Presence Of Gypsum Research Articles

Impact of permanent dam opening on the fate of polycyclic aromatic compounds in industrial sludges accumulated on river banks: In situ approach

The impact of permanent dam opening on the fate of organic contaminants was studied in the specific case of the Orne River industrial deposits. In the downstream part of the Orne River, the river banks were mainly constituted of steelmaking wastes accumulated for decades. Coring was performed before and after the permanent dam opening (performed in November 2019). The core layers were analysed for grain size, element content, mineralogy and polyclic aromatic compound (PAC) concentrations and distributions. The fine grain size, the high iron content (20–35 %), the presence of high temperature iron phases, the high zinc and lead contents were the main characteristics of these steelmaking sludges and came along with high polycyclic aromatic hydrocarbon (PAH) concentrations. The relative enrichment in low molecular weight PAHs associated to the abundance of furans signed the contribution of coal tar in specific layers. Element and grain size results revealed the erosion of about 12 cm of material during the first year of opening. Oxidative conditions were clearly demonstrated by the presence of gypsum along the entire length of the cores collected in 2020 and the years after. Comparing PAC features in the cores collected before and after dam opening, PAH concentrations did not show significant variations, but the molecular distribution of PACs presented significant changes, mainly in the first 30 cm. Indeed, the depletion of oxygenated PACs suggested the preferential leaching of these polar molecules. Leaching might have been enhanced by opening circumstances and/or the intense flood occurring few months after dam opening. Several PAC ratios were used to confirm the leaching and oxidative processes.

Long-term durability of iron-rich geopolymer concrete in sulphate, acidic and peat environments

This study assesses the behaviour of iron-rich type F fly ash geopolymer concretes (GC) exposed to simulated sulphate, acidic, and peat environments, typical of those encountered in tropical peatlands. GC and Portland cement (PC) concrete of comparable strengths were exposed to a range of simulated solutions for 18 months, including 5 % magnesium sulphate (MgSO4), 5 % sodium sulphate (Na2SO4), 1 % and 3 % sulfuric acid (H2SO4) and peat. The GC generally outperformed PC in all conditions. The GC showed a significant increase in strength in the first year, along with enhanced durability properties. Microstructural analysis indicated a decrease in total porosity and pore size. This was attributed to continuing geopolymerization leading to the foration of additional N-A-S-H gel, which filled the pores and solidified the concrete matrix. However, compressive strength decreased at 18 months due to crack propagation caused by drying shrinkage. In Na2SO4, GC attained an 8.9 % and 6.3 % increase in compressive strength at 12 and 18 months, respectively, again attributed to ongoing geopolymerization. GC exposed to MgSO4 exhibited a significant decrease in compressive strength of approximately 11 % at 12 months and 19.8 % at 18 months, attributed to the formation of lower-strength M-A-S-H from reaction between MgSO4 and N-A-S-H gel. After 12 months GC exposed to 1 % and 3 % H2SO4 demonstrated a decrease in compressive strength of approximately 1.2 % and 4.5 %, respectively, together with 2 % and 3 % mass loss. Chemical and microstructural data confirmed this strength reduction due to the vulnerability of N-A-S-H to when exposed to H2SO4. GC exposed to peat solution exhibited a 1.25 % increase in compressive strength at 12-month, but a decrease of 11.3 % at 18-month. Microstructural analysis observed a reduction in Na+ within GC matrix, and the presence of gypsum. The reduction in pore sizes and total porosity suggested generation of zeolite crystalline material was contributing to the pore filling.

Enhancing carbonation resistance of calcium sulfoaluminate belite-based concrete: comparative analysis and admixing strategies

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.

Speciation of Zn in Arid Soils With Saline Accumulations. Case Study of the Biskra Region, Algeria

Zinc (Zn) deficiency in plants is closely related to its bioavailability in soil. However, the behaviour of Zn in soils, especially in saline areas, remains complex. This research aims to clarify the distribution and dominant forms of Zn in arid soils with salt accumulations from the Biskra region by studying soil samples from ten representative profiles. Soil samples were collected from dif ferent horizons of each profile to a depth of 120 cm and subjected to speciation analysis using sequential extraction. The results indicate a deficiency of Zn in all soil samples, resulting in reduced concentrations of dif ferent forms of Zn. The dominant forms were residual Zn (R-Zn) and oxide-bound Zn (O-Zn), which accounted for over 90% of total Zn. The study revealed a negative correlation between soil salinity and all Zn forms, except for R-Zn, which showed a positive correlation. Additionally, Zn concentrations showed a negative correlation with gypsum, except for exchangeable Zn (E-Zn). It is important to note that the presence of gypsum in soils was significantly and negatively correlated with O-Zn. Although the sequential extraction method used may have limitations in accurately quantifying all forms of Zn, this study fills a gap in the literature on Zn assessment and speciation in arid soils. The study emphasizes the significance of soil characteristics, particularly salinity and gypsum content, in shaping Zn distribution. Overall, these results contribute to a better understanding of Zn availability and mobility in arid and saline environments, providing valuable insights for improved soil management practices in such regions.

Sedimentological and sequence stratigraphic analysis of Late Eocene Kirthar Formation, Central Indus Basin, Pakistan, Eastern Tethys

Rakhi Nala (Gorge) section of Eastern Sulaiman Range, Pakistan hosts world-class geological sections from the Cretaceous to the Recent. Here, Late Eocene Kirthar Formation is having a conformable lower contact with the greenish grey massive shale of the Baska Member of the Ghazij Formation. The rusty beds of the Oligocene Chitarwatta Formation are overlying the Kirthar Formation. To understand the detailed microfacies and depositional setting, detailed fieldwork was carried out in the Kirthar Formation in the outer Sulaiman Foldbelt. The late Eocene Kirthar Formation includes Habib Rahi Limestone, Domanda Shale, Pirkoh Limestone, and Drazinda Shale. Domanda Shale Member was deposited in transgression before Habib Rahi Limestone Member was deposited. It was followed up by the deposition of the second member Pirkoh Limestone and Marl Member. Habib Rahi Limestone, Pirkoh Limestone, and Marl Member have catch-up-to-keep-up deposition with rise and fall of sea level. Some facies of Drazinda and Domanda Shales represent a restricted setting supported by the presence of gypsum, while deep sea facies were also identified. This study will provide a guide for evaluating sedimentological concepts and understanding complex facies in highly oil and gas-prone stratigraphic sequences especially in the Eastern Tethys Region.

Recycling lithium slag into eco-friendly ultra-high performance concrete: Hydration process, microstructure development, and environmental benefits

To ascertain the viability of utilizing lithium slag (LS) in the development of eco-friendly ultra-high performance concrete (UHPC), this paper provides a detailed analysis of the effects of LS on UHPC. Specifically, the hydration and microstructural changes in UHPC containing LS (LS-UHPC) were comprehensively examined. Based on the results of isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP), LS primarily acts as a filler, promotes nucleation, provides internal curing, and participates in the pozzolanic reaction. Significantly, the internal curing effect and the pozzolanic reaction enhanced the strength development of LS-UHPC. UHPC with 20 % LS exhibited the highest 28 d compressive strength at 134.48 MPa and presented the densest microstructure. However, approximately 4 % of the calcium hydroxide in LS-UHPC would not be involved in the pozzolanic reaction. The presence of gypsum in LS led to increased ettringite formation in LS-UHPC. Although LS extended the induction period of UHPC, it intensified the hydration degree of cement. In LS-UHPC, the molar ratio of Ca/Si of C-(A)-S-H decreased, whereas the molar ratio of Al/Si increased, implying that the dissolved aluminum from LS was incorporated into the C–S–H chains. The integration of LS not only considerably reduced the carbon emissions and energy consumption of UHPC but also optimized LS recycling. Overall, the development of a sustainable UHPC by incorporating LS is both practicable and advantageous for environmentally conscious construction practices.

Insights into active and passive carbon sequestration and causticity reduction in hazardous red mud slurry

Batch experiments were conducted to collect data for obtaining insights into the chemical mechanisms and kinetics of red mud neutralization by both atmospheric (passive treatment) and injected CO2 (active treatment) in the absence and presence of gypsum. Active treatments allowed effective sequestration of CO2 within 1 h. A mixing ratio of gypsum to red mud at 0.04–0.06 enabled effective control of pH rebound, completely eliminating the causticity of the red mud by reducing the pH value of red mud to < 9. The carbonation of red mud was realized through the formation of carbon-containing minerals, mainly basic aluminium carbonates (largely dawsonite), sodium bicarbonate, sodium carbonate and calcite. The importance of calcite as a carbon carrier increased when gypsum was added. Passive treatments also allowed simultaneous causticity reduction and carbon sequestration but at a much slower rate compared to the active treatments. The research findings obtained from this study have implications for developing strategies to cost-effectively manage red mud. Where flue gas is available, active treatment could be a feasible option for simultaneously reducing the harmfulness of red mud and CO2 emission. Passive treatment can be used as a natural attenuation process for low-cost management of red mud. Where off-site utilization of red mud is feasible, gypsum addition at an optimal rate could be a more appropriate option. For future study, industrial-scale experiments are required to validate the research findings obtained from this laboratory-scale study.

STRUCTURE AND PROPERTIES OF THE ETRINGITE PHASE

Problem statement. Aluminate and sulfoaluminate cements are not produced in Ukraine, despite a rather significant need for binders of this class. The use of imported raw materials is limited by the high cost and certain disadvantages occurring during exploitation including rapid hardening, significant heat generation, which is associated with instability of some sulfoaluminates. At the same time, it is possible to highlight the following problems in the direction of expanding possibilities of using special cements of this type: stabilization over time and operating conditions of the hydrosulfate phase based on alumina cement, as well as modification of the compositions of mineral binders based on calcium sulfate dihydrate (CaSO4·2H2O) and development of binders of this class based on secondary production products. The main factor is that during hydration of sulfoaluminates and aluminates in the presence of gypsum (CaSO4·2H2O), a hydrosulfoaluminate phase is formed, which makes it possible to obtain a hardened cement paste structure with special properties. Then monocalcium hydrosulfoaluminate turns into hydrosulfoaluminate of the low-sulfate form С3А·СaSO4·12H2O with the release of gibbsite Al2O3·3H2O. Also, ettringite С3А·СaSO4·nH2O and 2(С2S)·nH2O is formed and hydrated calcium silicate CSH(B) can be formed. When gypsum is added to cement, ettringite is formed in this system. Etringite is one of the components. It is not formed initially, but through intermediate structures. During hydration reactions, ettringite is rearranged, neoplasms are formed, which can lead to gypsum corrosion. Etringite loses its stability. Herewith, the problem of primary and secondary ettringite arises. Primary ettringite creates conditions for strength. Secondary ettringite is formed already in the hardened system and leads to internal stresses. Formation of secondary ettringite can have both positive and negative consequences. The purpose of the atrticle is to investigate structure and properties of the ettringite phase. Conclusions. The hydration process depends on the Gibbs surface energy. Change in surface energy depends on the CaO/Al2O3 ratio. It was established that the surface energy increases with an increase in the CaO/Al2O3 ratio. The paper has studied influence caused by the ettringite phase on the main characteristics of alumina cement and gypsum in a modified gypsum binder. Studies have been conducted on formation of the maximum amount of ettringite phase. We have calculated the maximum amount of the ratio of alumina cement and gypsum to obtain the maximum amount of mineral – 70 % alumina cement and 30 % gypsum. The highest effect is achieved during the simultaneous use of С6АṤ3Н32 and АН3, which occurs during hydration of С4А3Ṥ. Taking into account the above, it is advisable to obtain clinker containing calcium sulfoaluminate and cements based on it.

Effect of gypsum waste inclusion on syngas production during CO2-assisted gasification of waste tires

Syngas production from co-gasification of waste tires and different amounts of drywall waste gypsum (CaSO4) was investigated using CO2 as the gasifying agent in a lab-scale reactor. Gypsum is known to react with carbon feedstocks through solid–solid reactions to produce CaS and CaO, CO, and CO2. The presence of gypsum in waste tires increased the syngas yield from the conversion of char and tars. Gypsum addition to the waste tire also increased syngas quality from increased syngas energy yield. The overall yield of syngas increased by up to 55% while the energy yield (MJ/ kg feedstock) improved by 40% with gypsum addition. The product gas yield, energy, H2, and CH4 yields increased with gypsum addition while CO only increased for lower gypsum concentrations. Higher gypsum addition increased CO2 yields. Aspen Plus simulation results revealed that for waste tires, temperatures < 1200 °C suppressed the transformation of sulfur present in gypsum into SO2 for all waste tires to gypsum feed mass ratios. At 50 wt% gypsum concentrations, only 2% of the sulfur in the feedstock was transferred into SO2. The results showed improved syngas yield and quality, without any increase in sulfur emissions showing the benefits of gypsum waste incorporation in waste tire gasification.

Synthesis, structure, and hydration of stoichiometric ye’elimite and iron-bearing ye’elimite

Ye’elimite is the primary mineral component in calcium sulfoaluminate cements and is responsible for their early hydraulic reactivity. Herein, ye’elimite was synthesized using a novel method with CaSO4 as the sole CaO source to achieve high purity. Stoichiometric ye’elimite and iron-bearing ye’elimite were synthesized, with the highest purity obtained through sintering at 1250°C for 4 h. The crystal structure of iron-bearing ye’elimite was represented through dynamical disordering of the SO4 tetrahedron and Ca atom with the space group I 4 ¯ 3m. Moreover, the early hydration behaviors of stoichiometric ye’elimite and iron-bearing ye’elimite reacting with and without gypsum were studied. In the absence of gypsum, stoichiometric ye’elimite reacts faster than iron-bearing ye’elimite. However, in the presence of gypsum, the hydration of the former is faster than that of the latter and the hydration rates of both these minerals are higher than those observed in the absence of gypsum.

Влияние основных типов химизма степени засоления почв и техногенных грунтов на всхожесть семян фитомелиорантов

Abstract. The purpose and objectives of the study is to establish the levels of influence of chemistry and the degree of salinity on the onset of half (LD50) and full (LD99) death of seeds of alfalfa blue hybrid and yellow clover. To identify the degree of participation of each factor in the death of legume seeds using the correlation coefficient and determination. To conduct a comparative assessment of the salt resistance of the seeds of sweet clover and alfalfa. Methods. The main natural types of salinization characteristic of the forest-steppe zone of Western Siberia are selected as objects of study. The germination energy and germination of seeds were determined according to GOST 12038-84. Model variants of salt solutions for germination of seeds of sweet clover and alfalfa were created taking into account the proportions of the formation of the main types of salinization. The types of salinization are represented by sulfate-soda, sulfate-chloride (neutral), and gypsum chloride-sulfate salt. Scientific novelty. Drilling slurries stored in barns during the extraction of hydrocarbon raw materials correspond to similar salinization conditions. Artificial salinization of water-salt solutions with a given concentration made it possible to identify half (LD50) and complete death (LD99) of clover and alfalfa seeds at the appropriate level and chemistry of salinization. Comparison of neutral and sulfate-soda salinization showed that the presence of soda in the solution determines its toxicity by 86–87 %. The negative effect of neutral salinization appears to a greater extent due to an increase in osmotic pressure. The presence of gypsum in the nutrient saline solution reduced the toxicity to seeds of phytomeliorant crops by 1.9–2.5 times. Results. It has been established that under conditions of neutral and sulfate-soda salinization, plants experience an acute deficiency in calcium. The introduction of gypsum during chemical reclamation of salt pans and drilling slurries eliminates this deficiency. The establishment of indicators (LD50) allows you to adjust the seeding rate of phytomeliorants. The indicator (LD99) indicates the expediency of applying gypsum on salt pans and drilling slurries.

Effect of the incorporation of an excavated earth fine grained fraction in cementitious mixes

In the current context of global warming, valorisation of waste materials is becoming a key issue in the cement and concrete industries. This research focuses on the effect of the incorporation of an excavated earth fine-grained fraction (< 63 μm) in cement mixes and its contribution to the cement hydration mechanisms which are mainly coming from the Paris region of France. This fine-grained fraction results from a washing and mechanical sorting of grains process for excavated earth. The omnipresence of gypsum in the subsoil of the Paris region, due to its geological context, is reflected in the fine-grained fraction with the presence of sulphates. Moreover, the fine-grained fraction is also composed of quartz, calcium carbonates and clay phases. The tests have been performed on cement pastes composed of a blast furnace slag cement and the fine-grained fraction as a sludge with its inherent humidity. Pastes with different sludge contents leading to different water-cement ratios (0.5, 0.7 and 0.8) have been studied. The impact of the incorporation of the fine particles and the water contained in the sludge on the rheology and the hydration of the cement pastes has been evaluated using water demand tests, thermogravimetric analysis and isothermal calorimetry. Results indicate that the incorporation of sludge in cementitious mixes increases the water demand, accelerates the hydration reactions and contributes to the formation of additional hydrate phases probably associated with the presence of gypsum in the studied sludge.

Triassic gypsum layers in Keban Metamorphics, eastern Tauride Belt, Southeastern Turkey: New data about Triassic rifting in northern Tethys margin

ABSTRACT A gypsum interlayer with 100 m thick was identified within the Early-Middle Triassic shelf type clastic and carbonates of the Keban Metamorphics, along the shore of the Fırat River, ~500 m west of Keban district (Elazığ, southeast Turkey). Gypsum layers have thickness of 15–50 cm, and exhibit the original sedimentary bedding intercalated with dolomitic carbonate rocks. They were subjected to hydrothermal alteration related to late Cretaceous magmatic intrusions. Hydrothermal activity caused the dissolution and recrystallization of gypsum, as well as occurrences of secondary gypsum, elemental sulphur and quartz (amethyst). The geochemical (trace element and sulphur and oxygen isotope) compositions of gypsum and dolomites indicate typical marine evaporite compositions. The δ34S and δ18O values of the Keban gypsum correspond to Early Triassic evaporites, based on Early-Middle Triassic seawater sulphate composition. Keban gypsum represents Triassic rifting along the northeastern margin of Gondwana and exhibits similar age (Early-Middle Triassic) and palaeogeographic setting to Kemer (Antalya, Turkey) gypsum, associated with opening of the Neotethyan Ocean between Gondwana (Pangea) and the Cimmerian microcontinent. However, the Keban gypsum is different from the late Triassic Honaz-Denizli and Nusaybin-Gaziantep gypsum representing the southern margin of the Paleo-Tethys Ocean (Tauride Belt) and southern margin of the Neo-Tethys (Arabian Plate). The presence of gypsum is observed on both passive continental margins of Neo-Tethys means that their deposition took place before the subduction of the Neo-Tethys Ocean during Late Triassic-Jurassic period.

Role of ionic diffusion in heat flow and chemical shrinkage of tricalcium aluminate hydration subjected to thermo-chemo-electrical coupled fields

The role of ion diffusion in the heat flow and chemical shrinkage of tricalcium aluminate (C3A) hydration was investigated using the proposed multi-ionic reactive transport model for C3A hydration. Ion diffusion, dissolution, and precipitation reactions were coupled in the governing equation of the chemical field during C3A hydration in the presence of gypsum. Ion diffusion and chemical reactions were also governed by the electric and temperature fields in the model. Theoretical computations were performed relating ion diffusion to heat flow and chemical shrinkage during all stages of C3A hydration. Excellent agreement was achieved by comparing the simulation results and the experimental data under various conditions. The effects of the gypsum content, specific surface area (SSA), and curing temperature on the ion diffusion, electrical potential, heat flow, and chemical shrinkage were numerically studied. The results indicated that (1) higher gypsum contents, SSAs, and curing temperatures increased the ion concentration gradient and improved the supersaturation concentration of sulfate near the C3A surface; (2) higher gypsum contents led to faster decreases in the Ca2+ and SO42− concentrations before the depletion of gypsum; and (3) the gypsum content affected the phase assemblage through spatial and temporal evolution of the ionic species. The proposed model may guide the design of the C3A-gypsum system and can be extended to optimize the fluidity and setting properties of the cement paste.

Single-Well Push–Pull Tracer Test Analyses to Determine Aquifer Reactive Transport Parameters at a Former Uranium Mill Site (Grand Junction, Colorado)

At a former uranium mill site where tailings have been removed, prior work has determined several potential ongoing secondary uranium sources. These include locations with uranium sorbed to organic carbon, uranium in the unsaturated zone, and uranium associated with the presence of gypsum. To better understand uranium mobility controls at the site, four single-well push–pull tests (with a drift phase) were completed with the goal of deriving aquifer flow and contaminant transport parameters for inclusion in a future sitewide reactive transport model. This goes beyond the traditional use of a constant sorption distribution coefficient (Kd) and allows for the evaluation of alternative remedial injection fluids, which can produce variable Kd values. Dispersion was first removed from the resulting data to determine possible reactions before conducting reactive transport simulations. These initial analyses indicated the potential need to include cation exchange, uranium sorption, and gypsum dissolution. A reactive transport model using multiple layers to account for partially penetrating wells was completed using the PHT-USG reactive transport modeling code and calibrated using PEST. The model results quantify the hydraulic conductivity and dispersion parameters using the injected tracer concentrations. Uranium sorption, cation exchange, and gypsum dissolution parameters were quantified by comparing the simulated versus observed geochemistry. All simulations required some cation exchange and calcite equilibrium, and one simulation required gypsum dissolution to improve the model fit for calcium and sulfate. Uranium sorption parameters were not strongly influenced by the other parameter values but were highly influenced by uranium concentrations during the drift phase, with possible kinetic rate limitations. Thus, a future recommendation for such push–pull tests is to collect more geochemical data during the drift phase. The final uranium sorption parameters were within the range of values determined from prior column testing. The flow and transport parameters derived from these single-well push–pull tests will provide initial parameters for any future sitewide reactive transport model.

Experimental Investigation of Capillary Rise in Unsaturated Gypseous Soils

Capillary rise is a phenomenon that must be considered an inevitable factor when dealing with unsaturated gypseous soil. This study investigates the behavior of gypseous unsaturated soil under capillary action, where different gypsum content and soil densities are experimentally tested in a developed laboratory model consisting of Transparent pipes 1 m long and 0.05 m in diameter. All the pipes are placed inside a rectangular basin with a dimension of (1500×500×500 mm). The soil was taken from Tikrit city in Iraq at a depth of (1.5 to 2 m) under the natural soil surface; the laboratory tests clarified that the soil is poorly graded sand with a gypsum percent of 59%. The three other gypseous soil samples were prepared by dissolving with HCl acid to gain the required percentages of gypsum (22, 37, and 6%). The results show that the presence of gypsum in the soil slows down the rise of water in the soil after rapid rising in the first stages of the test. The low and moderately gypseous soils required a shorter time to reach the maximum capillary rise than highly gypseous soils. Also, the existence of gypsum increased the max. The height of the capillary rise and the degree of saturation in the capillary zone were also noticed for all soil densities examined. The effective stress will be low in the fully saturated parts while it’s high in the low saturated parts.

Source areas of the Eastern Ebro Valley loess (NE Iberian Peninsula): Heavy mineral composition as a provenance indicator

AbstractLoess deposits of the Eastern Ebro Valley (NE Iberian Peninsula) occupy an area of ~2000 km2 mostly on the east of the Ebro depression and locally in the Móra Basin. We studied 38 samples of loess and 47 samples of their possible source areas, in order to determine the location of the origin of the loess materials, based on their particle size distribution and composition of heavy minerals. Our results clearly differentiate two depositional loess basins disconnected by the reliefs of the Pre‐Coastal Range with different mineralogical signatures: the Ebro Basin and the Móra Basin. The most relevant variables to discern source areas were the percentage of heavy minerals, the concentrations of zircon, staurolite, rutile and inosilicates, and the presence of gypsum. In the Ebro Basin, the largest set of loess deposits is located around a depocenter in the Batea region and along several lateral areas, with materials that come from the central alluvial plain of the Middle Ebro River (25 to &gt;100 km travel distance), in addition to deflated materials from Miocene interfluvial substrates. On the other hand, loess deposits of the Móra Basin come from more proximal source areas (&lt;15 km), originating from the alluvial materials of the Lower Ebro River that contain the contributions of its tributaries, the Cinca and Segre rivers. Taking into account the homogeneity in the mineralogical composition of complex loess sequences, we deduced a general WNW–ESE wind direction, which would have remained constant over the last two cold periods (MIS‐2 and MIS‐6). Along this axis, the Pàndols–Cavalls Range, with a height difference of 200–350 m, acted as a wind barrier separating the loess of Ebro Basin from the loess of Móra Basin.

Behavior of Square Footing Erected on Gypseous Soil Treated by Ceramic Wastes

Gypseous soil, as is well known, includes a specific quantity of gypsum. Gypsum is a water-soluble salt with a solubility of (2.2-2.6) gram/liter in distilled - water. As a result, the presence of gypsum poses a challenge when building structures on this soil, since gypsum dissolves when exposed to water, producing gaps between soil particles and so causing soil collapse. This study examines the behavior of a shallow foundation rested on gypseous soil. Three types of gypseous soil with gypsum contents of (61%, 45.3%, and 27.9%, respectively) are used, and treated with ceramic wastes, which is a waste product of construction. The Soil samples were collected from the site of Tikrit University's campus. The study consists of six test cases, two for each type of soil, one dry and the other wet, where the first test for each case was used as a baseline for comparison, which was the soil test without the addition of ceramic wastes, and the rest was added in three proportions (3%, 6%, and 9%) and three mixing depths for each ratio (B/2, B, 3B/2).The percentage 9% ceramic wastes gives best results of improving, the bearing capacity of the soil improved by 233%, 256 %, and 289% for high gypseous soil, and by 78%, 94%, and 111% for medium gypseous soil, with a percentage of 60%, 87%, and 113% for low gypseous soils. Adding ceramic wastes to wet gypseous soil improves the bearing strength of the soil, lowers settlement to some extent, and reduces the influence of water on it.

ENERGY SAVING FACTORS IN WINTER CONCRETING

This article considers energy-saving technologies for winter concreting of building structures and constructions. Various authors have studied mathematical models of the thermal regime of a three-dimensional building structure. The mathematical model of the heat balance equations in the concrete structure, the thermal conductivity coefficient, the dependences of the heat balance equations in the concrete structure and the junction, the thermal conductivity coefficient, the volumetric thermal conductivity, respectively, in the erected fragment and the previously erected part of the wall was implemented on a computer. The article considers the processes of cement and concrete strength gain during early freezing of concrete. In previous studies by various authors, it was found that with an increase in the time for gaining critical strength, the cost of electricity is reduced by 25-50%, due to the use of thermal inertia of the structure. The rate of cooling of monolithic structures at negative temperatures is revealed. The chemistry of cement hardening processes during early freezing is shown. Thermodynamic calculations set the limits of negative temperatures at which concrete strength curing stops, but under the action of repeated positive temperatures, the cement hydration process resumes and concrete continues to harden. The aluminum minerals of Portland cement clinker are usually the first to hydrate when the cement hardens with water, and in the presence of gypsum they form calcium hydrosulfoaluminate. This connection is very fragile and is destroyed by mechanical stress (repeated vibration) and over time even at normal temperatures. The article reviews the foreign experience of winter concreting and the preferred methods of work in this case.

In‐depth understanding the hydration process of Mn‐containing ferrite: A comparison with ferrite

AbstractManganese (Mn) is inevitably incorporated into cement from raw materials, and is mainly incorporated into the ferrite phase of cement. In this paper, the hydration kinetic was investigated for Mn‐containing ferrite and unmodified ferrite. The evolution of the solid phases, aqueous species, and both conductivity and pH were investigated for unmodified ferrite and Mn‐containing ferrite by a diluted suspension experiment. Isothermal calorimetry, transmission electron microscopy, and mechanical property measurements were conducted to explore the influence of Mn on the hydraulic activity of ferrite. The results showed that the incorporation of Mn enhances the hydraulic activity, alleviates the influence of gypsum on the retardation of ferrite, and improves the early strength in the presence of gypsum. Mn‐containing ferrite also accelerates dissolution, influencing the initial sulfate adsorption. Mn ions eventually incorporate into (Al, Fe)‐AFt and (Al, Fe)‐AFm. During the first several hours of hydration of ferrite, there is no sulfate consumption after the initial adsorption, accompanied by a decrease of Ca2+ and Al3+ concentration. And an “adsorption‐barrier” hypothesis is proposed to explain the dormant period of sulfate consumption.