non-destructive tests, and the flexural and compression strengths were assessed by destructive tests. Additional tests included density and porosity assessments, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. Results indicated that adding nano and micro silica particles posed challenges to the mechanical and physical properties. Despite this, vermiculite compositions showcased superior or similar properties to the commercial composition, while perlite compositions exhibited slightly lower properties. [ABSTRACT FROM AUTHOR]

Phosphogypsum is a common industrial solid waste that faces the challenges of high stockpiling and low utilization rates. This study focuses on the mechanical properties and internal characteristics of cementitious materials with a high phosphogypsum content. Specifically, we examined the effects of varying amounts of ground granulated blast furnace slag (5–28%), fly ash (5–20%), and hydrated lime (0.5–2%) on the stress–strain curve, unconfined uniaxial compressive strength, and elastic modulus (E50) of these materials. The test results indicate that increasing the ground granulated blast furnace slag content can significantly enhance the mechanical properties of phosphogypsum-based cementitious materials. Additionally, increasing the fly ash content can have a similar beneficial effect with an appropriate amount of hydrated lime. Furthermore, microscopic analysis of the cementitious materials using a scanning electron microscope revealed that the high sulfate content in phosphogypsum leads to the formation of calcium aluminate as the main product. Concurrently, a continuous reaction of the raw materials contributes to the strength development of the cementitious materials over time. The results could provide a novel method for improving the reusing phosphogypsum amount in civil engineering materials. [ABSTRACT FROM AUTHOR]

Recently, plaster has gained increasing attention as a mechanical and environmentally friendly option and is an effective alternative to traditional cement products. Additionally, polyester has an effective impact on the mechanical properties of materials, in addition to being one of the most environmentally friendly materials. However, studies are still ongoing to reach the best ratios of polyester resin, polyester hardener, and gypsum plaster that can improve mechanical properties. This research aims to investigate the impact of these components at various ratios (30%, 45%, and 60%) of gypsum plaster weight on the mechanical properties of plaster material. This study is carried out by conducting compression and tensile tests for three ratios, which are considered among the most important mechanical tests according to their applications. In addition, the environmental emissions resulting from the three different ratios of plaster are evaluated to determine their environmental impact. This study found that the largest ratio (30%) was the most effective from an economic and mechanical point of view, while achieving lower carbon emissions compared to the other ratios, which enhances the trend towards achieving the environmental goals of the Kingdom of Saudi Arabia's Vision 2030 to reach zero emissions. This study is highly significant both in terms of scientific research and practical application across a range of industries, since it integrates the enhancement of material performance with the achievement of environmental sustainability requirements. [ABSTRACT FROM AUTHOR]

This study investigated a binary blend of calcium sulfoaluminate cement and fly ash with a target compressive strength of more than 32.5 MPa based on the EN 197-1 standard, using as much fly ash as possible. In the binder system of calcium sulfoaluminate cement and fly ash, a decrease in the replacement level of fly ash results in an increase in compressive strength. Mortar with a 40% replacement level of fly ash for calcium sulfoaluminate cement and added gypsum shows 49.41 MPa strength at 28 d. Its hydrates are hydroxy-AFm, ettringite, crystalline aluminum hydroxide, amorphous aluminum hydroxide, strätlingite, and monosulfate. They are attributed to the hydration of ye'elimite, C2S, and C3A in calcium sulfoaluminate cement. The reactivity of fly ash is not observed until 28 d of hydration. The formation of ettringite is the main cause of the gains in compressive strength. [ABSTRACT FROM AUTHOR]

Calcium sulfoaluminate belite (CSAB)-based cement exhibits useful properties such as low CO2 footprint, high early-age strength and shrinkage compensating behavior. Our previous study examined the mechanism of carbonation in CSAB-based binder and reported a higher degree of carbonation in CSAB-based binder compared to Portland cement (PC) binder. This study examines the admixing strategies to improve the carbonation resistance of CSAB-based binders. The addition of gypsum or calcium hydroxide reduced the carbonation depth (in natural and accelerated environments) in the CSAB binder. Gypsum addition reduced the pH and resulted in pore refinement. Whereas calcium hydroxide addition increased the pH and promoted the formation of monosulfate (AFm). Although the carbonation depth was reduced in the presence of gypsum or calcium hydroxide, the addition of calcium hydroxide offered a better admixing strategy due to its higher pH which is crucial for the passivation of reinforcement. [ABSTRACT FROM AUTHOR]

In this paper, the dihydrate–hemihydrate recrystallization method was employed to produce β-hemihydrate gypsum. The effects of thermodynamic conditions such as temperature, sulfuric acid concentration, and phosphoric acid concentration on the removal of F and P impurities were investigated. Kinetic studies revealed that the throughflow impeller, when compared to the conventional impeller, demonstrates a higher removal rate for soluble phosphorus, while having little impact on soluble fluorine. This study contributes to the utilization of PG resources. [ABSTRACT FROM AUTHOR]

Localized leaching method is a new reclamation leaching technique. Localized leaching method by using drip tapes allows water to be applied directly to the areas of salt accumulation. This study applied localized leaching method on a sandy loam soil in a pistachio orchard in Kerman, Iran to evaluate the impact of three treatments: adding gypsum soil remediation (G), soil remediation with sulfuric acid (SA) andirrigation water (IW) on soil remediation. Three treatments (IW, G and SA) in four repetitions were used to remove soluble salts from the Main Active Root Zone (MARZ) in a pistachio orchard which irrigated by a subsurface irrigation system. The localized leaching method consist of two T-tape pipelines at a distance of 40 cm located on both sides of the tree rows. Soil sampling was carried out before and after leaching from soil unit profiles with 80 cm (Length) × 120 cm (Depth) with 20 cm intervals. Concentrations of sodium (Na), magnesium (Mg), calcium (Ca) cations, and electrical conductivity (EC) were examined before and after leaching process. Results revealed that application of G-treatment compared to IW-treatment and SA-treatment led to more leaching of Na and Mg from the soil by 61% and 50%, respectively. The amount of leached Ca in both G-treatment and SA-treatments was less than that of IW-treatment. The leaching efficiency of total soluble salts for G, IW and SA treatments were 58%, 56% and 45%, respectively. Gypsum application could be recommended as a soil amendment. In addition, the localized leaching technique offers water-saving potential opposed to traditional leaching methods which applying water to the entire field. [ABSTRACT FROM AUTHOR]

This work is an attempt to understand and optimize the rare earth elements leaching from Moroccan phosphogypsum using a nitric acid solution. The Plackett–Burman statistical design was used to identify the statistically significant factors responsible for the optimum leaching conditions. With this purpose, the following seven variables were studied: nitric acid concentration (X1), solid‐to‐liquid ratio (X2), temperature (X3), leaching time (X4), stirring speed (X5), drying (X6), and particle size (X7). Given that the leaching recovery of rare earth elements is limited by the quantity of dissolved phosphogypsum, we examined two simultaneous responses, namely, the leaching efficiency of rare earth elements YREEs and the leaching efficiency of calcium YCa (dissolution rate of phosphogypsum). The predicted values of the two fitted models were in good agreement with the experimental values by a coefficient of determination (R2) equal to 98.6% and 96.50%, respectively. In the model of YREEs, only the effect of drying was found to be statistically insignificant with a p‐value greater than 0.05. Nitric acid concentration, solid‐to‐liquid ratio, and temperature are the only variables having a statistically significant effect in the model of YCa. At a dissolution rate of phosphogypsum equal to 30.13%, the leaching efficiency of rare earth elements from our sample has reached a maximum of 87.55%. The optimal experimental conditions are a nitric acid concentration of 3.3 M, a solid‐to‐liquid ratio of 1/9, a temperature of 75°C, a leaching time of 20 min, a stirring speed of 200 rpm, and d ≤ 100 µm as a particle size. [ABSTRACT FROM AUTHOR]

The modern construction industry is looking for new ecological materials (available, cheap, recyclable) that can successfully replace materials that are not environmentally friendly. Fibers of natural origin are materials that can improve the properties of gypsum composites. This is an important issue because synthetic fibers (hardly biodegradable—glass or polypropylene fibers) are commonly used to reinforce gypsum boards. Increasing the state of knowledge regarding the possibility of replacing synthetic fibers with natural fibers is another step towards creating more environmentally friendly building materials and determining their characteristics. This paper investigates the possibility of manufacturing fiber–gypsum composites based on natural gypsum (building gypsum) and hemp (Cannabis sativa L.) fibers grown in Poland. The effect of introducing hemp fibers of different lengths and with varying proportions of mass (mass of gypsum to mass of fibers) into the gypsum matrix was investigated. The experimental data obtained indicate that adding hemp fibers to the gypsum matrix increases the static bending strength of the composites manufactured. The highest mechanical strength, at 4.19 N/mm2, was observed in fiber–gypsum composites with 4% hemp fiber content at 50 mm in length. A similar trend of increased strength was observed in longitudinal tension. Again, the composite variant with 4% fiber content within the gypsum matrix had the highest mechanical strength. Manufacturing fibers–gypsum composites with more than 4% hemp fiber content negatively affected the composites' strength. Mixing long (50 mm) hemp fibers with the gypsum matrix is technologically problematic, but tests have shown a positive effect on the mechanical properties of the refined composites. The article indicates the length and quantity limitations of hemp fibers on the basis of which fiber–gypsum composites were produced. [ABSTRACT FROM AUTHOR]

Most earthen sites are located in open environments eroded by wind and rain, resulting in spalling and cracking caused by shrinkage due to constant water absorption and loss. Together, these issues seriously affect the stability of such sites. Gypsum–lime-modified soil offers relatively strong mechanical properties but poor water resistance. If such soil becomes damp or immersed in water, its strength is significantly reduced, making it unviable for use as a material in the preparation of earthen sites. In this study, we achieved the composite addition of a certain amount of sodium methyl silicate (SMS), titanium dioxide (TiO2), and graphene oxide (GO) into gypsum–lime-modified soil and analyzed the microstructural evolution of the composite-modified soil using characterization methods such as XRD, SEM, and EDS. A comparative study was conducted on changes in the mechanical properties of the composite-modified soil and original soil before and after immersion using water erosion, unconfined compression (UCS), and unconsolidated undrained (UU) triaxial compression tests. These analyses revealed the micro-mechanisms for improving the waterproof performance of the composite-modified soil. The results showed that the addition of SMS, TiO2, and GO did not change the crystal structure or composition of the original soil. In addition, TiO2 and GO were evenly distributed between the modified soil particles, playing a positive role in filling and stabilizing the structure of the modified soil. After being immersed in water for one hour, the original soil experienced structural instability leading to collapse. While the water absorption rate of the composite-modified soil was only 0.84%, its unconfined compressive strength was 4.88 MPa (the strength retention rate before and after immersion was as high as 93.1%), and the shear strength was 614 kPa (the strength retention rate before and after immersion was as high as 96.7%). [ABSTRACT FROM AUTHOR]

Although gypsum-based building materials exhibit many positive characteristics, solutions are still being searched for to reduce the use of gypsum or improve the physico-mechanical properties of board materials. In this study, an attempt was made to produce gypsum boards with hemp fibers. Although hemp fibers can be a specific reinforcement for gypsum-based board materials, they negatively affect the gypsum setting process due to their hygroscopic characteristics. Fibers impregnated with derivatives based on polyvinyl acetate, styrene–acrylic copolymer and pMDI (polymeric diphenylmethane diisocyanate) were used in this study. Gypsum–fiber boards produced with impregnated fibers showed approximately 30% higher mechanical properties as determined by the 3-point bending test. The positive effect of the impregnates on the hemp fibers was confirmed by FTIR (Fourier-transform infrared spectroscopy) and TG/DTA (thermogravimetric analysis/thermal gravimetric analysis) analysis. [ABSTRACT FROM AUTHOR]

To realize the resource utilization of solid waste (coal slime) and further the dual carbon goals, utilizing coal slime and coal ash as adsorbates for CO2 capture is crucial. This study employed low-temperature N2 adsorption, low-pressure CO2 adsorption, X-ray diffraction, X-ray fluorescence, and isothermal adsorption tests to assess coal slime and coal ash's pore/mineral composition characteristics. Subsequently, the influence on CO2 adsorption was analyzed to reveal the CO2 adsorption mechanisms of pores and clay minerals, and CO2 molecule adsorption behavior. The results showed that: (1) ashing led to reductions in total pore volume, specific surface area, micropore volume, and micropore specific surface area, accompanied by substantial decreases in micropores and mesopores; (2) ashing generated high-temperature stable mineral species, including quartz, andalusite, hematite, and gypsum, while all calcite decomposed into CaO; (3) coal slime exhibited greater CO2 adsorption capacity than coal ash, influenced by pore structure and clay minerals; (4) the adsorption behavior of coal slime and coal ash likely aligns with micropore filling theory, suggesting CO2 is adsorbed within the 0.30–1.47 nm pore structure. This research contributes to optimizing coal by-product utilization in mining areas and exploring adsorbate materials for CO2 sequestration in abandoned goaf. [ABSTRACT FROM AUTHOR]

Arable soil and crop productivity are severely affected by salinization. Therefore, soil amendments are an important measure for improving saline-alkali soil for agricultural development. Desulfurized gypsum is a common soil amendment that has been used repeatedly alongside organic materials to improve the biological, physical, and chemical properties of saline soil. This study takes the typical saline-alkali farmland soil in Yulin as the research object, and five treatments were established: a blank treatment (CK), a single application 2.5 t ha-1 of desulfurized gypsum (T), 2.5 t ha-1 of desulfurized gypsum and 1.5 t ha-1 of green manure (TL), application 2.5 t ha-1 of desulfurized gypsum and 1.5 t ha-1 of straw (TS), and 2.5 t ha-1 of desulfurized gypsum and 1.5 t ha-1 of organic fertilizer (TV). The results show that the TV treatment achieved a significant improvement in soil nutrients, organic carbon, enzyme activity, and maize yield. In 2022 (2023), the compared of organic matter, TN, TP, TK, AP, and AK increased significantly compared with the CK treatment when the TV treatment was applied. Soil phosphatase activity (SPA), soil urease activity (SUA) and soil sucrase activity (SSA) significantly higher in the TV treatment compared with the other treatments and increased significantly over the two-year period. Furthermore, soil organic carbon (SOC), easily oxidizable organic carbon (EOC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC) also significantly increased with the 2022 and 2023 TV treatments. Correlation analysis revealed a positive relationship between maize yield and soil nutrients, organic carbon, and enzyme activity (P < 0.05). Thus, the TV treatment was determined to be the optimal treatment for soil improvement. This conclusion was supported by analyses performed using membership function analysis, gray correlation analysis, and entropy TOPSIS model evaluation. Therefore, this method increases soil quality, improves soil fertility, achieves high maize yields, and provides a scientific basis for enhancing and utilizing saline-alkali soil in the Loess Plateau. [ABSTRACT FROM AUTHOR]

Microorganisms inhabiting gypsum have been observed in environments that differ greatly in water availability. Gypsum colonized by microorganisms, including cyanobacteria, eukaryotic algae, and diverse heterotrophic communities, occurs in hot, arid or even hyperarid environments, in cold environments of the Antarctic and Arctic zones, and in saline and hypersaline lakes and ponds where gypsum precipitates. Fossilized microbial remnants preserved in gypsum were also reported. Gypsum protects the endolithic microbial communities against excessive insolation and ultraviolet radiation, while allowing photosynthetically active radiation to penetrate through the mineral substrate. We here review the worldwide occurrences of microbially colonized gypsum and the specific properties of gypsum related to its function as a substrate and habitat for microbial life on Earth and possibly beyond. Methods for detecting and characterizing endolithic communities and their biomarkers in gypsum are discussed, including microscopic, spectroscopic, chemical, and molecular biological techniques. The modes of adaptation of different microorganisms to life within gypsum crystals under different environmental conditions are described. Finally, we discuss gypsum deposits as possible targets for the search for microbial life or its remnants beyond Earth, especially on Mars, where sulfate-rich deposits occur, and propose strategies to detect them during space exploration missions. [ABSTRACT FROM AUTHOR]

The nature of the nonequilibrium states of materials upon rapid compression/decompression processes in the intermediate regime, between static and shock compression, is an emerging field of high pressure research. Rapid compression experiments were performed to examine the structural response of silicon (Si) up to 11 GPa and over compression rates ranging from 0.011 to 0.325 GPa/s, using a piezo‐driven dynamic diamond anvil cell (dDAC) coupled with time‐resolved Raman spectroscopy. The observed structural stability and the remarkable consistency in the pressure‐dependent Raman shift of the diamond cubic Si (Si‐I) showed its high potential as a Raman pressure scale for compression rate below 0.325 GPa/s. The validity of the derived Si scale was verified by in situ continuously monitoring pressure of two rapid compressed samples, that is, gypsum and ZnO. Results indicated that pressures determined using Si were in good agreement with those estimated from the ruby scale. Success in pressure calibration with Si, during time‐resolved Raman spectroscopy measurements of material under rapid compression using a dDAC, will greatly simplify the required hardware system in home‐laboratory and may also help in reaching a higher signal‐to‐noise in Raman measurement on a short time scale. [ABSTRACT FROM AUTHOR]

In order to study the strength characteristics of red clay stabilized by a high dosage of phosphogypsum, a mix proportion design was carried out at the ratio of phosphogypsum:red clay = 1:0.5, 1:1, 1:2, 1:3, 1:4, and 1:5 using 4%, 6%, and 8% cement as a curing agent, and this study was carried out through the unconfined compressive strength test, water stability test, California bearing ratio (CBR) test, and durability test. As the phosphogypsum content increases, the unconfined compressive strength of the mix shows a trend of increasing and then decreasing, the unconfined compressive strength of the mixture is the largest when the ratio is 1:3, and with the increase in the number of dry and wet cycles, the unconfined compressive strength of the mixture decreases, and the decay is the largest at 2–3 dry and wet cycles. The higher the phosphogypsum content, the better the water stability performance of the mix. In addition, the CBR value of the mixture can meet the requirements of freeway, primary highway, secondary highway bed, and embankment filler bearing ratio. In this paper, a mix durability test method is proposed to express the mix durability performance in terms of mass loss rate and durability coefficient; the mass loss rate of the mix increases with the increase in the number of wet and dry cycles, and the durability coefficient decreases with the increase in the number of wet and dry cycles; the higher the content of phosphogypsum, the better the durability performance of the mix. [ABSTRACT FROM AUTHOR]

The preparation of artificial soil is a potential cooperative resource utilization scheme for red mud and phosphogypsum on a large scale, with a low cost and simple operation. The characteristics of the bacterial community structure and function in three artificial soils were systematically studied for the first time. Relatively rich bacterial communities were formed in the artificial soils, with relatively high abundances of bacterial phyla (e.g., Cyanobacteria, Proteobacteria, Actinobacteriota, and Chloroflexi) and bacterial genera (e.g., Microcoleus_PCC-7113, Rheinheimera, and Egicoccus), which can play key roles in various nutrient transformations, resistance to saline–alkali stress and pollutant toxicity, the enhancement of various soil enzyme activities, and the ecosystem construction of artificial soil. There were diverse bacterial functions (e.g., photoautotrophy, chemoheterotrophy, aromatic compound degradation, fermentation, nitrate reduction, cellulolysis, nitrogen fixation, etc.), indicating the possibility of various bacteria-dominated biochemical reactions in the artificial soil, which can significantly enrich the nutrient cycling and energy flow and enhance the fertility of the artificial soil and the activity of the soil life. The bacterial communities in the different artificial soils were generally correlated with major physicochemical factors (e.g., pH, OM, TN, AN, and AP), as well as enzyme activity factors (e.g., S-UE, S-SC, S-AKP, S-CAT, and S-AP), which comprehensively illustrates the complexity of the interaction between bacterial communities and environmental factors in artificial soils, and which may affect the succession direction of bacterial communities, the quality of the artificial soil environment, and the speed and direction of the development and maturity of the artificial soil. This study provides an important scientific basis for the synergistic soilization of two typical industrial solid wastes, red mud and phosphogypsum, specifically for the microbial mechanism, for the further evolution and development of artificial soil prepared using red mud and phosphogypsum. [ABSTRACT FROM AUTHOR]

Phosphogypsum (PG) is a solid waste generated by phosphate fertilizer industries that is currently used in concrete materials. However, adding PG to concrete usually results in reducing its water resistance and corrosion resistance. This paper presents a new method of applying PG to concrete to improve its water resistance. In this paper, a green superhydrophobic PG (SPG) coating was prepared using modified PG as a hydrophobic medium and cement as the bonding material. The contact angle between the superhydrophobic phosphogypsum coating (SPG coating) and water was 156°, and the coating reached a superhydrophobic state with good self-cleaning ability. Even when sandpaper was used to polish the coating, the water contact angle of the coating was still greater than 150°, indicating that the coating had good wear resistance. In addition, the results of water absorption and electrochemical experiments indicated that mortar coated with SPG had better water resistance and corrosion resistance than ordinary mortar. The SPG coatings with water resistance, wear resistance, and self-cleaning properties have potential applications in building exterior walls. [ABSTRACT FROM AUTHOR]

The accumulation of phosphogypsum (PG) has become a significant environmental and economic challenge, making PG reuse an urgent concern. This study aims to explore the potential of combining PG with steel slag (SS), ground granulated blast-furnace slag (GGBS), and cement clinker (CC) to create excessive-sulfate phosphogypsum slag cement (EPSC) for use in self-compacting concrete (SCC). However, residual acid and other impurities in PG can significantly slow down the setting time of EPSC. To optimize the setting time, different methods including wet grinding, washing, and the addition of pure gypsum, limestone powder (LP), and aluminum cement (AC) are used. Results show that the wet grinding method and washing method remove soluble phosphorus impurities and reduce fluorine ion levels by 64%. However, nonsoluble impurities that cannot be removed by wet grinding and washing continue to affect EPSC's setting time. Furthermore, the addition of LP shortens the setting time, but not enough. Using a 3% dosage of AC successfully reduces the setting time to a satisfactory level and EPSC SCC with a 28-day strength greater than 40 MPa is produced using the paste rheological threshold method. [ABSTRACT FROM AUTHOR]

Copyright of University Chemistry is the property of Peking University, College of Chemistry & Molecular Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Calcium molybdate (CaMoO4) is of significant interest due to its unique properties and numerous industrial applications, such as catalysis, electrochemistry, and optoelectronics. In this study, we developed an economical and environmentally friendly method to synthesize calcium molybdate from Moroccan phosphogypsum (PG) industrial waste and sodium molybdate, all at room temperature. Comprehensive analysis through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman vibrational spectroscopy, and scanning electron microscopy (SEM) revealed the high purity of the synthesized calcium molybdate, with particle sizes of only 12 nm. Additionally, optical characteristics were studied using ultraviolet-visible spectroscopy (UV-vis), which showed an optical band gap of Egap = 3.96 eV for CaMoO4. These results confirm the successful synthesis of calcium molybdate nanoparticles from Moroccan phosphogypsum, demonstrating an effective pathway to valorize this industrial waste into a valuable material. This approach contributes to environmental sustainability by reducing dependence on rare chemicals while offering innovative solutions for the industry's sustainable development. [ABSTRACT FROM AUTHOR]

Copyright of Nonferrous Metals (Extractive Metallurgy) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High concentrations of sodium chloride dominate oilfield produced waters (brine) of the Williston Basin. When accidental spills of produced waters occur, there is an immediate need to reduce concentrations of chloride, to protect surface and groundwater systems and to reduce concentrations of sodium (Na) in soil to prevent any unwanted swelling and dispersion in soil. Swelling and dispersion of soils will likely occur if sodium adsorption ratio values are too high and the electrical conductivity drops below a certain threshold that is required to maintain flocculation. To prevent this, a calcium (Ca) amendment can be applied to replace Na with Ca on soil exchange sites. Historically, gypsum has been the most common Ca amendment used for improving brine impacted soils. Flue gas desulfurization gypsum is available in North Dakota but is still a sparingly soluble amendment. The purpose of this research was to investigate the use of calcium acetate (Ca‐Ac) as an amendment for brine‐impacted soils as compared to gypsum. Ca‐Ac has a similar concentration of Ca compared to gypsum but is over 100 times more soluble than gypsum. This laboratory experiment will compare how varying levels of gypsum and Ca‐Ac can influence soil hydraulic conductivity, and chemical and physical properties when mixed with oilfield brine‐impacted soils. Core Ideas: Calcium acetate can be a more effective amendment than gypsum to increase water flow in brine‐impacted soils.Clay mineralogy may impact the choice of amendment for brine‐affected soils.The surface area of gypsum impacts the movement of water and also the removal of sodium from soil. [ABSTRACT FROM AUTHOR]

The global extent of salt‐affected agricultural land, 20% of which is deemed gypsiferous, results in billions of dollars of annual economic loss, a serious problem deserving of attention. However, the analysis of gypsiferous saline soils, such as in the irrigated Lower Arkansas River Valley (LARV) of Colorado, can result in an inflated estimation of soil salinity when using the traditional soil saturated paste extract electrical conductivity (ECe), leading to inaccurate crop yield loss predictions and misguided decisions for remediation. Sparingly soluble gypsum (CaSO4·$\cdot$ 2H2O) in these soils dissolves more readily during laboratory preparation of saturated paste extracts because of excess soil water dilution coupled with sample disturbance. We present a pragmatic linear‐regression approach to correct for this phenomenon, calibrated using two adapted methods for correcting ECe on an individual sample basis. The novel approach used electrical conductivity of pore water samples from saline fields to evaluate the accuracy of the correction methods. The approach was applied on soil samples from two surface‐irrigated, saline fields in the LARV, which were mapped using electromagnetic induction data and analysis of covariance linear regression, calibrated for ECe and ECe corrected for excess gypsum dissoultion (ECeg). Average ECeg values are as much as 26% lower than uncorrected ECe in gypsum‐biased portions of the fields. Estimation of corn salinity hazard in these gypsum‐affected areas using ECeg in lieu of ECe in a traditional yield response function generated mean relative yield values that are higher by up to 13 percentage points. We discuss lessons learned and suggest enhancements to the techniques. Core Ideas: In gypsiferous soils, excess gypsum dissolution biases saturated paste extract (SPE) analysis.Electrical conductivity of SPE (ECe) was corrected with selective dilution and equilibrium geochemical modeling.Linear models were used to estimate gypsum‐corrected ECe values over study fields.Gypsum significantly affects assessment of salinity hazard and crop yield impact. [ABSTRACT FROM AUTHOR]

In vitro biomineralization, carried out under laboratory conditions, provides scope for highly controlled crystallization events, at different stages of the formation reaction. This crystallization control is exerted using foreign substances or additives, which are usually organic compounds. Here, we have shown how with the use of homeopathic medicine Symphytum Q, the morphology of calcium carbonate is changed from its rhombohedral, the most stable morphology to spherical morphology, while the phase remains the same. A study has also been done on the formation of gypsum with varying parameters. [ABSTRACT FROM AUTHOR]

Copyright of Romanian Journal of Civil Engineering / Revista Română de Inginerie Civilă is the property of Matrix Rom and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the effects of pre‐crack inclination angle and filling material on granite, uniaxial compression tests were performed on pre‐cracked granite specimens without filling material and specimens filled with epoxy resin, gypsum, and organosilicon. Results indicate that the peak strength and apparent stiffness of pre‐cracked granite without filling materials increase with increasing pre‐crack inclination angle. The strain energy absorbed by the filling material improves the energy storage limit, inhibits the energy release effect when microcracks are connected to each other, and ultimately improves the compressive resistance and energy storage capacity. The strengthening effect of gypsum and epoxy resin is relatively better, which is more significant when the pre‐crack inclination angle equals 0°–60°. Finally, a damage constitutive model is established, which is in good agreement with the test and numerical simulation data. The results can provide reference for the research of grouting reinforcement of rock masses. Highlights: The effects of pre‐crack inclination angle and filling material are analyzed.The evolution law of energy mechanism is analyzed.The damage constitutive (DC) model of cracked rocks is proposed.The strengthening mechanism of energy storage effect of filled cracks was discussed. [ABSTRACT FROM AUTHOR]

The selective flotation separation of gypsum and quartz in phosphogypsum (PG) is an urgent problem that is very important for the high‐value utilization of PG. In the work, dodecyl amine hydrochloride (DH) was introduced as a collector for the selective flotation separation of gypsum and quartz. The flotation property and selective mechanism of DH on the surface of gypsum and quartz were researched by single mineral flotation experiments, Fourier transform attenuated total reflection infrared spectroscopy analyzer, zeta potential analyzer, X‐ray photoelectron spectrum, molecular dynamic (MD) simulation, etc. Additionally, H+ was introduced into the mineral‐water system simulated by MD to take into account the effect of acidic conditions on the adsorption of DH. The pre‐adsorption of H+ on the quartz surface under strongly acidic conditions hindered the electrostatic force adsorption of DH on the quartz surface. Furthermore, DH was adopted as a collector in the direct flotation recovery of gypsum from PG, and the gypsum concentrates with productivity of 69.85%, CaSO4·2H2O content of 96.33%, and whiteness of 55.00% were obtained. The SiO2 content in the gypsum concentrate decreased from 9.08% to 0.616%. It suggested that DH could serve as a promising collector in the selective separation of gypsum and quartz in PG via flotation. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Three-dimensional printing (3DP) technology has shown great potential in rock mechanics and mining engineering due to its ability to create complex and customized objects with high precision and accuracy. At present, an emerging research focus is improving the mechanical properties of 3D-printed samples, which originally has low strength and stiffness, to match those of natural rocks. The objective of this study was to investigate the effectiveness of different post-treatments on the strength enhancement of 3D-printed gypsum samples. To achieve this goal, 3D-printed gypsum samples were subjected to different post-treatments including dipped infiltration treatment and vacuum infiltration treatment using different infiltrants: water, saltwater, ColorBond, and StrengthMax. Subsequently, each sample was subjected to ultrasonic wave velocity testing and uniaxial compression experiments to characterize their mechanical properties, CT scans to investigate their microstructural characteristics. Additionally, X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) tests were conducted to explore the underlying reasons for changes in macroscopic strength. Finally, the physical characteristics and mechanical properties of untreated and post-processed 3D-printed gypsum samples were compared with natural rocks. The results showed that the strength of samples treated with water and saltwater was much lower than that of those treated with ColorBond and StrengthMax, while the porosity was the opposite. In water-treated and saltwater-treated samples, water or saltwater treatment can alter particle characteristics, but weak adhesive bonding and numerous pores result in low mechanical strength. Samples treated with Colorbond or StrengthMax exhibit improved strength due to effective gap filling and cohesive structure formation, with StrengthMax-treated samples showing higher strength despite having more pores than Colorbond-treated ones. Moreover, the physical and mechanical properties of these treated samples matched a wider range of natural rock types compared to the untreated samples. Highlights: This study investigates the impact of different post-treatments and infiltrants on the physical and mechanical properties of 3D-printed gypsum samples. A novel method is proposed in this study to quantitatively evaluate the degree of infiltration by comparing the changes in porosity before and after vacuum infiltration of 3D-printed samples based on 2D CT images. The study provides an in-depth analysis of the mechanisms responsible for the macroscopic strength enhancement in 3D-printed samples after vacuum infiltration treatment. Vacuum infiltration treatment using StrengthMax significantly improves the physical and mechanical properties of 3D-printed gypsum rocks, allowing them to replicate a wider variety of natural rocks compared to untreated samples. [ABSTRACT FROM AUTHOR]

The soil mantle of the tropical karstic landscapes of Southern Mexico was shaped by specific processes of pedogenesis and long-term human impacts of ancient Maya agriculture. To understand the interaction between natural and human-induced soilforming processes in the calcareous mountains of Chiapas state, we studied soil toposequences around the Classic Maya site of Budsilhá and related them to the archaeological evidence of settlement and land-use distribution. Soil chemical analysis, micromorphological observations, and clay mineral identification were carried out in key soil profiles at the main geoforms. Limestone hills are occupied by shallow Rendolls which are usually perceived as incipient soils. However, high content of silicate clay composed of kaolinite and vermiculite and ferruginous clayey soil material observed at macro- and microscale backed the hypothesis that these soils were formed from the residues of thick Terra Rossa after their erosion. Swampy lowlands are occupied by thick clayey gleyic soils with clay mineral assemblages similar to those in the upland Rendolls. We suppose that the mineral matrix of the lowland soils is largely derived from the pedosediments of eroded upland Terra Rossa, which lost original ferruginous pigmentation and aggregation due to redoximorphic processes. Some wetland soils contain neoformed gypsum that is atypical for humid tropics; sulfidesulfate transformation under fluctuating redox conditions could promote gypsum synthesis. Ancient Maya land use was closely related to soil-geomorphic conditions: settlements with homegardens occupied calcareous hills, whereas the primary agricultural domain was developed on lowland soils after their drainage by artificial canals. [ABSTRACT FROM AUTHOR]

To expand plaster utilization as a binder, mechanical behavior of sandwich panels consisting of two faces of plaster reinforced with fiberglass fabrics and a core of extruded polystyrene foam was studied. Using software based on the finite element method, computational models were utilized to simulate the four-point bending test. Two scenarios were examined: assuming a linear stress-strain curve for the material and employing nonlinear geometric analysis. These computational simulations allowed to determine loading limits and vertical displacements. After determining the flexural stiffness, the vibration response was calculated via an analytical procedure. This investigation proved that sandwich panels with greater thicknesses and volumes of reinforcements on the plaster faces exhibited greater load-bearing capacity, smaller displacements, greater resistance to traction and compression, and greater stiffness. Notably, panel 3, which had the thickness and volume content of reinforcement in the composite faces 24.71 and 66.67% higher, respectively, than reference panel, presented the best static and vibrational responses. [ABSTRACT FROM AUTHOR]

In this article, a kind of original bamboo-fiber reinforced phosphogypsum composite wall was proposed. The axial compression tests of eight walls and finite element analysis were carried out. The failure modes and mechanical properties of the walls were explored, the influence of parameters on the axial compression performance of the walls was studied, and the calculation methods of the axial compression capacity and stiffness of the composite walls were proposed. The results show that the phosphogypsum cracked first in the composite walls during the loading process, the cracks gradually spreaded through and widened, and the bamboo tubes inside the composite walls were crushed. The buckling failure occurred in the pure original bamboo wall. The bearing capacity of the composite wall control specimen is 140% and 38.46% higher than that of the pure phosphogypsum wall and the pure original bamboo wall, respectively. The number of dovetail nails has no significant effect on the axial compression performance of the composite wall. The bearing capacity and stiffness of composite wall increase with the increase of bamboo number, wall thickness, bamboo wall thickness and phosphogypsum strength. The calculation method of axial bearing capacity and stiffness of composite wall based on bamboo content is proposed. The finite element simulation results are in good agreement with the experimental and theoretical calculation results. The theoretical calculation method has high accuracy. The composite wall realizes the complementary advantages of original bamboo and phosphogypsum, which provides reference for the development and application of green buildings. [ABSTRACT FROM AUTHOR]

This article provides information on ettringite, a hydrated calcium sulfoaluminate mineral that belongs to the ettringite group. It describes the physical characteristics of ettringite, such as its hexagonal, prismatic crystals and color variations. The article also mentions the origins of the name ettringite and its cotype localities in the Ettringen district of Germany. Additionally, it discusses the village of Ettringen and its association with outdoor activities like rock climbing in basalt quarries. The article further explores the Bellerberg volcanic lava flows and their use in manufacturing querns and millstones. It highlights the Kalahari manganese field in South Africa as the primary natural locality for ettringite specimens, with larger crystals than any others known. The article focuses on the identification and properties of yellow ettringite found in the Kalahari manganese field, emphasizing the challenges in visually distinguishing it from other minerals in the area. It also delves into the role of ettringite in the deterioration of concrete and its stability under different conditions. The research for this article was funded by the National Research Foundation and CIMERA. [Extracted from the article]