Addition Of Calcium Sulfate Research Articles

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.

Effects of calcium sulfate as activator on mechanical properties of PVA fiber reinforced cementitious composites with high-volume fly ash

In order to study the role of calcium sulfate as activator in cementitious composites, mixtures with different calcium sulfate content ratios were designed. On the basis of satisfying the engineering castability, the effects of calcium sulfate on the mechanical properties of PVA-ECC with high-volume fly ash were investigated by uniaxial compression and tensile tests. The microstructure was analyzed by SEM and XRD. The results show that the addition of calcium sulfate has a certain activation effect and can promote the formation of ettringite. The early strength of PVA-ECC with high-volume fly ash was improved, and the tensile strain decreased by less than 0.92%. The fiber failure mode was analyzed according to the material failure mechanism. The “slip-hardening type” makes ECCs work better with PVA fibers, showing obvious strain hardening and multiple cracking characteristics. Based on the theoretical analysis, the evaluation method of obtaining high tensile strain was established, and the optimal mix ratio and calcium sulfate content of PVA-ECC with high-volume fly ash were proposed.

Experimental Characteristics of Hydrocarbon Generation from Scandinavian Alum Shale Carbonate Nodules: Implications for Hydrocarbon Generation from Majiagou Formation Marine Carbonates in China’s Ordos Basin

The hydrocarbon source rocks of the marine carbonates of the Ordovician Majiagou Formation in the Ordos Basin are generally in the high-overmature stage and are, therefore, not suitable for hydrocarbon thermal simulation experiments. Their hydrocarbon generation potential and hydrocarbon generation characteristics are not clearly understood. Meanwhile, Nordic Cambrian carbonates are similar in lithology, parent material type, and sedimentary age, and are in the low evolution stage, which is suitable for hydrocarbon thermal simulation experiments. Therefore, in this study, we selected the Nordic carbonates for the gold tube thermal simulation experiment to analyze the content and geochemical characteristics of the thermal simulation products. The experimental results are also compared and analyzed with the characteristics of thermal simulation products of Pingliang Formation mud shale (contemporaneous with the Majiagou Formation) and Shanxi Formation coal (in the upper part of the Majiagou Formation), which are similar to the Majiagou Formation in the Ordos Basin. The results showed that the Nordic carbonate has different hydrocarbon production characteristics from the mud shale of the Pingliang Formation of the same parent material type, and although the hydrocarbon production yields of the two are not very different, the carbonate still produces methane at 600 °C. The hydrocarbon production yield of the Nordic carbonates is almost equivalent to that of type-II2 kerogen, indicating that the hydrocarbon production yield is not related to lithology and only to the organic matter type; however, the Nordic carbonate can produce a large amount of H2S. The alkane carbon isotope changes are mainly controlled by the degree of thermal evolution, showing gradual heaviness with increasing temperature. No carbon isotope sequence reversal occurred during the thermal simulation, and its distribution range is roughly the same as that of the alkane carbon isotope composition of the mud shale of the Pingliang Formation. The ethane carbon isotope composition is as heavy as −21.2‰ at the high-temperature stage, showing similar coal-type gas characteristics. The addition of calcium sulphate (CaSO4) causes the TSR reaction to occur, which has a significant impact on the methane content under high maturity conditions, reducing its content by more than 50% at 600 °C. However, the addition of CaSO4 increases the yield of heavy hydrocarbon gases, such as ethane, and promotes the production of C6-14 hydrocarbons and C14+ hydrocarbons at high-temperature stages, and the addition of CaSO4 substantially increases the yield of H2, CO2, and H2S. The thermal simulation results have implications for the hydrocarbon formation mechanism of the early Paleozoic marine carbonate formation system in the stacked basins of the Ordos Basin and the Tarim Basin in China.

The competitive hydration of [formula omitted] and Cl− in alkali-activated slag cementitious materials

This article presents a study on alkali-activated slag cementitious materials that were doped with varying levels of calcium chloride and calcium sulfate. The article delves into the hydration products and mechanisms of the cementitious material, utilizing pH values, X-ray diffraction (XRD), thermogravimetric (TG), and scanning electron microscopy (SEM). The results show that under the condition of Ca2+ dosage less than 2.5%, CaCl2 is more advantageous than CaSO4 in improving compressive strength. Under the condition of Ca2+ dosage of 2%, adding CaCl2 to the cement paste increased the compressive strength of the test block by 230% at 3 curing days and by 190% at 28 curing days compared to the sample with calcium oxide. After calcium chloride replaced calcium sulfate, the compressive strength was improved. At a Ca2+(CaCl2)-Ca2+(CaSO4) ratio of 1:1, the strength was increased by 44% and 18% at 3 days and 28 days, respectively, compared with the addition of calcium sulfate alone. SO42- can promote the formation of ettringite (AFt), while Cl− can promote the formation of Friedel's salt (3CaO·Al2O3·CaCl2·10H2O, F’s). The contribution of hydrated Friedel's salt to compressive strength is greater than that of AFt. As Cl− is added to the alkali-activated slag cementitious materials stimulated by SO42-, Cl− is dominant in the hydration process, and form Friedel's salt with hydrated calcium aluminate and calcium hydroxide, while promoting the increase of C-S-H gel quantity, thus improving the compressive strength of the material.

Hydrate assemblage stability of calcium sulfoaluminate-belite cements with varying sulfate content

To assess the feasibility of employing calcium sulfoaluminate (CSA)-belite cements for radioactive waste encapsulation purposes, a series of 40 mixes were conducted on a 3-litre scale. This series of tests incorporated two commercially available CSA-belite clinkers, gypsum or anhydrite addition at 15, 25 or 35 wt%, a water to solids ratio of 0.5, 0.6 or 0.7, and a high or low mixing shear regime. CSA clinkers chosen contain predominantly ye’elimite, with some belite, and a small quantity of calcium sulfate as anhydrite. This paper outlines the effect of these parameters upon the phase composition and structure of these CSA samples tested at 7, 28, and 90 days. The development of the hydrate assemblage was monitored in order to assess the suitability of these grouts for use in encapsulation processes. The trends in phase development and evolution are consistent across both clinkers tested. The levels of ettringite formed as a hydration product are dependent upon the levels of calcium sulfate addition and the availability of water, with ettringite production evident, though at a decreasing rate, from between 7 and 90 days. Throughout the entire catalogue of mixes, no ettringite decomposition was detected. The majority of belite within both clinkers appears to remain unreacted, with a small increase in mixes producing less ettringite. Simulations also show similar phase assemblages to those encountered experimentally, with little phase development after 90 days.

Understanding the effect of sulfate ions on the hydrothermal curing of autoclaved aerated concrete

The addition of calcium sulfate in the preparation of autoclaved aerated concrete (AAC) leads to improved mechanical properties but the precise mechanism is not well constrained. To study this, the hydrothermal curing process was monitored quantitatively with and without sulfate addition using ex situ and in situ X-ray diffraction. Higher concentrations of sulfate ions delayed the formation of the intermediate C-(A)-S-H phase and the dissolution of quartz. Once the additional sulfate ions were depleted by hydroxylellestadite formation, C-(A)-S-H formation and quartz dissolution started simultaneously at higher rates. This delayed reaction is suggested to enhance the mechanical strength by i) improving the diffusion of silicate ions in hydrothermal solution, ii) improving the distribution of C-(A)-S-H and tobermorite crystallites, and iii) closing larger capillary pores in the range of 1–5 μm. This could explain some of the ambiguous results from previous studies and provide an opportunity to optimize the AAC production process.

3D-printed composite, calcium silicate ceramic doped with CaSO4·2H2O: Degradation performance and biocompatibility

Calcium silicate is a common implant material with excellent mechanical strength and good biological activity. In recent years, the addition of strengthening materials to calcium silicate has been proven to promote bone tissue regeneration, but its degradation properties require further improvements. In this paper, calcium silicate was used as the matrix, and 10 wt% hydroxyapatite and 10 wt% strontium phosphate were added to im prove the biological activity of the scaffold. The effect of adding different amounts of calcium sulfate dihydrate (CaSO4·2H2O) on the degradation of the scaffold was explored. A porous ceramic scaffold was prepared by digital light processing (DLP) technology, and its performance was evaluated. Cell experiments showed that the addition of calcium sulfate improved cell proliferation and differentiation. Simulated body fluid (SBF) immersion tests showed that small amounts of apatite deposits appeared on the fourth day, larger deposits appeared on the 14th day, and degradation occurred on the surface after 28 days of immersion. Mechanical tests showed that the addition of 5 wt% CaSO4·2H2O improved the compressibility of the composite. After soaking in SBF for 14 days, it retained its compressive strength (11.8 MPa), which meets the requirements of cancellous bone, demonstrating its potential application value for bone repair.

Effect of the addition of calcium salts on the structure and anticorrosion properties of siloxane-poly(hydroxyethyl methacrylate) hybrid coating applied on Ti-6Al-4V alloy

Siloxane-pHEMA hybrid coatings with the addition of calcium chloride and calcium sulfate during the synthesis of the material were produced by the sol–gel method and deposited on Ti-6Al-4V alloy by dip-coating. The structural characteristics of the hybrid materials were analyzed by means of Nuclear Magnetic Resonance and Small/Wide Angle X-ray Scattering; their morphological properties were analyzed by means of Scanning Electron Microscopy and Atomic Force Microscopy. The electrochemical behavior and resistance to corrosion of hybrid coatings with and without addition of calcium salts were analyzed by means of Electrochemical Impedance Spectroscopy. The results showed that the coatings were homogeneous due to the rigid silica network formed during the polymerization, hydrolysis and reactions of condensation. In the sample, into which calcium sulfate was added, there was a decrease of the average roughness value (15.0 nm), while exhibiting regular topography and good adhesion to the substrate, suggesting that this coating has appealing characteristics for anticorrosive applications. Electrochemical tests in simulated body fluid (that underwent simulation) showed that the coatings with hybrid system showed better properties of a barrier with up to 96 h of immersion, in comparison to samples without coating. Therefore, these coatings showed promising features suitable for anticorrosion applications in biomaterials. Moreover, due to the addition of calcium sulfate, coatings made it possible to convey a good balance between biological and anticorrosion properties and, which in itself allows biocompatibility without compromising resistance to corrosion.

The importance of the calcium-to-magnesium ratio for phytoremediation of dairy industry wastewater using the aquatic plant Lemna minor L.

Lemnaceae are being exploited to remediate a variety of different wastewaters. Our aim was to remediate dairy processing waste, which is produced in large amounts, and contains valuable plant nutrients, for example, nitrate, ammonium, phosphate and iron. However, initial trials failed to establish the growth of Lemna minor on this medium. A lack of growth can be due to a lack of essential plant nutrients, or the presence of phytotoxic ingredients. In this study we show that not just nutrient concentrations, but also the ratios between them can be important in facilitating growth. Lab-scale experiments in which L. minor were grown on 100 mL of synthetic dairy industry wastewater demonstrated that the skewed Ca:Mg ratio in synthetic wastewater is a key obstacle to good growth. Experiments showed that a ratio which favors magnesium over calcium negatively affects L. minor growth and photosynthetic yield, leading to RGRs as low as 0.05 day−1. A change in this ratio to favor calcium, through the addition of calcium sulfate, leads to RGRs of 0.2–0.3 day−1. Experiments lead us to conclude that a Ca:Mg ratio of 1:1.6 or greater is necessary for L. minor growth, and therefore phytoremediation of dairy industry processing wastewater.

Effect of Waste-Derived Calcium Sulfate Additions on the Tribological Properties of Sintered Steel-Based Material

This study examined the effect of waste-derived calcium sulfate additions (2 to 8 weight percent) on the tribological properties of a sintered high-carbon steel material, commonly used for frictional applications. The calcium sulfate powder was obtained by crushing and subsequent calcination of waste plaster molds previously used for slip casting of ceramics. Samples were made using the powder metallurgy method. Powder mixtures were uniaxially die compacted and sintered at 1,100°C for 30 minutes in a reducing atmosphere. It was found that the density of the samples decreased with increased amounts of calcium sulfate. This was due to the lower theoretical density of the calcium sulfate as well as volumetric expansion of the samples. Ball-on-disc tribological testing was performed at room temperature. The addition of calcium sulfate resulted in an increase of the kinetic friction coefficient. The measured wear volume was slightly reduced with the addition of calcium sulfate less than 6 weight percent, beyond which the wear increased. The hardness of the samples was reduced with the addition of calcium sulfate. Increased calcium sulfate content decreased the sample deformation resistance while increasing the kinetic friction coefficient and the wear. This was likely due to the microstructural changes of the samples, which will be discussed.

Microbial decomposition of biomass residues mitigated hydrogeochemical dynamics in strongly alkaline bauxite residues

Effective neutralization of strongly alkaline conditions in bauxite residues (BR) is the fundamental step to initiate the process of eco-engineering BR into growth substrate (or soil-like medium) for direct phytostabilization with pioneer plant species. The present study aimed to evaluate the effectiveness of microbial decomposition of organic matter (OM) (i.e., biomass residues) in neutralizing the strong alkalinity of residues under saturated conditions, together with the regulatory role of calcium sulfate (CaSO4) addition. Admixing OM (i.e., sugarcane mulch, Lucerne hay) alone in the BR significantly lowered the porewater pH from 11.4 to around 9.0 by Day 7, which persisted until the end of incubation (Day 28). The pH reduction in the porewater of OM-amended BR coincided with the production of acidic organic compounds (mainly acetic acid). Diverse species of organotrophic bacteria (e.g., Enterobacteriales, Pasteurellales, Lactobacillales, and Streptophyta) were found to have colonized in the OM-amended BR, but which were dominated by haloalkaliphilic bacteria (e.g., Halomonas and Bacillaceae). The CaSO4 addition in the OM-amended BR further lowered pH to 8.3 in the porewater. Besides, the bioneutralization effects resulted in dramatic reduction (>90%) of soluble Al in the porewater, which is a prerequisite to lowering Al toxicity in plants. At the same time, the levels of major cations (i.e., K, Ca, Mg) in the porewater were elevated by the OM + CaSO4 amendment, which would facilitate subsequent leaching of these soluble salts to lower the salinity in the BR, and improve the diversity of organotrophic bacterial communities in the amended BR.

Reducing methane production with corn oil and calcium sulfate: Responses on whole-animal energy and nitrogen balance in dairy cattle

The addition of fat and calcium sulfate to diets fed to ruminants has resulted in a reduction in methane production, but the effects on energy balance have not been studied. A study using indirect calorimetry and 16 multiparous (8 Holstein and 8 Jersey; 78 ± 15 d in milk; mean ± standard deviation) lactating dairy cows was conducted to determine how mitigating methane production by adding corn oil or calcium sulfate to diets containing reduced-fat distillers grains affects energy and nitrogen balance. A replicated 4 × 4 Latin square design with 35-d periods (28 d of adaption and 4 d of collections) was used to compare 4 different dietary treatments. Treatments were composed of a control (CON) diet, which did not contain reduced-fat distillers grain and solubles (DDGS), and treatment diets containing 20% (dry matter basis) DDGS (DG), 20% DDGS with 1.38% (dry matter basis) added corn oil (CO), and 20% DDGS with 0.93% (dry matter basis) added calcium sulfate (CaS). Compared with CON, dry matter intake was not affected by treatment, averaging 29.6 ± 0.67 kg/d. Milk production was increased for diets containing DDGS compared with CON (26.3 vs. 27.8 ± 0.47 kg/d for CON vs. DDGS, respectively), likely supported by increased energy intake. Compared with CON, energy-corrected milk was greater in DG and CO (30.1 vs. 31.4, 31.7, and 31.0 ± 0.67 kg/d for CON, DG, CO, and CaS, respectively). Compared with CON, the addition of calcium sulfate and corn oil to diets containing DDGS reduced methane production per kg of dry matter intake (22.3, 19.9, and 19.6 ± 0.75 L/kg per d for CON, CO, and CaS, respectively). Similarly, methane production per kilogram of energy-corrected milk was reduced with the addition of calcium sulfate and corn oil to diets containing DDGS (14.2, 12.5, and 12.4 ± 0.50 L/kg per d for CON, CO, and CaS, respectively). Compared with CON and CaS, the intake of digestible energy was greater for DG and CO treatments (57.7, 62.1, 62.0, and 59.0 ± 1.38 Mcal/d for CON, DG, CO, and CaS, respectively). Intake of metabolizable energy was greater in all treatments containing DDGS compared with CON (50.5 vs. 54.0 ± 1.08 Mcal/d for CON vs. DDGS, respectively). Net balance (milk plus tissue energy) per unit of dry matter was greater in CO (containing DDGS and oil) than CON (1.55 vs. 1.35 ± 0.06 Mcal/kg for CO vs. CON, respectively). Tissue energy was greater in DG and CO compared with CON (6.08, 7.04, and 3.16 ± 0.99 Mcal/d for DG, CO, and CON, respectively. Results of this study suggest that the addition of oil and calcium sulfate to diets containing DDGS may be a viable option to reduce methane production and in the case of oil also improve net energy balance in lactating dairy cows.

Thermodynamical and catalytic aspects of zinc separation from aqueous solution

Abstract The present research work examines extraction mechanism of zinc by D2EHPA (Di-2-ethyl hexyl phosphoric acid) and comprehensively studies the main effective parameters on the process. Results of thermodynamic experiments showed that zinc extraction by D2EHPA was endothermic and spontaneous, and thermodynamic parameters including entropy and enthalpy were + 27.37 J·mol−1·K−1 and 25.21 kJ·mol−1, respectively. Gibbs free energy was varied between − 7.21 kJ·mol−1 and − 8.41 kJ·mol−1 with the variation of temperature from 20 °C to 70 °C. Solution ionic strength was increased by addition of potassium and lithium sulfate solution while addition of calcium sulfate decreased ionic strength whereby zinc extraction efficiency was also decreased. TBP showed positive synergism at concentration of 5% (v/v) and negative synergism effect at concentrations of 2% and 10%. Simultaneous addition of both TBP and salt caused extraction efficiency to drop significantly and lower both TBP and ionic strength efficiency. Results showed that a continuous addition of TBP tends to effectively improve the zinc extraction efficiency. Experiments in the presence of catalyst Ni-Raney demonstrated that zinc extraction kinetic increases remarkably and due to easy recycling of the catalyst, we can propose a novel idea in solvent extraction field.

Effect of sulfate additions on hydration and performance of ternary slag-limestone composite cements

The global cement industry is striving to reduce its carbon footprint. Common approaches have included reduced clinker factors by blending cement clinker with supplementary cementitious materials (SCM). However supplies of SCMs are not sufficient to achieve replacement above about 30%. Limestone ternary cements offer the opportunity to reduce the clinker factor of cements while maximizing the efficiency of SCMs. In these cements, calcite from limestone reacts with dissolved aluminates to form carboaluminate and in the process influence hydration of other constituents. However, sulfates which are conventionally added to regulate the early reactions in cement also compete for aluminates. Here we have used complementary techniques to investigate the effects of calcium sulfate additions on hydration, microstructure and performance of composite Portland clinker-slag-limestone cements.The results show that the presence of sulfate influenced the early-age reaction kinetics of the clinker phases and supplementary cementitious materials. However, even after sulfate depletion, the course of hydration and microstructures formed were significantly influenced. Increasing the sulfate level resulted in a gradual increase of the fraction of ettringite over AFm phases, coarser porosity and lower water content of the C-S-H. These microstructural changes impact the total porosity and hence cement strength in opposing ways, namely porosity is reduced with increasing ettringite fraction while the space filling capacity of the C-S-H is also reduced due to the lower water content of the C-S-H. These findings have important implications for optimizing the mechanical properties and durability of ternary blends.

Effect of additives on hydration and hardening of magnesia compositions

The article is devoted to the investigation of the influence of technological factors on the hydration and hardening of magnesia compositions. The objective – is investigation magnesia compositions with different additives. Factors which impact activity of magnesium oxide in compositions of different structure are investigated. Influence of liquid density on hardening of magnesium bindings is defined. Processes of hydration and hardening of magnesium bindings with participation of minerals – silicates are investigated. It is revealed that the addition of semi-aquatic calcium sulfate contributes to the hardening of magnesia binders. Defined effect of concentration calcium sulfate hemihydrate to the hardening of caustic magnesite. Here are proposed structures of sulphomagnesium compositions containing technogenic components. It revealed a beneficial effect on the hardening of ferrous component of the mixed magnesia binder. Composition of hydration products of magnesium binding with participation of ferriferous minerals is presented. Transformations of phases at hydration of magnesium binding are revealed. Influence of structure of bindings on transformations of hydrates is established. Results of research of magnesia bindings of long hardening are given. It is shown that the durability of stone of bindings is provided with dense structure of hydrates. In researches are used X – Ray and thermal methods, electronic microscopy.

Properties of Sintered Bronze-Graphite Containing Calcium Sulfate Derived from Waste Plaster Molds

This study examined the effect of calcium sulfate additions on the microstructure and frictional properties of a 95bronze-5graphite material, commonly used for frictional applications. The samples were prepared using a powder metallurgy process. The calcium sulfate powder was obtained from recycled plaster molds previously used for ceramic slip casting. The plaster molds were cleaned, crushed and ball milled to obtain powder, which was calcined at 400 °C for 4 hours and screened. 2 to 8 weight percent calcium sulfate powder was added to a premixed powder composed of copper and tin and mixed before the graphite was added. The powder mixture was compacted into a disc shape under a pressure of 500 MPa. The compacted samples were sintered at 750 °C for 30 minutes in a reducing atmosphere. It was found that the green density of the samples decreased with increased amounts of calcium sulfate. After sintering, the densities were found to have decreased due to sample expansion. A finer microstructure was observed in the samples containing calcium sulfate powder, possibly due to a grain boundary pinning effect. The addition of calcium sulfate resulted in the reduction of both the measured friction coefficient and wear of the bronze-graphite samples. However, the addition of calcium sulfate powder above 6 weight percent appeared to show decreasing effects.

Carbonation of calcium sulfoaluminate mortars

This study investigated potential physical and chemical parameters that could govern the carbonation rate of calcium sulfoaluminate (CSA) mortars and endeavored to elucidate the microstructural and chemical factors that govern CSA cement's carbonation rate. Experiments included: water absorption, oxygen diffusion, mercury intrusion porosimetry, quantitative X-ray diffraction, thermogravimetric analysis, accelerated carbonation, compression and flexure tests. Additionally, the carbonation process was investigated using thermodynamic modeling. The results show that CSA mortars carbonate much faster than Portland cement mortars and at approximately the same rate as calcium aluminate cement mortars. Additionally, CSA mortars carbonate slower with decreasing w/c, and the anhydrite content of the CSA mortars strongly affects the ye'elimite reaction kinetics which plays an important role in imparting carbonation resistance in CSA mortars. Finally, calcium sulfate additions to CSA clinker to produce CSA cement dilutes the clinker content and reduces the amount of CO2 that the CSA cement can ultimately bind.

Development of a chemical model to predict the doses of calcium sulfate and tartaric acid to acidify musts in Sherry area

Calcium sulfate is normally used as a complementary acidifier combined with tartaric acid. The doses corresponding to each one depend on the desired reduction of pH and on the composition of musts. However, considering that there are several interrelated chemical equilibria implied (tartaric acid dissociation, calcium tartrate and potassium bitartrate precipitation, etc.), it is not easy to predict the effect on pH of a mixed tartaric acid and calcium sulfate addition and to determine the necessary doses to reach the final pH required by the winemaker. In a model previously developed by the authors, the prediction of pH after an acidification was properly achieved. On the contrary, in the same model the prediction of the necessary doses of acidifiers to achieve a desired pH have higher errors due to some parameters, as pH and pK, are found as exponential functions in the equations. This work develops and verify the necessary corrections to the models so that appropriate predictions of the doses are obtained. With these corrections, prediction errors of less than 5% were obtained for all doses of acidifiers, confirming the good comprehension of the chemical equilibria involved in this practice.

XRD and TGA, Swelling and Compacted Properties of Polymer Treated Sulfate Contaminated CL Soil

Abstract In this study, the effect of up to 4 % calcium sulfate contamination on the soil properties of a natural clay with low liquid limit (CL) soil with and without polymer treatment was investigated and compared to 6 % lime treated soil. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) methods were used to identify and quantify the changes in the contaminated CL clay soil. XRD analyses showed the major constituents of the soil were calcium silicate (CaSiO3), aluminum silicate (Al2SiO5), magnesium silicate (MgSiO3), and quartz (SiO2). With 4 % calcium sulfate contamination, the liquid limit (LL) and plasticity index (PI) of the CL soil increased by 30 and 45 %, respectively. The addition of calcium sulfate resulted in the formation of calcium silicate sulfate (Ternesite Ca5(SiO4)2SO4) and aluminum silicate sulfate (Al5(SiO4)2SO4). TGA analyses showed a notable reduction in the weight of calcium sulfate contaminated soil between 600 and 800°C, possibly due to changes in soil mineralogy. In addition, the total weight loss at 800°C for 1.5 % polymer treated soil was about 40 % less than the 4 % calcium sulfate contaminated soil, and it was similar to the weight loss observed in the uncontaminated CL soil. The maximum dry density of compacted soil decreased and the optimum moisture content increased with 4 % of calcium sulfate. The addition of 4 % calcium sulfate increased the free swelling of compacted soil by 67 %. The addition of 6 % lime resulted in the formation of ettringite (Ca6Al2 (SO4)3(OH)12·26H2O). Polymer treatment decreased the LL, PI, swelling index, and optimum moisture content of the soil and increased the compacted maximum dry density. Behavior of sulfate contaminated CL soil with and without treatment was quantified using a unique model that represented both linear and nonlinear responses. Also the model predictions were compared with published data in the literature.

A kaolinitic clay from Yantai (China): Improvement of properties and microstructure

The properties and microstructure of a kaolinitic clay were improved by sintering at 1085–1095°C with addition of cinder powder and calcium sulfate. Both sintering temperature and the additive content have great effect on the properties and microstructure of the clay. The clay sintered with 15–20wt% additive at 1085–1095°C possesses a high open porosity of 34.2–38.1%, flexural strength of 10.8–14.8MPa, low volume shrinkage of 2.4–6.2%, tailored microstructure and well–connected open pores, which is considered suitable for manufacturing irrigation pitchers and units for water seepage and filtration.