Gypsum Content Research Articles

Investigating the influence of sample size on measurement of collapse of gypseous soil

This study aims to analyze the behavior of soils containing gypsum, specifically focusing on the impact of gypsum content and different soil parameters. Several physical tests and assessments were conducted on synthetic gypseous soil, which consists of silty clay and different proportions of gypsum (20%, 40%, and 60%). The research emphasizes the notable influence of gypsum concentration on soil collapsibility, whereby higher levels of gypsum are associated with a heightened propensity for collapse. The soil behavior is significantly influenced by various factors, including but not limited to the initial void ratio, total unit weight, and degree of saturation. Quantitative predictive models have been constructed to describe these interactions, offering significant tools for engineers and researchers engaged in the study of gypseous soils. Furthermore, this study provides insights into the intricate patterns of human settlement throughout history, focusing on the significance of gypsum bonding and unit weight in reducing soil settlement. The results demonstrate that the single oedometer test exhibits greater collapse potential values at 200 kPa compared to the double oedometer test, showing an increase of 27% and 44%, respectively. The observed discrepancy can be ascribed to softening and gypsum dissolving, which commence before reaching a pressure of 200 kPa in the double oedometer test. Moreover, the research presents a modified collapse test with a more dependable methodology for identifying collapsible gypseous soil in contrast to conventional techniques. The proposed methodology entails employing larger sample sizes and achieving complete particle saturation by upward water flow, mitigating the drawbacks observed in traditional methodologies, namely inadequate sample sizes and incomplete particle saturation. In general, this study greatly enhances our comprehension of the mechanics of gypseous soil and offers useful methodologies for evaluating and addressing soil collapsibility in geotechnical and building endeavors.

Hydraulic characteristics of gypseous sand soil using modeled oedometer cell

The current study investigates the permeability of the sand soil using a modified Odometer cell with a constant head connected to a data logger and computer software. The soil sample is taken from the Al-Jameah district in Al-Najaf city, Iraq. The soil is classified as “SP” according to the unified soil classification system, with a gypsum content of 29%. A modified Oedometer with computerized water volume change is adopted. The samples are disturbed and remolded into the Odometer cell with different densities of 90% and 95% of the maximum Proctor dry density and initially dry. Each of the specific density samples is subjected to three different water heads: 80, 100, and 120 cm. The first head (80cm) is applied to the initially dry soil up to a saturated and steady state. While the other heads are subjected after the completion of the first one. The results of the modification are verified with the results in the literature and it is more flexible and accurate due to the digital recording of the data by the Linear Variable Differential Transformer (LVDT). The results of the water volume change versus time and the coefficient of permeability state that the dry condition (first head) of the specimen is the longest duration of the test for both 90% and 95% density in the change from dry to saturated and then to steady condition. For a 95% density longer than the 90% as expected, but after completing the saturation by the first head, there are method results of the 90% and 95% density, and this may be attributed to the higher water head and/or the effect of the gypsum dissolution.

Reliability of Soil Water Characteristics Curve under Different Normal Stresses for Unsaturated Sand

The soil water characteristics curve (SWCC) demonstrates a link between soil moisture content and suction. The SWCC is almost treated as an index parameter in unsaturated soil. The soil permeability and shear strength can be linked to SWCC. SWCC is established using filter paper for the wetting path. This paper compares SWCC for both cases stress-dependent and no stress (reference) in the wetting path. The samples of soil are brought from Al-Najaf City with a gypsum content of 29%, Iraq. The stress-SWCC is studied using a modified Oedometer cell with controlled water and air entrance to apply a specific matric suction. While the reference SWCC is estimated using the filter paper method. Matric suction is conducted at a range of pressures from 90 kPa to 0 kPa. The tests use three net normal stresses of 100, 200, and 400 kPa. The results show that there are decreasing values of the SWCC with increasing normal stresses. An interesting result is that this decrease is high and has zero matric suction. The water entry value (WEV) with the most significant value of the water entry change is represented by the matric suction of 50 kPa.

Comparison of Some Land Suitability Evaluating Methods for a Selected Gypsiferous Part in the Northern Karma Region for Irrigated Agriculture

To compare the efficiency of three systems to evaluate the suitability of Gypsiferous land for irrigated agriculture, an area of 8885.4 hectares was selected in the Tharthar region – Iraq within the Euphrates terrace, which formed at Pleistocene period and mainly consisted of gypsum, the study included a semi-detailed survey of the area's soil using the Free-lance method, by selecting three parallel transects, according to the variations in texture class, soil salinity and content of gypsum, five representative pedons locations were identified and morphologically described, also soil samples from each horizon were obtained, as well as we obtained water samples from the Euphrates river-Tharthar canal and every wells located in the study area, it's transferred to the laboratory and the required analyzes were performed. The result showed the predominance of the medium soil texture class and slightly saline soil class (S1) in the study area, with a decrease in the soil carbonate content, on the contrary the soil gypsum content was increased. All wall waters was salinity, which poses a danger to agricultural use, compared to the water of the Euphrates river. A discrepancy was observed between the obtained land suitability classes. While the Sys and Verheye, 1972 system showed two poor suitability classes, Sys et al. 1991 and Al-Baji et al. 2010 has improved the appropriateness of the varieties, but the Kadhim, 2012 system was the best in terms of application in order to include the quality of irrigation water within the classification, so its results were more close to the reality diagnosed during the field visits to the study area and the questionnaire from the land users of the region

In Vitro Comparison of Differences in Setting Time of Premixed Calcium Silicate-Based Mineral Trioxide Aggregate According to Moisture Content of Gypsum.

Recently, a paste-type premixed calcium silicate-based mineral trioxide aggregate (MTA) product that quickly solidifies through a pozzolanic reaction was introduced to replace existing MTA, which has the disadvantage of a long setting time. In this study, we evaluated the effect of moisture content in the root canal on the setting time of premixed calcium silicate-based MTA in a simulated root canal environment using Endoseal MTA and Well-Root ST, among commercially available products. The setting time was measured according to ISO 6876/2012. A mold made using grades 2, 3, and 4 dental gypsum according to the classification of ISO 6873/2013 was used to reproduce the difference in moisture environment. Differences in moisture content were measured using micro-computed X-ray tomography (micro-CT). The micro-CT results showed that the moisture content was the highest and lowest in the grade 2 and 4 gypsum molds, respectively. Moreover, the setting time indicated by the manufacturer was the shortest for the grade 2 gypsum mold. Hence, the differences in moisture content significantly affect the setting time of MTA. This result can help set future experimental conditions and develop premixed calcium silicate-based MTA products.

Geotechnical Behaviour of Gypseous Soil Treated by Geopolymer Additives

Gypseous soil is well-known for its numerous engineering problems. When this soil is exposed to water, the gypsum in the soil dissolves, causing the buildings built on it to collapse; so, treating gypseous soil is important for improving its engineering characteristics. The present paper focuses on studying the effect of adding geopolymer on mechanical characteristics of gypseous soil. This study presents the results obtained from a series of experimental tests, including direct shear, consolidation, and collapsibility tests. Tests were conducted on samples of gypseous soil taken from depth 1.5 meters below ground level with gypsum content of 41%. The geopolymer was used in three different molarities for the collapse test (10M, 12M, and 14M) and a 14 molarity only for the shear and consolidation tests, where equal proportions of fly ash were combined with an alkaline activator that was composed of sodium hydroxide and sodium silicate. The binder (fly ash + alkaline) to the soil was added to the treated samples during mixing at a rate of 20% by weight. The findings showed that treating the soil with geopolymer leads to a notable enhancement in the angle of internal friction of the soil particles from (37 to 42) degrees. as well as a reduction in the soil compressibility and a reduction in the susceptibility of the soil to collapse, with an improvement degree of 64% when using a geopolymer with a molarity of 14 M. This improvement was achieved by using a geopolymer with a higher concentration of NaOH. The best results were achieved when a geopolymer with a molarity of 14 was used, which is the ideal ratio.

Preparation and characterization of novel spontaneous foam ceramics based on all-solid waste

Foam ceramics were prepared through spontaneous foaming behavior using silicomanganese slag and desulfurization gypsum as raw materials. The effects of desulfurization gypsum content and firing temperature on foam ceramics' pore morphology and physical properties were investigated. The phases and microstructure of the samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and comprehensive thermal analysis (TG-DSC). The results showed that increasing the desulfurized gypsum content is beneficial for promoting the formation of a liquid phase and a uniform pore structure. The prepared ceramics exhibited low density (0.54 g/cm3), high porosity (80.56%), and compressive strength (5.85 MPa). Analyzing the toxic leaching behavior of heavy metal ions in the samples confirmed that all samples were safe and harmless. Furthermore, it was demonstrated through the self-foaming mechanism that desulfurization gypsum could be employed as a new type of spontaneous foam solid waste. This study provides an effective method for the synergistic preparation of foamed ceramics using silicomanganese slag and desulfurization gypsum. The utilization of solid waste in foamed ceramic production not only addresses the issue of significant waste accumulation but also offers economic benefits.

Comparison between two gypsum content determination methods applied to the study of soils in arid regions

With the scarcity, degradation of soils, the growing populations and the need to guarantee their food security, the valorization of gypsum soils widespread in arid and semi-arid regions is becoming a necessity. North African countries have a large part of their land area located in arid regions. It is therefore important to characterize the gypsum content using simple, rapid, economical and, environmentally friendly methods. Several methods have been proposed in the literature (chemical, thermogravimetric, and x-ray techniques). In this work, a comparison between two methods for gypsum determination in soils was undertaken. The first method of Coutinet is chemical and based on the use of BaSO4 for the precipitation of sulfate ions. The second method is Artieda method which is based on measuring the weight difference caused by the loss of crystalline water from gypsum molecules between the temperatures of 70 and 90 °C. To achieve the objective of this work, forty-three soil samples were analyzed. They were taken from two arid regions (Ouargla and Touggourt) located in the northern Sahara (Algeria). The soils contain gypsum accumulations. The results showed that most of the samples are slightly gypsiferous, with 36 and 32 samples for the Coutinet and Artieda methods respectively. A strong positive correlation (R2 = 0.95) exists between the results of the two methods studied. For gypsum contents higher than 2 %, the correlation coefficient is 0.94. However, for samples with contents less than 2 %, the correlation is very weak with R2=0.19. The Artieda method is thus encouraged for the gypsum quantification in soils of arid regions. This method is easy, requiring simple laboratory equipment (mainly a ventilated oven and a precision balance). Chemical methods have the disadvantage of being time-consuming and using expensive chemicals that are dangerous for the environment and human health.

Effect of Initial Water Content on the Collapsibility of Natural and Cement-Treated Gypseous Soils

Abstract Soils that exhibit high volume change when its water content is changed are considered collapsible soils. Gypseous soils are one of the main types of collapsible soils which can be found in arid and semiarid areas. In this study, the effect of initial water content on the collapsibility properties of natural and treated gypseous soils with 5% of cement is experimentally investigated. The soils tested at different initial moisture content i.e. 5 %, 10 %, 15 %, 20 %. Two types of soil were used with different gypsum content 28.43 % and 43.62 % named soil 1 and soil 2 respectively. The soils were taken from Tikrit city in Saladin governorate – Iraq. The results show that the initial water content has significant effect on the collapse potential. The reduction in collapse for natural soils reaches up to 70 % when the initial water content was 20 %. Furthermore, the reduction in collapse for natural soils was greater than that for treated soils with different initial water content. It can be concluded that increasing initial water content can reduce the sudden collapse which is a major problem.

The Effect of Addition Humic and Fulvic Acid on the Adsorption of Copper in Gypsum Soils

In order to study the interaction between humic acids and gypsum levels and their effect on the adsorption of copper in soil, three soil levels with gypsum content were chosen and prepared in the laboratory. They were treated with three levels of humic acids: (H0) with no addition (0%), (H1) with an addition of (1%), and (H2) with an addition of (2%). Copper ions were measured for the adsorption experiment. The data were treated using Langmuir and Freundlich equations to describe the adsorption nature. The results were as follows: both soils had high values for both Freundlich (82%) and Langmuir (92%) equations. Thus, the second equation outperformed the first equation by a difference of 10%. The adsorption values using the Langmuir equation ranged from (2500-588), while for the Freundlich equation, the sorption capacity values ranged from (186.98-47.53). Only the Langmuir equation recorded values for binding energy, which ranged from (53.76-1.059), and the highest binding energy values were associated with humic acid additions compared to untreated soil.

Suction Variation of Natural and Treated Unsaturated Gypseous Soils During Wetting

Abstract The current work is directed to study the variation of suction with time and soil water characteristics curve (SWCC) for natural and treated gypseous soil treated with two types of additive (lime and silica fume) compacted at different initial degrees of saturation S0 = 20 and 50 %. Soil subjected to wetting in an upward direction. Three types of gypsum soils were experimented with different gypsum content 15, 35, and 60 % taken from various sites in Salah Al-dean government, Iraq. The main results show that the air-entry value, residual values, and the time required for the entire saturation stage increases with increasing gypsum content and treatment with lime and silica fume and they for soil treated with silica fume are greater than for soil treated with lime. The rate of flow for soil treated with silica fume is less than that of soil treated with lime. The treated soil is more effective in increasing the time required for the entire saturation stage and decreasing the rate of flow when compacted at an effective degree of saturation S0 = 50 %.

Exploring sulfate optimization techniques in Limestone Calcined Clay Cements (LC3): limitations and insights

This study assessed the feasibility of different methods for sulfate optimization of limestone calcined clay cements (LC3). LC3-based pastes were studied with kaolinite and montmorillonite calcined clays and different gypsum contents. Quartz powder was used in reference systems. The sulfate optimization was done using isothermal calorimetry, compressive strength, thermogravimetric analysis, and chemical shrinkage analysis at different ages. Overall, there is no single best technique to predict sulfate optimization in LC3, carefully combining multiple techniques can assist in more coherent decision-making, such as isothermal calorimetry with compressive strength within 72 h. We recommend the optimum LC3 sulfate content based on criteria established by the decision-maker (academia or industry). Either based on mechanisms and kinetics reactions, phase assemblage, compressive strength, or shrinkage of LC3 mixtures containing different SO3 content. Also, the results of montmorillonite-LC3 systems were satisfactory without accelerated sulfate depletion.

Comparison of Hydraulic Conductivity Estimation using Falling Head and Mini Disk Infiltrometer in Gypsiferous Soil

Hydraulic conductivity (K) was calculated using falling head (FH) and Mini Disk Infiltrometer (MDI) for 15 Gypsiferous soil. In this study the hydraulic conductivity was predicted by basic infiltration rate (BIR) and using two methods, Wooding-Gardner (W-G) and van Genuchten-Zhang (V-Z). Hydraulic conductivity was measured using a falling head permeability test, and the results were compared to the expected values. A statistical analysis (t-test) was performed to show the significant differences between the two methods and the falling head. The results showed high agreement between (K) values estimated by (FH) and (BIR) for different gypsum content, the results showed that Both methods did not succeed in estimating the hydraulic conductivity for different gypsum content. Values derived from (W-G) method are exaggerated and the values derived from the (V-Z) method are very low compared to the values derived from (FH).

Effect of long-term drying on the performance of sulfoaluminate cement

The effect of continuous drying for 360 days on the performance of sulfoaluminate cement (SAC) with different contents of gypsum was investigated, with ordinary Portland cement (OPC) selected as the control. First, the compressive strengths and deformation of mortars dried at 40 °C for different times were tested. Meanwhile, for the hardened cement pastes dried under the same condition, the mineral phase, micromorphology, and pore structure evolutions were monitored. Results indicated that the compressive strength of SAC mortars showed a significant decrease after 360 days of drying, whereas the compressive strength of OPC mortar was still higher than that before drying. Moreover, the SAC mortars with high gypsum content exhibited significant shrinkage after drying. This was because the ettringites lost crystal water during the drying process, and the crystallinity decreased gradually until they were amorphous. Meanwhile, the ettringites showed a shriveled morphology after drying, and became weaker than before drying. Besides, both the pore size and total porosities of the SAC hardened cement pastes showed a noticeable increase after 360 days of drying. However, the hydration products of OPC were stable under the same dry condition. This study provides direct evidence to explain the mechanical strength reduction of SAC in service.

Comparing Two Saline-Gypseous Wetland Soils in NE Spain

Small (<1 km2) saline wetlands scattered across the landscape often go unnoticed or are threatened by urbanization or other interventions, despite their role as biodiversity shelters. This study is needed to show methods for monitoring this specific kind of wetland, and to guide the selection of analytical techniques. We provide data and comparisons for salient soil traits of two quasi-pristine gypsiferous and saline wetlands named Farrachuela (FA) and Agustín (AG). The soil characteristics presented in this article are a more sensitive indicator of their ecological status than some of the most used indicators, such as birds and plants. We found significant differences between the two saladas in percent water saturation, equivalent calcium carbonate, gypsum content, and soil salinity expressed as electrical conductivity both of 1:5 soil-to-water ratio and of saturation extracts. The differences were also significant in the concentrations of Mg2+, Na+, and Cl−, while they were non-significant for Ca2+, HCO32−, and SO42−. The mean contents of the six ions were lower in FA than in AG. Both pH and sodium adsorption ratios were significantly different between the two wetlands. The data are mainly examined and plotted by displaying their non-parametric statistics, a synoptic approach that will allow us to monitor the evolution of the wetlands against both traditional agricultural pressures and emerging green energy infrastructures. Last but not least, we discuss the shortcomings of some standard laboratory methods when applied to gypsum-rich soils.

TRANSFORMATION OF PHOSPHOROUS IN GYPSIFEROUS SOILS AS AFFECTED BY DIFFERENT FERTILIZERS, LAND USE AND INCUBATION PERIODS

This study was investigated the P transformation in three soils gathered from different locations (Agricultural researches center in Tel Afar, Ain-Talawi and Sinu in Singar) in north of Iraq representing different gypsum content and land use [wheat (W), vegetable (V), uncultivated (Un)] after incubation period of (0, 5, 10, 30, 60, and 90) days. The soils were treated with 200 mg P kg-1 as superphosphate (S) or 30 g kg-1 soil manure as a cattle manure (A) or compost (p). The appropriate amounts of water were added to bring soil to estimated field capacity. After the specified time of each incubation period, sub-sample of soil analyzed for P, pH, EC and Ca. The results showed that P status affected by amendments and incubation periods. The soil which has more available P was the soil which treated with cattle manure. Generally, P was more available under (V) use compared to (W) use. After 90 days of incubation P solubility generally was higher than after 30 days. It appears from P solubility diagram that the best treatment was (A) which almost located between the two more soluble P compounds DCPD and DCP.

Positive and negative impacts of flue gas desulfurization (FGD) gypsum on water quality

Flue gas desulfurization (FGD) gypsum, a by-product of carbon-based energy sources, has typically been incorporated as a component of concrete mixes and wallboard and beneficially used as an agricultural amendment to enhance terrestrial crop production and improve the quality of runoff. These various uses for the by-product aid in reducing the amount that is ultimately landfilled. Limited studies have investigated its benefits when used directly in aquatic settings, such as ponds and lakes, to increase hardness and potentially mitigate eutrophication. A 36-day field mesocosm experiment tested a larger range of FGD gypsum concentrations (500–2000 mg/L) than those previously tested in the literature to investigate its desired and potentially undesired impacts on water quality, including the algal community. High FGD gypsum concentrations, 1000 and 2000 mg/L, were found to have more undesired impacts than the 500 mg/L treatment, including an initial spike in cyanobacteria, a decrease in total zooplankton abundance, and an increase in certain trace metals in the highest treatment. Ultimately, the 500 mg/L FGD gypsum treatment was found to have fewer undesired impacts while still resulting in significant desired effects, including those on hardness and pH, as well as moderate reductions in algal abundance. This experiment provides a better understanding of the effects of FGD gypsum when directly used in an aquatic setting, determines an optimal dose for future field experiments, and helps provide the groundwork for developing an upper threshold on FGD gypsum so as to not have the negative effects outweigh the positive.

Enhancement of Gypseous Soil Engineering Properties Through High-Density Polyethylene Polymer Addition: A Comprehensive Experimental Assessment

An experimental investigation was conducted to scrutinize the influence of high-density polyethylene (HDPE) polymer on the engineering properties of gypseous soil. Soil samples, possessing 38% gypsum content, were extracted from the Tikrit region, Iraq, and were subsequently subjected to varying HDPE polymer concentrations of 1%, 3%, and 6%. An observed augmentation in the maximum dry density was noted when a minuscule quantity of 1% HDPE polymer was incorporated. However, a subsequent increase in polymer concentration resulted in a discernible decrease in dry density. Examination via the double oedometer test elucidated a significant reduction in collapse potential by 64%, 77.7%, and 83.2% upon addition of 1%, 3%, and 6% HDPE polymer, respectively. Direct shear test outcomes revealed a complex influence of HDPE polymer on soil cohesion. In the dry state, a 1% and 6% HDPE polymer addition led to a cohesion increase by 50% and 16.67%, respectively, whereas a 33.3% decrease was observed at a 3% polymer concentration. Conversely, in the soaked state, cohesion was found to decrease by 50% at 1% and 6% HDPE polymer concentrations, and entirely diminished with a 3% polymer addition. Interestingly, the internal friction angle (ϕ) exhibited an increase in both dry and soaked states with escalating HDPE polymer percentages. A contradictory behavior was noted in the California Bearing Ratio (CBR), which decreased in the dry state but increased in the soaked state with a rise in HDPE polymer ratios. In conclusion, the present study substantiates that the addition of HDPE polymer induces modifications in the engineering behavior of gypseous soil. Further research is encouraged to optimize the HDPE polymer concentration for ground enhancement applications.

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.

Implementing GIS and linear regression models to investigate partial building failures

One of the most dangerous field problems in the civil engineering discipline is the suddenly developed cracks in the building, which could be caused by the swelling of the subsurface soil. Thus, this work has focused on employing a procedure in the geographic information system known as the inverse distance weighted (IDW) technique, to analyze the extent of cracks in a residential complex in the city of Kirkuk in Iraq using the physical and chemical soil data for seven boreholes from the field of the study. Physical soil parameters such as liquid limit (LL), gravel, sand, silt and clay percentages were characterized first, followed by chemical properties such as gypsum content (GYP), total suspended solids (TSS), potential of hydrogen (pH), and organic content (ORG). Furthermore, statistical studies such as plasticity index (PI) and soil characteristics association, linear single, and various linear multi-regression models were used. The data analysis shows that there are significantly positive and negative relationships between PI as a swelling indicator and the physical and chemical soil properties, although weak to moderate correlations were observed between PI and these variables. The PI values were accurately predicted by the proposed linear multi-regression models of the physical and integrated physical and chemical soil characteristics, with multiple R values of 0.92 for both models. As a result, the suggested statistical models can provide complete geographic and mechanical explanations for the crack sources in the investigated residential complex.