Addition Of Gypsum Research Articles

Effect of Gypsum, Cover Crop, and Crop Rotation on Bulk Density and Aggregate Properties of Soils

ABSTRACT Soybean production, worldwide, typically involves full tillage resulting in much less biomass than other crops, leading to decreased soil organic matter and increased soil degradation. The goal of this study was to evaluate the potential benefits of an innovative management system that includes the combinations of no-till, crop rotation, cover crop, and gypsum application on continuous soybean production. The response of soil physical properties, i.e. bulk density and water-stable aggregates, was evaluated across a range of soil types and climatic conditions. Treatments consisted of comparing (1) continuous soybean to a soybean-corn and corn-soybean rotation, (2) cereal rye [Secale cereale (L.)] cover crop to no cover crop, and (3) gypsum surface‐applied at 0, 1.1, and 2.2 Mg ha−1. The study was replicated at four different sites in the United States, including Shorter (AL), Farmland (IN), Hoytville (OH), and Piketon (OH). At the end of the 5-year study, soil bulk density and aggregate stability were determined. Soil bulk density and water-stable aggregates were unaffected by gypsum addition regardless of the location. Including cereal rye as a winter cover increased soil aggregation and bulk density at the Hoytville location only. Rotating the soybeans with corn (compared to continuous soybeans) resulted in soil aggregation and bulk density improvements at all research locations. Results indicated that soybean production that included crop rotation into management system improved soil aggregate stability, whereas cover crop benefits were less effective and amending the soil with gypsum did not significantly affect these soil properties.

Effect of gypsum on transport of IMX-104 constituents in overland flow under simulated rainfall.

Residue of energetic formulations, which is deposited on military training grounds following incomplete detonation, poses biotic hazards. This residue can be transported off-site, adsorb to soil clays and organic matter, transform or degrade, or taken up by plants and animals. Its harmful effects can be mitigated by localizing the energetics at the site of initial deposition using soil amendments and allowing them to bio- and photodegrade in situ. Small plots with coarse loamy soil were used to study the effect of gypsum (CaSO4·2H2O) on transport and redistribution under simulated rainfall of various sizes of insensitive munition explosive (IMX)-104 particles, which consist of 3-nitro-1,2,4-triazol-5-one (NTO), 2,4-dinitroanisole (DNAN), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tertranitro-1,3,5,7-tetrazocine (HMX). The addition of gypsum more than doubled infiltration and decreased sediment loss by 16% compared to the control. The post-rainfall mass balance of IMX-104 in the order from greater to smaller pools was as follows: (1) soil surface retention, (2) off-site loss to overland flow, and (3) sub-surface infiltration. Overall, the application of gypsum significantly decreased concentration and the total mass loss of dissolved DNAN, RDX, and HMX in surface runoff. In addition, gypsum significantly decreased (for NTO, DNAN, and HMX) or delayed (for NTO, DNAN, RDX, and HMX) the peak discharge of <2mm particulate energetics. The infiltration of NTO in the gypsum treatment was fivefold greater than in the control. Moreover, DNAN and RDX were also present in infiltration, while in the gypsum-free control none were found. Gypsum shifted the total mass balance of energetics toward subsurface flow. This study indicates that gypsum may decrease off-site transport of energetic constituents in the soils that are subject to surface sealing.

Performance and life cycle of Portland limestone cement mixes admixed with gypsum

In this study, the life cycle and performance of normal concrete containing 35% limestone and 2% gypsum made in different ratios of water to binder (w/b) were examined. Its cost and CO2 emissions were found to be 13% and 35% lower compared to the control concrete. However, because of the greater replacement of cement with limestone filler, there is a reduction in its workability, the development of heat and strength, and the penetration resistance of water and chloride ions, especially in the early ages. The addition of gypsum marginally improved these concrete properties, but its quantity should be limited to 2% by weight of the binder. The use of gypsum beyond this limit led to a significant decrease in the properties of concrete. Anorthite, a calcium aluminosilicate mineral, was found in this concrete, and its fractured morphology was found to be more occupied with unreacted angular limestone particles. This low-carbon concrete showed an improvement in compressive strength with decreasing w/b ratios. The limestone reserve in India is abundant and spread evenly across its length and depth, and its use as the main replacement for cement in normal strength mixes would greatly reduce the impact of CO2 on the environment.

Potential of desulfurized gypsum as a sulfate alternative in preparing solid waste-based limestone calcined clay cement (LC3) and its effects on early properties

Desulfurized gypsum (DG) presents significant challenges in recycling with the rapid development of industrialization. To explore the feasibility of DG as a sulfate source in producing limestone calcined clay cement (LC3), this study investigates the differences between LC3 samples containing DG and those containing natural gypsum (NG) in terms of hydration, workability and mechanical properties. Results indicate that at the same addition of gypsum, DG samples exhibited lower promotion in rheological parameters and weaker retardation in setting time relative to NG samples. For strength development, the optimal content of NG samples was 3 wt%, whereas no such similarity was observed in DG samples. Furthermore, the mixture incorporating higher amounts of sulfate exhibited a lower aluminate peak and slower consumption of capillary water. Although differences in the sulfate source had no effect on the phase species of LC3, the amount of ettringite increased with the addition of gypsum (especially NG), while exhibiting a further growing trend as the curing age prolonged. This study is expected to develop novel LC3 binder formulations by promoting the utilization of DG, thereby achieving sustainable development.

The Gypsum Influence on the Formation of Secondary Phases During Autoclave Leaching of Gold-Bearing Concentrates and the Silver Recovery Using Cyanidation.

Autoclave leaching of sulfide concentrates may produce various ferric secondary phases, depending on the arsenic content and temperature. Silver is converted to argentojarosite, from which it is not recoverable by standard cyanidation methods. To increase silver recovery, it is necessary to reduce the argentojarosite formation during autoclave leaching. This study was devoted to the influence of gypsum on the formation of secondary phases of ferric arsenate and the subsequent recovery of gold and silver by cyanidation. The addition of gypsum at a consumption of 0.1 g/g(concentrate) helped to increase silver extraction from 13.4 to 98% at cyanidation. Gold recovery was 99%. An increase in gypsum consumption contributed to the ferric arsenate sulfate formation with an increased sulfate sulfur content, and a decrease in the As/S(sulfate) molar ratio in the cake from 3.7 to 0.88 contributed to an increase in silver extraction at cyanidation of up to 98%. Basic ferric sulfate is not formed in this case, since according to EDS mapping, the distribution of arsenic and sulfur over ferric-containing particles is uniform. According to TCLP, stable, sparingly soluble ferric arsenate phases are formed and the cake obtained after cyanidation is stable and suitable for disposal, since the final arsenic concentration in the solution was 0.45 mg/dm3.

New elucidating into the microstructural evolution mechanisms and micromechanical properties of C4AF and gypsum synergistic hydration

Increasing the C4AF content significantly enhances the sulfate and impact resistance of Portland cement-based materials. However, the research on the microstructural evolution mechanisms and micromechanical properties of the binary synergistic hydration products of C4AF and gypsum is not yet sufficiently deep. This study employed thermodynamic simulations, phase structure characterization, and nanoindentation techniques to investigate the microstructure evolution of gypsum-assisted C4AF hydration. Results indicated that the final hydration product of C4AF, C3(A,F)H6, formed through the stacking of lamellar OH-AFm phases. The addition of gypsum altered the formation pathway of C3(A,F)H6, causing it to precipitate directly from an amorphous iron-aluminum gel, which resulted in smaller particles with higher crystallinity. Gypsum also filled pores in the hydration products, thereby positively influenced their micromechanical properties.

Research on the Configuration of Multi-Component Solid Waste Cementitious Materials and the Strength Characteristics of Consolidated Aeolian Sand

Developing green, low-carbon building materials has become a viable option for managing bulk industrial solid waste. This paper presents a kind of all solid waste cementitious material (SWCM), which is made entirely from six common industrial wastes, including carbide slag and silica fume, that demonstrate strong mechanical properties and effectively stabilize aeolian sand (AS). Initially, we investigated the mechanical strength of waste-based cementitious materials in various mix ratios, focusing on their ability to stabilize river sand (RS) and aeolian sand. The results show that it is necessary to use alkaline solid waste carbide slag to provide a suitable reaction environment to achieve the desired strength. In contrast, the low reactivity of coal gangue powder did not contribute effectively to the strength of the cementitious material. Further orthogonal experiments determined the impact of different waste dosages on the strength of stabilized AS. It was found that increasing the amounts of carbide slag, silica fume, and blast furnace slag powder improved strength, while increasing fly ash first increased and then decreased strength. In contrast, higher additions of desulfurization gypsum and coal gangue powder led to a continuous decrease in strength. The optimized mix is carbide slag—desulfurization gypsum—fly ash—silica fume—blast furnace slag powder in a ratio of 4:2:2:3:3. The experimental results using SWCM to stabilize AS indicated a proportional relationship between strength and SWCM content. When the content is ≥20%, it meets the strength requirements for road subbases. The primary hydration products of stabilized AS are C-(A)-S-H, AFt, and CaCO3. Increasing the SWCM content enhances the reaction degree of the materials, thereby improving mechanical strength. This study highlights the mechanical properties of cementitious materials made entirely from waste for stabilizing AS. It provides a reference for the large-scale utilization of industrial solid waste and practical applications in desert road construction.

Limestone particle sizes and sulfate impact on the early hydration of limestone calcined clay cement

This study explores the underlying mechanisms behind the varying grain size distribution of limestone and sulfate requirement in Limestone Calcined Clay Cements (LC3) on the effects of early hydration and rheological properties. In this paper, the experimental study involving a 45 % replacement of cement demonstrates that the filler effect increases with the fineness of limestone. This is evidenced by the observed acceleration and enhancement of silicate reaction, as monitored through isothermal calorimetry (ICC). The precipitation rate of calcium-silicate-hydrate (C-S-H) increases, and the sulfate adsorption by C-S-H is also augmented correspondingly, leading to accelerated depletion of gypsum during the hydration process. The effect of limestone on the particle size of rheology was also shown that the finer the limestone, the greater the yield stress, while the sulfate has the opposite effect. The results of the Krstulovic-Dabic kinetic model indicated that the exponent and rate constant values decreased with the finer limestone and increased with the addition of gypsum. These results aid in understanding the role of limestone and sulfate requirements on LC3 systems.

Vermicompost and flue gas desulfurization gypsum addition to saline-alkali soil decreases nitrogen losses and enhances nitrogen storage capacity by lowering sodium concentration and alkalinity

Saline-alkali soils have poor N storage capacity, high N loss and inadequate nutrient supply potential, which are the main limiting factors for crop yields. Vermicompost can increase organic nutrient content, improve soil structure, and enhance microbial activity and function, and the Ca2+ in flue gas desulfurization (FGD) gypsum can replace Na+ and neutralize alkalinity in saline-alkali soils though chemical improvement. This study aimed to determine if vermicompost and FGD gypsum addition could improve the N storage capacity through decreasing NH3 volatilization and 15N/NO3− leaching from saline-alkali soils. The results indicate that the combined application of vermicompost and FGD gypsum led to the displacement and leaching Na+ in the upper soil layer (0–10 cm), as well as the neutralization of HCO3− by the reaction with Ca2+. This treatment also improved soil organic matter content and macroaggregate structure. Also, these amendments significantly increased the abundance of nifH and amoA genes, while concurrently decreasing the abundance of nirK gene. The structural improvements and the lowering of Na + concentration in and alkalinity decreased cumulative NH3 volatilization, and leaching of 15N and NO3− to the deep soil layer (20–30 cm). FGD gypsum increased the 15N stocks and inorganic N stocks of saline-alkali soil, whereas vermicompost not only increased the 15N and inorganic N stocks, but also increased the total N stocks, the combination of vermicompost and FGD gypsum can not only increase the available N storage capacity, but also enhance the potential for N supply. Therefore, vermicompost and FGD gypsum decrease N loss and increase N storage capacity through structural improvement, and lowering of Na+ concentration and alkalinity, which is crucial for improving the productivity of saline-alkali soil.

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.

Long-term Effect of Sodic Water for Irrigation on Soil Quality and Wheat Yield in Rice-Wheat Cropping System

Increasing scarcity of good quality water in many arid and semi-arid regions necessitates the use of poor quality groundwater for irrigation. Soil degradation resulting from alkali water irrigation has become a serious threat to soil health. In the present study, we conducted an investigation (2021-22) on the physicochemical properties (soil organic carbon, available Na, and available K) of sandy loam soil under a semi-controlled lysimeter. Wheat was grown as an experimental crop, which was irrigated with synthetic alkali waters having similar salts (total electrolyte concentration, TEC = 30 me L−1) and sodium adsorption ratio (SARiw 10 mmol L−1) but varying in residual sodium carbonate (RSC) are being continuously applied since 2004 (20 years). Five types of irrigation water having different levels of residual sodium carbonate comprised. (T1) best available groundwater, (T2) residual sodium carbonate water 1 (RSC- 5 me L–1), (T3) RSC water 2 (RSC 10 me L–1), (T4) RSC water 3 [RSC 10 treated with gypsum (RSC 10 neutralized to RSC 5 me L–1 with gypsum)] and (T5) RSC water 4 [RSC 10 treated with sulphur (RSC 10 neutralized to RSC 5 me L–1 with sulphur)]. Soil samples were collected after harvesting two wheat varieties (KRL 210 and HD 3226). Long-term irrigations with alkali water increased the available Na and K in the soil. Furthermore, soil organic carbon (SOC) decreased significantly with increasing alkalinity of irrigation water. Continuous irrigation with alkali water reduced grain yield of wheat by 31.7% over BAW. Moreover, the addition of gypsum and sulphuric acid has shown some capacity to partially restore soil properties, although not to the level of BAW. The majority of soil parameters under both crop cultivars showed a similar trend. The study's findings led to the conclusion that continuous applications of alkali water drastically degrade soil physicochemical properties. Partial neutralization of alkali water did not allow for the sustained existence of soil physicochemical properties. Consequently, it is recommended that the rate at which amendments are added to alkali water be adjusted to restore the decline in soil physicochemical properties.

Исследование закономерностей изменения солевого состава буровых шламов в процессе их утилизации

Drill cuttings in their natural state have viscous-plastic properties; in a dry state they are cohesive and hard. This is due to the content of sodium ions in the absorbing complex. Features of the physical and mechanical properties of drill cuttings indicate its ability to absorb and retain dissolved salts. When gypsum is added to drill cuttings in different percentages of the waste volume, the concentration of chloride ion changes in all samples, and chloride-sulfate salinization is observed. The content of sulfate ion increases with a minimum volume fraction of gypsum application. The addition of gypsum in a volume fraction of 15 and 20% affects the reduction of phosphate and carbonate ions. A change in electrical conductivity indicates an increase in the concentration of water-soluble salts in the water extract, which is confirmed by a direct high correlation. When adding gypsum from 7–20% volume fractions, a significant reduction in the dense residue occurs. The use of gypsum increases the filtration capacity of drill cuttings. The use of gypsum makes it possible to lighten the granulometric composition of drill cuttings due to the active coagulation of colloids. As a result of the removal of water-soluble salts, optimal water-physical properties of drill cuttings are created, structuring and filtration properties of drill cuttings are increased. A mathematical model for predicting the dissolution of salts in drill cuttings allows taking into account uncontrollable factors (density, particle size distribution, filtration coefficient, content of water-soluble salts).

Gasification of municipal solid wastes with gypsum wastes under different gasifying environments

The global increase in population and rapid urbanization has been followed by a growing generation of municipal solid wastes and construction and demolition sector wastes. This has put increasing pressure on countries around the world to come up with sustainable ways to deal with issues related to waste generation, climate change, and social and environmental degradation. This paper investigates a novel means of co-utilization of municipal solid wastes (MSW) with gypsum wastes from the construction and demolition sector for energy recovery and materials recycling and explores synergistic improvement in their processed value. We investigated high-temperature pyrolysis and gasification under different gasifying environments of inert (N2), 10 % O2, 20 % CO2, and 70 % H2O at two different temperatures of 800 and 900 °C, in a semi-batch fixed bed reactor. Syngas obtained was analyzed for its composition and yield, while the solid residue obtained was analyzed for the crystalline phases of the inorganic content using powder-XRD (X-ray diffraction) diagnostics. These analyses revealed that increasing temperature as well as the addition of gypsum can significantly improve the carbon conversion and overall product gas yields.When comparing the gasifying environments, steam gasification provided increased syngas mass yields by up to 184 %, 425 % and 377 % respectively, as compared to CO2 gasification, O2 gasification, and pyrolysis environments. Adding gypsum at equal mass proportions (1:1) to MSW pyrolysis at 900 °C increased the syngas yield by 10 % compared to the non-catalytic case, while adding it at 800 °C reduced syngas yield by 6 % compared to the non-catalyzed pyrolytic case at 800 °C. Adding gypsum during O2 gasification increased the syngas yield by 25 % compared to the non-catalytic cases at 900 °C and increased by 12.5 % at 800 °C. However, the syngas yield was reduced by 84 % when gypsum was added at equal mass proportions (1:1) to steam gasification of MSW at 900 °C and 50 % for 800 °C. Adding gypsum to CO2 gasification also reduced the cumulative yield of syngas for both temperatures under investigation. However, the syngas quality was improved with gypsum addition as the yields of hydrocarbon were reduced. The char/solid residue was found to contain significant portions of CaS suggesting sulfur fixation capability of this process into the ash which can improve the ash characteristics in terms of metal recovery along with the improved waste conversion.

EXPERIMENTAL RESEARCH ON MECHANICAL PROPERTIES OF MAGNESIUM OXYCHLORIDE-BASED TITANIUM GYPSUM CONCRETE

To alleviate the environmental pollution, waste of resources of titanium gypsum (TG) and the industrial residue from the production of titanium dioxide by sulfuric acid method, and to develop new building materials, the effects of different dosage on the strength and microscopic properties of magnesium oxychloride cement (MOC) were studied by methods such as unlimited compressive strength, scanning electron microscope (SEM) and X-ray diffractometer (XRD). Results show that the compressive strength of the samples increases first and then decreases with the increase of the amount of titanium gypsum. In the control group, when the dosage was 0%, the compressive strength of the samples was 40.37 MPa. The compressive strength is 34.29 MPa at 50% dosage, which is lower than the compressive strength of the control group by 15.06%. The internal structure changes, and there is an incomplete reaction of SiO2. The addition of titanium gypsum increases the ductility of concrete, but has little effect on its elastic modulus. Therefore, the proper inclusion of TG in the TG-MOC gelling material can improve its deformation ability and maintain a certain strength. This provides a useful reference and guidance for the application of magnesium oxychloride-based titanium gypsum in engineering practice. Keywords: Magnesium oxychloride cement, Titanium gypsum, Mechanical propertie, Microscopic analysis, Compressive strength.

Effect of gypsum on hydration properties, composition and kinetics of low carbon belite-ye'elimite-Q phase-ferrite clinker

In this study, a new low-carbon clinker, belite-ye'elimite-Q phase-ferrite (BYQF), was produced and hydrated with and without gypsum at 8 %, 15 % and 30 % mass concentrations. The results show an optimum compressive strength of 122 MPa (90 days) with 30 wt% gypsum addition. The gypsum content determines the development of the compressive strength, which can be increased by 30 % to 105 % due to the change in gypsum content compared to BYF clinker. Gypsum inhibited strength decrease at late stage and shortened the induction period. Although 30 wt% gypsum reduced the dissolution rate of C2S and C4AF, it increased ettringite and AH3 content in the middle and late stages, which reduced porosity and promoted strength growth. Based above results, BYQF shows outstanding performance and is expected to be used as a sustainable building material.

Evaluation of Technological Properties of Mortars with the Addition of Plaster Byproduct

The incorporation of waste into construction materials is a potential topic for study and is seen as a solution for many industries that face the following impasse: the risk to the environment due to the accumulation of waste in yards. In view of this, during the production of lactic acid, which is widely used in industries, gypsum is produced as a byproduct, yielding one ton for each ton of lactic acid. Aiming at a functional destination for this byproduct, this study proposes its addition in mortars for covering walls and ceilings. The research proposal was a mortar in a 1:6 ratio (cement:sand) with the addition of 0, 3, 6 and 10% of industrial plaster byproduct. The cement used to prepare the mortar was CPII-E32. To characterize the raw materials, scanning electron microscopy, X-ray fluorescence and X-ray diffraction analysis were carried out. To evaluate the properties in the fresh state, a consistency index and mass density and entrained air tests were carried out. In the hardened state, mass density, axial compression strength, flexural tensile strength and water absorption via capillarity were evaluated after 28 days of age. Microstructural characterization techniques were also carried out on the reference mixtures and with 3% addition of the byproduct gypsum, such as scanning electron microscopy and X-ray diffraction. The results showed that the byproduct is hemihydrate and its addition improved the workability of the mortar. Mortars with the addition of byproduct gypsum showed a reduction in mechanical resistance. The most satisfactory results were for the mixes with a 3% addition, indicating greater resistance to axial compression and flexural traction, with 3.90 MPa and 1.14 MPa, respectively.

Increased monocarbonate formation during long-term hydration of CAC-limestone binder by calcium sulfate addition – A temperature-dependent XRD study

The long-term hydration of a mix with and without gypsum addition was investigated at 10, 23 and 40 °C by QXRD analysis. In addition, thermodynamic modelling was performed on all systems using GEMS to determine the stable phase composition and the influence of water loss during hydration. The results show that the formation of conversion-sensitive phases such as CAH10 is accelerated at 10 °C and hindered at 23 and 40 °C by the addition of gypsum. Moreover, at all different temperatures, monocarbonate forms next to AH3 as the main hydrate phase and the final phase composition is reached after at least 14 d (at 23 °C and 40 °C already after 2 d). Formation of low amounts ettringite only occurs at 10 and 23 °C during the entire storage time. At 40 °C, however, ettringite is not observed, which is probably due to water loss in the mix until 2 d.

Potential of Gypsum Waste as a Substitution and Filler Material in Concrete Manufacturing

Gypsum is a dental and construction material that used only at certain times. Gypsum waste can be mixed with food waste so that it endangers the environment. The gypsum waste needs to be separated and recycled. This study examines the potential use of gypsum waste as substitute and filler material in concrete manufacture, including: gypsum characteristic based on XRF, concrete maximum load, concrete compressive strength, concrete water absorption and heavy metal concentration analysis. Gypsum compositions used is 0%, 10%, 20%, 30%, 40% and 50%. The gypsum characterization results showed that there was 98.92% oxide, gypsum was included in type III gypsum, heavy metals such as: Fe = 10 ppm and Al = 16500 ppm, metallic elements such as: Si = 1950 ppm, Ca = 182900 ppm, Mg = 4560 ppm, K = 2200 ppm, and non-metallic elements namely: P = 580 ppm. The highest and lowest of maximum load and concrete compressive strength in the gypsum use as substitute and filler material are produced at the addition of 50% and 10% gypsum, respectively. The gypsum addition as substitute or filler material reduces the concrete water percentage. The heavy metals concentrations resulting from the 28-day-old concrete immersion were: Fe = &lt;0.084 ppm and Al = &lt;0.156 ppm.

Physical, mechanical and microstructural properties of one-part semi-lightweight geopolymers based on metakaolin modified with gypsum and lime

The elemental composition of precursors is crucial for the performance development of geopolymers. Metakaolin (MK) was used to produce one-part geopolymers (OPG), and the influence of calcium-based components (lime and gypsum) on their properties was investigated. The experimental results show that the use of lime instead of MK increases the fluidity of the mixture, while the addition of gypsum decreases the fluidity. Meanhwlie, the use of lime to replace a small amount of MK increases the concentration of activator by consuming water and the dissolution of calcium ions also participates in the geopolymerization reaction, which enhances the mechanical properties and durability of OPG. When 10 % lime is applied, the 7-d and 28-d compressive strengths of OPG are increased by 210 % and 157.14 % compared with the plain sample, respectively. The addition of gypsum generates AFt in OPG, which reduces the compactness of the microstructure, which is not conducive to the development of the strength and durability of OPG. When 10 % gypsum is applied, the 28-d compressive and flexural strengths of OPG are decreased by 32.14 % and 26.67 % compared with plain samples, respectively. As the lime content increases, further addition of gypsum to OPG has a more negative effect on OPG due to the plundering of calcium ions in the lime. The 28-d dry density of OPG is between 1585 and 1729 kg/m3, which makes it have a lower thermal conductivity (0.87–0.94 W/m·K).

Նեֆելինային սիենիտներից կավահողաբելիտային ցեմենտի բաղադրության մշակում

The paper studies the nepheline syenites of the Hrazdan Tezh Mountain deposit as a raw material for the production of alumina-belite cement. Based on the research results, a two-component raw material mixture was calculated using limestone travertines from the Ararat deposit, with the addition of gypsum and a mineral-forming additive to the composition of the charge from limestone and syenite. Belite and low-basic calcium aluminates were identified as the main phases in the clinkers fired from these components.