Sample records for gypsum cement

  1. Cements containing by-product gypsum

    Bensted, J. [University of Greenwich, London (United Kingdom). School of Biological and Chemical Sciences


    Chemical by-product gypsum can readily replace natural gypsum in Portland cements and in blended cements like Portland pfa cement and Portland blast furnace cement without technical detriment in many instances. Indeed, sometimes the technical performance of the cement can be enhanced. The hydration chemistry is often changed, in that where there is at least some retardation of setting, more AFT phase (ettringite) is formed during early hydration at the expense of calcium silicate hydrates. By-product gypsum can also replace natural gypsum in speciality products like calcium aluminate cement-Portland cement mixes for producing quick setting cements and in calcium sulphoaluminate-type expansive cements. However, by-products gypsum have proved to be less successful for utilization in API Classes of oilwell cements, because of the greater difficulty in obtaining batch-to-batch consistency in properties like thickening time and slurry rheology. 11 refs., 3 figs., 5 tabs.

  2. Tunisian gypsums: Characteristics and use in cement

    Mahmoudi, Salah; Bennour, Ali; Chalwati, Youssef; Souidi, Khouloud; Thabet, Manel; Srasra, Ezzedine; Zargouni, Fouad


    Gypsum materials of hundred meters thickness and interbedded with marine claystones and limestones from different paleogeographic sectors in the Tunisian territory are studied to assess their suitability for cement production. For this reason, thirty representative samples are analysed by chemical, physical and geotechnical tests. The obtained results for the studied gypsum materials are compared to Tunisian and European norms and with the local cements, currently marketed and which obey international norms. Indeed, for all samples hydraulic modulus HM, silica modulus SM and alumina modulus AM vary from (2.37-2.44), (2.48-2.68) and (1.45-2.5), respectively; whereas the required values for these modulus are (1.5-2.5), (2-3) and (1.5-2.5). The same behavior is observed for mineralogical analyses of C3S, C2S, C3A and C4AF and compressive strength at different ages. Briefly, Tunisia contains important reserves of gypsum scattered and spread over the Tunisian territory and can be used for cement production.

  3. Physical, mechanical, and durability properties of gypsum-Portland cement-natural pozzolan blends

    Colak A


    This paper deals with the effect of gypsum Portland cement and gypsum Portland cement natural pozzolan ratios on the physical, mechanical, and durability properties of gypsum Portland cement natural pozzolan blends...


    Mikheenkov Mikhail Arkad'evich


    Full Text Available In the article, the authors consider the feasibility of development of water-hardened gypsum that is capable of hardening in the water. The gypsum in question is made of the gypsum binding material, sulphated Portland cement, and granulated blast-furnace slag. The gypsum developed hereunder has a softening coefficient over 1 while the building gypsum content exceeds 75 %.

  5. Use of waste gypsum to replace natural gypsum as set retarders in portland cement.

    Chandara, Chea; Azizli, Khairun Azizi Mohd; Ahmad, Zainal Arifin; Sakai, Etsuo


    The present study is focused on clarifying the influence of waste gypsum (WG) in replacing natural gypsum (NG) in the production of ordinary Portland cement (OPC). WG taken from slip casting moulds in a ceramic factory was formed from the hydration of plaster of paris. Clinker and 3-5wt% of WG was ground in a laboratory ball mill to produce cement waste gypsum (CMWG). The same procedure was repeated with NG to substitute WG to prepare cement natural gypsum (CMNG). The properties of NG and WG were investigated via X-ray Diffraction (XRD), X-ray fluorescence (XRF) and differential scanning calorimetry (DSC)/thermogravimetric (TG) to evaluate the properties of CMNG and CMWG. The mechanical properties of cement were tested in terms of setting time, flexural and compressive strength. The XRD result of NG revealed the presence of dihydrate while WG contained dihydrate and hemihydrate. The content of dihydrate and hemihydrates were obtained via DSC/TG, and the results showed that WG and NG contained 12.45% and 1.61% of hemihydrate, respectively. Furthermore, CMWG was found to set faster than CMNG, an average of 15.29% and 13.67% faster for the initial and final setting times, respectively. This was due to the presence of hemihydrate in WG. However, the values obtained for flexural and compressive strength were relatively the same for CMNG and CMWG. Therefore, this result provides evidence that WG can be used as an alternative material to NG in the production of OPC.

  6. Petroleum Sludge as gypsum replacement in cement plants: Its Impact on Cement Strength

    Benlamoudi, Ali; Kadir, Aeslina Abdul; Khodja, Mohamed


    Due to high cost of cement manufacturing and the huge amount of resources exhaustion, companies are trying to incorporate alternative raw materials or by-products into cement production so as to produce alternative sustainable cement. Petroleum sludge is a dangerous waste that poses serious imparts on soil and groundwater. Given that this sludge contains a high percentage of anhydrite (CaSO4), which is the main component of gypsum (CaSO4.2H2O), it may play the same gypsum role in strength development. In this research, a total replacement of gypsum (100%) has been substituted by petroleum sludge in cement production and has led to an increase of 28.8% in UCS values after 28 curing days. Nevertheless, the burning of this waste has emitted a considerable amount of carbon monoxide (CO) gas that needs to be carefully considered prior to use petroleum sludge within cement plants.

  7. Synthesis of partial stabilized cement-gypsum as new dental retrograde filling material

    Sadhasivam, S. [Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan (China); Division of Medical Engineering Research, National Health Research Institute, Zhunan, Miaoli County, Taiwan (China); Chen, Jung-Chih [Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan (China); Medical Device Innovation Center, National Cheng Kung University, Tainan,Taiwan (China); Savitha, S. [Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan (China); Hsu, Ming-Xiang; Hsu, Chung-King [Institute of Materials Science and Engineering, National Taipei University of Technology, Taipei, Taiwan (China); Lin, Chun-Pin [School of Dentistry and Graduate Institute of Clinical Dentistry, College of Medicine, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan (China); Lin, Feng-Huei, E-mail: [Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan (China); Division of Medical Engineering Research, National Health Research Institute, Zhunan, Miaoli County, Taiwan (China)


    The study describes the sol-gel synthesis of a new dental retrograde filling material partial stabilized cement (PSC)-gypsum by adding different weight percentage of gypsum (25% PSC + 75% gypsum, 50% PSC + 50% gypsum and 75% PSC + 25% gypsum) to the PSC. The crystalline phase and hydration products of PSC-gypsum were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The handling properties such as setting time, viscosity, tensile strength, porosity and pH, were also studied. The XRD and microstructure analysis demonstrated the formation of hydroxyapatite and removal of calcium dihydrate during its immersion in simulated body fluid (SBF) on day 10 for 75% PSC + 25% gypsum. The developed PSC-gypsum not only improved the setting time but also greatly reduced the viscosity, which is very essential for endodontic surgery. The cytotoxic and cell proliferation studies indicated that the synthesized material is highly biocompatible. The increased alkaline pH of the PSC-gypsum also had a remarkable antibacterial activity. - Highlights: Black-Right-Pointing-Pointer A new dental retrograde filling material PSC-gypsum was developed. Black-Right-Pointing-Pointer PSC-gypsum cement has shown excellent initial and final setting time as 15-35 min. Black-Right-Pointing-Pointer It not only improved the setting time but also retain the viscosity, 2 Pa{center_dot}s. Black-Right-Pointing-Pointer High alkaline pH of the cement had a remarkable antibacterial activity. Black-Right-Pointing-Pointer Cytotoxicity studies revealed that the synthesized material is highly biocompatible.

  8. Gypsum

    Crangle, R.D.


    The United States is the world’s fifth ranked producer and consumer of gypsum. Production of crude gypsum in the United States during 2012 was estimated to be 9.9 Mt (10.9 million st), an increase of 11 percent compared with 2011 production. The average price of mined crude gypsum was $7/t ($6.35/st). Synthetic gypsum production in 2012, most of which is generated as a flue-gas desulphurization product from coal-fired electric powerplants, was estimated to be 11.8 Mt (13 million st) and priced at approximately $1.50/t ($1.36/st). Forty-seven companies produced gypsum in the United States at 54 mines and plants in 34 states. U.S. gypsum exports totaled 408 kt (450,000 st). Imports were much higher at 3.2 Mt (3.5 million st).

  9. Sulfate specifications as a constraint to gypsum addition to cement and possible replacement of gypsum as an additive. Quarterly technical progress report, June-August 1979

    Kantro, D.L.


    Potential alternatives to gypsum for controlling set in commercial cement, additives to deter sulfate-induced expansion, and the influence of clinker manufacture on expansion potential in cements were studied. If limitations on sulfate content were less restrictive, it would be possible to use kiln fuels with higher sulfur contents, and to employ energy efficient preheater kiln technology without risk of exceeding sulfate specifications. (FS)

  10. Geotechnical properties of peat soil stabilised with shredded waste tyre chips in combination with gypsum, lime or cement

    M. Saberian


    Full Text Available Peat has a high content of water and organic substances. These weak components can cause low bearing capacity and high consolidation settlement under load, which means that peat deposits must usually be stabilised if they are to bear constructions such as buildings or roads. In this study we investigated the performance of waste tyre chips (10 % by weight and sand (400 kg m-3 supplemented with a pozzolanic binder (gypsum, lime or cement at a range of dosages (5 %, 10 % or 15 % by weight as a stabiliser for peat soil. Peat samples were taken from a fen peatland at Chaghakhor Wetland in Chahar Mahal and Bakhtiari Province, Iran. In total, 162 test specimens were prepared and subjected to laboratory strength testing (unconfined compression test and direct shear test. Additionally, the pH of each admixture was recorded immediately after mixing, elemental compositions were determined by X-Ray Fluorescence (XRF, and structures were examined using Scanning Electron Microscopy (SEM. It was observed that: (1 the total percentage of pozzolanic compounds in the peat soil was well below the minimum of 70 % set by the standard ASTM C 618 (ASTM 2000, so an additive such as cement, lime or gypsum would certainly be required; (2 specimens stabilised with gypsum or lime showed improvements in unconfined compressive strength (UCS, but those stabilised with ordinary Portland cement exhibited the greatest improvement in UCS (up to 12,200 % as well as improvements in the direct shear parameters c and φ; (3 according to the XRF tests, additives such as cement, lime and gypsum introduced considerable amounts of Si, Al, Ca and O, which are important for pozzolanic reactions in peat soils; and (4 on the basis of the results of UCS and direct shear tests, the optimum percentage of the additives tested would be 5 %.

  11. Use of the “red gypsum” industrial waste as substitute of natural gypsum for commercial cements manufacturing

    Gázquez, M. J.


    Full Text Available The main objective of this research has been the valorisation of a waste from the TiO2 production process (sulphate method, called red gypsum, in the production of cements. This waste is mainly formed by di-hydrate calcium sulphate and iron hydroxides. To cover this objective it has been necessary to perform the physico-chemical characterisation of the red gypsum as well as the main components in the production of cements and of the new cements generated. Moreover, for the red gypsum, has been analyzed its radioactive content because it is generated in a NORM (Naturally Occurring Radioactive Materials industry. Finally, the most important properties of the obtained cements with different proportions of red gypsum in their composition have been studied by comparing them with the standard ones obtained in a Portland cement. Lastly, we have demonstrated that the new cements fulfil all the quality tests imposed by the European legislation.

    El objetivo de esta investigación ha sido analizar la valorización de un residuo generado en el proceso de producción de dióxido de titanio (vía sulfato, denominado yeso rojo, en la producción de cementos. Dicho residuo está compuesto fundamentalmente por sulfato de calcio di-hidratado e hidróxidos de hierro. Para ello, ha sido necesaria la caracterización físico-química del yeso rojo, así como la de los otros componentes fundamentales en la fabricación de cementos y de los cementos generados con el mencionado residuo. Además, en el caso del yeso rojo, se ha analizado su contenido radiactivo al generarse éste en una industria NORM (Natural Occurring Radioactive Materials. Posteriormente, se han estudiado las propiedades más importantes de los cementos producidos con diferentes porcentajes de yeso rojo añadido, comparando estas mezclas con las propiedades de un cemento Portland comercial, comprobándose que se cumplen todas las normas Europeas de calidad exigibles.

  12. Manufacturing of mortars and concretes non-traditionals, by Portland cement, metakaoline and gypsum (15.05%

    Talero, R.


    Full Text Available In a thorough previous research (1, it appeared that creation, evolution and development of the values of compressive mechanical strength (CS and flexural strength (FS, measured in specimens 1x1x6cm of mortar type ASTM C 452-68 (2, manufactured by ordinary Portland cement P-1 (14.11% C3A or PY-6 (0.00% C3A, metakaolin and gypsum (CaSO4∙2H2O -or ternary cements, CT-, were similar to the ones commonly developed in mortars and concretes of OPC. This paper sets up the experimental results obtained from non-traditional mortars and concretes prepared with such ternary cements -TC-, being the portland cement/metakaolin mass ratio, as follows: 80/20, 70/30 and 60/40. Finally, the behaviour of these cements against gypsum attack, has been also determined, using the following parameters: increase in length (ΔL%, compressive, CS, and flexural, FS, strengths, and ultrasound energy, UE. Experimental results obtained from these non-traditional mortars and concretes, show an increase in length (ΔL, in CS and FS, and in UE values, when there is addition of metakaolin.

    En una exhaustiva investigación anterior (1, se pudo comprobar que la creación, evolución y desarrollo de los valores de resistencias mecánicas a compresión, RMC, y flexotracción, RMF, proporcionados por probetas de 1x1x6 cm, de mortero 1:2,75, selenitoso tipo ASTM C 452-68 (2 -que habían sido preparadas con arena de Ottawa, cemento portland, P-1 (14,11% C3A o PY- 6 (0,00% C3A, metacaolín y yeso (CaSO4∙2H2O-, fue semejante a la que, comúnmente, desarrollan los morteros y hormigones tradicionales de cemento portland. En el presente trabajo se exponen los resultados experimentales obtenidos de morteros y hormigones no tradicionales, preparados con dichos cementos ternarios, CT, siendo las proporciones porcentuales en masa ensayadas, cemento portland/metacaolín, las siguientes: 80/20, 70

  13. Preliminary Examination of the System Fly Ash-Bottom Ash-Flue Gas Desulphurization Gypsum-Portland Cement-Water for Road Construction

    R. Tokalic


    Full Text Available This paper describes an investigation into the use of three power plant wastes: fly ash, flue gas desulphurization gypsum, and bottom ash for subbase layers in road construction. Two kinds of mixtures of these wastes with Portland cement and water were made: first with fly ash consisting of coarser particles (<1.651 mm and second with fly ash consisting of smaller particles (<0.42 mm. The mass ratio of fly ash-Portland cement-flue gas desulphurization gypsum-bottom ash was the same (3 : 1 : 1 : 5 in both mixtures. For both mixtures, the compressive strength, the mineralogical composition, and the leaching characteristics were determined at different times, 7 and 28 days, after preparation. The obtained results showed that both mixtures could find a potential use for subbase layers in road construction.


    BING MA,


    Full Text Available The objective of this study was the preparation and characterization of high belite sulfoaluminate cement (HBSC from industrial residues. HBSC promises eco-friendly building materials with great mechanical performance at earlier ages than Ordinary Portland Cement (OPC. Preliminary results show the formation of main phase dicalcium silicate (C2S and ye’elimite (C4A3$ at 1250°C, as determined by X-ray diffraction (XRD, are promising. The formation of minerals in the clinker was analyzed by differential scanning calorimetry-thermogravimetry (DSC–TG. Likewise, Scanning electron microscope (SEM and XRD were used to carry out the analysis of the micro-structural and hydration products. The main HBSC hydration products, Ettringite and amorphous Al(OH3, were formed in the early stages; however, during the later stages, monosulfate and Strätlingite were formed. Isothermal conduction calorimetry measurements indicate that hydration properties of the cements are comparable to OPC; the total hydration heat after 3 days was 438 J/g. The optimum compressive strength values of the mortars after 1-, 3-, 7-, and 28-days were 24.9 MPa, 33.2 MPa, 35.6 MPa and 52.8 MPa which can meet the requirement of special structures.

  15. Use of a simplified generalized standard additions method for the analysis of cement, gypsum and basic slag by slurry nebulization ICP-OES.

    Marjanovic, Ljiljana; McCrindle, Robert I; Botha, Barend M; Potgieter, Herman J


    The simplified generalized standard additions method (GSAM) was investigated as an alternative method for the ICP-OES analysis of solid materials, introduced into the plasma in the form of slurries. The method is an expansion of the conventional standard additions method. It is based on the principle of varying both the sample mass and the amount of standard solution added. The relationship between the sample mass, standard solution added and signal intensity is assumed to be linear. Concentration of the analyte can be found either geometrically from the slope of the two-dimensional response plane in a three-dimensional space or mathematically from the ratio of the parameters estimated by multiple linear regression. The analysis of a series of certified reference materials (CRMs) (cement CRM-BCS No 353, gypsum CRM-Gyp A and basic slag CRM No 382/I) introduced into the plasma in the form of slurry is described. The slurries contained glycerol and hydrochloric acid and were placed in an ultrasonic bath to ensure good dispersion. "Table curve 3D" software was used to fit the data. Results obtained showed that the method could be successfully applied to the analysis of cement, gypsum and slag samples, without the need to dissolve them. In this way, we could avoid the use of hazardous chemicals (concentrated acids), incomplete dissolution and loss of some volatiles. The application of the simplified GSAM for the analysis did not require a CRM with similar chemical and mineralogical properties for the calibration of the instrument.

  16. Physical properties and cytotoxicity comparison of experimental gypsum-based biomaterials with two current dental cement materials on L929 fibroblast cells

    Nafsiyah Mahshim


    Full Text Available Aim: To evaluate physical properties and cytotoxicity of pure gypsum-based (pure-GYP and experimental gypsum-based biomaterials mixed with polyacrylic acid (Gyp-PA. The results were compared with calcium hydroxide (CH and glass ionomer cement (GIC for application as base/liner materials. Materials and Methods: Vicat′s needle was used to measure the setting time and solubility (% was determined by percentage of weight loss of the materials following immersion in distilled water. For cytotoxicity test, eluates of different concentrations of materials were obtained and pipetted onto L-929 mouse fibroblast cultures and incubated for 3 days. Cellular viability was assessed using Dimethylthiazol diphenyltetrazolium bromide test to determine the cytotoxicity level. Statistical significance was determined by one-way analysis of variance followed by post hoc test ( P Gyp-PA > CH = GIC. The pure-Gyp was found as the least cytotoxic materials at different concentrations. At 100 mg/mL dilutions of materials in growth medium highest cytotoxicity was observed with CH group. Conclusion: Cytotoxic effect was not observed with pure-Gyp; application of this novel biomaterial on deeper dentin/an exposed pulp and possibility of gradual replacement of this biodegradable material by dentin like structure would be highly promising.

  17. The Gypsum: White gold of Rajasthan, introduction, uses and future prospective

    Sharma, Gayatri


    Rajasthan is mineral based state and Bikaner and its surrounding district have been gifted with Gypsum. Mt of Gypsum is available in these districts. Gypsum has multiple uses including basic raw material for POP industry, addition in cement and a natural fertilizer. This mineral has changes the economic scenario in the remote areas of Bikaner, Nagaur, Hanumangarh, Sanchore, Shriganganagar etc. Gypsum and selenite are mined about 3.0 million tons per year. There is huge demand from cement industry as Gypsum is added for improving setting time of cement. Gypsum is a natural fertilizer for alkaline land and it role is vital in state like India where alkaline land is major role. Its high use as fertilizer has potential to change millions of poor farmer families and improving in crop production. Cement Industry has started importing Gypsum from Thailand, Bankong, Pakistan, Iran etc. The mining of gypsum of purity of 70% CaSO4.2H2O is cooperative effort between the land owners and Rajasthan State Mines and Minerals Limited. Gypsum fulfills the demand of POP and Cement industry in Rajasthan and powder gypsum used in agriculture for recon dining of alkaline soil. This paper deals with multiple uses, availability, and future prospective of Gypsum, a white gold of Rajasthan.

  18. Early Stage Hydration Process of Cementitious Material Prepared with Red Mud, Slag, Gypsum and Small Smounts of Cement Clinker%赤泥-矿渣-石膏-少熟料胶凝材料的初期水化过程

    祝丽萍; 倪文; 高术杰; 王中杰; 张玉燕


    赤泥-矿渣-石膏-少熟料胶凝材料在胶结充填过程中表现出良好的保水性及早强、高强等性能,可以作为充填专用胶结剂.本文综合净浆试块的凝结时间、强度发展以及扫面电镜下的微观结构,分析了材料的初期水化过程,并采用XPS研究了不同元素之间旧组合分解和新组合的形成.结果表明水化3h时体系生成Ca(OH)2和凝胶类物质,这些水化产物使得浆体凝结硬化.4h后矿渣中的部分硅氧四面体参与反应,缩聚成了聚合度较高的硅酸盐矿物,净浆试块产生强度.水化6h后,S2 p3/2的结合能大幅增长,体系生成了较多的硫酸盐矿物,它们对强度的发展起到了较大作用.%The cementitious material prepared with red mud, ground granulated blast furnace slag ( GGBS) , flue gas desulfurization gypsum ( FGDG) and a small amount of cement clinker obtained good performances in water-retention, early strength and high strength when it used for cemented backfilling. This material can be used as special cement for backfilling. The early stage hydration of the material was analyzed through the setting time, strength development and microstructure. The decomposition of old system and the formation of the new mineral were also studied by X-ray photoelectron spectroscopy (XPS). Results show that Ca(0H)2 and gels formed at 3 h after hydration, resulting in the setting and hardening for the cement paste. The samples obtained strength at 4 h, which is attributed to the formation of silicates with higher polymerization degree, which condensed from oxygen-silicon tetrahedron. At 6 h, the binding energy of S2 p3/2 increased suddenly, and some sulfate minerals formed, which made a great contribution to the rise of strength.

  19. 泥浆雾化电感耦合等离子体光谱法用于水泥和石膏的分析%Slurry Nebulization for the Analysis of Gypsum and Cement by Inductively Coupled Plasma Spectrometry

    RobertIMccrindle; LjiljanaMarjanovic


    本文详细地论述了用泥浆雾化电感耦合等离子光谱法分析水泥和石膏.%The usual form of presentation for a sample to be analyzed by an inductively coupled plasma-optical emission spectrometer is in the form of a liquid.For the analysis of solids,this involves a dissolution step and in the case of complex matrices this may be long and difficult.Should it be possible to analyse the sample without prior dissolution, then the problems associated with obtaining a solution would be resolved.A method for analyzing samples is to make use of slurry nebulization.Samples with complex matrices, such as cement and gypsum were selected and analysed as in the form of a slurry.Using different concentrations of slurry of a certified reference materials,calibration curves were obtained,from which the unknown samples could be determined directly.Use of aqueous solutions for calibration was also investigated.The method was evaluated using other reference materials or results obtained by an independent laboratory using different technique for the analysis.The slurry method was found to be accurate and precise.


    Anto Gabrić


    Full Text Available The occurences and deposits of gypsum can be found in big karst poljes (Sinjsko, Vrličko, Petrovo, Kosovo and Kninsko as well as in tectonnically predestined river valleys of Zrmanja, Butišnica and Una. There also appear spatially localized occurences on the island of Vis and in the vicinity of Samobor. Evaporites (gypsum and anhydrite with adjoining overlying clastic rocks (red sandstones, siltites and pelites, carbonate rocks (dolomites and limestones and porous carbonate breccias (Rauhwackes were deposited during the period of Upper Permian. The recent position of the Upper Permian beds is a result of complex tectonic, particularly neotectonic, movements and diapiric displacements. Evaporites were deposited in marginal areas of the epicontinental marine basin, in a period of favourable conditions for the sabkha and playa sedimentation due to the continuous shoreline progradation. The Upper Permian age of these sediments in Dalmatio is proved by the characteristic mineral paragenesis and palinological determinations in elastics rocks, as well as by isotope analyses of sulphure in gypsum. Gypsum is a significant ore mineral resource in building, cement production, as well as in a number of tehnological processes used in chemical industry and elsewhere. According to the recent investigations gypsum is predestined to serve as an ore mineral resource of significant perspectives (the paper is published in Croatian.



    The Portland cement is equivalently substituted by slag micropowders with various specific areas. The workability,activity and acid-corrosion resistance of the slag-substituted cements are investigated,the activation of gypsum is discussed,also the porosity and pore distribution of mortars of the slag micropowders cement are determined by mercury intrusion porosimetry.

  2. Gypsum karst in Great Britain

    Cooper A.H.


    Full Text Available In Great Britain the most spectacular gypsum karst development is in the Zechstein gypsum (late Permian mainly in north-eastern England. The Midlands of England also has some karst developed in the Triassic gypsum in the vicinity of Nottingham. Along the north-east coast, south of Sunderland, well-developed palaeokarst, with magnificent breccia pipes, was produced by dissolution of Permian gypsum. In north-west England a small gypsum cave system of phreatic origin has been surveyed and recorded. A large actively evolving phreatic gypsum cave system has been postulated beneath the Ripon area on the basis of studies of subsidence and boreholes. The rate of gypsum dissolution here, and the associated collapse lead to difficult civil engineering and construction conditions, which can also be aggravated by water abstraction.

  3. Mechanism of gypsum hydration

    Pacheco, G.


    Full Text Available There is an hypothesis that the mechanism o f gypsum hydration and dehydration is performed through two simultaneous phenomena. In this study we try to clear up this phenomenon using chlorides as accelerators or a mixture of ethanol-methanol as retarders to carry out the gypsum setting. Natural Mexican gypsum samples and a hemihydrate prepared in the laboratory are used. The following analytical techniques are used: MO, DRX, DTA, TG and DTG. In agreement with the obtained results, it can be concluded: that colloid formation depends on the action of accelerators or retarders and the crystals are a consequence of the quantity of hemihydrate formed.

    En el mecanismo de hidratación y deshidratación del yeso existe la hipótesis de que éste se efectúa por dos fenómenos simultáneos. Este estudio intenta esclarecer estos fenómenos, empleando: cloruros como aceleradores o mezcla etanol-metanol como retardadores para efectuar el fraguado del yeso. Se emplean muestras de yeso de origen natural mexicano y hemihydrate preparado en laboratorio; se utilizan técnicas analíticas: MO, DRX, DTA, TG y DTG. De acuerdo a los resultados obtenidos se puede deducir: que la formación del coloide depende de la acción de los agentes aceleradores o retardadores y que los cristales son consecuencia de la cantidad de hemihidrato formado.

  4. Use of Deep Peat-Processing Products for Hydrophobic Modification of Gypsum Binder

    Misnikov Oleg


    Full Text Available The article deals with the issue of gypsum binder quality reduction during its storage and transportation. The study provides the main methods to protect gypsum from unauthorized exposure to moisture and water vapor. The author proposes hydrophobic modification as a perspective method for the preservation of gypsum activity and its water absorption reduction. The substantiation of cement hydrophobization with the bitumen released during peat thermolysis is provided. The author proposes to use this method in the technology of gypsum binder production. The basic idea is to combine the hydrophobization process with the calcination of calcium sulfate dehydrate. This is facilitated by temperature ranges used for dehydration of natural gypsum and the initial stage of thermal decomposition of the organic matter of peat. The author defined experimentally an optimal concentration of the organic component in gypsum binder. After adding 0.5-1% of the peat additive, the gypsum plaster preserved its grade strength and increased its storage time without caking and hydration, also under adverse conditions. The proposed method is adapted to the technological processes presently used in the production and doesn’t require changing any equipment. The price of mineral raw materials and semi-finished products of peat are approximately equal which reduces the probability of increasing of the cost of hydrophobically modified gypsum binder.

  5. Microstructure and mechanical properties of gypsum composites reinforced with recycled cellulose pulp

    Magaly Araújo Carvalho


    Full Text Available The use of waste fibers for the reinforcement of brittle matrices is considered opportune for the sustainable management of urban solid residues. This paper examines the microstructure and mechanical properties of a composite material made of gypsum reinforced with cellulose fibers from discarded Kraft cement bag. Two different kinds of gypsum were used, natural gypsum (NG and recycled gypsum (RG, both with an addition of 10% by mass of limestone. For the production of samples, slurry vacuum de-watering technique followed by pressing was evaluated revealing to be an efficient and innovative solution for the composites under evaluation. The composite was analyzed based on flexural strength tests, scanning electron microscopy (SEM imaging, secondary electron (SE detection, and pseudo-adiabatic calorimetry. The morphology of the fractured surfaces of flexural test samples revealed large gypsum crystals double the original size surrounding the fibers, but with the same overall aspect ratio. Natural fibers absorb large amounts of water, causing the water/gypsum ratio of the paste to increase. The predominance of fiber pullout, damaged or removed secondary layers and incrusted crystals are indicative of the good bonding of the fiber to the gypsum matrix and of the high mechanical resistance of composites. This material is a technically better substitute for the brittle gypsum board, and it stands out particularly for its characteristics of high impact strength and high modulus of rupture.

  6. Influence of Calcium Sulfate State and Fineness of Cement on Hydration of Portland Cements Using Electrical Measurement

    WEI Xiaosheng; LI Zongjin; XIAO Lianzhen; THONG Wangfai


    The influence of calcium sulfate state and fineness of cement on hydration of Portland cement was studied using electrical resistivity measurement. The bulk resistivity curve of the paste from the abnormal cement mainly with hemihydrate had a characteristic abnormal peak and rapid increase in early period. The resistivity measurement technique can be used to discriminate abnormal setting. For normal cement with gypsum, the increase in fineness of the Portland cement decreases the minimum resistivity due to a higher ionic concentration and increases the 24 hour resistivity due to a reduction in macroscopic pore size. Thesetting time, compressive strength, pore structure of pastes made from different cements were carried out to compare the influence of water to cement ratio, calcium sulfate state and fineness. It is found that the electrical and mechanical properties are strongly affected by the initial porosity, the presence of hemihydrate or gypsum, and the fineness of cement.

  7. Osteotransductive bone cements.

    Driessens, F C; Planell, J A; Boltong, M G; Khairoun, I; Ginebra, M P


    Calcium phosphate bone cements (CPBCs) are osteotransductive, i.e. after implantation in bone they are transformed into new bone tissue. Furthermore, due to the fact that they are mouldable, their osteointegration is immediate. Their chemistry has been established previously. Some CPBCs contain amorphous calcium phosphate (ACP) and set by a sol-gel transition. The others are crystalline and can give as the reaction product dicalcium phosphate dihydrate (DCPD), calcium-deficient hydroxyapatite (CDHA), carbonated apatite (CA) or hydroxyapatite (HA). Mixed-type gypsum-DCPD cements are also described. In vivo rates of osteotransduction vary as follows: gypsum-DCPD > DCPD > CDHA approximately CA > HA. The osteotransduction of CDHA-type cements may be increased by adding dicalcium phosphate anhydrous (DCP) and/or CaCO3 to the cement powder. CPBCs can be used for healing of bone defects, bone augmentation and bone reconstruction. Incorporation of drugs like antibiotics and bone morphogenetic protein is envisaged. Load-bearing applications are allowed for CHDA-type, CA-type and HA-type CPBCs as they have a higher compressive strength than human trabecular bone (10 MPa).

  8. The mineralogy and chemistry of cement and cement raw materials In the united arab emirates

    Nasir, Sobhi J. [صبحي جابر نصر; El Etr, H.


    The raw materials, clinkers and cements from different cement factories in the United Arab Emirates have been investigated using polarizing microscopy, X-ray diffraction (XRD), Scanning electron microscopy (SEM), and chemical analyses. The chemical and mineralogical analyses indicate that the local raw materials are suitable for cement industry. Geological review shows that there is a good potential for industrial-grade local occurrences of limestone, marl, gypsum and iron oxide, that may be ...

  9. Influence of sodium borate on the early age hydration of calcium sulfoaluminate cement

    Champenois, Jean-Baptiste; Dhoury, Mélanie [CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze Cedex (France); Cau Dit Coumes, Céline, E-mail: [CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze Cedex (France); Mercier, Cyrille [LMCPA, Université de Valenciennes et du Hainaut Cambrésis, 59600 Maubeuge (France); Revel, Bertrand [Centre Commun de Mesure RMN, Université Lille1 Sciences Technologies, Cité Scientifique, 59655 Villeneuve d' Ascq Cedex (France); Le Bescop, Patrick [CEA, DEN, DPC, SECR, F-91192 Gif-sur-Yvette (France); Damidot, Denis [Ecole des Mines de Douai, LGCgE-GCE, 59508 Douai (France)


    Calcium sulfoaluminate (CSA) cements are potential candidates for the conditioning of radioactive wastes with high sodium borate concentrations. This work thus investigates early age hydration of two CSA cements with different gypsum contents (0 to 20%) as a function of the mixing solution composition (borate and NaOH concentrations). Gypsum plays a key role in controlling the reactivity of cement. When the mixing solution is pure water, increasing the gypsum concentration accelerates cement hydration. However, the reverse is observed when the mixing solution contains sodium borate. Until gypsum exhaustion, the pore solution pH remains constant at ~ 10.8, and a poorly crystallized borate compound (ulexite) precipitates. A correlation is established between this transient precipitation and the hydration delay. Decreasing the gypsum content in the binder, or increasing the sodium content in the mixing solution, are two ways of reducing the stability of ulexite, thus decreasing the hydration delay.

  10. Activation of Anhydrate Phosphogypsmn by K2SO4 and Hemihydrate Gypsum

    YANG Min; QIAN Jueshi


    Lime pretreated phosphogypsum(PG) was calcined at 500 ℃ to produce anhydrate gypsum cement.Due to the slow hydration of anhydrate gypsum,additives,K2SO4 and hemihydrate gypsum were selected to accelerate the hydration of anhydrate.The hydration characteristics,the resistance to hydrodynamic water,and the mineralogical studies were investigated.The experimental results suggest that activated by K2SO4 and hemihydrate,anhydrate PG hydrates much more rapidly than that in the presence of only K2SO4 or in the absence of additives.The binder has proper setting time,good strength development,and relatively better resistance to water.The hardened binder has hydrated products of rod or stick like shaped dihydrate gypsum crystals.

  11. Properties of mortars made by uncalcined FGD gypsum-fly ash-ground granulated blast furnace slag composite binder.

    Zhong, Shiyun; Ni, Kun; Li, Jinmei


    A series of novel mortars were developed from composite binder of uncalcined FGD gypsum, fly ash (FA) and ground granulated blast furnace slag (GGBFS) for the good utilization of flue gas desulphurization (FGD) gypsum. At a fixed ratio (20%) of GGBFS to the composite binder, keeping consistency of the mortar between 9.5 and 10.0 cm, the properties of the composite mortar were studied. The results show that higher water/binder (W/B) is required to keep the consistency when increasing the percentage of FGD gypsum. No obvious influences of the W/B and content of FGD gypsum on the bleeding of paste were observed which keeps lower than 2% under all experimental conditions tried. The highest compressive and flexural strengths (ratio is 20% FGD gypsum, 20% GGBFS and 60% FA) are 22.6 and 4.3 MPa at 28 days, respectively. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicate that massive ettringite crystals and C-S-H gels exist in the hydration products. At 90 days the mortars with FGD gypsum is dramatically smaller drying shrinkage (563-938 micro strain) than that without FGD gypsum (about 2250 micro strain). The release of the SO(4)(2-) from the mortar was analyzed, indicating that the dissolution of sulfate increases with FGD gypsum. The concentration of SO(4)(2-) releasing from the mortar with 10% FGD gypsum is almost equal to that obtained from the mortar without FGD gypsum. The release of SO(4)(2-) from the mortar with 20% FGD gypsum is 9200 mg·m(-2), which is lower than that from the mortar with 95% cement clinker and 5% FGD gypsum.

  12. Consolidation of archaeological gypsum plaster by bacterial biomineralization of calcium carbonate.

    Jroundi, Fadwa; Gonzalez-Muñoz, Maria Teresa; Garcia-Bueno, Ana; Rodriguez-Navarro, Carlos


    Gypsum plasterworks and decorative surfaces are easily degraded, especially when exposed to humidity, and thus they require protection and/or consolidation. However, the conservation of historical gypsum-based structural and decorative materials by conventional organic and inorganic consolidants shows limited efficacy. Here, a new method based on the bioconsolidation capacity of carbonatogenic bacteria inhabiting the material was assayed on historical gypsum plasters and compared with conventional consolidation treatments (ethyl silicate; methylacrylate-ethylmethacrylate copolymer and polyvinyl butyral). Conventional products do not reach in-depth consolidation, typically forming a thin impervious surface layer which blocks pores. In contrast, the bacterial treatment produces vaterite (CaCO3) biocement, which does not block pores and produces a good level of consolidation, both at the surface and in-depth, as shown by drilling resistance measurement system analyses. Transmission electron microscopy analyses show that bacterial vaterite cement formed via oriented aggregation of CaCO3 nanoparticles (∼20nm in size), resulting in mesocrystals which incorporate bacterial biopolymers. Such a biocomposite has superior mechanical properties, thus explaining the fact that drilling resistance of bioconsolidated gypsum plasters is within the range of inorganic calcite materials of equivalent porosity, despite the fact that the bacterial vaterite cement accounts for only a 0.02 solid volume fraction. Bacterial bioconsolidation is proposed for the effective consolidation of this type of material. The potential applications of bacterial calcium carbonate consolidation of gypsum biomaterials used as bone graft substitutes are discussed.

  13. Polymer composites based on gypsum matrix

    Mucha, Maria; Mróz, Patrycja; Kocemba, Aleksandra [Faculty of Process and Environmental Engineering, Lodz University of Technology, Wólczańska 215 street, 90–924 Łódź (Poland)


    The role of polymers as retarder additives is to prolong the workability connected with setting time of gypsum. Various cellulose derivatives, soluble in water in concentration up to 1,5% by weight were applied taking different water/binder ratio. The hydration process of calcium sulfate hemihydrate (gypsum binder) into dihydrate (gypsum plaster) was observed by setting and calorimetric techniques. Scanning electron microscopy confirmed that the gypsum microstructure was varied when polymers are used. The mechanical properties of gypsum plasters were studied by bending strength test and they are correlated with sample microstructure.

  14. Study on the Possibility of Using Vine Stalk Waste ( Vitis Vinifera) for Producing Gypsum Particleboards

    Rangavar, H.; Khosro, S. Kh.; Payan, M. H.; Soltani, A.


    The objective of this study was the production of gypsum particleboards with vine stalk waste and the investigation of some physical and mechanical properties of the boards. For this purpose, boards were made from gypsum, oven-dried mass of vine stalk waste, and the white portland cement in various ratios. The thickness swelling and water absorption after 2 and 24 hours of immersion in water, the modulus of rupture, the modulus of elasticity, and the internal bond strength of the boards were determined according to the European Norms standard. The results show that, by selecting proper ratios between the constituents, particleboards with good physicomechanical properties can be produced.

  15. Urban mining : Recycling gypsum waste in Vancouver

    McCamley, J.A. [New West Gypsum Recycling Inc., Vancouver, BC (Canada)


    Wallboard manufacturing, construction and deconstruction activities in North America, Europe and Japan result in large amounts of gypsum scrap, which creates an environmental problem. Disposing of this gypsum scrap in landfills often leads to hydrogen sulfide emissions and metallic sulfide groundwater leachates. Europe has dealt with the problem by enacting legislation that will come into effect in July 2005. The legislation is designed to strongly encourage gypsum recycling throughout entire jurisdictions. It is estimated that approximately 10 to 17 per cent of all gypsum used in the wallboard industry ends up as gypsum scrap. In North America, it represents almost one per cent of total waste. Each year in the United States, between 2.5 and 4.5 million tonnes of gypsum scrap are generated, with numbers very similar to Europe (the higher use of brick and concrete in Europe reduces the percentage of total tonnage). Gypsum has been banned from the landfills of British Columbia's Greater Vancouver region, forcing the recycling of all gypsum scrap. Large quantities of gypsum scrap are processed by New West Recycling, a Canadian firm using proprietary technology. This process leads to the re-incorporation of scrap gypsum into new wallboard, with the percentages sometimes reaching as high as 25 per cent. A case study of New West Recycling Inc., located in Langley, British Columbia was presented and recommendations were made concerning how other urban regions can implement gypsum scrap recycling programs modeled after this one. 6 refs.

  16. Biodeterioration of the Cement Composites

    Luptáková, Alena; Eštoková, Adriana; Mačingová, Eva; Kovalčíková, Martina; Jenčárová, Jana


    The destruction of natural and synthetic materials is the spontaneous and irreversible process of the elements cycling in nature. It can by accelerated or decelerated by physical, chemical and biological influences. Biological influences are represented by the influence of the vegetation and microorganisms (MO). The destruction of cement composites by different MO through the diverse mechanisms is entitled as the concrete biodeterioration. Several sulphur compounds and species of MO are involved in this complex process. Heterotrophic and chemolithotrophic bacteria together with fungi have all been found in samples of corroding cement composites. The MO involved in the process metabolise the presented sulphur compounds (hydrogen sulphide, elemental sulphur etc.) to sulphuric acid reacting with concrete. When sulphuric acid reacts with a concrete matrix, the first step involves a reaction between the acid and the calcium hydroxide forming calcium sulphate. This is subsequently hydrated to form gypsum, the appearance of which on the surface of concrete pipes takes the form of a white, mushy substance which has no cohesive properties. In the continuing attack, the gypsum would react with the calcium aluminate hydrate to form ettringite, an expansive product. The use supplementary cementing composite materials have been reported to improve the resistance of concrete to biodeterioration. The aim of this work was the study of the cement composites biodeterioration by the bacteria Acidithiobacillus thiooxidans. Experimental works were focused on the comparison of special cement composites and its resistance affected by the activities of used sulphur-oxidising

  17. Properties of expansive cements, made with Portland cement, gypsum and high alumina cement

    Monfore, G. E.


    Full Text Available Not availableLos cementos expansivos se han desarrollado durante las tres décadas pasadas, principalmente por las investigaciones llevadas a cabo en Francia, URSS y Estados Unidos. Los cementos expansivos que fueron utilizados en los estudios de los cuales se da cuenta en el presente trabajo se obtuvieron mediante la mezcla de cemento Portland, cemento aluminoso y yeso. En las investigaciones se utilizaron morteros con los cuales se pudo determinar los efectos de la composición, tiempo y temperatura de curado sobre las resistencias, dilatación libre, retracción y desarrollo de resistencias en probetas pretensadas. Se hace una revisión sobre los estudios hechos con cementos expansivos y desarrollados en la Universidad de California. Las propiedades de taIes hormigones son, en términos generales, comparables a aquellos obtenidos con mezclas de cementos portland, cemento aluminoso y yeso. Es necesaria más información sobre pérdidas de tensión en los aceros y durabilidad de los hormigones autopretensados.

  18. The cement solidification systems at LANL

    Veazey, G.W.


    There are two major cement solidification systems at Los Alamos National Laboratory. Both are focused primarily around treating waste from the evaporator at TA-55, the Plutonium Processing Facility. The evaporator receives the liquid waste stream from TA-55's nitric acid-based, aqueous-processing operations and concentrates the majority of the radionuclides in the evaporator bottoms solution. This is sent to the TA-55 cementation system. The evaporator distillate is sent to the TA-50 facility, where the radionuclides are precipitated and then cemented. Both systems treat TRU-level waste, and so are operated according to the criteria for WIPP-destined waste, but they differ in both cement type and mixing method. The TA-55 systems uses Envirostone, a gypsum-based cement and in-drum prop mixing; the TA-50 systems uses Portland cement and drum tumbling for mixing.

  19. Water-resistant gypsum binder

    Panchenko Alexander I.


    Full Text Available The authors developed a multi-component gypsum binder (MGB with an improved (by 1.8 to 2.2 times water resistance value in comparison with the initial gypsum and a softening factor value within the range of 0.85 to 0.91 through the introduction of a complex additive containing carbide mud and bio-silica. The use of a complex additive provides for the formation of a denser structure due to the formation of low-base calcium hydrated silicates at early stages of the hardening process under wet or dry air conditions. The developed binding agent has a lower (by 2.5 to 3 times open porosity, a greater compressive strength (by 1.4 to 1.6 times for a dry state and by 2.6 times in a water-saturated state and does not require any special curing conditions in contrast to the other multi-component gypsum binders. The authors show the influence of mud-and-silica additive on the properties of hardened MGB and suggest a method of computation of the optimum MGB composition for given components.

  20. Petroleum sludge treatment and reuse for cement production as setting retarder

    Aeslina, A. K.; Ali, B.


    Petroleum sludge is a dangerous waste that needs to be treated to avoid any contamination of soil and groundwater due to its disposal. As an attempt to treat this waste, it has been incorporated into cement production as substitution for gypsum. As results, 5% of petroleum sludge has shown effective results and could play the same role of gypsum in delaying the flash setting of cement clinker.


    Taher Abu-Lebdeh


    Full Text Available The disposal of scrap tires is a challenging task and hence an innovative solution to meet these challenges is needed. Extensive work has been done on the utilization of waste tires in a variety of applications in asphalt pavements and concrete. However, previous investigations focus only on the mechanical properties of the rubberized materials, but few on the thermal performance. This is especially true for rubberized gypsum. Limited or no experimental data on the thermal performance of rubberized gypsum board are available. In this study, an experimental program is established to investigate the effect of amount and size of crumb rubber on the thermal properties of gypsum materials. Gypsum is replaced by four different percentage of crumb rubber: 10, 20, 30 and 40% by weight of gypsum and two sizes of crumb rubber (#30, #10_20 to make eight rubberized gypsum specimens. The prepared specimens were tested for thermal conductivity using an apparatus specially designed and constructed for this purpose. The experimental program was concluded by proposing an empirical equation to predict the thermal conductivity of rubberized gypsum board. Results indicated better thermal performance of the gypsum board due to the addition of crumb rubber. Thermal conductivity of the rubberized gypsum was 18-38% lower than the ordinary gypsum. It is concluded that thermal conductivity of rubberized gypsum decreases with the increase of crumb rubber regardless the size of the rubber and that thermal conductivity of mixtures contained 40% of rubber was about 38% lower than conventional mixture when crumb rubber #10_20 was added, while the thermal conductivity reduced by 22% when crumb rubber #30 was added. The study suggested for future work to investigate the effect of air voids size and ratio on the thermal conductivity of rubberized gypsum.

  2. Cement Conundrum


    China aims to streamline the crowded cement industry Policymakers are looking to build a concrete wall around the cement-making industry as they seek to solidify the fluid cement market and cut excessive production.

  3. Contribution to Portland cement hemihydrite and gypsum content determination

    Moreno Arús, F.


    Full Text Available Not availableLa mayoría de los técnicos de cemento eceptan que las anormalidades del fraguado, conocidas como "falso fraguado" en el cemento portland, se deben primordialmente a la presencia de yeso parcialmente deshidratado (SO4Ca 1/2H2O. Si el clinker que se muele está enriquecido en cal libre, o la temperatura del molino es elevada (superior a los 110 ºC o hay escasa ventilación de éste, se llega a originar una parcial deshidratación del yeso, que se mantiene durante el proceso de ensilado y origina las anormalidades del fraguado anteriormente referidas. Por esta razón creemos muy importante el poder conocer el grado de deshidratación en que se encuentra el yeso en un cemento.

  4. Investigation of the type and content of gypsum on the dimensional stability and mechanical properties of gypsum particleboard

    Hossein Rangavar


    Full Text Available In this study in order to investigate the effect of gypsum type on the physical and mechanical properties of gypsum Particleboard were used from two type Jebel and Micronize gypsum. To obtain the suitable amount of gypsum in manufacturing gypsum particleboard was used from the three levels 2.5:1, 2.75:1 and 3:1 of gypsum to dried mass of wooden materials. Physical and mechanical properties of manufactured board were carried out in accordance with European Norms (EN standard. The result showed that gypsum particleboard manufactured Jebel gypsum have the most mechanical properties (Bending strength, modulus of elasticity and internal bond strength, but physical properties (water absorption and thickness swelling of this boards was more than the boards manufactured from Micronize gypsum. Furthermore using 2.75 times gypsum to dried mass of wooden materials is also suitable in production gypsum particleboard.

  5. Measurement of soil moisture using gypsum blocks

    Friis Dela, B.

    the building. Consequently, measuring the moisture of the surrounding soil is of great importance for detecting the source of moisture in a building. Up till now, information has been needed to carry out individual calibrations for the different types of gypsum blocks available on the market and to account......For the past 50 years, gypsum blocks have been used to determine soil moisture content. This report describes a method for calibrating gypsum blocks for soil moisture measurements. Moisture conditions inside a building are strongly influenced by the moisture conditions in the soil surrounding...

  6. Measurement of soil moisture using gypsum blocks

    Friis Dela, B.

    For the past 50 years, gypsum blocks have been used to determine soil moisture content. This report describes a method for calibrating gypsum blocks for soil moisture measurements. Moisture conditions inside a building are strongly influenced by the moisture conditions in the soil surrounding...... the building. Consequently, measuring the moisture of the surrounding soil is of great importance for detecting the source of moisture in a building. Up till now, information has been needed to carry out individual calibrations for the different types of gypsum blocks available on the market and to account...

  7. Effects of gypsum on trace metals in soils and earthworms

    Mined gypsum has been beneficially used for many years as an agricultural amendment. Currently a large amount of flue gas desulfurization (FGD) gypsum is produced by removal of SO2 from flue gas streams when fuels with high S content are burned. The FGD gypsum, similar to mined gypsum, can enhance c...

  8. Dry mixtures based on aluminate cements for self-leveling floors

    Kaddo Maria


    Full Text Available In this study the results of the structure, shrinkage and physical and mechanical properties of concrete obtained from dry mixes on the base of aluminate cements for self-leveling floors are presented. Principle possibility of obtaining unshrinkable concretes with the formation of ettringite using aluminate cement, gypsum and modern superplasticizers. Studies of free shrinkage of mixed binder showed that binder can be attribute to binders with compensated shrinkage. Cracking resistance of the composition is provided by the fact that the vast expansion in the initial stage of curing and shrinkage of the final stage is in 5…10 times lower than these values for gypsum and portland cement.

  9. Sustainable Development of the Cement Industry and Blended Cements to Meet Ecological Challenges

    Konstantin Sobolev


    Full Text Available The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA cement helps to improve its ecological compatibility. HVMA cement technology is based on the intergrinding of portland cement clinker, gypsum, mineral additives, and a special complex admixture. This new method increases the compressive strength of ordinary cement, improves durability of the cement-based materials, and - at the same time - uses inexpensive natural mineral additives or industrial by-products. This improvement leads to a reduction of energy consumption per unit of the cement produced. Higher strength, better durability, reduction of pollution at the clinker production stage, and decrease of landfill area occupied by industrial by-products, all provide ecological advantages for HVMA cement.

  10. Sustainable development of the cement industry and blended cements to meet ecological challenges.

    Sobolev, Konstantin


    The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA) cement helps to improve its ecological compatibility. HVMA cement technology is based on the intergrinding of portland cement clinker, gypsum, mineral additives, and a special complex admixture. This new method increases the compressive strength of ordinary cement, improves durability of the cement-based materials, and--at the same time--uses inexpensive natural mineral additives or industrial by-products. This improvement leads to a reduction of energy consumption per unit of the cement produced. Higher strength, better durability, reduction of pollution at the clinker production stage, and decrease of landfill area occupied by industrial by-products, all provide ecological advantages for HVMA cement.


    Gypsum wallboard with repeated or prolonged exposure to water or excess moisture can lose its structural integrity and provide a growth medium for biological contaminants. Poorly sealed buildings, leaking or failed plumbing systems, or improperly constructed HVAC systems can all ...

  12. Mechanical properties of simulated Mars materials: gypsum-rich sandstones and lapilli tuff

    Morrow, Carolyn; Lockner, David; Okubo, Chris


    Observations by the Mars Exploration Rover (MER) Opportunity, and other recent studies on diagenesis in the extensive equatorial layered deposits on Mars, suggest that the likely lithologies of these deposits are gypsum-rich sandstones and tuffaceous sediments (for example, Murchie and others, 2009; Squyres and others, 2012; Zimbelman and Scheidt, 2012). Of particular interest is how the diagenesis history of these sediments (degree of cementation and composition) influences the strength and brittle behavior of the material. For instance, fractures are more common in lower porosity materials under strain, whereas deformation bands, characterized by distributed strain throughout a broader discontinuity in a material, are common in higher porosity sedimentary materials. Such discontinuities can either enhance or restrict fluid flow; hence, failure mode plays an important role in determining the mechanics of fluid migration through sediments (Antonellini and Aydin, 1994; 1995; Taylor and Pollard, 2000; Ogilvie and Glover, 2001). As part of a larger study to characterize processes of fault-controlled fluid flow in volcaniclastic and gypsum-rich sediments on Mars, we have completed a series of laboratory experiments to focus on how gypsum clast content and degree of authigenic cementation affects the strength behavior of simulated Mars rocks. Both axial deformation and hydrostatic pressure tests were done at room temperature under dry conditions.

  13. Cement Formation

    Telschow, Samira; Jappe Frandsen, Flemming; Theisen, Kirsten


    Cement production has been subject to several technological changes, each of which requires detailed knowledge about the high multiplicity of processes, especially the high temperature process involved in the rotary kiln. This article gives an introduction to the topic of cement, including...... an overview of cement production, selected cement properties, and clinker phase relations. An extended summary of laboratory-scale investigations on clinkerization reactions, the most important reactions in cement production, is provided. Clinker formations by solid state reactions, solid−liquid and liquid...

  14. The Stabilizing Granular Soil with Slow-setting and Slight-expansive Cement

    ZHOU Ming-kai; SHENG Wei-guo; TIAN Zhong-qing


    According to the characteristics of granular soil, the technological requirements of the specialpurpose cement for stabilizing granular soil are pat forward to meet the demands of implementation of highway base engineering. A kind of slow-setting and slight-expansive cement is developed by the cross experiment method in slag-clinker-gypsum-alkaline system, the final setting time of the cement can be prolonged to 8 h, and it has properties of low dry shrirkage , high flexural strength and good crack resistance. The strength of granular soil stabilized by the cement is increased by 20% compared with that stabilized by Chinese 425-Grade slag cement.

  15. Experimental Study of Stabilized Soil Utilizing Circulating Fluidized Bed Combustion Desulfurization Ash with Carbide Slag and Desulfurization Gypsum

    Dezhi Shao


    Full Text Available This paper discusses the feasibility of preparing soil stabilizer which is circulating fluidized bed combustion ash-based, supplemented with carbide slag and desulfurization gypsum, composed entirely of complete industrial wastes. The results show that CFBC ash has better pozzolanic activity than fly ash. When stabilizer total content is 10% and the ratio of CFBC ash : carbide slag : desulfurization gypsum is 7.2 : 1.8 : 1, compressive strength of stabilized soil can reach the maximum of 2.12 MPa at the age of 28 d of curing. Stabilizer can meet the strength requirements of cement-soil mixing pile composite foundation and cement-soil mixing pile waterproof curtain.

  16. Valorization of apatites and phospho gypsum's residues procured by treatment of wastewater's textile; Valorisation des residus d'apatites et du phosphogypse obtenus apres traitement des eaux textiles

    Rais, Z.; Chaqroune, A.; Madji, M. [Faculte des Sciences Dhar El Mehrez, Lab. de Chimie Physique, Fes (Morocco); Maghnouj, J.; Hassani, E. [Centre de Recherches et d' Etudes des Phosphates, CERPHOS, Casablanca (Morocco); Nejjar, R. [Laboratoire de Controle Qualite CIOR, Fes (Morocco); Kherbeche, A. [Laboratoire de Catalyse et d' Environnement, Fes (Morocco)


    This work concerns the study of different methods of enrichment of apatite and phosphogypsum's residues gotten after treatment of the textile wastewater. The survey based on chemical composition properties, has been directed into three axis. The first one is the utilisation of apatite's residues as secondary constituent into cement whether substituting a part of clinker for an Artificial Portland Cement CPA or a part of limestone for a Portland Cement with Additions CPJ. The second one, is the substitution of the natural gypsum, used by the cement factory, by phosphogypsum's residues as cement's hold up. Finally the mixture of apatite and phosphogypsum's residues in the optimal conditions procured into cement. The results show that the use of apatite's residues and those of the phosphogypsum in cement industry has a good income and improves important physics and mechanical properties by report to the witness cement. (author)

  17. Sustainable production of blended cement in Pakistan through addition of natural pozzolana

    Ahmad Muhammad Imran


    Full Text Available In this work pozzolana deposits of district Swabi, Pakistan were investigated for partial substitution of Portland cement along with limestone filler. The cement samples were mixed in different proportions and tested for compressive strength at 7 and 28 days. The strength activity index (SAI for 10 % pozzolana, and 5% limestone blend at 7 and 28 days was 75.5% and 85.0% satisfying the minimum SAI limit of ASTM C618. Twenty two percents natural pozzolana and five percents limestone were interground with clinker and gypsum in a laboratory ball mill to compare the power consumption with ordinary Portland cement (OPC (95% clinker and 5% gypsum. The ternary blended cement took less time to reach to the same fineness level as OPC due to soft pozzolana and high grade lime stone indicating that intergrinding may reduce overall power consumption. Blended cement production using natural pozzolana and limestone may reduce the energy consumption and green house gas emissions.

  18. Gypsum karst in Italy: a review

    De Waele, Jo; Chiarini, Veronica; Columbu, Andrea; D'Angeli, Ilenia M.; Madonia, Giuliana; Parise, Mario; Piccini, Leonardo; Vattano, Marco; Vigna, Bartolomeo; Zini, Luca; Forti, Paolo


    Although outcropping only rarely in Italy, gypsum karst has been described in detail since the early XXth century (Marinelli, 1917). Gypsum caves are now known from almost all Italian regions (Madonia & Forti, 2003), but are mainly localised along the northern border of the Apennine chain (Emilia Romagna and Marche regions), Calabria, and Sicily, where the major outcrops occur. Recently, important caves have also been discovered in the underground gypsum quarries in Piedmont (Vigna et al., 2010). During the late 80s and 90s several multidisciplinary studies have been carried out in many gypsum areas. All this work converged into a comprehensive overview in 2003 (Madonia & Forti, 2003). Further detailed studies focused on the gypsum areas of Emilia Romagna (Chiesi et al., 2010; Forti & Lucci, 2010; Demaria et al., 2012; De Waele & Pasini, 2013; Ercolani et al., 2013; Columbu et al., 2015; Lucci & Piastra, 2015; Tedeschi et al., 2015) and of Sicily (Madonia & Vattano, 2011). Sinkholes related to Permo-Triassic gypsum have been studied in Friuli Venezia Giulia (Zini et al., 2015). This presentation will review the state of the art regarding different aspects of evaporite karst in Italy focusing on the main new results. References Chiesi M., et al. (2010) - Origin and evolution of a salty gypsum/anhydrite karst spring: the case of Poiano (Northern Apennines, Italy). Hydrogeology Journal, 18, pp. 1111-1124. Columbu A. et al. (2015) - Gypsum caves as indicators of climate-driven river incision and aggradation in a rapidly uplifting region. Geology, 43(6), 539-542. Demaria D. et al. (Eds.) (2012), Le Grotte Bolognesi, GSB-USB, 431 p. De Waele J., Pasini G. (2013) - Intra-messinian gypsum palaeokarst in the northern Apennines and its palaeogeographic implications. Terra Nova 25, pp. 199-205. Ercolani M., et al. (Eds.) (2013), I Gessi e la Cave i Monte Tondo. Studio multidisciplinare di un'area carsica nella Vena del Gesso Romagnola. Memorie Ist. It. Spel. II(26), 559 p

  19. Effect of high temperatures on gypsum paste and mortar

    Krejsová, Jitka; Doleželová, Magdalena; Vimmrová, Alena


    This paper describes the influence of high temperatures on some physical and mechanical properties of gypsum mixtures. Two gypsum mixtures were designed, first one was composed of gypsum and citric acid and the second one contained standardized sand also. The samples were exposed to temperatures from 50°C to 1000°C. Results show, that strength changes caused by high temperatures are significant in both mixtures and that the thermal shrinkage is reduced by adding sand to a gypsum mixture.

  20. Mechanical properties of gypsum board at elevated temperatures

    S.M. Cramer; O.M. Friday; R.H. White; G. Sriprutkiat


    Gypsum board is a common fire barrier used in house and general building construction. Recently, evaluation of the collapses of the World Trade Center Towers highlighted the potential role and failure of gypsum board in containing the fires and resisting damage. The use of gypsum board as primary fire protection of light-flame wood or steel construction is ubiquitous....

  1. Dissolution of Gypsum from field observations

    Klimchouk A.


    Full Text Available The paper reports the results of field measurements of gypsum dissolution in various countries (Ukraine, Spain, Italy and others and in different environments (river waters, precipitation, vadose zone, unconfined aquifer, perched cave lakes, ephemeral streams in caves, confined aquifer, cave air.

  2. Experimental study of phosphorous gypsum based insulation mortar powder material%磷石膏基保温砂浆胶粉料试验研究

    王玉麟; 赖振斌; 黄巧玲; 漆贵海


    The article studies on preparation of thermal insulation mortar powder materials with phosphorus gypsum which was an industrial waste residue, supplemented with cement and slag powder. Phosphorous gypsum based thermal insulation mortar powder material is prepared by experimental study and analysis on the influence of various factors to the mechanical properties and softening coefficient of phosphorous gypsum based mineral binder. The optimized formulation is verified. Through the comparison of mechanical properties and water absorption of gypsum based reference specimen, it is obtained that in the prepared phosphorus gypsum-based insulation mortar, the phosphorus gypsum amount is 54%, slag content is 30%, lime is 5%, cement is 10% and admixture is 1%, which provides a new approach for comprehensive utilization of phosphorus gypsum.%利用工业废渣磷石膏作为主要胶凝材料,辅以水泥、矿渣粉等研制保温砂浆胶粉料.通过各因素对磷石膏基胶粉料力学性能与软化系数影响的试验研究及分析,配制出了磷石膏基保温砂浆胶粉料.并对优化后的配方进行了验证;石膏基准试件的力学性能与吸水率进行了比较,得出磷石膏基保温砂浆中的磷石膏用量为54%时,矿渣掺量为30%,石灰为5%,水泥为10%,外加剂为1%,以期为磷石膏的有效利用提供新的途径.

  3. Some aspects on improvement of water resistant perfornace of gypsum binders

    Fomina Ekaterina


    Full Text Available The study reports that control of water resistant and strength performance of composite binder can be accomplished by using nanostructured gypsum silicate binder and portland cement and reduction of calcium sulfate dihydrate. Formation of an arranged more dense packing in crystal matrix of binder structure can be achieved through polydispersity of nanostructured silicon component. Highly reactive silica particles participate in synthesis of microcrystalline compounds such as hydroxylellestadite and serve as nucleation sites providing an increase of surface contact area between crystal structures. Cement in the system provides conditions to synthesis of stable flat-like hydroxysulfoaluminates. Upon hydration of a binder crystals of calcium sulfate dihydrate impound to a mass of water resistant crystalhydrate new formations, type and morphology of which promotes decreasing of intercrystal porosity followed by density, strength and water resistance increase of the composite.

  4. Galvanic corrosion of Mg-Zr fuel cladding and steel immobilized in Portland cement and geopolymer at early ages

    Rooses, Adrien; Lambertin, David; Chartier, David; Frizon, Fabien


    Galvanic corrosion behaviour of Mg-Zr alloy fuel cladding and steel has been studied in Ordinary Portland cement and Na-geopolymer. Portland cements implied the worse magnesium corrosion performances due to the negative effects of cement hydrates, grinding agents and gypsum on the galvanic corrosion. Galvanic corrosion in Na-geopolymer paste remains very low. Silicates and fluoride from the geopolymer activation solution significantly improve the corrosion resistance of the magnesium alloy while coupling with a cathode.

  5. Preparation of sulphoaluminate belite cement from fly ash

    Sahu, S.; Majling, J. (Slovak Technical Univ., Bratislava (Slovakia). Dept. of Ceramics, Glass and Cement)


    Sulphoaluminate belite cements containing the phases C[sub 2]S, C[sub 4]A[sub 3][bar S], C[sub 4]AF, C[bar S] were synthesized from limestone, fly ash and gypsum at 1,200 C. The correspondence between the predicted phase composition and real phase composition were checked. The influence of quantities of different phases in the hydration behavior and strength development were verified. Results show that an optimum proportion of phase quantities help in high strength development in early age. These cements fulfill all the requirement of Portland cement and have very high early strength. Porosity measurements show that the total pore volume in early period is comparatively less than that of Ordinary Portland Cement. Thus these cements can be usable for special purposes.


    Taher Abu-Lebdeh; Ellie Fini; Ashraf Fadiel


    The disposal of scrap tires is a challenging task and hence an innovative solution to meet these challenges is needed. Extensive work has been done on the utilization of waste tires in a variety of applications in asphalt pavements and concrete. However, previous investigations focus only on the mechanical properties of the rubberized materials, but few on the thermal performance. This is especially true for rubberized gypsum. Limited or no experimental data on the thermal performance of rubb...

  7. Speleothems in gypsum caves and their paleoclimatological significance

    Calaforra, J. M.; Forti, P.; Fernandez-Cortes, A.


    This article highlights the relationship between speleothems growing inside gypsum caves and the particular climate that existed during their development. Speleothems in gypsum caves normally consist of calcium carbonate (calcite) or calcium sulphate (gypsum) and the abundance of such deposits greatly differs from zone to zone. Observations carried out over the last 20 years in gypsum caves subjected to very different climates (Italy, Spain, New Mexico, northern Russia, Cuba, Argentina) highlight wide variation in their cave deposits. In arid or semi-arid climates, the speleothems are mainly composed of gypsum, whilst in temperate, humid or tropical regions, carbonate formations are largely predominant. In polar zones no speleothems develop. These mineralogical details could be useful paleoclimatic indicators of climate change. The interpretation proposed is based on the fact that in gypsum karst the kind of speleothems deposited is determined by competition between the two principal mechanisms that cause precipitation of calcite and gypsum. These mechanisms are completely different: calcite speleothem evolution is mainly controlled by CO2 diffusion, while gypsum deposits develop mostly due to evaporation. Therefore, the prevalence of one kind of speleothem over the other, and the relationship between the solution precipitation processes of calcite and gypsum, may provide evidence of a specific paleoclimate. Additionally, other non-common deposits in gypsum caves like moonmilk, cave rafts and dolomite speleothems can be used as markers for the prevalence of long, dry periods in humid areas, seasonal changes in climate, or rainfall trends in some gypsum areas. Moreover, the dating of gypsum speleothems could contribute paleoclimatic data relating to dry periods when calcite speleothems are not deposited. In contrast, the dating of calcite speleothems in gypsum caves could identify former wet periods in arid zones.

  8. Minerals of expansive and non-shrinkage sulfomineral cements

    Samchenko Svetlana V.


    Full Text Available Usually to obtain expansive cements sulfoaluminate clinker or mix aluminate clinker with calcium sulfates (gypsum, hemihydrate, anhydrate are used. For these cements ettringite is an important hydration product and kinetic reaction of this phase plays an important role in determinаting performance. The alternative aluminate phases may be ferrite containing ones. This article deals with the composition and properties of solid solution of calcium sulfoaluminate, sulfoferrite and sulfoaluminoferrite cements. It was studied an influence of calcium sulfate on structure and properties of calcium aluminate and ferrite phases, and their stability under high temperatures. Beside that the properties of cements containing these phases were studied. The investigation of hydration and properties of sulfomineral cements shows that ettringite and its analogies are formed in such way to provide expansion and compression of cement stone. Degree of expansion and self-stressing of cement stone depends not only on composition of sulfated minerals but on ratio and types of clinkers. The higher expansion is reached by the use of high alite containing Portland cement clinker together with sulfoaluminate or sulfoalumoferrite one, the lower expansion is reached by addition of sulfoalumoferrite and sulfoferrite clinkers. These cements are classified as self-stressing, expansive or shrinkage-compensating ones depend on the degree of their expansion after 28 days of curing.

  9. Preparation of Super Composite Cement with a Lower Clinker Content and a Larger Amount of Industrial Wastes

    HE Zhen; LIANG Wen-quan; LI Bei-xing; LI Xiang-guo


    The effects of the grinding mode,fineness, gypsum kinds and dosage, mix proportions on properties of the composite cements consisting of slag,fly ash, limestone and a lower content clinker were investigated,respectively. The results show that when the proportions among slag, fly ash and limestone are appropriate, the grinding technology and system are reasonable, the optimized gypsums and additives are effective, the 52.5 R grade cement (52.5 R grade cement means a higher strength than 52.5 at early age ) can be prepared by clinker dosage of 50% in weight, the 42.5R or 42.5,32.5 grade composite cement containing 40% and 30% clinker also may be made, respectively. Moreover, the high performance concrete prepared from the above composite cements was studied experimentally.

  10. The hardening of Portland cement studied by ? NMR stray-field imaging

    Nunes, Teresa; Randall, E. W.; Samoilenko, A. A.; Bodart, P.; Feio, G.


    Hydration and hardening processes of Portland cement (type I) were studied by analysis of the one-dimensional projections (profiles) obtained periodically with the 0022-3727/29/3/044/img8 stray-field imaging technique over two days. The influence of additives, such as gypsum, in Portland cement (type IA) was also investigated. The decay of the signal intensity as a function of time was found to be bi-exponential for type I and mono-exponential for type IA.

  11. Alabaster and Selenite Gypsum:I-Dehydration-Rehydration Comparison Studies


    Two types of gypsum raw materials, selenite and alabaster, were used to prepare dental stone (α-hemihydrate).Gypsum lumps (0.8~2.5 cm) were hydrothermally treated at 135, 160 and 180°C for 6, 2 and 1 h respectively.The physicochemical properties and composition characteristics of the α-hemihydrates prepared from selenite and alabaster raw gypsum were determined. The results indicated that both the selenite and alabaster raw gypsum show the same chemical and mineralogical composition of calcium sulphate dihydrate. They differs only in their microstructure, selenite raw gypsum exhibits perfect regular crystals while alabaster gypsum, on the other hand,exhibits irregular, large size and interlocked crystals. Selenite is more accessible to dehydration than alabaster raw gypsum. The α-hemihydrate samples prepared from alabaster raw gypsum showed a very short setting time and a lower compressive strength values in relation to that prepared from selenite gypsum. The compressive strength values of the all prepared samples were higher than that specified by A.D.A specification for dental use. To optimize the setting time of both products further studies are needed.

  12. Computation of X-ray powder diffractograms of cement components and its application to phase analysis and hydration performance of OPC cement

    Rohan Jadhav; N C Debnath


    The importance of computed X-ray diffraction patterns of various polymorphs of alite (3, 1, ), belite (, ), aluminate (cubic, orthorhombic), aluminoferrite, gypsum and hemihydrate in the quantitative phase analysis of cement and its early stage hydration performance is highlighted in this work with three OPC samples. The analysis shows that the predominant silicate phases present in all the samples are 3-alite phase and -belite phase, respectively. Both cubic and orthorhombic phases of C3A, brownmillerite, gypsum and hemihydrates are present at different levels. Quantitative phase analysis of cement by Rietveld refinement method provides more accurate and comprehensive data of the phase composition compared to Bogue method. The comparative hydration performance of these samples was studied with / ratio, 0.5 and the results are interpreted in the light of difference in phase compositions viz. -C2S/C3S ratio, fraction of finer cement particles present in the samples and theoretical modeling of C3S hydration.

  13. Health survey in gypsum mines in India

    Nandi Subroto


    Full Text Available Background: Mining is a hazardous occupation in which workers are exposed to adverse conditions. In India, gypsum mining is mainly carried out in the state of Rajasthan, which contributes about 99% of the total production. Objective: The present study was carried out in 12 different gypsum mines in Rajasthan state to determine the health status of the miners. Materials and Methods: One hundred and fifty workers engaged in mining activities were included in the study and their health status was compared with that of 83 office staff of the same mines. The health status of the employees was evaluated using a standardized medical questionnaire and pulmonary function testing. Statistical Analysis: The unpaired ′t′ test was used to determine whether there was any significant difference between the miners and the controls and the chi-square test to compare the prevalences of various respiratory impairments in workers with that in controls; we also examined the differences between smokers and nonsmokers. Results: Our findings show that the literacy rate is low (42% among the miners. Pulmonary restrictive impairment was significantly higher amongst smokers as compared to nonsmokers in both miners and controls. Hypertension (22.6%, diabetes (8.8%, and musculoskeletal morbidity (8% were the common diseases in miners. Conclusion: This study shows that there is high morbidity amongst miners, thus indicating the need for regular health checkups, health education, use of personal protective devices, and engineering measures for control of the workplace environment.

  14. Geology of the Gypsum Gap quadrangle, Colorado

    Cater, Fred W.


    The Gypsum Gap quadrangle is one eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comparative study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through a arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The core consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

  15. Flue gas desulfurization gypsum and fly ash


    The Cumberland Fossil Plant (CUF) is located in Stewart County, Tennessee, and began commercial operation in 1972. This is the Tennessee Valley Authority`s newest fossil (coal-burning) steam electric generating plant. Under current operating conditions, the plant burns approximately seven million tons of coal annually. By-products from the combustion of coal are fly ash, approximately 428,000 tons annually, and bottom ash, approximately 115,000 tons annually. Based on historical load and projected ash production rates, a study was initially undertaken to identify feasible alternatives for marketing, utilization and disposal of ash by-products. The preferred alternative to ensure that facilities are planned for all by-products which will potentially be generated at CUF is to plan facilities to handle wet FGD gypsum and dry fly ash. A number of different sites were evaluated for their suitability for development as FGD gypsum and ash storage facilities. LAW Engineering was contracted to conduct onsite explorations of sites to develop information on the general mature of subsurface soil, rock and groundwater conditions in the site areas. Surveys were also conducted on each site to assess the presence of endangered and threatened species, wetlands and floodplains, archaeological and cultural resources, prime farmland and other site characteristics which must be considered from an environmental perspective.

  16. Raman spectroscopy of shocked gypsum from a meteorite impact crater

    Brolly, Connor; Parnell, John; Bowden, Stephen


    Impact craters and associated hydrothermal systems are regarded as sites within which life could originate on Earth, and on Mars. The Haughton impact crater, one of the most well preserved craters on Earth, is abundant in Ca-sulphates. Selenite, a transparent form of gypsum, has been colonized by viable cyanobacteria. Basement rocks, which have been shocked, are more abundant in endolithic organisms, when compared with un-shocked basement. We infer that selenitic and shocked gypsum are more suitable for microbial colonization and have enhanced habitability. This is analogous to many Martian craters, such as Gale Crater, which has sulphate deposits in a central layered mound, thought to be formed by post-impact hydrothermal springs. In preparation for the 2020 ExoMars mission, experiments were conducted to determine whether Raman spectroscopy can distinguish between gypsum with different degrees of habitability. Ca-sulphates were analysed using Raman spectroscopy and results show no significant statistical difference between gypsum that has experienced shock by meteorite impact and gypsum, which has been dissolved and re-precipitated as an evaporitic crust. Raman spectroscopy is able to distinguish between selenite and unaltered gypsum. This shows that Raman spectroscopy can identify more habitable forms of gypsum, and demonstrates the current capabilities of Raman spectroscopy for the interpretation of gypsum habitability.

  17. Hydrogen sulfide release from dairy manure storages containing gypsum bedding

    Recycled gypsum products can provide a cost-effective bedding alternative for dairy producers. Manufacturers report reduced odors, moisture and bacteria in the stall environment when compared to traditional bedding. Gypsum provides a sulfate source that can be converted to hydrogen sulfide under ana...


    Nediljka Gaurina-Međimurec


    Full Text Available During a well cementing special place belongs to the cement slurry design. To ensure the best quality of cementing, a thorough understanding of well parameters is essential, as well as behaviour of cement slurry (especially at high temperatures and application of proven cementing techniques. Many cement jobs fail because of bad job planning. Well cementing without regarding what should be accomplished, can lead to well problems (channels in the cement, unwanted water, gas or fluid production, pipe corrosion and expensive well repairs. Cementing temperature conditions are important because bot-tomhole circulating temperatures affect slurry thickening time, arheology, set time and compressive strength development. Knowing the actual temperature which cement encounters during placement allows the selection of proper cementing materials for a specific application. Slurry design is affected by well depth, bottom hole circulating temperature and static temperature, type or drilling fluid, slurry density, pumping time, quality of mix water, fluid loss control, flow regime, settling and free water, quality of cement, dry or liquid additives, strength development, and quality of the lab cement testing and equipment. Most Portland cements and Class J cement have shown suitable performances in geot-hermal wells. Cement system designs for geothermal wells differ from those for conventional high temperature oil and gas wells in the exclusive use of silica flour instead of silica sand, and the avoidance of fly ash as an extender. In this paper, Portland cement behaviour at high temperatures is described. Cement slurry and set cement properties are also described. Published in literature, the composition of cement slurries which were tested in geothermal conditions and which obtained required compressive strength and water permeability are listed. As a case of our practice geothermal wells Velika Ciglena-1 and Velika Ciglena-la are described.

  19. Modification of FGD gypsum in hydrothermal mixed salt solution

    WU Xiao-qin; WU Zhong-biao


    A novel utilization way of the sludge from wet calcium-based flue gas desulfurization (FGD) processes has been developed in this paper. This study focused on the conversion of the FGD gypsum into α-hemihydrate calcium sulfate by a hydrothermal salt solution method at atmospheric pressure. Experimental study has been carried out in a batch reactor. Qualitative and quantitative analyses were made by DSC/TG thermal analysis, SEM, XRD, metalloscope and chemical analysis. The experimental results showed that the modification of FGD gypsum was controlled by the dissolution and recrystallization mechanisms. With the introduction of FGD gypsum the salt solution was supersaturated, then crystal nucleus of α-hemihydrate calcium sulfate were produced in the solution. With the submicroscopic structure of FGD gypsum crystal changed, the crystal nucleus grew up into α-hemihydrate calcium sulfate crystals. Thus, the modification of FGD gypsum was fulfilled.

  20. Incorporation of gypsum waste in ceramic block production: Proposal for a minimal battery of tests to evaluate technical and environmental viability of this recycling process.

    Godinho-Castro, Alcione P; Testolin, Renan C; Janke, Leandro; Corrêa, Albertina X R; Radetski, Claudemir M


    Civil engineering-related construction and demolition debris is an important source of waste disposed of in municipal solid waste landfills. After clay materials, gypsum waste is the second largest contributor to the residential construction waste stream. As demand for sustainable building practices grows, interest in recovering gypsum waste from construction and demolition debris is increasing, but there is a lack of standardized tests to evaluate the technical and environmental viability of this solid waste recycling process. By recycling gypsum waste, natural deposits of gypsum might be conserved and high amounts of the waste by-product could be reused in the civil construction industry. In this context, this paper investigates a physical property (i.e., resistance to axial compression), the chemical composition and the ecotoxicological potential of ceramic blocks constructed with different proportions of clay, cement and gypsum waste, and assesses the feasibility of using a minimal battery of tests to evaluate the viability of this recycling process. Consideration of the results for the resistance to axial compression tests together with production costs revealed that the best formulation was 35% of plastic clay, 35% of non-plastic clay, 10% of Portland cement and 20% of gypsum waste, which showed a mean resistance of 4.64MPa. Energy dispersive X-ray spectrometry showed calcium and sulfur to be the main elements, while quartz, gypsum, ettringite and nacrite were the main crystalline compounds found in this formulation. Ecotoxicity tests showed that leachate from this formulation is weakly toxic toward daphnids and bacteria (EC(20%)=69.0 and 75.0, respectively), while for algae and fish the leachate samples were not toxic at the EC(50%) level. Overall, these results show that the addition of 20% of gypsum waste to the ceramic blocks could provide a viable substitute for clay in the ceramics industry and the tests applied in this study proved to be a useful tool

  1. Energy recovery from wastes : experience with solid alternative fuels combustion in a precalciner cement kiln

    Tokheim, Lars-André; Gautestad, Tor; Axelsen, Ernst Petter; Bjerketvedt, Dag


    Today virtually all cement clinker burning processes take place in rotary kilns. A mixture of calcareous and argilaceous materials is heated to a temperature of about 1450 °C. In this process decarbonation followed by partial fusion occurs, and nodules of so-called clinker are formed. The cooled clinker is mixed with a few percent of gypsum, and ground into a fine meal – cement. The most modern cement kilns are equipped with a precalciner, in which most of the calcium carbonate...

  2. Lunar cement

    Agosto, William N.


    With the exception of water, the major oxide constituents of terrestrial cements are present at all nine lunar sites from which samples have been returned. However, with the exception of relatively rare cristobalite, the lunar oxides are not present as individual phases but are combined in silicates and in mixed oxides. Lime (CaO) is most abundant on the Moon in the plagioclase (CaAl2Si2O8) of highland anorthosites. It may be possible to enrich the lime content of anorthite to levels like those of Portland cement by pyrolyzing it with lunar-derived phosphate. The phosphate consumed in such a reaction can be regenerated by reacting the phosphorus product with lunar augite pyroxenes at elevated temperatures. Other possible sources of lunar phosphate and other oxides are discussed.

  3. Characterisation of Cements From Dominantly Volcanic Raw Materials of the Carpathian Bend Zone

    Halmagy Timea


    Full Text Available This paper presents the results of laboratory investigations regarding the production of cements from local raw materials, such as limestone from Varghis, gypsum from Nucsoara, basaltic scoria from Racosul de Jos, volcanic tuff from Racosul de Sus, diatomite from Filia, and red mud from Oradea. The raw mixtures, based on modified Bogue calculations, contain limestone, gypsum, and one or two of the above-mentioned materials. The cements resulted from clinker grinding in a laboratory gas furnace at 1260-1300 °C, with one hour at the peak temperatures, and were characterised for Blaine specific surface area, specific density, and mineral phases. Physico-mechanical properties, such as water content for normal consistency, setting time, soundness, and compressive strength were also determined. Results show that these cements contain belite, ferrite, calcium sulphoaluminate, anhydrite, and some minor compounds.

  4. Investigation of Dynamic Crack Coalescence Using a Gypsum-Like 3D Printing Material

    Jiang, Chao; Zhao, Gao-Feng; Zhu, Jianbo; Zhao, Yi-Xin; Shen, Luming


    Dynamic crack coalescence attracts great attention in rock mechanics. However, specimen preparation in experimental study is a time-consuming and difficult procedure. In this work, a gypsum-like material by powder bed and inkjet 3D printing technique was applied to produce specimens with preset cracks for split Hopkinson pressure bar (SHPB) test. From micro X-ray CT test, it was found that the 3D printing technique could successfully prepare specimens that contain preset cracks with width of 0.2 mm. Basic mechanical properties of the 3D printing material, i.e., the elastic modulus, the Poisson's ratio, the density, the compressive strength, the indirect tensile strength, and the fracture toughness, were obtained and reported. Unlike 3D printed specimens using polylactic acid, these gypsum-like specimens can produce failure patterns much closer to those observed in classical rock mechanical tests. Finally, the dynamic crack coalescence of the 3D printed specimens with preset cracks were captured using a high-speed camera during SHPB tests. Failure patterns of these 3D printed specimens are similar to the specimens made by Portland cement concrete. Our results indicate that sample preparation by 3D printing is highly competitive due to its quickness in prototyping, precision and flexibility on the geometry, and high material homogeneity.

  5. Effect of background electrolytes on gypsum dissolution

    Burgos-Cara, Alejandro; Putnis, Christine; Ruiz-Agudo, Encarnacion


    Knowledge of the dissolution behaviour of gypsum (CaSO4· 2H2O) in aqueous solutions is of primary importance in many natural and technological processes (Pachon-Rodriguez and Colombani, 2007), including the weathering of rocks and gypsum karst formations, deformation of gypsum-bearing rocks, the quality of drinking water, amelioration of soil acidity, scale formation in the oil and gas industry or measurement of water motion in oceanography. Specific ions in aqueous solutions can play important but very different roles on mineral dissolution. For example, the dissolution rates and the morphology of dissolution features may be considerably modified by the presence of the foreign ions in the solution, which adsorb at the surface and hinder the detachment of the ions building the crystal. Dissolution processes in the aqueous environment are closely related to the rearrangement of water molecules around solute ions and the interaction between the solvent molecules themselves. The rearrangement of water molecules with respect to solute species has been recognized as the main kinetic barrier for crystal dissolution in many systems (Davis, 2000; De Yoreo and Dove 2004; Wasylenki et al. 2005). Current research suggest that the control that electrolytes exert on water structure is limited to the local environment surrounding the ions and is not related to long-range electric fields emanating from the ions but results from effects associated with the hydration shell(s) of the ions (Collins et al. 2007) and the ions' capacity to break or structure water (i.e. chaotropic and kosmotropic ions, respectively). These effects will ultimately affect the kinetics of crystal dissolution, and could be correlated with the water affinity of the respective background ions following a trend known as the lyotropic or Hofmeister series (Kunz et al. 2004; Dove and Craven, 2005). In situ macroscopic and Atomic Force Microscopy (AFM) flow-through dissolution experiments were conducted at a

  6. Natural Radioactivity in Tanzania Cements and their Raw Materials

    Aloyce Isaya Amasi


    Full Text Available This paper presents the study of natural radioactivity in Tanzania Portland cements and their raw materials. Samples collected as raw materials were pozzolan, sandstone, limestone, clay, gypsum and cement as finished products. The natural radioactivity due to the presence of radium 226Ra, thorium 232Th and potassium 40K were measured by means of gamma spectrometer coupled with HPGe detector. The mean measured activity concentrations of 226Ra, thorium 232Th and potassium 40K in the raw materials range from 2.6 to 93.2, 1.3 to 172.8 and 6.3 to 997 Bq/kg, respectively with higher activity concentrations in pozzolan and lower in gypsum. Activity concentrations of natural radionuclides in raw materials (excluding some materials from Songwe deposits in Mbeya region are comparative with the worldwide average concentrations of these radionuclides in soil. The average activity concentration of 226Ra, thorium 232Th and potassium 40K in the cements are 46, 28 and 228 Bq/kg, respectively. The calculated values of radiological indices are below 60% of the upper recommended values for building materials. The average annual effective dose to an occupant from use of these materials equals to 0.45 mSv. Average activity concentrations of the mentioned radionuclides in Tanzania cements are in the middle of the variability interval of the national averages.

  7. Effect of Fly Ash and Silica Fume on the Mechanical Properties of Cement Paste at Different Stages of Hydration


    material is a fine white powder byproduct from silicon metal or ferrosilicon alloy production is very reactive in cement. Silicon dioxide makes up a...of cement concrete . The ferrite goes through two progressive reactions with the gypsum. The first reaction is when the ettringite reacts with the...resulting from the combustion of ground or powdered coal, which is transported from the firebox through the boiler by flue gases. Fly ash consists of

  8. Water defluoridation using Malawi’s locally sourced gypsum

    Masamba, W. R. L.; Sajidu, S. M.; Thole, B.; Mwatseteza, J. F.

    Free fluoride levels above the WHO guideline maximum value of 1.5 mg/l have been reported in several parts of Malawi. Dental fluorosis has also been observed in the same areas such that search for local defluoridation techniques has become important in the country. The present research intended to determine the potential of using Malawi gypsum in defluoridation, identify the best pre-treatment of the gypsum and optimum conditions under which effective water defluoridation with the gypsum may be obtained. Laboratory experiments were carried out to explore defluoridation of drinking water using locally sourced gypsum and gypsum calcined at high temperatures. A 400 °C calcined phase of gypsum gave the highest defluoridation capacity of 67.80% compared to raw (uncalcined) gypsum, 200, 300 and 500 °C calcined phases. Powder X-ray diffraction (PXRD) pattern of the 400 °C phase revealed existence of less crystalline CaSO 4 that was thought to be responsible for such relatively high defluoridation capacity. The dependence of the fluoride removal by the 400 °C calcined phase on other drinking water quality parameters was assessed by simple correlation analysis. Reaction kinetics and mechanisms of fluoride removal by the materials were also investigated. It was found that ion exchange was the dominant mechanism through which fluoride was removed from water by the materials.

  9. Contribution study to the thermal insulation of the builders in the desert regions of exploiting gypsum fiber reinforced palm

    Hafsi, Fouad; Kriker, Abdelouahed; Abani, Said


    Algerian Desert areas were characterized by very hot climate in summer and very cold in winter. The most widely used building material in these areas are concrete, mortar cement, which has a bad thermal insulation, causing a significant increase in cooling and heating costs; in order to avoid this problem it become a must to replace these materials with a good thermal isolation material and lower production cost. This work is part of the evaluation of local materials by improving their performance in the field of thermal insulation, which is considered a first step in the development of new local materials to be used in the construction field, the material used in this study is the gypsum reinforced with date palm fiber. In fact, Algeria has extraordinary resources in natural fibers (from Palm, Abaca, Hemp…) but without any large valorization in building materials. The aim of this work is then to characterization of those date palm fibers in new building materials approved for use in the construction of buildings in the desert areas. The date palm fibers were added to samples of the gypsum material in the form of cutting layers at different volume fraction, so as to determine the extent of their impact in the improvement of the thermal performance. The results were very satisfactory, reaching improvement rate of 16% for samples gypsum reinforced with single cut fiber form, and 32% of the samples reinforced with fiber in the form of layers.

  10. Sustainable Uses of FGD Gypsum in Agricultural Systems: Introduction.

    Watts, Dexter B; Dick, Warren A


    Interest in using gypsum as a management tool to improve crop yields and soil and water quality has recently increased. Abundant supply and availability of flue gas desulfurization (FGD) gypsum, a by-product of scrubbing sulfur from combustion gases at coal-fired power plants, in major agricultural producing regions within the last two decades has attributed to this interest. Currently, published data on the long-term sustainability of FGD gypsum use in agricultural systems is limited. This has led to organization of the American Society of Agronomy's Community "By-product Gypsum Uses in Agriculture" and a special collection of nine technical research articles on various issues related to FGD gypsum uses in agricultural systems. A brief review of FGD gypsum, rationale for the special collection, overviews of articles, knowledge gaps, and future research directions are presented in this introductory paper. The nine articles are focused in three general areas: (i) mercury and other trace element impacts, (ii) water quality impacts, and (iii) agronomic responses and soil physical changes. While this is not an exhaustive review of the topic, results indicate that FGD gypsum use in sustainable agricultural production systems is promising. The environmental impacts of FGD gypsum are mostly positive, with only a few negative results observed, even when applied at rates representing cumulative 80-year applications. Thus, FGD gypsum, if properly managed, seems to represent an important potential input into agricultural systems. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  11. Alfalfa Responses to Gypsum Application Measured Using Undisturbed Soil Columns

    Rebecca Tirado-Corbalá


    Full Text Available Gypsum is an excellent source of Ca and S, both of which are required for crop growth. Large amounts of by-product gypsum [Flue gas desulfurization gypsum-(FGDG] are produced from coal combustion in the United States, but only 4% is used for agricultural purposes. The objective of this study was to evaluate the effects of (1 untreated, (2 short-term (4-year annual applications of gypsum totaling 6720 kg ha−1, and (3 long-term (12-year annual applications of gypsum totaling 20,200 kg ha−1 on alfalfa (Medicago sativa L. growth and nutrient uptake, and gypsum movement through soil. The study was conducted in a greenhouse using undisturbed soil columns of two non-sodic soils (Celina silt loam and Brookston loam. Aboveground growth of alfalfa was not affected by gypsum treatments when compared with untreated (p > 0.05. Total root biomass (0–75 cm for both soils series was significantly increased by gypsum application (p = 0.04, however, increased root growth was restricted to 0–10 cm depth. Soil and plant analyses indicated no unfavorable environmental impact from of the 4-year and 12-year annual application of FGDG. We concluded that under sufficient water supply, by-product gypsum is a viable source of Ca and S for land application that might benefit alfalfa root growth, but has less effect on aboveground alfalfa biomass production. Undisturbed soil columns were a useful adaptation of the lysimeter method that allowed detailed measurements of alfalfa nutrient uptake, root biomass, and yield and nutrient movement in soil.

  12. Influence of ferrite phase in alite-calcium sulfoaluminate cements

    Duvallet, Tristana Yvonne Francoise

    Since the energy crisis in 1970's, research on low energy cements with low CO2- emissions has been increasing. Numerous solutions have been investigated, and the goal of this original research is to create a viable hybrid cement with the components of both Ordinary Portland cement (OPC) and calcium sulfoaluminate cement (CSAC), by forming a material that contains both alite and calcium sulfoaluminate clinker phases. Furthermore, this research focuses on keeping the cost of this material reasonable by reducing aluminum requirements through its substitution with iron. The aim of this work would produce a cement that can use large amounts of red mud, which is a plentiful waste material, in place of bauxite known as an expensive raw material. Modified Bogue equations were established and tested to formulate this novel cement with different amounts of ferrite, from 5% to 45% by weight. This was followed by the production of cement from reagent chemicals, and from industrial by-products as feedstocks (fly ash, red mud and slag). Hydration processes, as well as the mechanical properties, of these clinker compositions were studied, along with the addition of gypsum and the impact of a ferric iron complexing additive triisopropanolamine (TIPA). To summarize this research, the influence of the addition of 5-45% by weight of ferrite phase, was examined with the goal of introducing as much red mud as possible in the process without negatively attenuate the cement properties. Based on this PhD dissertation, the production of high-iron alite-calcium sulfoaluminateferrite cements was proven possible from the two sources of raw materials. The hydration processes and the mechanical properties seemed negatively affected by the addition of ferrite, as this phase was not hydrated entirely, even after 6 months of curing. The usage of TIPA counteracted this decline in strength by improving the ferrite hydration and increasing the optimum amount of gypsum required in each composition

  13. Natural γ-ray-emitting radionuclides in Egyptian cement



    Samples of cement manufactured in Egypt and the raw materials have been analyzed using gamma-spectroscopy, in order to determine the concentration of natural radionuclides and associated radiological hazard. The mean of specific activity due to radionuclides of 226Ra, 232Th and 40K was found to be (20±4), (11± 2),(320±18) (gypsum), (41±8), (27±5), (410±27) (clay), (58±11), (18±3), (321±20) (iron ore) and (37.6±6), (11.8±3),phate resistant cement (S.R.C.), clinker and white cement, while the mean specific activities of 226Ra and 232Th are activities (concentrations) are in the same range as the data released in other countries. The calculated radiation hazard parameters for all the samples are still lower than the acceptable values in Egypt and other countries.

  14. Origin and diagenetic evolution of gypsum and microbialitic carbonates in the Late Sag of the Namibe Basin (SW Angola)

    Laurent, Gindre-Chanu; Edoardo, Perri; Ian, Sharp R.; Peacock, D. C. P.; Roger, Swart; Ragnar, Poulsen; Hercinda, Ferreira; Vladimir, Machado


    analyses reveal successive dissolution, recrystallisation and cementation phases that occurred during burial, uplift and exhumation, implying a complex diagenetic evolution of both gypsum and carbonates, influenced by pore fluids of diverse composition which distinctly varied from meso- to telogenetic domains.

  15. Gypsum crystals in the inner shelf sediments off Maharashtra, India

    Hashimi, N.H.; Ambre, N.V.

    Gypsum crystals have been found in the inner shelf silty clay/clayey silt off the Maharashtra Coast between Vengurla and Bombay. Generally these occur as euhedral single or twinned crystals of selenite. Very often shells are found embedded within...


    Ustinova Yuliya Valer'evna; Sivkov Sergey Pavlovich; Barinova Ol'ga Pavlovna; Sanzharovskiy Aleksandr Yur'evich


    Nowadays, functional additives represented by multiple classes of substances and compounds, including polymers of different origin, are available for introduction into dry mixtures based on gypsum binders. However, their impact onto the growth and formation of calcium sulfate dihydrate (CaSO∙2HO) crystals generated in the course of hardening of gypsum binders is not quite clear. Therefore, the objective of the research was to analyze the processes of growth and formation of calcium sulfate di...

  17. Estimation of radioactivity level and associated radiological hazards of limestone and gypsum used as raw building materials in Rawalpindi/Islamabad region of Pakistan.

    Gul, Rahmat; Ali, Safdar; Hussain, Manzur


    This study was undertaken to asses the radioactivity level of limestone and gypsum and its associated radiological hazard due to the presence of naturally occurring radioactive materials. Representative samples of limestone and gypsum were collected from cement factories located in the Rawalpindi/Islamabad region of Pakistan and were analysed by using an N-type high-purity germanium detector of 80 % relative efficiency. The average activity concentration of (40)K, (226)Ra and (232)Th were 60.22±3.47, 29.25±5.23 and 4.07±3.31 Bq kg(-1), respectively, in limestone and 70.86±4.1, 5.01±2.10 and 4.49±3.1 Bq kg(-1), respectively, in gypsum. The radiological hazard parameters radium equivalent activities, absorbed dose rate in air, external hazard index, internal hazard index, annual effective dose equivalent, gamma index and alpha index were computed. The results of the average activity concentrations of (40)K, (226)Ra and (232)Th and radiological hazard parameters were within the range of the reported average worldwide/United Nations Scientific Committee on the Effect of Atomic Radiation values. It is concluded that limestone and gypsum used in the Rawalpindi/Islamabad region does not pose any excessive radiological health hazard as a building raw materials and in industrial uses.

  18. A Scanning Transmission X-ray Microscopy Study of Cubic and Orthorhombic C3A and Their Hydration Products in the Presence of Gypsum

    Vanessa Rheinheimer


    Full Text Available This paper shows the microstructural differences and phase characterization of pure phases and hydrated products of the cubic and orthorhombic (Na-doped polymorphs of tricalcium aluminate (C3A, which are commonly found in traditional Portland cements. Pure, anhydrous samples were characterized using scanning transmission X-ray microscopy (STXM, X-ray photoelectron spectroscopy (XPS and X-ray diffraction (XRD and demonstrated differences in the chemical and mineralogical composition as well as the morphology on a micro/nano-scale. C3A/gypsum blends with mass ratios of 0.2 and 1.9 were hydrated using a water/C3A ratio of 1.2, and the products obtained after three days were assessed using STXM. The hydration process and subsequent formation of calcium sulfate in the C3A/gypsum systems were identified through the changes in the LIII edge fine structure for Calcium. The results also show greater Ca LII binding energies between hydrated samples with different gypsum contents. Conversely, the hydrated samples from the cubic and orthorhombic C3A at the same amount of gypsum exhibited strong morphological differences but similar chemical environments.


    Fred Sabins


    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, a comparison study of the three cement systems examined the effect that cement drillout has on the three cement systems. Testing to determine the effect of pressure cycling on the shear bond properties of the cement systems was also conducted. This report discusses testing that was performed to analyze the alkali-silica reactivity of ULHS in cement slurries.

  20. Manufacture of Durable Stucco Gypsum in Outdoor Plastering Engineering%耐久型室外粉刷石膏的性能及微观结构

    余红发; 丁向群


    研究白水泥等作激发剂的难溶性无水石膏的性能,并制备出用于室外条件下的耐久型粉刷石膏.用XRD和SEM-EDAX分析了耐久型粉刷石膏外墙饰面使用18年后的相组成和显微结构.%The properties of anhydrite [1 with white protland cement as accelerating agent are studied, and the durable stucco gypsum in outdoor condition are prepared successfully. The phase composition and microstructure of the durable stucco gypsum external veneer after 18 years' exposure are analyzed by XRD and SEM-EDAX.

  1. Interaction of gypsum with lead in aqueous solutions

    Astilleros, J.M., E-mail: [Dpto. Cristalografia y Mineralogia, Universidad Complutense de Madrid, Jose Antonio Novais, 2, E-28040 Madrid (Spain); Godelitsas, A. [Department of Mineralogy and Petrology, Faculty of Geology and Geoenvironment, University of Athens, Panepistimioupoli Zographou, 15784 Athens (Greece); Rodriguez-Blanco, J.D. [School of Earth and Environments, Faculty of Environment, University of Leeds, Leeds LS2 9JT (United Kingdom); Fernandez-Diaz, L. [Dpto. Cristalografia y Mineralogia, Universidad Complutense de Madrid, Jose Antonio Novais, 2, E-28040 Madrid (Spain); Prieto, M. [Dpto. de Geologia, Universidad de Oviedo, E-30005 Oviedo (Spain); Lagoyannis, A.; Harissopulos, S. [Tandem Accelerator Laboratory, Institute of Nuclear Physics, NCSR ' Demokritos' , GR-15310 Attiki (Greece)


    Sorption processes on mineral surfaces are a critical factor in controlling the distribution and accumulation of potentially harmful metals in the environment. This work investigates the effectiveness of gypsum (CaSO{sub 4}.2H{sub 2}O) to sequester Pb. The interaction of gypsum fragments with Pb-bearing solutions (10, 100 and 1000 mg/L) was monitored by performing macroscopic batch-type experiments conducted at room temperature. The aqueous phase composition was periodically determined by Atomic Absorption Spectrometry (AAS), Ion Chromatography (IC) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Regardless of the [Pb{sub aq}]{sub initial}, a [Pb{sub aq}]{sub final} < 4 mg/L was always reached. The uptake process was fast (t < 1 h) for [Pb{sub aq}]{sub initial} {>=} 100 mg/L and significantly slower (t > 1 week) for [Pb{sub aq}]{sub initial} = 10 mg/L. Speciation calculations revealed that after a long time of interaction (1 month), all the solutions reached equilibrium with respect to both gypsum and anglesite. For [Pb{sub aq}]{sub initial} {>=} 100 mg/L, sorption takes place mainly via the rapid dissolution of gypsum and the simultaneous formation of anglesite both on the gypsum surface and in the bulk solution. In the case of [Pb{sub aq}]{sub initial} = 10 mg/L, no anglesite precipitation was observed, but surface spectroscopy (proton Rutherford Backscattering Spectroscopy, p-RBS) confirmed the formation of Pb-bearing surface layers on the (0 1 0) gypsum surface in this case also. This study shows that the surface of gypsum can play an important role in the attenuation of Pb in contaminated waters.

  2. Unravelling the mechanisms for plant survival on gypsum soils: an analysis of the chemical composition of gypsum plants from Turkey.

    Bolukbasi, A; Kurt, L; Palacio, S


    Depending on their specificity to gypsum, plants can be classified as gypsophiles (gypsum exclusive) and gypsovags (non-exclusive). The former may further be segregated into wide and narrow gypsophiles, depending on the breadth of their distribution area. Narrow gypsum endemics have a putative similar chemical composition to plants non-exclusive to gypsum (i.e. gypsovags), which may indicate their similar ecological strategy as stress-tolerant plant refugees on gypsum. However, this hypothesis awaits testing in different regions of the world. We compared the chemical composition of four narrow gypsum endemics, one widely distributed gypsophile and six gypsovags from Turkey. Further, we explored the plasticity in chemical composition of Turkish gypsovags growing on high- and low-gypsum content soils. Differences were explored with multivariate analyses (RDA) and mixed models (REML). Narrow gypsum endemics segregated from gypsovags in their chemical composition according to RDAs (mainly due to higher K and ash content in the former). Nevertheless, differences were small and disappeared when different nutrients were analysed individually. All the gypsovags studied accumulated more S and ash when growing on high-gypsum than on low-gypsum soils. Similar to narrow gypsum endemics from other regions of the world, most local gypsum endemics from Turkey show a similar chemical composition to gypsovags. This may indicate a shared ecological strategy as stress-tolerant plants not specifically adapted to gypsum. Nevertheless, the narrow gypsum endemic Gypsophila parva showed a chemical composition typical of gypsum specialists, indicating that various strategies are feasible within narrowly distributed gypsophiles. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

  3. Fate of Mercury in Synthetic Gypsum Used for Wallboard Production

    Jessica Marshall Sanderson


    This report presents and discusses results from Task 5 of the study ''Fate of Mercury in Synthetic Gypsum Used for Wallboard Production,'' performed at a full-scale commercial wallboard plant. Synthetic gypsum produced by wet flue gas desulfurization (FGD) systems on coal-fired power plants is commonly used in the manufacture of wallboard. The FGD process is used to control the sulfur dioxide emissions which would result in acid rain if not controlled. This practice has long benefited the environment by recycling the FGD gypsum byproduct, which is becoming available in increasing quantities, decreasing the need to landfill this material, and increasing the sustainable design of the wallboard product. However, new concerns have arisen as recent mercury control strategies developed for power plants involve the capture of mercury in FGD systems. The objective of this study is to determine whether any mercury is released into the atmosphere when the synthetic gypsum material is used as a feedstock for wallboard production. The project is being co-funded by the U.S. DOE National Energy Technology Laboratory (Cooperative Agreement DE-FC26-04NT42080), USG Corporation, and EPRI. USG Corporation is the prime contractor, and URS Group is a subcontractor. The project scope includes five discrete tasks, each conducted at various USG wallboard plants using synthetic gypsum from different FGD systems. The five tasks were to include (1) a baseline test, then variations representing differing power plant (2) emissions control configurations, (3) treatment of fine gypsum particles, (4) coal types, and (5) FGD reagent types. However, Task 5, which was to evaluate gypsum produced from an alternate FGD reagent, could not be conducted as planned. Instead, Task 5 was conducted at conditions similar to a previous task, Task 3, although with gypsum from an alternate FGD system. In this project, process stacks in the wallboard plant have been sampled using the Ontario

  4. Fate of Mercury in Synthetic Gypsum Used for Wallboard Production

    Jessica Sanderson


    This report presents and discusses results from the project 'Fate of Mercury in Synthetic Gypsum Used for Wallboard Production', performed at five different full-scale commercial wallboard plants. Synthetic gypsum produced by wet flue gas desulfurization (FGD) systems on coal-fired power plants is commonly used in the manufacture of wallboard. This practice has long benefited the environment by recycling the FGD gypsum byproduct, which is becoming available in increasing quantities, decreasing the need to landfill this material, and increasing the sustainable design of the wallboard product. However, new concerns have arisen as recent mercury control strategies involve the capture of mercury in FGD systems. The objective of this study has been to determine whether any mercury is released into the atmosphere at wallboard manufacturing plants when the synthetic gypsum material is used as a feedstock for wallboard production. The project has been co-funded by the U.S. DOE National Energy Technology Laboratory (Cooperative Agreement DE-FC26-04NT42080), USG Corporation, and EPRI. USG Corporation is the prime contractor, and URS Group is a subcontractor. The project scope included seven discrete tasks, each including a test conducted at various USG wallboard plants using synthetic gypsum from different wet FGD systems. The project was originally composed of five tasks, which were to include (1) a base-case test, then variations representing differing power plant: (2) emissions control configurations, (3) treatment of fine gypsum particles, (4) coal types, and (5) FGD reagent types. However, Task 5,could not be conducted as planned and instead was conducted at conditions similar to Task 3. Subsequently an opportunity arose to test gypsum produced from the Task 5 FGD system, but with an additive expected to impact the stability of mercury, so Task 6 was added to the project. Finally, Task 7 was added to evaluate synthetic gypsum produced at a power plant from an

  5. Investigation on the potential of waste cooking oil as a grinding aid in Portland cement.

    Li, Haoxin; Zhao, Jianfeng; Huang, Yuyan; Jiang, Zhengwu; Yang, Xiaojie; Yang, Zhenghong; Chen, Qing


    Although there are several methods for managing waste cooking oil (WCO), a significant result has not been achieved in China. A new method is required for safe WCO management that minimizes the environmental threat. In this context, this work was developed in which cement clinker and gypsum were interground with various WCOs, and their properties, such as grindability, water-cement ratio required to achieve a normal consistency, setting times, compressive strength, contents of calcium hydroxide and ettringite in the hardened paste, microstructure and economic and environmental considerations, were addressed in detail. The results show that, overall, WCO favorably improves cement grinding. WCO prolonged the cement setting times and resulted in longer setting times. Additionally, more remarkable effects were found in cements in which WCO contained more unsaturated fatty acid. WCOs increased the cement strength. However, this enhancement was rated with respect to the WCO contents and components. WCOs decreased the CH and AFt contents in the cement hardened paste. Even the AFt content at later ages was reduced when WCO was used. WCO also densify microstructure of the hardened cement paste. It is economically and environmentally feasible to use WCOs as grinding aids in the cement grinding process. These results contribute to the application of WCOs as grinding aids and to the safe management of WCO. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. 脱硫石膏砌块力学性能的研究%Study on Mechanical Properties of Desulfurization Gypsum Block

    何廷树; 孟晓林; 史琛


    Industrial waste gypsum, lfy ash mixed with small amount of cement and expanded polystyrene particles are used as mixed material to reduce weight and ensure the strength through experimental study on the mechanical properties and the change of apparent density of desulfurization gypsum block. The experimental results show that the optimal ratio were 0.42% lignosulphonate calcium water reducers, 0.12% citric acid retarder, 0.06% lignocellulose, 15% cement, 10% lfy ash, 75% desulphurization gypsum, 25% polystyrene particles. Light desulfurization gypsum block with density of 964kg/m3 and 10.1MPa of 28 d compressive strength can be obtained.%为达到脱硫石膏砌块减重且保证强度的目的,利用工业废料脱硫石膏、粉煤灰,掺加少量水泥、膨胀聚苯颗粒作为混合材料,研究脱硫石膏实心砌块的力学性能及表观密度的变化。结果表明,制备脱硫石膏砌块最优配比为:木钙减水剂0.42%、柠檬酸缓凝剂0.12%、木质纤维素0.06%、水泥15%、粉煤灰10%、脱硫石膏75%、聚苯颗粒25%,此条件下可获得密度为964 kg/m3,28 d抗压强度达10.1 MPa的轻质脱硫石膏砌块。

  7. Synthesis on research results of FGD gypsum briquetting

    Kosturkiewicz Bogdan


    Full Text Available FGD gypsum products can be characterized by significant solubility in water and dusting in dry state. These characteristics can cause a considerable pollution of air, water and soil. Among many approaches of preparing utilization of this waste, the process of compaction using briquetting has proved to be very effective. Using FGD gypsum products a new material of fertilizers characteristics has been acquired and this material is resistant to the conditions of transportation. This paper presents results of experimental briquetting of flue gas desulphurisation products in a roll press. The experiments were conducted in a laboratory roll presses LPW 450 and LPW 1100 equipped with two interchangeable forming rings that form material into saddle-shaped briquettes with volume 6,5 cm3 and 85 cm3. The experiments were conducted with various percentage amounts of FGD gypsum moisture. The results provided information regarding influence of moisture and roll press configuration on quality of briquettes. On the basis of obtained results, technological process and a general outline of technological line for FGD gypsum were developed. Two roll presses of own construction with different outputs were identified as appropriate for this purpose. A range of necessary works related to their adaptation for the FGD gypsum briquetting were pointed out.

  8. Converting SDAP into gypsum in a wet limestone scrubber

    Fogh, F. [Faelleskemikerne, Elsamprojekt A/S, Fredericia (Denmark)


    The ELSAM power pool has an installed electrical capacity of approx. 5 GW{sub e}, mainly firing import coal. The major base load units are equipped with desulphurization units and three different desulphurization technologies are used: the wet limestone gypsum process, the spray dry absorption process and a sulphuric acid process. Gypsum and sulphuric acid are commercialized, whereas it has been difficult to utilize the spray dry absorption product (SDAP). The main constituents of SDAP are calcium sulphide, calcium chloride, hydrated lime and impurities mainly originating from fly ash. Sulphide can be oxidized into sulphate in acidic solution - the reaction is utilized in the wet limestone gypsum process - and the possibility of using any spare capacity in the wet limestone gypsum units to oxidize the sulphide content of SDAP into sulphate and produce usable gypsum has been investigated in the laboratory and in a 400 MW{sub e} equivalent wet limestone unit. The limestone inhibition effect of the addition of SDAP is currently being studied in the laboratory in order to determine the effect of different SDAP types (plant/coal sources) on limestone reactivity before further long-term full-scale tests are performed and permanent use of the process planned. (EG)

  9. Using stable isotopes (δ^{18}O and δ$D) of gypsum hydration water to unravel the mode of gypsum speleothem formation in semi-arid caves

    Gázquez, Fernando; Calaforra, Jose Maria; Evans, Nicholas P.; Hodell, David A.


    Subaerial gypsum speleothems form during the evaporation of calcium-sulfate-rich solutions in caves. The evaporation of infiltration water is the widely accepted mechanism to explain precipitation of gypsum speleothems; i.e., the dissolution of gypsum host-rock (e.g. Messinian marine gypsum) supplies Ca2+ and SO42- ions to cave waters and subsequent evaporation leads to gypsum saturation. However, water condensation actively occurs in caves of semi-arid regions and plays a key role in subaerial cave speleogenesis and recharge of aquifers in low-rainfall environments. To date, water condensation in karstic environments has not been considered as an important factor in gypsum speleothem formation. We collected speleothem samples from the upper passages of Covadura Cave in the gypsum karst of Sorbas (Almeria, SE Spain). This cave is located in a temperate (annual mean temperature of 19.5oC), semi-arid region (

  10. Study on property ,of foam FGD-gypsum concrete block%脱硫石膏泡沫凝土砌块的性能研究

    谢建海; 向仁科


    以脱硫石膏为主要材料,通过添加水泥、矿渣粉、自制添加剂改性,外掺少量CaO、促凝剂和发泡剂制备出了不同密度等级的脱硫石膏泡沫混凝土砌块。研究了不同外加剂掺量对胶凝材料初终凝时间和力学性能的影响;利用导热系数测定仪测试了石膏泡沫混凝土的导热系数;对脱硫石膏基胶凝材料水化产物机理进行了分析。研究表明:脱硫石膏泡沫混凝土砌块与其他类型砌块相比具有强度高、耐抽陛好、导热系数低等优良性能。%The foam FGD-gypsum concrete blocks in different density are made of desulphurization gypsum, slag, Portland cement, self-made modifier, small amount of CaO, c the flue gas oagulator and foaming agent . The influence of different additives on the initial-final coagulation times and mechanics performance of gelled material are test. The thermal conductivity of foam gypsum concrete is test by coefficient of thermal conductivity detector. And the hydration products mechanism of desulphurization gypsum based gelled material is analyzed. The results indicate that the foam FGD-gypsum concrete block are of higher strength, better water impermeability and lower thermal conductivity comparing with others.

  11. 石膏种类对富水充填材料凝结硬化性能与机理的影响%Impact of gypsum type on the setting and hardening performance and mechanism of water-rich filling materials

    刘娟红; 马翼; 王祖琦; 高萌; 周茜


    As for the problem that different gypsum types have different influence on the condensation performance of water-rich filling materials, micro experiments, such as X-ray diffraction, scanning electron microscopy and infrared spectroscopy, were used to analyze the composition of the hardened body and investigate the influence of dihydrate gypsum and hemihydrate gypsum on the setting and hardening characteristics of water-rich filling materials. It is found that in a water-rich filling material system of sulphoaluminate cement-gypsum-lime, the gypsum type should be dihydrate gypsum so as to ensure the normal condensation setting and hardening;if hemihydrate gypsum is used as a raw material, the water-rich filling material has not strength after hydrating for 7 d. When dihydrate gypsum is adequate, the generated ettringite crystals are fine needle-like; but when dihydrate gypsum is inadequate, the generated ettringite crystals are short hexagonal columnar. The strength of the water-rich filling material is mainly derived from ettringite genera-ted by the reaction of sulphoaluminate cement gypsum and lime, rather than the hydration products of cement generated by itself such as hydration calcium sulphoaluminate, alumina gel and calcium hydroxide.%针对富水充填材料的凝结性能受石膏种类影响的问题,采用X射线衍射、扫描电镜、红外光谱等微观实验,分析富水充填材料硬化体的组成,探讨二水石膏和半水石膏对富水充填材料性能影响的机理. 结果表明:以硫铝酸盐水泥-石膏-石灰为主的富水充填材料体系中,为保证正常的凝结硬化,石膏应为二水石膏;如以半水石膏为原材料,在7d龄期时仍不具有强度;二水石膏充足时生成的钙矾石晶体呈细针状,二水石膏不足时生成的钙矾石晶体为六棱短柱状;富水充填材料的强度主要来源于硫铝酸盐水泥-石膏-石灰反应生成的钙矾石,而不是水泥自身水化的水化硫铝酸钙、铝胶和氢氧化钙.

  12. The behavior of biogenic silica-rich rocks and volcanic tuffs as pozzolanic additives in cement

    Fragoulis, Dimitris; Stamatakis, Michael; Anastasatou, Marianthi


    Cements currently produced, include a variety of pozzolanic materials, aiming for lower clinker addition and utilization of vast deposits of certain raw materials and/or mining wastes and byproducts. The major naturally occurring pozzolanic materials include glassy tuffs, zeolitic tuffs, diatomites and volcanic lavas rich in glassy phase, such as perlites. Therefore, based on the available raw materials in different locations, the cement composition might vary according to the accessibility of efficient pozzolanic materials. In the present investigation, the behavior of pozzolanic cements produced with representative samples of the aforementioned materials was studied, following the characterization of the implemented pozzolanas with respect to their chemical and mineralogical characteristics. Laboratory cements were produced by co-grinding 75% clinker, 5% gypsum and 20% pozzolana, for the same period of time (45 min). Regarding pozzolanic materials, four different types of pozzolanas were utilized namely, diatomite, perlite, zeolite tuff and glassy tuff. More specifically, two diatomite samples originated from Australia and Greece, with high and low reactive silica content respectively, two perlite samples originated from Turkey and from Milos Island, Greece, with different reactive silica contents, a zeolite tuff sample originated from Turkey and a glassy tuff sample originated from Milos Island, Greece. The above pozzolana samples, which were ground in the laboratory ball mill for cement production performed differently during grinding and that was reflected upon the specific surface area (cm2/gr) values. The perlites and the glassy tuff were the hardest to grind, whereas, the zeolite tuff and the Australian diatomite were the easiest ones. However, the exceedingly high specific surface area of the Australian diatomite renders cement difficult to transport and tricky to use for concrete manufacturing, due to the high water demand of the cement mixture. Regarding

  13. Calcium isotopic fractionation in microbially mediated gypsum precipitates

    Harouaka, Khadouja; Mansor, Muammar; Macalady, Jennifer L.; Fantle, Matthew S.


    Gypsum (CaSO4·2H2O) precipitation experiments were carried out at low pH in the presence of the sulfur oxidizing bacterium Acidithiobacillus thiooxidans. The observed Ca isotopic fractionation (expressed as Δ44/40Cas-f = δ44/40Casolid-δ44/40Cafluid) at the end of each experimental time period (∼50 to 60 days) was -1.41‰ to -1.09‰ in the biotic experiments, -1.09‰ in the killed control, and -1.01‰ to -0.88‰ in the abiotic controls. As there were no strong differences in the solution chemistry and the rate at which gypsum precipitated in the biotic and abiotic controls, we deduce a biological Ca isotope effect on the order of -0.3‰. The isotope effect correlates with a difference in crystal aspect ratios between the biotic experiments (8.05 ± 3.99) and abiotic controls (31.9 ± 8.40). We hypothesize that soluble and/or insoluble organic compounds selectively inhibit crystal growth at specific crystal faces, and that the growth inhibition affects the fractionation factor associated with gypsum precipitation. The experimental results help explain Ca isotopic variability in gypsum sampled from a sulfidic cave system, in which gypsum crystals exhibiting a diversity of morphologies (microcrystalline to cm-scale needles) have a broad range of δ44/40Ca values (∼1.2-0.4‰) relative to the limestone wall (δ44/40Ca = 1.3‰). In light of the laboratory experiments, the variation in Ca isotope values in the caves can be interpreted as a consequence of gypsum precipitation in the presence of microbial organic matter and subsequent isotopic re-equilibration with the Ca source.

  14. Gypsum scaling in pressure retarded osmosis: experiments, mechanisms and implications.

    Zhang, Minmin; Hou, Dianxun; She, Qianhong; Tang, Chuyang Y


    Pressure retarded osmosis (PRO) is an osmotically-driven membrane process that can be used to harvest salinity-gradient power. The PRO performance (both water flux and power density) can be severely limited by membrane fouling. The current study, for the first time, investigates PRO scaling in a bench-scale pressurized system using calcium sulfate dihydrate (gypsum) as a model scalant. In addition to the bulk feed solution (FS) saturation index (SI bulk), gypsum scaling was found to be strongly affected by the draw solution (DS) type and concentration, the applied hydraulic pressure, and the membrane orientation. The commonly recommended active layer facing draw solution (AL-DS) orientation was highly prone to internal scaling. In this orientation, severe internal concentration polarization (ICP) of scaling precursors induced gypsum clogging in membrane support layer even when the FS was undersaturated (e.g., SI bulk = 0.8). At higher SI bulk values, external gypsum crystal deposition occurred in addition to internal scaling. More severe scaling was observed when the DS contained scaling precursors such as Ca(2+) or SO4(2-), suggesting that the reverse diffusion of these precursors into the FS can significantly enhanced gypsum scaling. Increasing applied hydraulic pressure could enhance reverse solute diffusion and thus result in more severe gypsum scaling when the DS contained scaling precursors. A conceptual model, capturing the two important PRO scaling mechanisms (ICP of scaling precursors from FS and reverse diffusion of scaling precursors from the DS), is presented to rationalize the experimental results. Our results provide significant implications for PRO scaling control.

  15. Triple oxygen isotope systematics of structurally bonded water in gypsum

    Herwartz, Daniel; Surma, Jakub; Voigt, Claudia; Assonov, Sergey; Staubwasser, Michael


    The triple oxygen isotopic composition of gypsum mother water (gmw) is recorded in structurally bonded water in gypsum (gsbw). Respective fractionation factors have been determined experimentally for 18O/16O and 17O/16O. By taking previous experiments into account we suggest using 18αgsbw-gmw = 1.0037; 17αgsbw-gmw = 1.00195 and θgsbw-gmw = 0.5285 as fractionation factors in triple oxygen isotope space. Recent gypsum was sampled from a series of 10 ponds located in the Salar de Llamara in the Atacama Desert, Chile. Total dissolved solids (TDS) in these ponds show a gradual increase from 23 g/l to 182 g/l that is accompanied by an increase in pond water 18O/16O. Gsbw falls on a parallel curve to the ambient water from the saline ponds. The offset is mainly due to the equilibrium fractionation between gsbw and gmw. However, gsbw represents a time integrated signal biased towards times of strong evaporation, hence the estimated gmw comprises elevated 18O/16O compositions when compared to pond water samples taken on site. Gypsum precipitation is associated with algae mats in the ponds with lower salinity. No evidence for respective vital effects on the triple oxygen isotopic composition of gypsum hydration water is observed, nor are such effects expected. In principle, the array of δ18Ogsbw vs. 17Oexcess can be used to: (1) provide information on the degree of evaporation during gypsum formation; (2) estimate pristine meteoric water compositions; and (3) estimate local relative humidity which is the controlling parameter of the slope of the array for simple hydrological situations. In our case study, local mining activities may have decreased deep groundwater recharge, causing a recent change of the local hydrology.

  16. Mercury enrichment and its effects on atmospheric emissions in cement plants of China

    Wang, Fengyang; Wang, Shuxiao; Zhang, Lei; Yang, Hai; Wu, Qingru; Hao, Jiming


    The cement industry is one of the most significant anthropogenic sources of atmospheric mercury emissions worldwide. In this study of three typical Chinese cement plants, mercury in kiln flue gas was sampled using the Ontario Hydro Method (OHM), and solid samples were analyzed. Particulate matter recycling, preheating of raw materials, and the use of coal and flue gas desulfurization derived gypsum contributed to emissions of Hg in the air and to accumulation in cement. Over 90% of the mercury input was emitted into the atmosphere. Mercury emission factors were 0.044-0.072 g/t clinker for the test plants. The major species emitted into the atmosphere from cement plants is oxidized mercury, accounting for 61%-91% of the total mercury in flue gas. The results of this study help improve the accuracy of the mercury emission inventory in China and provide useful information for developing mercury controls.

  17. Fate of Mercury in Synthetic Gypsum Used for Wallboard Production

    Jessica Sanderson; Gary M. Blythe; Mandi Richardson


    This report presents and discusses results from Task 6 of the study 'Fate of Mercury in Synthetic Gypsum Used for Wallboard Production,' performed at a full-scale commercial wallboard plant. Synthetic gypsum produced by wet flue gas desulfurization (FGD) systems on coal-fired power plants is commonly used in the manufacture of wallboard. This practice has long benefited the environment by recycling the FGD gypsum byproduct, which is becoming available in increasing quantities, decreasing the need to landfill this material, and increasing the sustainable design of the wallboard product. However, new concerns have arisen as recent mercury control strategies involve the capture of mercury in FGD systems. The objective of this study is to determine whether any mercury is released into the atmosphere when the synthetic gypsum material is used as a feedstock for wallboard production. The project is being co-funded by the U.S. DOE National Energy Technology Laboratory (Cooperative Agreement DE-FC26-04NT42080), USG Corporation, and EPRI. USG Corporation is the prime contractor, and URS Group is a subcontractor. The project scope now includes six discrete tasks, each conducted at various USG wallboard plants using synthetic gypsum from different FGD systems. The project was originally composed of five tasks, which were to include (1) a baseline test, then variations representing differing power plant: (2) emissions control configurations, (3) treatment of fine gypsum particles, (4) coal types, and (5) FGD reagent types. However, Task 5, which was to include testing with an alternate FGD reagent, could not be conducted as planned. Instead, Task 5 was conducted at conditions similar to Task 3, although with gypsum from an alternate FGD system. Subsequent to conducting Task 5 under these revised conditions, an opportunity arose to test gypsum produced at the same FGD system, but with an additive (Degussa Corporation's TMT-15) being used in the FGD system. TMT-15


    Kaziliunas A.


    Full Text Available Preparation of phosphogypsum to produce the binders requires a much higher input than preparation of natural gypsum stone. This makes it uncompetitive material. The investigations presented therein are meant to reduce this input by looking for the ways of rendering impurities harmless. Soluble acid orthophosphates are the main harmful impurity of phosphogypsum. The studies show that dry insoluble calcium orthophosphates hydrates (1.09 % and 2.18 % P2O5 in gypsum have little effect on W/C, setting times and soundness of Portland cement pastes. Insoluble calcium orthophosphates hydrates {CaHPO4∙2H2O, Ca8(HPO42(PO44∙5H2O and Ca9(HPO4(PO45(OH∙4H2O} formed in acidic medium (pH = 4.2 - 5.9 have been destroyed in alkaline medium and reduce standard compressive strength of cement up to 28 %. Calcium orthophosphates hydrates of hydroxyapatite group are stable in alcaline medium, while in dry state they reduce the standard compressive strength of cement until 10 %, but their suspensions prolong setting times of Portland cement as soluble orthophosphates – 2 - 3 times. Alkalis in cement increase pH of paste, but do not change the process of formation of calcium orthophosphates hydrates of hydroxyapatite group: it takes place through an intermediate phase - CaHPO4·2H2O, whose transformation into apatite lasts for 2 - 3 months.

  19. Influence of sulfate on cement mixtures containing fly ash or blast-furnace slag

    Bhanumathidas, N.; Kalidas, N. [Inst. for Solid Waste Research and Ecological Balance, Visakhapatnam (India)


    The development of FaL-G, a cementitious mixture of fly ash, lime and gypsum was initiated by the desire to improve the early strength of blended portland cement. Fly ash and granulated blast-furnace slag both contain reactive alumina. The strength of some fly ash-lime mixtures, in the presence of gypsum, can be enhanced 3 to 6 times at all ages. This study showed that high-volume fly ash blended portland cements also increase in strength with the addition of gypsum or anhydrite. Ground granulated blast-furnace slag behaves in a similar manner to blended portland cement. The enhanced strength is due to the formation of calcium sulphoaluminate hydrates. This study shows that it is possible to use large volumes of fly ash and slag to conserve on cost-intensive and energy-intensive clinker. Bricks and blocks made according to FaL-G technology are replacing fired clay bricks used in masonry construction. This research is of particular interest for the conservation of agricultural soils, minerals and energy. The study also shows that it is possible to convert major industrial waste into useful construction products. 7 refs., 3 tabs., 1 fig.

  20. Contribution to the determination of gypsum and hemihydrates content in Portland cements

    Moreno Arús, Fernando


    Full Text Available Not availableLa mayoría de los técnicos de cemento, aceptan, que las anormalidades del fraguado, conocidas como "falso fraguado" en el cemento portland, se deben primordialmente a la presencia de yeso parcialmente deshidratado (S04Ca1/2H20. Si el clínker que se muele está enriquecido en cal libre, o la temperatura del molino es elevada (superior a los 110 °C o hay escasa ventilación de éste, se llega a originar una parcial deshidratación del yeso, que se mantiene durante el proceso de ensilado y que origina las anormalidades del fraguado al que anteriormente nos hemos referido. Por esta razón creemos muy importante poder conocer el grado de deshidratación en que se encuentra el yeso en un cemento.

  1. Long-term Performance of Moderate Heat Portland Cement with Double-expansive Sources

    YE Qing; CHEN Huxing; KONG Deyu; WANG Shangxian; LOU Zonghan


    The long-term performance of moderate heat Portland cement with double-expansive sources (DE cement) in the system of high MgO clinker and gypsum was studied by XRD, SEM/EDAX and test methods for strength and expansion of cement. Results indicate that the periclase particle, whose size was 5-7.5 μm in DE cement clinker containing 4.8 % MgO, existed individually. The periclase hydration in hardened DE cement paste started at about 60 days and completed up to 2 000 days, and ettringite in the paste was stable from 3 days to 2 000 days. Under the conditions of 4.5%-5.0 % MgO in clinker and 2.8%-3.4 %SO3 in cement,ettringite expansion and brucite expansion in DE cement paste had a continuity, entirety and stability. At the ages of 90, 365, 730 and 2 000 days the expansion of the paste reached 0.07%-0.11%, 0.16%-0.21%, 0.21%-0.27% and 0.29%-0.38 %, respectively. The results suggest that by using this cement in mass concrete it may compensate its temperature shrinkage and autogenous shrinkage to some extent.

  2. Physicochemical Properties and Cellular Responses of Strontium-Doped Gypsum Biomaterials

    Amir Pouria


    Full Text Available This paper describes some physical, structural, and biological properties of gypsum bioceramics doped with various amounts of strontium ions (0.19–2.23 wt% and compares these properties with those of a pure gypsum as control. Strontium-doped gypsum (gypsum:Sr was obtained by mixing calcium sulfate hemihydrate powder and solutions of strontium nitrate followed by washing the specimens with distilled water to remove residual salts. Gypsum was the only phase found in the composition of both pure and gypsum:Sr, meanwhile a shift into lower diffraction angles was observed in the X-ray diffraction patterns of doped specimens. Microstructure of all gypsum specimens consisted of many rod-like small crystals entangled to each other with more elongation and higher thickness in the case of gypsum:Sr. The Sr-doped sample exhibited higher compressive strength and lower solubility than pure gypsum. A continuous release of strontium ions was observed from the gypsum:Sr during soaking it in simulated body fluid for 14 days. Compared to pure gypsum, the osteoblasts cultured on strontium-doped samples showed better proliferation rate and higher alkaline phosphatase activity, depending on Sr concentration. These observations can predict better in vivo behavior of strontium-doped gypsum compared to pure one.

  3. Suitability of coarse-grade gypsum for sodic soil reclamation: a laboratory experiment

    Elshout, van den S.; Kamphorst, A.


    Costs of sodic soil reclamation can be reduced when coarse-grade gypsum is used, as the production and transport prices of this gypsum are much lower than that of agricultural-grade gypsum. In a feasibility study laboratory experiments were conducted to evaluate the leaching water requirements for f


    Fred Sabins


    The objective of this project is to develop an improved ultra-lightweight cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary of Halliburton Energy Services (HES) and BJ Services historical performance data for lightweight cement applications. These data are analyzed and compared to ULHS cement and foamed cement performances. Similar data is expected from Schlumberger, and an analysis of this data will be completed in the following phases of the project. Quality control testing of materials used to formulate ULHS cements in the laboratory was completed to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS and foamed cement. This protocol is presented and discussed. Results of further testing of ULHS cements are presented along with an analysis to establish cement performance design criteria to be used during the remainder of the project. Finally, a list of relevant literature on lightweight cement performance is compiled for review during the next quarter.

  5. Evaluation of gypsum rates on greenhouse crop production

    This study was to determine the potential of an added value distribution channel for gypsum waste by evaluating various greenhouse crops with captious pH and calcium needs. Three studies consisting of: Zonal geranium (Pelargonium x hortorum) and petunia (Petunia x hybrida); tomato (Solanum lycoper...

  6. 氟石膏泡沫混凝土砌块的性能研究%Study on properties of fluorine gypsum foam concrete block

    谢建海; 赵党会; 向仁科


      以氟石膏、粉煤灰和水泥为基材,加入自制添加剂改性,外掺少量促凝剂、CaO和减水剂,再掺加适量发泡剂制备出不同密度等级的氟石膏泡沫混凝土砌块。研究了不同外加剂掺量对胶凝材料初终凝时间和力学性能的影响,测试了氟石膏泡沫混凝土的导热系数。实验表明:氟石膏泡沫混凝土砌块强度高、导热系数低,产品综合性能优良,是实现工业副产品氟石膏资源化利用途径之一。%  The fluorine gypsum foam concrete block is made of the fluorine gypsum, fly ash and cement as base material, mixed with modifier,small amount of coagulant, CaO, water reducer and proper quantity foaming agent and so on. The influence of different admixture on the initial-final setting times and mechanical performance of gelling material is researched, and the thermal conductivity of fluorine gypsum foam concrete is measured. Experiments show that the fluorine gypsum foam concrete blocks have high strength, low thermal conductivity, and excellent comprehensive properties.

  7. Sulphate behaviour from dissolution of gypsum in organic acids

    Baruah, M.K.; Gogoi, P.C.; Kotoky, P. [NNS College, Titabar (India). Dept. of Chemistry


    The solubility of gypsum in organic acids namely acetic, oxalic, tartaric and succinic acids at low temperature (30{degree}C) was studied. The results show that sulphate sulphur content increases with increasing acid concentration from 0.1 to 0.25 M and decreases again at higher concentration. It is suggested that different behaviour of the acids beyond 0.25 M solution could be due to incorporation of sulphate into the co-ordination sphere of calcium-organic complexes. It is suggested that the occurrence of free and fixed sulphate in the solution is highly pH dependent. The nature of incorporation of sulphate in a system containing calcium species and natural organic matter has also been studied. Humic acids, extracted from forest and tea-garden soils, were treated with a solution of gypsum (CaSO{sub 4}.2H{sub 2}O) at room temperature and the infrared spectra of the gypsum treated samples reveal that sulphate has been incorporated into the calcium complex as a monodentate ligand. Further an inorganic-sulphur free high-sulphur coal when treated with the gypsum solution, incorporated sulphate as bidentate ligand. It is concluded that the nature of the organic matter plays an important role for the occurrence of various fixed sulphates either as monodentate or bidentate ligand in natural systems. This work is a novel breakthrough for the occurrence of varying sulphate content in some of the natural environments and has considerable environmental and geochemical interest. Short communication. 46 refs., 3 figs.

  8. Comparison of Energy Dissipation, Stiffness, and Damage of Structural Oriented Strand Board (OSB, Conventional Gypsum, and Viscoelastic Gypsum Shearwalls Subjected to Cyclic Loads

    Andrew S. Blasetti


    Full Text Available A key element in the seismic load resisting system of a wood framed structure is the shear wall which is typically sheathed on one side with plywood or oriented strand board (OSB and gypsum on the other. The shear capacity of gypsum sheathed shear walls is typically neglected in high seismic areas due to the susceptibility of conventional drywall screw connections to damage caused by earthquakes. The earthquake resistance of an innovative viscoelastic (VE gypsum shearwall is evaluated and compared to conventional structural and non-structural walls. Ten 8 ft × 8 ft wood framed wall specimens of three configurations [nailed-OSB, screw-gypsum, and VE polymer-gypsum] were subjected to a cyclic test protocol. The energy dissipation, stiffness, and damage characteristics of all shearwalls are reported herein. Testing results indicate the VE-gypsum walls can dissipate more energy than the OSB structural panels and 500% more energy that the conventional gypsum sheathed walls and contains a constant source of energy dissipation not seen in the structural and non-structural walls. The wall stiffness of the OSB wall degrades at a far greater rate that the VE gypsum wall and at continued cycling degrades below the VE wall stiffness. Unlike both of the conventional wall types, the VE wall showed no visible or audible signs of damage when subjected to shear displacements up to 1.

  9. Manufacturing of calcium phosphate scaffolds by pseudomorphic transformation of gypsum

    Araujo Batista, H. de.; Batista Cardoso, M.; Sales Vasconcelos, A.; Vinicius Lia Fook, M.; Rodriguez Barbero, M. A.; Garcia Carrodeguas, R.


    Carbonated hydroxyapatite (CHAp) and β-tricalcium phosphate (β-TCP) have been employed for decades as constituents of scaffolds for bone regeneration because they chemically resemble bone mineral. In this study, the feasibility to manufacture CHAp/β-TCP scaffolds by pseudomorphic transformation of casted blocks of gypsum was investigated. The transformation was carried out by immersing the precursor gypsum block in 1 M (NH{sub 4}){sub 2}HPO{sub 4}/1.33 M NH{sub 4}OH solution with liquid/solid ratio of 10 mL/g and autoclaving at 120 degree centigrade and 203 kPa (2 atm) for 3 h at least. Neither shape nor dimensions significantly changed during transformation. The composition of scaffolds treated for 3 h was 70 wt.% CHAp and 30 wt.% β-TCP, and their compressive and diametral compressive strengths were 6.5 ± 0.7 and 5.3 ±0.7 MPa, respectively. By increasing the time of treatment to 6 h, the composition of the scaffold enriched in β-TCP (60 wt.% CHAp and 40 wt.% β-TCP) but its compressive and diametral compressive strengths were not significantly affected (6.7 ± 0.9 and 5.4 ± 0.6 MPa, respectively). On the basis of the results obtained, it was concluded that this route is a good approach to the manufacturing of biphasic (CHAp/β-TCP) scaffolds from previously shaped pieces of gypsum. (Author)

  10. Differences in gypsum plant communities associated with habitat fragmentation and livestock grazing.

    Pueyo, Y; Alados, C L; Barrantes, O; Komac, B; Rietkerk, M


    The negative consequences of habitat fragmentation for plant communities have been documented in many regions of the world. In some fragmented habitats, livestock grazing has been proposed to be a dispersal mechanism reducing isolation between fragments. In others, grazing acts together with fragmentation in a way that increases habitat degradation. Iberian gypsum plant communities have been grazed and fragmented by agricultural practices for centuries. Although their conservation is considered a priority by the European Community, the effects of fragmentation on gypsum plant communities and the possible role of livestock grazing remain unknown. In addition, a substantial proportion of plant species growing in gypsum environments are gypsum specialists. They could be particularly affected by fragmentation, as was found for other habitat specialists (i.e., serpentine and calcareous specialists). In this study (1) we investigated the effect of fragmentation and grazing on gypsum plant community composition (species and life-forms), and (2) we tested to see if gypsum specialists were differently affected by fragmentation and grazing than habitat generalists. A vegetation survey was conducted in the largest gypsum outcrop of Europe (Middle Ebro Valley, northeast Spain). Fragmented and continuous sites in grazed and ungrazed areas were compared. Measurements related to species and composition of life-forms were contrasted first for the whole gypsum plant community and then specifically for the gypsum specialists. In the whole community, our results showed lower plant species diversity in fragmented sites, mainly due to the larger dominance of species more tolerant to fragmented habitat conditions. With livestock grazing, the plant species richness and the similarity in plant species composition between remnants was larger, suggesting that animals were acting as dispersal agents between fragments. As expected, gypsum specialists were less abundant in fragmented areas

  11. Effect of alkali ions on the strength development of cement paste by Mössbauer spectrometry

    Hassaan, M. Y.; Moutawie, M. A.; Eissa, N. A.


    Two clinker raw mixtures (83 wt% limestone +12 wt% clay +5 wt% α-Fe2O3) were fired at 1150°C for three hours in open furnace, each with 100 wt%-in addition-of an alkali carbonate (Na2CO3 and K2CO3) respectively. Each produced cliker was mixed with 5 wt% natural gypsum to produce portland cement, then with 25 wt% tap water. Compressive strength, ultrasonic pulse test, X-ray diffraction and Mossbauer effect measurements were carried out each at different times of hydration (21, 28 and 45 days). The effect of alkali ions on the strength development of cement pastes is discussed, the accuracy of Mössbauer, spectrometer in determining the cement strength is demonstrated.


    Fred Sabins


    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems: foamed and sodium silicate slurries. Comparison studies of the three cement systems examined several properties: tensile strength, Young's modulus, water permeability, and shear bond. Testing was also done to determine the effect that temperature cycling has on the shear bond properties of the cement systems. In addition, analysis was carried out to examine alkali silica reactivity of slurries containing ULHS. Data is also presented from a study investigating the effects of mixing and pump circulation on breakage of ULHS. Information is also presented about the field application of ULHS in cementing a 7-in. intermediate casing in south Texas.

  13. Guidebook for Using the Tool BEST Cement: Benchmarking and Energy Savings Tool for the Cement Industry

    Galitsky, Christina; Price, Lynn; Zhou, Nan; Fuqiu , Zhou; Huawen, Xiong; Xuemin, Zeng; Lan, Wang


    The Benchmarking and Energy Savings Tool (BEST) Cement is a process-based tool based on commercially available efficiency technologies used anywhere in the world applicable to the cement industry. This version has been designed for use in China. No actual cement facility with every single efficiency measure included in the benchmark will likely exist; however, the benchmark sets a reasonable standard by which to compare for plants striving to be the best. The energy consumption of the benchmark facility differs due to differences in processing at a given cement facility. The tool accounts for most of these variables and allows the user to adapt the model to operational variables specific for his/her cement facility. Figure 1 shows the boundaries included in a plant modeled by BEST Cement. In order to model the benchmark, i.e., the most energy efficient cement facility, so that it represents a facility similar to the user's cement facility, the user is first required to input production variables in the input sheet (see Section 6 for more information on how to input variables). These variables allow the tool to estimate a benchmark facility that is similar to the user's cement plant, giving a better picture of the potential for that particular facility, rather than benchmarking against a generic one. The input variables required include the following: (1) the amount of raw materials used in tonnes per year (limestone, gypsum, clay minerals, iron ore, blast furnace slag, fly ash, slag from other industries, natural pozzolans, limestone powder (used post-clinker stage), municipal wastes and others); the amount of raw materials that are preblended (prehomogenized and proportioned) and crushed (in tonnes per year); (2) the amount of additives that are dried and ground (in tonnes per year); (3) the production of clinker (in tonnes per year) from each kiln by kiln type; (4) the amount of raw materials, coal and clinker that is ground by mill type (in tonnes per

  14. Effects of blended-cement paste chemical composition changes on some strength gains of blended-mortars.

    Kirgiz, Mehmet Serkan


    Effects of chemical compositions changes of blended-cement pastes (BCPCCC) on some strength gains of blended cement mortars (BCMSG) were monitored in order to gain a better understanding for developments of hydration and strength of blended cements. Blended cements (BC) were prepared by blending of 5% gypsum and 6%, 20%, 21%, and 35% marble powder (MP) or 6%, 20%, 21%, and 35% brick powder (BP) for CEMI42.5N cement clinker and grinding these portions in ball mill at 30 (min). Pastes and mortars, containing the MP-BC and the BP-BC and the reference cement (RC) and tap water and standard mortar sand, were also mixed and they were cured within water until testing. Experiments included chemical compositions of pastes and compressive strengths (CS) and flexural strengths (FS) of mortars were determined at 7th-day, 28th-day, and 90th-day according to TS EN 196-2 and TS EN 196-1 present standards. Experimental results indicated that ups and downs of silica oxide (SiO2), sodium oxide (Na2O), and alkali at MP-BCPCC and continuously rising movement of silica oxide (SiO2) at BP-BCPCC positively influenced CS and FS of blended cement mortars (BCM) in comparison with reference mortars (RM) at whole cure days as MP up to 6% or BP up to 35% was blended for cement.

  15. Effects of Blended-Cement Paste Chemical Composition Changes on Some Strength Gains of Blended-Mortars

    Mehmet Serkan Kirgiz


    Full Text Available Effects of chemical compositions changes of blended-cement pastes (BCPCCC on some strength gains of blended cement mortars (BCMSG were monitored in order to gain a better understanding for developments of hydration and strength of blended cements. Blended cements (BC were prepared by blending of 5% gypsum and 6%, 20%, 21%, and 35% marble powder (MP or 6%, 20%, 21%, and 35% brick powder (BP for CEMI42.5N cement clinker and grinding these portions in ball mill at 30 (min. Pastes and mortars, containing the MP-BC and the BP-BC and the reference cement (RC and tap water and standard mortar sand, were also mixed and they were cured within water until testing. Experiments included chemical compositions of pastes and compressive strengths (CS and flexural strengths (FS of mortars were determined at 7th-day, 28th-day, and 90th-day according to TS EN 196-2 and TS EN 196-1 present standards. Experimental results indicated that ups and downs of silica oxide (SiO2, sodium oxide (Na2O, and alkali at MP-BCPCC and continuously rising movement of silica oxide (SiO2 at BP-BCPCC positively influenced CS and FS of blended cement mortars (BCM in comparison with reference mortars (RM at whole cure days as MP up to 6% or BP up to 35% was blended for cement.

  16. Effects of Blended-Cement Paste Chemical Composition Changes on Some Strength Gains of Blended-Mortars

    Kirgiz, Mehmet Serkan


    Effects of chemical compositions changes of blended-cement pastes (BCPCCC) on some strength gains of blended cement mortars (BCMSG) were monitored in order to gain a better understanding for developments of hydration and strength of blended cements. Blended cements (BC) were prepared by blending of 5% gypsum and 6%, 20%, 21%, and 35% marble powder (MP) or 6%, 20%, 21%, and 35% brick powder (BP) for CEMI42.5N cement clinker and grinding these portions in ball mill at 30 (min). Pastes and mortars, containing the MP-BC and the BP-BC and the reference cement (RC) and tap water and standard mortar sand, were also mixed and they were cured within water until testing. Experiments included chemical compositions of pastes and compressive strengths (CS) and flexural strengths (FS) of mortars were determined at 7th-day, 28th-day, and 90th-day according to TS EN 196-2 and TS EN 196-1 present standards. Experimental results indicated that ups and downs of silica oxide (SiO2), sodium oxide (Na2O), and alkali at MP-BCPCC and continuously rising movement of silica oxide (SiO2) at BP-BCPCC positively influenced CS and FS of blended cement mortars (BCM) in comparison with reference mortars (RM) at whole cure days as MP up to 6% or BP up to 35% was blended for cement. PMID:24587737

  17. Crystallisation of Gypsum and Prevention of Foaming in Wet Flue Gas Desulphurisation (FGD) Plants

    Hansen, Brian Brun; Kiil, Søren; Johnsson, Jan Erik


    The aim of this project is to investigate two operational problems, which have been experienced during wet flue gas desulphurisation (FGD) operation, i.e. poor gypsum dewatering properties and foaming. The results of this work can be used for the optimization of wet FGD-plants in terms of reliability of operation and consistency of the gypsum quality obtained. This work may furthermore be of interest to other industrial systems in which foaming or gypsum crystallisation may take place. FGD is...

  18. Investigation of Parameters Affecting Gypsum Dewatering Properties in a Wet Flue Gas Desulphurization Pilot Plant

    Hansen, Brian Brun; Kiil, Søren


    Wet flue gas desulphurization (FGD) plants with forced oxidation, installed at coal and oil fired power plants for removal of SO2(g), must produce gypsum of high quality. However, quality issues such as an excessive moisture content, due to poor gypsum dewatering properties, may occur from time to time. In this work, the particle size distribution, morphology, and filtration rate of wet FGD gypsum formed in a pilot-scale experimental setup, operated in forced oxidation mode, have been studied...

  19. Carbonate replacement of lacustrine gypsum deposits in two Neogene continental basins, eastern Spain

    Anadón, P.; Rosell, L.; Talbot, M. R.


    Bedded nonmarine gypsum deposits in the Miocene Teruel and Cabriel basins, eastern Spain, are partly replaced by carbonate. The Libros gypsum (Teruel Graben) is associated with fossiliferous carbonate wackestones and finely laminated, organic matter-rich mudstones which accumulated under anoxic conditions in a meromictic, permanent lake. The gypsum is locally pseudomorphed by aragonite or, less commonly, replaced by calcite. Low δ 13C values indicate that sulphate replacement resulted from bacterial sulphate reduction processes that were favoured by anacrobic conditions and abundant labile organic matter in the sediments. Petrographic evidence and oxygen isotopic composition suggest that gypsum replacement by aragonite occurred soon after deposition. A subsequent return to oxidising conditions caused some aragonite to be replaced by diagenetic gypsum. Native sulphur is associated with some of these secondary gypsum occurrences. The Los Ruices sulphate deposits (Cabriel Basin) contain beds of clastic and selenitic gypsum which are associated with limestones and red beds indicating accumulation in a shallow lake. Calcite is the principal replacement mineral. Bacterial sulphate reduction was insignificant in this basin because of a scarcity of organic matter. Stable isotope composition of diagenetic carbonate indicates that gypsum replacement occurred at shallow burial depths due to contact with dilute groundwaters of meteoric origin. Depositional environment evidently has a major influence upon the diagenetic history of primary sulphate deposits. The quantity of preserved organic matter degradable by sulphate-reducing bacteria is of particular importance and, along with groundwater composition, is the main factor controlling the mechanism of gypsum replacement by carbonate.

  20. Hydrology of marginal evaporitic basins during the Messinian Salinity Crisis: isotopic investigation of gypsum deposits

    El Kilany, Aida; Caruso, Antonio; Dela Pierre, Francesco; Natalicchio, Marcello; Rouchy, Jean-Marie; Pierre, Catherine; Balter, Vincent; Aloisi, Giovanni


    The deposition of gypsum in Messinian Mediterranean marginal basins is controlled by basin restriction and the local hydrological cycle (evaporation/precipitation rates and relative importance of continental vs marine water inputs). We are using the stable isotopic composition of gypsum as a proxy of the hydrological cycle that dominated at the moment of gypsum precipitation. We studied the Messinian Caltanissetta (Sicily) and Tertiary Piedmont (north western Italy) basins where we carried out a high-resolution isotopic study of gypsum layers composing gypsum-marl cycles. These cycles are thought to be the sedimentary expression of astronomical precession cycles, lasting approximately 20 kyr, during which the marginal basins experienced a succession of arid and a wet conditions. We determined the isotopic composition of gypsum hydration water (18O and D), of the sulphate ion (34S, 18O) and of Strontium (87/86Sr), all of which are potentially affected by the hydrological cycle. In our samples, the mother water from which gypsum precipitated is considerably lighter (-4.0 planning a detailed petrographic investigation of gypsum crystals to look for evidence of dissolution/precipitation processes at the micro-scale. This is an essential step in interpreting the isotopic signals of gypsum because we can expect the 18O and D composition of Messinian continental input to be not too dissimilar from that of modern meteoric waters involved in diagenetic processes.

  1. Characterization and utilization of cement kiln dusts (CKDs) as partial replacements of Portland cement

    Khanna, Om Shervan

    mineralogical phases within CKDs. It was found that CKDs can contain significant amounts of amorphous material (>30%) and clinker compounds (>20%) and small amounts of slag and/or flyash (reactive and high free lime contents (>20%). The blends with the two CKDs from preheater/precalciner plants had higher paste water demand, lower mortar flows, and higher heat generation during initial hydrolysis in comparison to all other CKD-PC blends and control cements. The hardened properties of CKD as a partial substitute of PC appear to be governed by the sulfate content of the CKD-PC blend (the form of the CKD sulfate is not significant). According to analysis of the ASTM expansion in limewater test results, the CKD-PC blend sulfate content should be less than ˜0.40% above the optimum sulfate content of the PC. It was also found that the sulfate contribution of CKD behaves similar to gypsum. Therefore, CKD-PC blends could be optimized for sulfate content by using CKD as a partial substitute of gypsum during the grinding process to control the early hydration of C3A. The wet and long-dry kiln CKDs contain significant amounts of calcium carbonate (>20%) which could also be used as partial replacement of limestone filler in PC.

  2. Strength of Limestone-based Non-calcined Cement and its Properties

    LIN Zongshou; ZHAO Qian


    A new type of cement was prepared with ground limestone powder,blastfurnace slag,steel slag and gypsum without calcination.The fraction of ground limestone powder in the cement was as high as 40 wt%-60 wt%without Portland clinker.All of its physical properties can meet the requirements of masonry cement standards.The impact of limestone content on physical properties of the cement and determined its impact on law was investigated.The steel slag can excit the aquation activity of this cement effectively,and the influence of its quantity on the strength of the materials was studied,which shows that the optimum quantity of mixing is 10%.By way of changing the different content of the lime stone by quartzy sample,the law of the compression strength and the PH value was determined,confirming that the lime stone can promote the early aquation of the slag and improve the early strength.The main hydration product of this cement is calcium aluminate hydrate, ettringite and calcium silicate hydrate,as indicated by XRD and SEM analysis.

  3. Prospection of Portland cement raw material: A case study in the Marmara region of Turkey

    Özgüner, A. M.


    Representative sampling of the raw materials used to make Portland cement, correct calculations for the possible clinker mixtures, sufficient reserves of the raw materials and selection of the correct infrastructure for the location of a cement factory are essential to the protection of the great investment in the factory. The results of chemical analyses of pipe samples taken in the field at right angles to the strikes of favourable limestone, clay, shale, and marl outcrops were used in Kind's lime saturation formula for clinker calculations of the possible mixtures. The cement modulus values were calculated using the corresponding clinker oxide ratios and were confirmed to be within the standard intervals for positive cement raw material mixtures. The most promising raw material source, a double lithologic mixture of limestone and mudstone was found during the prospection in north of Bilecik Province, where rhyolitic tuff outcrops with pozzolanic properties also exist. Some marble quarries nearby have been inclined to dispose of their marble wastes for use in cement production to prevent polluting the environment with them. The nearby Gemlik fertiliser factory provides inexpensive waste gypsum that can be used as a cool cement mixing material. The limestone, mudstone and trass raw material reserves in this area were calculated to be sufficient for the factory's requirements for more than 100 years of operation as results of the detailed geological mapping. The regional infrastructure is most suitable for distribution and marketing of cement products. The cement factory described in this study has been producing cement for the last 3 years, after coring and testing of the raw material reserves.

  4. Cement and concrete

    Corley, Gene; Haskin, Larry A.


    To produce lunar cement, high-temperature processing will be required. It may be possible to make calcium-rich silicate and aluminate for cement by solar heating of lunar pyroxene and feldspar, or chemical treatment may be required to enrich the calcium and aluminum in lunar soil. The effects of magnesium and ferrous iron present in the starting materials and products would need to be evaluated. So would the problems of grinding to produce cement, mixing, forming in vacuo and low gravity, and minimizing water loss.

  5. Ancient gypsum mortars from Cyprus: characterization and reinvention

    Theodoridou, M.; Ioannou, I.


    Mortars with various binding materials have been used across different pre-historic and historic periods to meet several construction applications, such as jointing masonry blocks, finishing walls and isolating water bearing structures. In the framework of an ongoing research programme (NEA ΥΠOΔOMH/NEKΥΠ/0308/17) funded by the Cyprus Research Promotion Foundation, the Republic of Cyprus and the European Union Regional Development Fund, 25 samples of gypsum mortars from different archaeological sites in Cyprus were collected and characterized following a systematic analytical approach. Petrographic observations of thin sections were carried out using polarizing optical microscope. Scanning electron microscopy equipped with energy dispersive X-ray microanalyser (SEM-EDX) was used to examine the microstructure and texture of the mortar samples and to determine semi-quantitatively the chemical composition and interface of their binders. X-ray diffraction (XRD) was performed to identify the main mineral crystalline phases of the specimens' binder and aggregates. Thermal analyses (TG/DTA) were used as a further confirmation of the material composition. The pore structure and volume of the ancient mortars were also determined by mercury intrusion porosimetry (MIP) analysis. Last but not least, a portable drilling resistance measurement system (DRMS) was used for micro-destructive assessment of the mechanical state of the samples. The results confirmed the predominant presence of hydrous calcium sulphate in all samples. Calcite was also found both in the binder and aggregates. Small proportions of SiO2 were also detected. The common ratio of binder to aggregates was 1:2.5. MIP showed porosity values between 14-48% and real densities between 1-1.7 g/cm3. The average pore diameters were smaller in the case of mortars with lower porosity. The use of DRMS indicated lower resistance to drilling for the case of joint mortars (as opposed to analysed gypsum plasters). This


    Hasan KAPLAN; Hanifi BİNİCİ


    Cement, one of the basic material of construction engineering, has an important place in view of strength and cost of structures. Cement consumption is increasing parallel to development of building construction sector. For cement producers, minimal cost is desired by using new and economical material sources. On the other hand, the controllers and contractors need cheaper, safer and higher strength materials. From this respect cement industry tends to use cement with pozzolan. In Türkiye, ce...

  7. Light in the darkening on Naica gypsum crystals

    Castillo-Sandoval, I.; Fuentes-Cobas, L. E.; Esparza-Ponce, H. E.; Carreno-Márquez, J.; Montero-Cabrera, M. E., E-mail: [Centro de Investigación en Materiales Avanzados (CIMAV), Miguel de Cervantes 120, Chihuahua, Chih 31109, México (Mexico); Fuentes-Montero, M. E. [Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Campus Universitario#2, Circuito Universitario, C.P.31125, Chihuahua, Chih. México (Mexico); Reyes-Cortes, M. [Facultad de Ingeniería. Universidad Autónoma de Chihuahua, Campus Universitario#2, Circuito Universitario, C.P.31125, Chihuahua, Chih. México (Mexico)


    Naica mine is located in a semi-desertic region at the central-south of Chihuahua State. The Cave of Swords was discovered in 1910 and the Cave of Crystals 90 years later at Naica mines. It is expected that during the last century the human presence has changed the microclimatic conditions inside the cave, resulting in the deterioration of the crystals and the deposition of impurities on gypsum surfaces. As a contribution to the clarification of the mentioned issues, the present work refers to the use of synchrotron radiation for the identification of phases on these surfaces. All the experiments were performed at the Stanford Synchrotron Radiation Lightsource. Grazing incidence X-ray diffraction (GIXRD) and radiography-aided X-ray diffraction (RAXRD) experiments were performed at beamline 11-3. X-Ray micro-fluorescence (μ-SXRF) and micro-X-ray absorption (μ-XANES) were measured at beamline 2-3. Representative results obtained may be summarized as follows: a) Gypsum, galena, sphalerite, hematite and cuprite at the surface of the gypsum crystals were determined. b) The samples micro-structure is affected by impurities. c) The elemental distributions and correlations (0.6-0.9) of Cu, K, Fe, Mn, Pb, Zn, Ca and S were identified by μ-SXRF. The correlations among elemental contents confirmed the phase identification, with the exception of manganese and potassium due to the amorphous nature of some impurity compounds in these samples. The compounds hematite (Fe{sub 2}O{sub 3}), β-MnO{sub 2}, Mn{sub 2}O{sub 3}, MnO and/or MnCO{sub 3}, PbS, PbCO{sub 3} and/or PbSO4, ZnO{sub 4}, ZnS and/or smithsonite (ZnCO{sub 3}), CuS + Cu Oxide were identified by XANES. Plausibly, these latter compounds do not form crystalline phases.

  8. Luminescence of Speleothems in Italian Gypsum Caves: Preliminary Report

    Shopov, Yavor Y; Forti, Paolo


    The luminescence of 3 speleothem samples from the Acquafredda karst system and 1 from the Novella Cave (Gessi Bolognesi Natural Park, Italy) has been recorded using excitation by impulse Xe- lamp. All these carbonate speleothems are believed to be formed only from active CO2 from the air, because the bedrock of the cave consist of gypsum and does not contain carbonates. The obtained photos of luminescence record the climate changes during the speleothem growth. U/Th and 14C dating proved that studied speleothems started to grow since about 5,000 years ago. The detailed analyses of the luminescence records is still in progress.

  9. Limestone, gypsum, and magnesium oxide influence restoration of an abandoned Appalachian pasture

    Ritchey, K.D.; Snuffer, J.D. [USDA ARS, Beaver, WV (United States). Appalachian Farming Systems Research Centre


    When restoring abandoned pastures on acidic hill-land soils to productivity, it is important to bring soil Ca and Mg to adequate levels. Gypsum is a readily available Ca amendment that is sufficiently soluble to move rapidly into the soil when surface-applied. Gypsum has been shown to reduce detrimental effects of subsurface acidity in soils of the southeastern USA. A 4-yr experiment was initiated to measure effects of surface gypsum application on forage production and to evaluate Mg-containing amendments to avoid gypsum-induced Mg deficiency. The study site was a southern West Virginia Gilpin silt loam (fine-loamy, mixed, mesic, Typic Hapludult) where abandoned hill-and pasture was being restored to productivity. Treatments included 0, 1000, 8000; 16 000, and 32 000 kg/ha flue gas desulfurization coal combustion by-product gypsum (gypsum) together with dolomitic limestone and five additional treatments to evaluate sources of supplemental Mg. Application of 16 000 kg/ha gypsum together with limestone increased forage yields of mixed orchardgrass (Dactylis glomerata L.) and tall fescue (Festuca arundinacea Schreb) pasture during establishment by 42% and production by 11% compared with limestone alone. About 8% of the mean 790 kg/ha yield increase could be attributed to acidity-neutralizing effects of alkaline constituents in the gypsum by-product. Plants in higher gypsum treatments had higher concentrations of K and P, but gypsum application decreased soil and plant Mg concentrations. This indicated that gypsum should not be applied on typical acid soils without supplemental Mg.

  10. Co-treatment of gypsum sludge and Pb/Zn smelting slag for the solidification of sludge containing arsenic and heavy metals.

    Li, Yuan-Cheng; Min, Xiao-Bo; Chai, Li-Yuan; Shi, Mei-Qing; Tang, Chong-Jian; Wang, Qing-Wei; Liang, Yan-Jie; Lei, Jie; Liyang, Wen-Jun


    Wastewater treatment sludge from a primary lead-zinc smelter is characterized as hazardous waste and requires treatment prior to disposal due to its significant arsenic and heavy metals contents. This study presents a method for the stabilization of arsenic sludge that uses a slag based curing agent composed of smelting slag, cement clinker and limestone. The Unconfined Compressive Strength (UCS) test, the China Standard Leaching Test (CSLT), and the Toxicity Characteristic Leaching Procedures (TCLP) were used to physically and chemically characterize the solidified sludge. The binder ratio was determined according to the UCS and optimal experiments, and the optimal mass ratio of m (smelting slag): m (cement clinker): m (gypsum sludge): m (limestone) was 70:13:12:5. When the binder was mixed with arsenic sludge using a mass ratio of 1:1 and then maintained at 25 °C for 28 d, the UCS reached 9.30 MPa. The results indicated that the leached arsenic content was always less than 5 mg/L, which is a safe level, and does not contribute to recontamination of the environment. The arsenic sludge from the Zn/Pb metallurgy plant can be blended with cement clinker and smelting slag materials for manufacturing bricks and can be recycled as construction materials. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Direct nanoscale observations of the coupled dissolution of calcite and dolomite and the precipitation of gypsum.

    Offeddu, Francesco Giancarlo; Cama, Jordi; Soler, Josep Maria; Putnis, Christine V


    In-situ atomic force microscopy (AFM) experiments were performed to study the overall process of dissolution of common carbonate minerals (calcite and dolomite) and precipitation of gypsum in Na2SO4 and CaSO4 solutions with pH values ranging from 2 to 6 at room temperature (23 ± 1 °C). The dissolution of the carbonate minerals took place at the (104) cleavage surfaces in sulfate-rich solutions undersaturated with respect to gypsum, by the formation of characteristic rhombohedral-shaped etch pits. Rounding of the etch pit corners was observed as solutions approached close-to-equilibrium conditions with respect to calcite. The calculated dissolution rates of calcite at pH 4.8 and 5.6 agreed with the values reported in the literature. When using solutions previously equilibrated with respect to gypsum, gypsum precipitation coupled with calcite dissolution showed short gypsum nucleation induction times. The gypsum precipitate quickly coated the calcite surface, forming arrow-like forms parallel to the crystallographic orientations of the calcite etch pits. Gypsum precipitation coupled with dolomite dissolution was slower than that of calcite, indicating the dissolution rate to be the rate-controlling step. The resulting gypsum coating partially covered the surface during the experimental duration of a few hours.

  12. Gypsum's influence on corn yield and p loss from an eroded southern piedmont soil

    Gypsum (CaSO4) has been shown to reduce dissolved P in surface water runoff from pastures fertilized with poultry litter (PL). However, limited research has evaluated gypsum’s influence on P loss under row crops. Moreover, can gypsum effectively reduce P loss when applied only to grass buffer strips...

  13. The Growth of Gypsum in the Presence of Hexavalent Chromium: A Multiscale Study

    Juan Morales


    Full Text Available The sorption of dissolved inorganic pollutants into the structure of minerals is an important process that controls the mobility and fate of these pollutants in the Earth’s crust. It also modifies the surface structure and composition of the host mineral, affecting its crystallization kinetics. Here, we investigate the effect of hexavalent chromium, Cr(VI, on the nucleation and growth of gypsum by conducting two types of experiments: (i in situ atomic force microscopy (AFM observations of the growth of gypsum {010} surfaces in the presence of Cr(VI and (ii gypsum precipitation experiments by mixing aqueous solutions containing variable amounts of Cr(VI. Gypsum precipitation is progressively delayed when occurring from solutions bearing increasing Cr(VI concentrations. Chemical analyses of gypsum precipitates show that gypsum incorporates small Cr(VI amounts that correlate with the content of this ion in the aqueous solution. Gypsum cell parameters variation reflects this incorporation. At the molecular scale, Cr(VI induces a slowdown of step advance rates on gypsum {010} surfaces accompanied by the roughening of nanostep edges and the so-called “template effect”. This effect involves the reproduction of the original nanotopography after the completion of individual advancing monolayers and appears as a general nanoscale phenomenon occurring during growth of solid solutions from aqueous solutions even in the case of compositionally-restricted solid solutions.

  14. Pre-contamination of new gypsum wallboard with potentially harmful fungal species

    Andersen, Birgitte; Dosen, Ina; Lewinska, Anna Malgorzata;


    Gypsum wallboard is a popular building material, but is also very frequently overgrown by Stachybotrys chartarum after severe and/or undetected water damage. The purpose of this study was to determine whether Stachybotrys and other fungi frequently isolated from wet gypsum wallboard are already p...

  15. Authigenic gypsum in a deep sea core from Southeastern Arabian Sea

    Guptha, M.V.S.

    Authigenic gypsum has been encountered in a deep sea core RC9-157 from the southeastern Arabian Sea at a depth of 4111 m which is a zone of lysocline. The formation of gypsum in the deep sea region is attributed to the prevailing sulphate rich...

  16. Impact of FGD gypsum on soil fertility and plant nutrient uptake

    Use of FGD gypsum is thought to improve soil productivity and increase plant production. Thus, a study was conducted to evaluate the effects of FGD gypsum on yield, plant nutrient uptake and soil productivity. The study was conducted on an established bermudagrass pasture. Poultry litter was applied...

  17. An important tool with no instruction manual: A review of gypsum use in agriculture

    Land application of gypsum has been studied and utilized in agriculture and environmental remediation for many years. Most of the published literature has focused on gypsum application impacts on soil properties rather than crop yields. This literature review was conducted to (i) gather results from...

  18. Pre-contamination of new gypsum wallboard with potentially harmful fungal species

    Andersen, Birgitte; Dosen, Ina; Lewinska, Anna Malgorzata


    Gypsum wallboard is a popular building material, but is also very frequently overgrown by Stachybotrys chartarum after severe and/or undetected water damage. The purpose of this study was to determine whether Stachybotrys and other fungi frequently isolated from wet gypsum wallboard are already p...

  19. In-situ early-age hydration study of sulfobelite cements by synchrotron powder diffraction

    Álvarez-Pinazo, G.; Cuesta, A.; García-Maté, M.; Santacruz, I.; Losilla, E.R. [Departamento de Química Inorgánica, Universidad de Málaga, Campus Teatinos S/N., 29071 Málaga (Spain); Sanfélix, S.G. [Unidad Técnica de Investigación de Materiales, AIDICO, Avda. Benjamín Franklin, 17 Paterna, Valencia (Spain); Fauth, F. [CELLS-Alba synchrotron, Carretera BP 1413, Km. 3.3, E-08290 Cerdanyola, Barcelona (Spain); Aranda, M.A.G. [Departamento de Química Inorgánica, Universidad de Málaga, Campus Teatinos S/N., 29071 Málaga (Spain); CELLS-Alba synchrotron, Carretera BP 1413, Km. 3.3, E-08290 Cerdanyola, Barcelona (Spain); De la Torre, A.G., E-mail: [Departamento de Química Inorgánica, Universidad de Málaga, Campus Teatinos S/N., 29071 Málaga (Spain)


    Eco-friendly belite calcium sulfoaluminate (BCSA) cement hydration behavior is not yet well understood. Here, we report an in-situ synchrotron X-ray powder diffraction study for the first hours of hydration of BCSA cements. Rietveld quantitative phase analysis has been used to establish the degree of reaction (α). The hydration of a mixture of ye'elimite and gypsum revealed that ettringite formation (α ∼ 70% at 50 h) is limited by ye'elimite dissolution. Two laboratory-prepared BCSA cements were also studied: non-active-BCSA and active-BCSA cements, with β- and α′{sub H}-belite as main phases, respectively. Ye'elimite, in the non-active-BCSA system, dissolves at higher pace (α ∼ 25% at 1 h) than in the active-BCSA one (α ∼ 10% at 1 h), with differences in the crystallization of ettringite (α ∼ 30% and α ∼ 5%, respectively). This behavior has strongly affected subsequent belite and ferrite reactivities, yielding stratlingite and other layered phases in non-active-BCSA. The dissolution and crystallization processes are reported and discussed in detail. -- Highlights: •Belite calcium sulfoaluminate cements early hydration mechanism has been determined. •Belite hydration strongly depends on availability of aluminum hydroxide. •Orthorhombic ye’elimite dissolved at a higher pace than cubic one. •Ye’elimite larger reaction degree yields stratlingite formation by belite reaction. •Rietveld method quantified gypsum, anhydrite and bassanite dissolution rates.

  20. Calcium sulfoaluminate (Ye'elimite) hydration in the presence of gypsum, calcite, and vaterite

    Hargis, Craig W. [Department of Civil and Environmental Engineering, University of California, Berkeley, CA (United States); Telesca, Antonio [School of Engineering, University of Basilicata, Potenza (Italy); Monteiro, Paulo J.M., E-mail: [Department of Civil and Environmental Engineering, University of California, Berkeley, CA (United States)


    Six calcium sulfoaluminate-based cementitious systems composed of calcium sulfoaluminate, calcite, vaterite, and gypsum were cured as pastes and mortars for 1, 7, 28 and 84 days. Pastes were analyzed with X-ray diffraction, thermogravimetric and differential thermal analyses. Mortars were tested for compressive strength, dimensional stability and setting time. Furthermore, pastes with a water/cementitious material mass ratio of 0.80 were tested for heat evolution during the first 48 h by means of isothermal conduction calorimetry. It has been found that: (1) both calcite and vaterite reacted with monosulfoaluminate to give monocarboaluminate and ettringite, with vaterite being more reactive; (2) gypsum lowered the reactivity of both carbonates; (3) expansion was reduced by calcite and vaterite, irrespective of the presence of gypsum; and (4) both carbonates increased compressive strength in the absence of gypsum and decreased compressive strength less in the presence of gypsum, with vaterite's action more effective than that of calcite.

  1. The gypsum-brushite system: crystallization from solutions poisoned by phosphate ions

    Rinaudo, C.; Lanfranco, A. M.; Boistelle, R.


    Gypsum and a non-stoichiometric calcium phosphate sulphate hydrate (CPSH) were grown from solutions poisoned by phosphate ions. The pH ranged from 4.7 to 5.6 and the sulphate over phosphate ratios from 1.5 to 9. In some cases, when the phosphate concentration was high (30%-40%) CPSH was stable. When the phosphate concentration was lower (10%-20%), CPSH formed as first phase in association with gypsum, but dissolved as soon as gypsum crystallized and grew at its expense. In that case, gypsum contained up to 10% phosphate. On the other hand, when gypsum crystallized alone, as first phase, it did not contain detectable amounts of phosphate.

  2. Alleviation of Subsoil Acidity of Red Soil in Southeast China with Lime and Gypsum



    Application of lime or gypsum is a common agricultrual practice to ameliorate soils with low pH which prohibits crop prduction,Its integrated effect on soil properties in a red soil derved from Quaternary red clay in Southeast China is discussed in this paper,Application of gypsum in the topsoil without leaching raised soil pH and promoted the production of soil NH4,but lime addition had a contrary effect.Generally,application of lime and /or gypsum has little on soil electrical properties.Gypsum had a little effect on soil exchange complex and its effect went down to 30 cm in depth ,The effect of lime reached only to 5 cm below its application layer.With leaching,Ca transferred from top soil to subsoil and decreased exchangeable Al in subsiol.Gypsum application led to a sharp decrease in soil exchangeable Mg but had no effect on K.

  3. Engineering and sustainability aspect of palm oil shell powder in cement

    Karim, Mohammad Razaul; Hossain, Md. Moktar; Yusoff, Sumiani Binti


    Palm oil shell (POS) is a waste material which significantly produced in palm oil mills. In current practice, this waste is dumped in open land or landfill sites or is used as fuel to run a steam turbine of a boiler, which leads to environmental pollutions. The characterization, engineering and sustainability aspect of this waste for using in cement-based applications lead to reduce the emission of carbon dioxide and cost, save natural resources for cement production and also sustainable usage of waste material. The characterization was carried out using particle size analyzer, XRF, SEM and total organic carbon analyzer. ASTM standard methods were used to observe the setting time and water for normal consistency. The compressive strength of palm oil shell powder (POSP) blended cement was explored with the water to cement and cement to sand ratio of 0.40 and 0.50, respectively up to 40% replacement levels of OPC. Result found that the setting time and water demand were increased, but compressive strength was decreased to replacement levels. However, the incorporation of POSP in cement was reduced 9.6% of CO2 emission, 25 % of the cost and save natural resource, i.e. limestone, clay, iron ore, silica shale and gypsum of 35.1%, 4.95%, 0.9%, 4.05 % and 1.2 %, respectively at 30% replacement level of OPC. The results of this extensive study on POSP characterization, effect on basic cement properties and sustainability aspect provide the guidance for using the POSP at industrial scale for cement production.

  4. Heat storage in gypsum. Final report to the Energy Agency; Vaermelagring i Gips. Slutrapport foer Energimyndigheten

    Chaudhuri, Punya (Process Improvements, Plankgatan 26, Norrkoeping (Sweden)); Kindh, Torgny (Environnet AB, Norrkoeping (Sweden)); Lawrence, David; Wahlstroem, Krister (Dept. of Physics, Chemistry and Biology, Linkoeping Univ., Linkoeping (Sweden))


    The Swedish Energy Agency's project 'energy storage in gypsum', began in April 2007 and finished a year later. The objective was to demonstrate the potential of using gypsum to store and retrieve low-grade heat at a pilot scale (i.e. using 200 kg of gypsum). Gypsum undergoes a reversible reaction with water in which it stores or releases energy. Preliminary work indicated that when using commercially available gypsum powder, a packed bed would not allow sufficient mass or heat transfer. Preliminary work also revealed that simple fluidization was not possible with the very fine particles: stirred fluidization was the solution used. A pilot-scale unit was constructed (essentially a closed tank about 1 m in diameter and 1 m high). To store energy, hot, dry air is contacted with the gypsum to bring the temperature of the powder to about 110 deg C. Once the powder is 'dried' it is returned to room temperature and isolated from the surroundings - in this state energy is stored indefinitely. To recover the heat, water was atomized, mixed with warm air (to vaporize the water) and reacted with the gypsum. Typically we were able to recover about 6 kWh of energy, which is only about 20% of what is possible. This is partly the result of too little insulation on the reactor and a hesitation to over-hydrate the gypsum (which would result in solid plaster). We anticipate that this will at least double with increased operating experience. Overall gypsum behaves at a pilot scale as was expected; in terms of energy storage for space heating, it shows great promise. Our experiences to date have shown that using gypsum with a larger particle size (to allow simple fluidization) is an important improvement.

  5. The role of biofilms in the sedimentology of actively forming gypsum deposits at Guerrero Negro, Mexico.

    Vogel, Marilyn B; Des Marais, David J; Turk, Kendra A; Parenteau, Mary N; Jahnke, Linda L; Kubo, Michael D Y


    Actively forming gypsum deposits at the Guerrero Negro sabkha and saltern system provided habitats for stratified, pigmented microbial communities that exhibited significant morphological and phylogenetic diversity. These deposits ranged from meter-thick gypsum crusts forming in saltern seawater concentration ponds to columnar microbial mats with internally crystallized gypsum granules developing in natural anchialine pools. Gypsum-depositing environments were categorized as forming precipitation surfaces, biofilm-supported surfaces, and clastic surfaces. Each surface type was described in terms of depositional environment, microbial diversity, mineralogy, and sedimentary fabrics. Precipitation surfaces developed in high-salinity subaqueous environments where rates of precipitation outpaced the accumulation of clastic, organic, and/or biofilm layers. These surfaces hosted endolithic biofilms comprised predominantly of oxygenic and anoxygenic phototrophs, sulfate-reducing bacteria, and bacteria from the phylum Bacteroidetes. Biofilm-supported deposits developed in lower-salinity subaqueous environments where light and low water-column turbulence supported dense benthic microbial communities comprised mainly of oxygenic phototrophs. In these settings, gypsum granules precipitated in the extracellular polymeric substance (EPS) matrix as individual granules exhibiting distinctive morphologies. Clastic surfaces developed in sabkha mudflats that included gypsum, carbonate, and siliclastic particles with thin gypsum/biofilm components. Clastic surfaces were influenced by subsurface brine sheets and capillary evaporation and precipitated subsedimentary gypsum discs in deeper regions. Biofilms appeared to influence both chemical and physical sedimentary processes in the various subaqueous and subaerially exposed environments studied. Biofilm interaction with chemical sedimentary processes included dissolution and granularization of precipitation surfaces, formation of

  6. Gypsum effects on crop yield and chemistry of soil, crop tissue, and vadose zone water: A meta-analysis.

    Gypsum has various potential benefits as a soil amendment, but data are lacking on gypsum effects on crop yields and on environmental impacts across diverse field sites. Gypsum studies were conducted in six states using a common design with three rates each of mined and flue gas desulfurization (FGD...

  7. PPF-reinforced, ESP-lightened gypsum plaster

    García Santos, A.


    Full Text Available A new construction material has been obtained by adding aggregate to gypsum plaster which, without reducing the bending strength of plain gypsum plaster without aggregates, lowers its density, and consequently the weight of the construction elements made from the agglomerated material, by half.The aggregates used were expanded polystyrene beads and short polypropylene fibre.The new material addresses one of the issues of cardinal interest in construction materials and construction element research, namely the need to lighten materials so as to ease the burden on buildings’ bearing structures while facilitating assembly of construction units, by a single worker wherever possible.With a water / binder ratio of 0.7 and 2% (by weight of plaster of expanded polystyrene and 2% of polypropylene fibre aggregates, the decline in density achieved was 50,88% over plain gypsum plaster and 32.88% over plasterboard.Se ha obtenido un nuevo material de construcción aditivando el yeso o la escayola, mediante la incorporación de agregados, de modo que sin reducir la resistencia a flexotracción de una escayola sin ningún tipo de adición, reduce su densidad a la mitad, y por tanto, el peso de los elementos constructivos que puedan realizarse basándose en él.El material está compuesto por una adición de gránulos de poliestireno expandido y fibras cortadas de polipropileno.El nuevo material incide sobre aquellos aspectos de más interés en el campo de la investigación en construcción, en donde se intenta reducir el peso de los materiales, de modo que se grave lo menos posible la estructura resistente de las edificaciones, a la par que se facilitan los procedimientos de montaje de las unidades constructivas, al poder ser manejadas por un solo operario.La escayola, con relación de agua/conglomerante de 0,7, y con adiciones del 2% en peso (sobre la cantidad de escayola, tanto de poliestireno expandido como de fibras de polipropileno, permite reducir la


    Fred Sabins


    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses tasks performed in the fourth quarter as well as the other three quarters of the past year. The subjects that were covered in previous reports and that are also discussed in this report include: Analysis of field laboratory data of active cement applications from three oil-well service companies; Preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; Summary of pertinent information from Russian ultra-lightweight cement literature review; and Comparison of compressive strengths of ULHS systems using ultrasonic and crush methods Results reported from the fourth quarter include laboratory testing of ULHS systems along with other lightweight cement systems--foamed and sodium silicate slurries. These comparison studies were completed for two different densities (10.0 and 11.5 lb/gal) and three different field application scenarios. Additional testing included the mechanical properties of ULHS systems and other lightweight systems. Studies were also performed to examine the effect that circulation by centrifugal pump during mixing has on breakage of ULHS.

  9. XRD and mineralogical analysis of gypsum dunes at White Sands National Monument, New Mexico and applications to gypsum detection on Mars

    Lafuente, B.; Bishop, J. L.; Fenton, L. K.; King, S. J.; Blake, D.; Sarrazin, P.; Downs, R.; Horgan, B. H.


    A field portable X-ray Diffraction (XRD) instrument was used at White Sands National Monument to perform in-situ measurements followed by laboratory analyses of the gypsum-rich dunes and to determine its modal mineralogy. The field instrument is a Terra XRD (Olympus NDT) based on the technology of the CheMin (Chemistry and Mineralogy) instrument onboard the Mars Science Laboratory (MSL) rover Curiosity which is providing the mineralogical and chemical composition of scooped soil samples and drilled rock powders collected at Gale Crater [1]. Using Terra at White Sands will contribute to 'ground truth' for gypsum-bearing environments on Mars. Together with data provided by VNIR spectra [2], this study clarifies our understanding of the origin and history of gypsum-rich sand dunes discovered near the northern polar region of Mars [3]. The results obtained from the field analyses performed by XRD and VNIR spectroscopy in four dunes at White Sands revealed the presence of quartz and dolomite. Their relative abundance has been estimated using the Reference Intensity Ratio (RIR) method. For this study, particulate samples of pure natural gypsum, quartz and dolomite were used to prepare calibration mixtures of gypsum-quartz and gypsum-dolomite with the 90-150μm size fractions. All single phases and mixtures were analyzed by XRD and RIR factors were calculated. Using this method, the relative abundance of quartz and dolomite has been estimated from the data collected in the field. Quartz appears to be present in low amounts (2-5 wt.%) while dolomite is present at percentages up to 80 wt.%. Samples from four dunes were collected and prepared for subsequent XRD analysis in the lab to estimate their composition and illustrate the changes in mineralogy with respect to location and grain size. Gypsum-dolomite mixtures: The dolomite XRD pattern is dominated by an intense diffraction peak at 2θ≈36 deg. which overlaps a peak of gypsum, This makes low concentrations of dolomite

  10. The formation and potential importance of cemented layers in inactive sulfide mine tailings

    Blowes, David W.; Reardon, Eric J.; Jambor, John L.; Cherry, John A.


    Investigations of inactive sulfide-rich tailings impoundments at the Heath Steele (New Brunswick) and Waite Amulet (Quebec) minesites have revealed two distinct types of cemented layers or "hardpans." That at Heath Steele is 10-15 cm thick, occurs 20-30 cm below the depth of active oxidation, is continuous throughout the tailings impoundment, and is characterized by cementation of tailings by gypsum and Fe(II) solid phases, principally melanterite. Hardpan at the Waite Amulet site is only 1-5 cm thick, is laterally discontinuous (10-100 cm), occurs at the depth of active oxidation, and is characterized by cementation of tailings by Fe(III) minerals, principally goethite, lepidocrocite, ferrihydrite, and jarosite. At Heath Steele, an accumulation of gas-phase CO 2, of up to 60% of the pore gas, occurs below the hardpan. The calculated diffusivity of the hardpan layer is only about 1/100 that of the overlying, uncemented tailings. The pore-water chemistry at Heath Steele has changed little over a 10-year period, suggesting that the cemented layer restricts the movement of dissolved metals through the tailings and also acts as a zone of metal accumulation. Generation of a cemented layer therefore has significant environmental and economic implications. It is likely that, in sulfide-rich tailings impoundments, the addition of carbonate-rich buffering material during the late stages of tailings deposition would enhance the formation of hardpan layers.

  11. Attack of Limestone Cement-based Material Exposed to Magnesium Sulfate Solution at Low Temperature

    ZHANG Fengchen; WU Shengxing; FANG Yonghao; ZHOU Jikai; LI Zhonghua


    Limestone in cement could be a source of CO32-needed for thaumasite formation which will result in thaumasite form of sulfate attack (TSA) probably. TSA has more deterioration than ettringite or gypsum form of sulfate attack because it targets the calcium silicate hydrates (C-S-H) which is the main binder phase in all Portland cement-based materials. By means of physical and mechanical property testing as well as erosion phases analysis, magnesium sulfate attack of cement-based material containing 35% limestone powder by mass at 5 ± 2℃is investigated. The compressive strength and flexural strength of mortar specimen immersed in MgSO4 solution increase firstly, then decrease rapidly with the immersing age. Relative dynamic elastic modulus of mortar specimen changes in a phased process. After immersing in MgSO4 solution for 15 weeks, the main erosion phases in paste specimen change from four phases compounds, three phases compounds to two phases compounds from surface to inside. Deterioration course of limestone cement-based material exposed to magnesium sulfate aggressive environment appears progressive damage layer by layer, and every layer probably suffers four stages, which are property strengthening stage, initial degradation stage, thaumasite formation stage and cementation loss stage, respectively.

  12. The effect of sulfate activation on the early age hydration of BFS:PC composite cement

    Collier, N.C., E-mail:; Li, X.; Bai, Y.; Milestone, N.B.


    Blast furnace slag/Portland cement composites are routinely used for immobilising intermediate level nuclear wastes in the UK. Using high cement replacement levels reduces hydration exotherm and lowers pH. Although a lower grout pH will be beneficial in reducing the corrosion of certain encapsulated reactive metals such as aluminium, the degree of slag reaction will also be lower which may result in the formation of less hydration products and which in turn may reduce the capacity to immobilise waste ions. Adding neutral salts such as calcium and sodium sulfate to the composite cement can potentially increase slag activation without significantly altering the pH of the cement matrix. Thus the corrosion of any encapsulated metals would not be affected. This paper describes some of the properties of a hydrated 9:1 blast furnace slag:Portland cement matrix containing added sulfates of calcium and sodium. The findings show that all additives caused an increase in the amount of slag that reacted when cured for up to 28 days. This produced more material able to chemically bind waste ions. Activation with gypsum produced the highest rate of slag reaction.

  13. The formation and potential importance of cemented layers in inactive sulfide mine tailings

    Blowes, D.W.; Reardon, E.J.; Cherry, J.A. (Univ. of Waterloo, Ontario (Canada)); Jambor, J.L. (CANMET, Ontario (Canada))


    Investigations of inactive sulfide-rich tailings impoundments at the Heath Steele (New Brunswick) and Waite Amulet (Quebec) minesites have revealed two distinct types of cemented layers or hardpans. That at Heath Steele is 10-15 cm thick, occurs 20-30 cm below the depth of active oxidation, is continuous throughout the tailings impoundment, and is characterized by cementation of tailings by gypsum and Fe(II) solid phases, principally melanterite. Hardpan at the Waite Amulet site is only 1-5 cm thick, is laterally discontinuous (10-100 cm), occurs at the depth of active oxidation, and is characterized by cementation of tailings by Fe(III) minerals, principally goethite, lepidocrocite, ferrihydrite, and jarosite. At Heath Steele, an accumulation of gas-phase CO{sub 2}, of up to 60{percent} of the pore gas, occurs below the hardpan. The calculated diffusivity of the hardpan layer is only about 1/100 that of the overlying, uncemented tailings. The pore-water chemistry at Heath Steele has changed little over a 10-year period, suggesting that the cemented layer restricts the movement of dissolved metals through the tailings and also acts as a zone of metal accumulation. Generation of a cemented layer therefore has significant environmental and economic implications. It is likely that, in sulfide-rich tailings impoundments, the addition of carbonate-rich buffering material during the late stages of tailings deposition would enhance the formation of hardpan layers.


    Milan Drabik


    Full Text Available Essential focus of the study has been to acquire thermoanalytical events, incl. enthalpies of decompositions - ΔH, of technological materials based on two types of Portland cements. The values of thermoanalytical events and also ΔH of probes of technological compositions, if related with the data of a choice of minerals of calcium-silicate-sulfate-aluminate hydrates, served as a valued input for the assessment of phases present and phase changes due to the topical hydraulic processes. The results indicate mainly the effects of "standard humidity" or "wet storage" of the entire hydration/hydraulic treatment, but also the presence of cement residues alongside calcium-silicate-sulfate-aluminate hydrates (during the tested period of treatment. "A diluting" effect of unhydrated cement residues upon the values of decomposition enthalpies in the studied multiphase system is postulated and discussed

  15. Corrosion of bare and galvanized steel in gypsum

    Gómez, Mercedes


    Full Text Available Gypsum is a relatively low-cost building material much abounding in our country. When it is put in contact with steel, it may produce high corrosion rates due to its pH value (close to 7. This work reports the results obtained in studying the corrosion rates of bare and galvanized steel in contact with gypsum and plaster, as well as the influence curing thermal treatment applied to gypsum, enviromental relative humidity and addition of compounds with different natures and purposes may have in such process. In-situ observations, as well as the measurement of the Polarization Resistance and the weight loss have been used as measurement technics. From the results obtained it has been possible to deduce that galvanized steel has better behaviour in dry enviroments than bare steel in the same conditions and moist atmosphere induces proportionally more corrosion in galvanized steel than in bare one. Additions to gypsum do not modified these conclusions, though it may be pointed out that addition of nitrites or lime improves the behaviour of bare steel, while galvanized behaviour is not modified. The addition of lime is not recommended because phenomena of dilated along time expansion may take place.

    El yeso es un material de construcción de relativo bajo coste y que, además, es muy abundante en nuestro país. Debido a su pH cercano a la neutralidad, cuando entra en contacto con el acero, este puede corroerse a elevadas velocidades. En esta comunicación se presentan los resultados de un estudio sobre la velocidad de corrosión del acero desnudo y galvanizado en contacto con yeso y escayola y la influencia que tienen: el tratamiento térmico del curado del yeso, la humedad relativa ambiental y la adición de aditivos de diversa naturaleza y finalidad. Como técnicas de medida se han utilizado la medida de la Resistencia de Polarización y de la pérdida de peso, así como observaciones visuales. De los resultados se puede deducir que en

  16. Constructive applications of composite gypsum reinforced with Typha Latifolia fibres

    Garcia Santos, A.


    Full Text Available The present research analyses the possibility to reinforce gypsum using enea fibres (Typha Latifolia creating a compound material in wich the fibres contribute to increase mechanical resistance, producing as well a reduction of the weight and a possible regulation of the set time.

    La investigación presente analiza la posibilidad de reforzar los morteros de escayola mediante la utilización dé fibras de Typha Latifolia, creando un material compuesto en el que las fibras contribuyen al aumento de resistencia mecánica, a la vez que se produce una reducción del peso y una regulación de los tiempos de fraguado. Las propiedades de estos materiales hacen que, en determinadas aplicaciones, su utilización resulte ventajosa con respecto a materiales tradicionales.

  17. Calcium Sulfates at Gale Crater and Limitations on Gypsum Stability

    Vantiman, D. T.; Martinez, G. M.; Rampe, E. B.; Bristow, T. F.; Blake, D. F.; Yen, A. H.; Ming, D. W.; Rapin, W.; Meslin, P. -Y.; Morookian, J. M.; hide


    The Mars Science Laboratory rover has been exploring sedimentary rocks of the Bradbury group and overlying Murray formation, as well as the unconformably overlying Stimson formation. Early in exploration, and continuing to present, there have been observations of many Ca-sulfate veins that cut all three stratigraphic units. The CheMin XRD instrument on Curiosity provides complete mineralogy for drilled or scooped samples, with explicit identification of gypsum, bassanite, and anhydrite (crystal structure of so-called "soluble anhydrite," or gamma-CaSO4, is so similar to bassanite that it can't be distinguished at CheMin 2-theta resolution; here we refer to these similar dehydrated forms simply as bassanite).

  18. Carbonate speleothems from western Mediterranean gypsum karst: palaeoclimate implications

    Columbu, Andrea; Drysdale, Russell; Woodhead, Jon; Chiarini, Veronica; De Waele, Jo; Hellstrom, John; Forti, Paolo; Sanna, Laura


    Gypsum caves are uncommon environments for carbonate speleothems (cave deposits). Contrary to limestone caves, the only source of non-atmospheric carbon is from biogenic CO2 produced by the overlying soils. Enhanced CO2 content in soils is in turn related with climate, where warm temperatures and high humidity favour plant activity .().....(Fairchild and Baker, 2012). Although poorly decorated, the exploration of northern Italian and Spanish gypsum karst systems reveals the existence of several generations of carbonate speleothems, which have been dated with the U-Th series method .()......(Hellstrom, 2003; Scholz and Hoffmann, 2008). Their ages coincide with current and previous two interglacials (MIS 1, 5e and 7e and Greenland interstadials (GIS) 19, 20, 21 and 24. Considering that these periods are amongst the most pronounced warm-wet pulsations over the last 250,000 ...(Martrat et al., 2007; NGRIP, 2004), and that CO2 has a fundamental role in this karst process, this study explores the climate-driven hydrogeological conditions necessary to trigger carbonate deposition in gypsum voids. The further correlation with sapropel events 5, 4, 3 and 1, considered symptomatic of enhanced rainfall across the whole Mediterranean basin .(.)(Emeis et al., 1991), highlights the importance of flow-rate in the fracture network and infiltration of meteoric water into the caves. The combination of high CO2 and a phreatic status of the fracture network is thus indispensable for the formation of carbonate speleothems in gypsum karst. This condition appears to be triggered by periods of orbital precession minimum, when the monsoonal activity peaked in the Atlantic area. Stable oxygen isotope signatures suggest that the speleothems did not grow during any interglacial-glacial or main interstadial-stadial transitions, confirming that variations from optimum climate conditions may hamper the formation of this category of speleothems. New speleological exploration and sampling campaign

  19. The mechanical effect of the existing cement mantle on the in-cement femoral revision.

    Keeling, Parnell


    Cement-in-cement revision hip arthroplasty is an increasingly popular technique to replace a loose femoral stem which retains much of the original cement mantle. However, some concern exists regarding the retention of the existing fatigued and aged cement in such cement-in-cement revisions. This study investigates whether leaving an existing fatigued and aged cement mantle degrades the mechanical performance of a cement-in-cement revision construct.

  20. Cement Mason's Curriculum. Instructional Units.

    Hendirx, Laborn J.; Patton, Bob

    To assist cement mason instructors in providing comprehensive instruction to their students, this curriculum guide treats both the skills and information necessary for cement masons in commercial and industrial construction. Ten sections are included, as follow: related information, covering orientation, safety, the history of cement, and applying…

  1. Reducing cement's CO2 footprint

    van Oss, Hendrik G.


    The manufacturing process for Portland cement causes high levels of greenhouse gas emissions. However, environmental impacts can be reduced by using more energy-efficient kilns and replacing fossil energy with alternative fuels. Although carbon capture and new cements with less CO2 emission are still in the experimental phase, all these innovations can help develop a cleaner cement industry.

  2. Technology Roadmaps: Cement



    To support its roadmap work focusing on key technologies for emissions reductions, the International Energy Agency (IEA) also investigated one particular industry: cement. Cement production includes technologies that are both specific to this industry and those that are shared with other industries (e.g., grinding, fuel preparation, combustion, crushing, transport). An industry specific roadmap provides an effective mechanism to bring together several technology options. It outlines the potential for technological advancement for emissions reductions in one industry, as well as potential cross-industry collaboration.

  3. Cementing a wellbore using cementing material encapsulated in a shell

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Floyd, III, William C.; Spadaccini, Christopher M.; Vericella, John J.; Cowan, Kenneth Michael


    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  4. Cementing a wellbore using cementing material encapsulated in a shell

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael


    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  5. Cementing a wellbore using cementing material encapsulated in a shell

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael


    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  6. Enhanced gypsum scaling by organic fouling layer on nanofiltration membrane: Characteristics and mechanisms.

    Wang, Jiaxuan; Wang, Lei; Miao, Rui; Lv, Yongtao; Wang, Xudong; Meng, Xiaorong; Yang, Ruosong; Zhang, Xiaoting


    To investigate how the characteristics of pregenerated organic fouling layers on nanofiltration (NF) membranes influence the subsequent gypsum scaling behavior, filtration experiments with gypsum were carried out with organic-fouled poly(piperazineamide) NF membranes. Organic fouling layer on membrane was induced by bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA), respectively. The morphology and components of the scalants, the role of Ca(2+) adsorption on the organic fouling layer during gypsum crystallization, and the interaction forces of gypsum on the membrane surface were investigated. The results indicated that SA- and HA-fouled membranes had higher surface crystallization tendency along with more severe flux decline during gypsum scaling than BSA-fouled and virgin membranes because HA and SA macromolecules acted as nuclei for crystallization. Based on the analyses of Ca(2+) adsorption onto organic adlayers and adhesion forces, it was found that the flux decline rate and extent in the gypsum scaling experiment was positively related to the Ca(2+)-binding capacity of the organic matter. Although the dominant gypsum scaling mechanism was affected by coupling physicochemical effects, the controlling factors varied among foulants. Nevertheless, the carboxyl density of organic matter played an important role in determining surface crystallization on organic-fouled membrane.

  7. Use of Fluidized Bed Combustion Ash and Other Industrial Wastes as Raw Materials for the Manufacture of Calcium Sulphoaluminate Cements

    Marroccoli, M.; Montagnaro, F.; Pace, M. L.; Telesca, A.; Valenti, G. L.

    Calcium sulphoaluminate cements, mainly composed by 4CaO·3Al2O3·SO3 and 2CaO·SiO2, are special hydraulic binders which require limestone, bauxite and gypsum as natural raw materials for their manufacture. In order to save bauxite and natural gypsum, it has been explored the possibility of using, among the raw mix components, FBC waste together with pulverised coal fly ash or anodization mud and, when necessary, flue gas desulphurization gypsum. Mixtures containing limestone (29-39%), FBC waste (30-44%), pulverised coal fly ash (0-13%) or anodization mud (0-32%), bauxite (0-18%) and flue gas desulphurization gypsum (0-8%) were heated for 2 hours in a laboratory electric oven at temperatures ranging from 1150° to 1300°C. The X-ray diffraction patterns on the burnt products generally showed a good conversion of the reactants and a high selectivity degree towards 4CaO·3Al2O3·SO3, particularly at 1250°C.

  8. The effects of K2SO4 solution on the compressive strength of dental gypsum type III

    Adeilina, T.; Triaminingsih, S.; Indrani, D. J.


    Dental gypsum type III is used as a material for manufacturing working models of dentures. The aim of this study was to identify the effects of the addition of a K2SO4 solution on the compressive strength of gypsum type III. A compressive strength test was performed using a universal testing machine with a crosshead speed of 1 mm/min. The data were analyzed using a one-way ANOVA. The results showed that the compressive strength of gypsum type III with a 1.5% K2SO4 solution added was higher than for gypsum type III alone but lower than the compressive strength of gypsum type IV.

  9. Effect of the cement type on compatibility with carboxylate super plasticisers; Influencia de la naturaleza del cemento en la compatibilidad con aditivos superplastificantes basados en carboxilatos

    Bundyra-Oracz, G.; Kurdowski, W.


    An empirical study was conducted to gain a fuller understanding of the interactions taking place in cement superplasticiser systems. To this end, two clinkers of clinkers of known chemical and phase composition were prepared in this study to gain insight into such interactions. One contained no tricalcium aluminate (C1), while the other had a 9% C{sub 3}A content (C2). These clinkers were ground to approximately 340 m{sup 2}/kg and blended with gypsum only or gypsum and Klein compound (3CaO{center_dot}3Al{sub 2}O{sub 3}{center_dot}CaSO{sub 4}) (1, 2). Sufficient compound was added to C1 to ensure the formation of about the same amount of ettringite after 0.5 and 1 h of hydration as found in cement C2 + gypsum. The admixture used was a carboxylate superplasticiser. Rheology measurements showed that while paste yield stress was correlated to ettringite formation, no such simple relationship was observed for plastic viscosity. Plastic viscosity depended on the total hydrates formed, i.e., not only as ettringite but also as C-S-H gel. The findings revealed that in clinkers with very low sulfate and potassium contents, the rheology of carboxylate-containing cement paste is primarily controlled by ettringite formation. (Author) 15 refs.

  10. Influence of shelf life on the setting time of type IV gypsum

    Hapsari, M. L.; Irawan, B.; Damiyanti, M.


    Although expired materials can exhibit a deterioration in their properties, expired type IV gypsum can still be found on the market. In order to evaluate the influence of the shelf life on its setting time, two groups of type IV gypsum (GC Fuji rock EP) with different expiration dates were used in this research. The setting time tests were done in a mold using a Vicat Needle apparatus. The results of the statistical analysis showed a significant difference (p<0.05) between the two different expiration date groups. Therefore, the shelf life did influence the setting time of the type IV gypsum.

  11. The Mechanical Properties and Hydration Characteristics of Cement Pastes Containing Added-calcium Coal Gangue

    LI Dongxu; SONG Xuyan


    The mechanical properties of several kinds of coal gangue calcined with limestone were Researched so as to find the optimum way of calcinations with limestone. Mierostructure and property of hydration process of cement pastes containing added-calcium coal gangue were analyzed by means of scanning electron microscope (SEM) and method of mercury in trusion poremeasurement (MIP), etc. The experiment can approve those results: when proper amounst of gypsum and fluorite were taken as mineralizers in the course of calcinations of added-calcium coal gangue, activity of coal gangue can be effectively improved. The results of mechanical property and structural characteristic such as hydration process, hydration product and microstructure etc. of cement pastes containing added-calcium coal gangue are consistent.

  12. The effect of cement creep and cement fatigue damage on the micromechanics of the cement-bone interface.

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.


    The cement-bone interface provides fixation for the cement mantle within the bone. The cement-bone interface is affected by fatigue loading in terms of fatigue damage or microcracks and creep, both mostly in the cement. This study investigates how fatigue damage and cement creep separately affect

  13. Investigation of the gypsum quality at three full-scale wet flue gas desulphurisation plants

    Hansen, Brian Brun; Kiil, Søren; Johnsson, Jan Erik


    In the present study the gypsum (CaSO4·2H2O) quality at three full-scale wet flue gas desulphurisation (FGD) plants and a pilot plant were examined and compared. Gypsum quality can be expressed in terms of moisture content (particle size and morphology dependent) and the concentration of residual...... or accumulation of fly ash and impurities from the sorbent. The crystal morphology obtained in the pilot plant was columnar with distinct crystal faces as opposed to the rounded shapes found at the full-scale plants. All the investigated full-scale plants consistently produced high quality gypsum (High purity......, low moisture content and low impurity content). An episode concerning a sudden deterioration in the gypsum dewatering properties was furthermore investigated, and a change in crystal morphology, as well as an increased impurity content (aluminium, iron and fluoride), was detected....

  14. Primary Evaporites for the Messinian Salinity Crisis: the shallow gypsum vs. deep dolomite formation paradox solved

    De Lange, Gert J.; Krijgsman, Wout


    The Messinian Salinity Crisis (MSC) is a dramatic event that took place ~ 5.9 Ma ago, and resulted in the deposition of 0.3-3 km thick evaporites at the Mediterranean seafloor. A considerable and long-lasting controversy existed on the modes of their formation. During the CIESM Almeria Workshop a consensus was reached on several aspects. In addition, remaining issues to be solved were identified, such as for the observed shallow gypsum versus deep dolostone deposits for the early phase of MSC. The onset of MSC is marked by deposition of gypsum/sapropel-like alternations, thought to relate to arid/humid climate conditions. Gypsum precipitation only occurred at marginal settings, while dolomite containing rocks have been reported from deeper settings. A range of potential explanations have been reported, most of which cannot satisfactorily explain all observations. Biogeochemical processes during MSC are poorly understood and commonly neglected. These may, however, explain that different deposits formed in shallow versus deep environments without needing exceptional physical boundary conditions for each. We present here a unifying mechanism in which gypsum formation occurs at all shallow water depths but its preservation is mostly limited to shallow sedimentary settings. In contrast, ongoing anoxic organic matter (OM) degradation processes in the deep basin result in the formation of dolomite. Gypsum precipitation in evaporating seawater takes place at 3-7 times concentrated seawater; seawater is always largely oversaturated relative to dolomite but its formation is thought to be inhibited by the presence of dissolved sulphate. Thus the conditions for formation of gypsum exclude those for the formation of dolomite and vice versa. Another process that links the saturation states of gypsum and dolomite is that of OM degradation by sulphate reduction. In stagnant deep water, oxygen is rapidly depleted through OM degradation, then sulphate becomes the main oxidant for OM

  15. Heat transfer and thermal storage behaviour of gypsum boards incorporating micro-encapsulated PCM

    Lai, Chi-ming [Department of Civil Engineering, National Cheng-Kung University, 1, University Road, Tainan City 701 (China); Chen, R.H.; Lin, Ching-Yao [Department of Mechanical Engineering, Southern Taiwan University (China)


    In the application of energy storage and thermal environmental control, PCM (Phase Change Material) is a very promising material choice. This study incorporated mPCM (micro-encapsulated PCM) into gypsum to make mPCM gypsum board and then investigated the physical properties, heat transfer and thermal storage behaviour. The major control parameters are wall temperatures and the weight percentages of mPCM added to the gypsum boards. A melting fraction correlation, reduced from our test data and based on Stefan number (Ste), subcooling (Sb) and Fourier number, is proposed. It shows that case with a higher Ste or Sb can have a higher heat transfer through the hot wall. Thermal storage behaviour of mPCM gypsum boards is then analyzed. (author)

  16. Characterization of gypsum plasterboard with polyurethane foam waste reinforced with polypropylene fibers

    L. Alameda


    Full Text Available Gypsum plasterboard that incorporates various combinations of polyurethane foam waste and polypropylene fibers in its matrix is studied. The prefabricated material was characterized in a series of standardized tests: bulk density, maximum breaking load under flexion stress, total water absorption, surface hardness, thermal properties, and reaction to fire performance. Polypropylene fibers were added to the polyurethane gypsum composites to improve the mechanical behavior of the plasterboard under loading. The results indicate that increased quantities of polymer waste led to significant reductions in the weight/surface ratio, the mechanical strength and the surface hardness of the gypsum, as well as improving its thermal resistance. The polypropylene fibers showed good adhesion to the polymer and the gypsum matrix, which enhanced the mechanical performance and the absorption capacity of these compounds. The non-combustibility test demonstrated the potential of the new material for use in internal linings.

  17. Fossil-fired steam/electric gypsum plant + wallboard plant + powerplant = win-win-win



    The Tennessee Valley Authority has invested in a wall board plant adjacent to its Cumberland power plant to process gypsum slurry. Synmat built the gypsum processing plant to dewater and concentrate the slurry to produce gypsum cake; Temple-Inland build a wallboard plant on 124 acres nearby, the two facilities being linked by conveyor. A 20-ft-high hill of gypsum that had accumulated since 1994 and 1999 when the wallboard plant was built is utilized to meet shortfalls in raw material. The slurry is retrieved from a 10-ft deep water-filled pit that was dug into the stockpile to accept an unmanned floating pump dredge and then pumped through a 6-in line to the Synmat plant. 3 photos.

  18. Coal Combustion Residual Beneficial Use Evaluation: Fly Ash Concrete and FGD Gypsum Wallboard

    This page contains documents related to the evaluation of coal combustion residual beneficial use of fly ash concrete and FGD gypsum wallboard including the evaluation itself and the accompanying appendices

  19. Final Critical Habitat for the Gypsum wild-buckwheat (Eriogonum gypsophilum)

    US Fish and Wildlife Service, Department of the Interior — To provide the user with a general idea of areas where final critical habitat for gypsum wild-buckwheat (Eriogonum gypsophilum) occur based on the description...

  20. Recycling Jorf Lasfar fly ash as an additive to cement

    Hamadi A


    Full Text Available Recycling fly ash is a good example of valorization of waste. It gives a solution the environmental problem by avoiding land filling, and reducing CO2 emission in the atmosphere. In this work we studied the physical-chemical characteristics of Jorf Lasfar fly ash. The parameters investigated were particle size, density, specific surface Blaine, chemical and mineralogical compositions. The techniques used are scanning electronic microscope (SEM, transmission electronic microscope (TEM, X-rays fluorescence (XRF, X-rays diffraction (XRD and atomic spectrometry emission coupled with inductive plasma ICP. We also conducted a study on the mechanical behavior of type CPJ45 cements produced from a combined grinding of clinker, limestone and gypsum. The substitution of a portion of the clinker by different percentages of fly ash was conducted. We noticed that the compression and bending resistances for these mixtures went through a maximum at 28 days with the addition of 7% (by mass of ash. This result showed that the mineral and chemical compositions of this ash conferred a Pozzoulanic power to the cement studied.

  1. Gypsum-induced decay in granite monuments in Northwestern Spain

    Silva Hermo, B.


    Full Text Available One of the most common forms of decay in granite monuments is the detachment of the superficial layer of the stone (plaques, plaquettes and scales. Previous studies of granite monuments in the northwest Iberian Peninsula revealed a direct relation between this type of weathering and the presence of calcium sulphate, and a mechanism whereby the salt causes this type of decay was suggested. In the present study, various hypotheses as regards the origin of the gypsum found in granite monuments are proposed. The study involved analysis of the contents of ions soluble in water, the results of X-ray diffraction analyses and the ratios of CaO/SO3 in samples of stone, mortar and deposits collected from different monuments. It was concluded that in most cases the gypsum originated from old paintworks or/and from the joint mortars, although inputs from other sources cannot be discounted, as discussed

    Una de las formas de deterioro más frecuente en los monumentos graníticos es la separación de la capa superficial de la piedra (placas, plaquetas y escamas. En trabajos anteriores centrados en monumentos del noroeste de la Península Ibérica, se constató la relación directa entre esta forma de alteración y la presencia de sulfato de calcio y se propuso el mecanismo a través del cual esta sal provoca este tipo de deterioro. En este trabajo se plantean varias hipótesis acerca del origen del yeso encontrado en monumentos graníticos. Para ello se comparan los contenidos de iones solubilizados en agua, los resultados de difracción de rayos X y las relaciones OCa/SO3 de muestras de piedra, morteros y depósitos recogidas en diferentes monumentos. Se llega a la conclusión de que en la mayor parte de los casos el yeso procede de antiguas pinturas o de revestimientos superficiales y de los morteros de juntas entre sillares, pero no se puede descartar la contribución de otros aportes, los cuales se discuten también en este artículo.

  2. Rehabilitation of gypsum-mined lands in the Indian desert

    Sharma, K.D.; Kumar, S.; Gough, L.P.


    The economic importance of mining in the Indian Desert is second only to agriculture. Land disturbed by mining, however, has only recently been the focus of rehabilitation efforts. This research assesses the success of rehabilitation plans used to revegetate gypsum mine spoils within the environmental constraints of the north-west Indian hot-desert ecosystem. The rehabilitation plan first examined both mined and unmined areas and established assessments of existing vegetative cover and the quality of native soils and mine spoils. Tests were made on the effect of the use, and conservation, of available water through rainwater harvesting, amendment application (for physical and chemical spoil modification), plant establishment protocols, and the selection of appropriate germ plasm. Our results show that the resulting vegetative cover is capable of perpetuating itself under natural conditions while concurrently meeting the needs of farmers. Although the mine spoils are deficient in organic matter and phosphorus, they possess adequate amounts of all other nutrients. Total boron concentrations (>5.0 mg kg-1) in both the topsail and mine spoil indicate potentially phytotoxic conditions. Electrical conductance of mine spoil is 6-10 times higher than for topsail with a near-neutral pH. Populations of spoil fungi, Azotobactor, and nitrifying bacteria are low. The soil moisture storage in rainwater harvesting plots increased by 8% over the control and 48% over the unmined area. As a result of rehabilitation efforts, mine spoils show a steady buildup in organic carbon, and P and K due to the decomposition of farmyard manure and the contribution of nitrogen fixation by the established leguminous plant species. The rehabilitation protocol used at the site appears to have been successful. Following revegetation of the area with a mixture of trees, shrubs, and grasses, native implanted species have become established. Species diversity, measured in terms of species richness

  3. Design of Cold-Formed Steel Screw Connections with Gypsum Sheathing at Ambient and Elevated Temperatures

    Wei Chen


    Full Text Available Load-bearing cold-formed steel (CFS walls sheathed with double layers of gypsum plasterboard on both sides have demonstrated good fire resistance and attracted increasing interest for use in mid-rise CFS structures. As the main connection method, screw connections between CFS and gypsum sheathing play an important role in both the structural design and fire resistance of this wall system. However, studies on the mechanical behavior of screw connections with double-layer gypsum sheathing are still limited. In this study, 200 monotonic tests of screw connections with single- or double-layer gypsum sheathing at both ambient and elevated temperatures were conducted. The failure of screw connections with double-layer gypsum sheathing in shear was different from that of single-layer gypsum sheathing connections at ambient temperature, and it could be described as the breaking of the loaded sheathing edge combined with significant screw tilting and the loaded sheathing edge flexing fracture. However, the screw tilting and flexing fracture of the loaded sheathing edge gradually disappear at elevated temperatures. In addition, the influence of the loaded edge distance, double-layer sheathing and elevated temperatures is discussed in detail with clear conclusions. A unified design formula for the shear strength of screw connections with gypsum sheathing is proposed for ambient and elevated temperatures with adequate accuracy. A simplified load–displacement model with the post-peak branch is developed to evaluate the load–displacement response of screw connections with gypsum sheathing at ambient and elevated temperatures.

  4. Utilization Alternatives and Potentiality for FGD Gypsum from Coal-Fired Power Plants

    Tian Hezhong; Hao Jiming; Zhao Zhe; Kong Xiangying; Yang Chao; Lu Guangjie; Liu Hanqiang; Xu Fenggang; Chu Xue


    @@ It is estimated that an installed capacity of thermal power units with desulphurization equipment will come up to 40-50 GW by the end of 2020, which affords a good opportunity for opening up and development of the market of the by-product gypsum from thermal power desulphurization. Therefore, it is necessary to research the present situation and restrictive factors in the comprehensive utilization of FGD gypsum.

  5. Authigenic gypsum found in gas hydrate-associated sediments from Hydrate Ridge, the eastern North Pacific

    WANG; Jiasheng; Erwin; Suess; Dirk; Rickert


    Characteristic gypsum micro-sphere and granular mass were discovered by binocular microscope in the gas hydrate-associated sediments at cores SO143-221 and SO143/TVG40-2A respectively on Hydrate Ridge of Cascadia margin, the eastern North Pacific. XRD patterns and EPA analyses show both micro-sphere and granular mass of the crystals have the typical peaks and the typical main chemical compositions of gypsum, although their weight percents are slightly less than the others in the non-gas hydrate-associated marine regions. SEM pictures show that the gypsum crystals have clear crystal boundaries, planes, edges and cleavages of gypsum in form either of single crystal or of twin crystals. In view of the fact that there are meanwhile gas hydrate-associated authigenic carbonates and SO42(-rich pore water in the same sediment cores, it could be inferred reasonably that the gypsums formed also authigenically in the gas hydrate-associated environment too, most probably at the interface between the downward advecting sulfate-rich seawater and the below gas hydrate, which spilled calcium during its formation on Hydrate Ridge. The two distinct forms of crystal intergrowth, which are the granular mass of series single gypsum crystals at core SO143/TVG40-2A and the microsphere of gypsum crystals accompanied with detrital components at core SO143-221 respectively, indicate that they precipitated most likely in different interstitial water dynamic environments. So, the distinct authigenic gypsums found in gas hydrate-associated sediments on Hydrate Ridge could also be believed as one of the parameters which could be used to indicate the presence of gas hydrate in an unknown marine sediment cores.

  6. Research of gypsum binder of phosphogypsum and dry mortar on its basis

    Казимагомедов, Ибрагим Эмирчубанович; Дехтярюк, Ольга Игоревна


    Gypsum binder was received by the method of intensive dehydration and the influence of admixture in phosphogypsum on the hydration process of gypsum binder was researched. Phase composition of phosphogypsum before and after calcination, using XFA, IR-spectroscopy and crystal optic analysis was defined. Dry mortar for plaster of interior walls of buildings on the basis of CaSO4·0,5H2O obtained from phosphogypsum is investigated. Its advantages and physical and chemical characteristics are shown

  7. Mineral resource of the month: hydraulic cement

    van Oss, Hendrik G.


    Hydraulic cements are the binders in concrete and most mortars and stuccos. Concrete, particularly the reinforced variety, is the most versatile of all construction materials, and most of the hydraulic cement produced worldwide is portland cement or similar cements that have portland cement as a basis, such as blended cements and masonry cements. Cement typically makes up less than 15 percent of the concrete mix; most of the rest is aggregates. Not counting the weight of reinforcing media, 1 ton of cement will typically yield about 8 tons of concrete.


    Hasan KAPLAN


    Full Text Available Cement, one of the basic material of construction engineering, has an important place in view of strength and cost of structures. Cement consumption is increasing parallel to development of building construction sector. For cement producers, minimal cost is desired by using new and economical material sources. On the other hand, the controllers and contractors need cheaper, safer and higher strength materials. From this respect cement industry tends to use cement with pozzolan. In Türkiye, cement with pozzolan is produced by adding the pozzolan, which has a large reservoir in the country, in cement in sertain amount. However this type of cement is consumed in the construction sector, sortage of scientific investigation and speculative news on the subject.are worried the users and producers. In this paper, prior to an experimental study on the cements having pozzolan additive, historical development of pozzolan, reservoir of Turkiye, and comparison with portland cement is carried out. Advantages and disadvantages of pozzolan are also discussed in some points.

  9. Cement from magnesium substituted hydroxyapatite.

    Lilley, K J; Gbureck, U; Knowles, J C; Farrar, D F; Barralet, J E


    Brushite cement may be used as a bone graft material and is more soluble than apatite in physiological conditions. Consequently it is considerably more resorbable in vivo than apatite forming cements. Brushite cement formation has previously been reported by our group following the mixture of nanocrystalline hydroxyapatite and phosphoric acid. In this study, brushite cement was formed from the reaction of nanocrystalline magnesium-substituted hydroxyapatite with phosphoric acid in an attempt to produce a magnesium substituted brushite cement. The presence of magnesium was shown to have a strong effect on cement composition and strength. Additionally the presence of magnesium in brushite cement was found to reduce the extent of brushite hydrolysis resulting in the formation of HA. By incorporating magnesium ions in the apatite reactant structure the concentration of magnesium ions in the liquid phase of the cement was controlled by the dissolution rate of the apatite. This approach may be used to supply other ions to cement systems during setting as a means to manipulate the clinical performance and characteristics of brushite cements.

  10. Evaluating portland cement concrete degradation by sulphate exposure through artificial neural networks modeling

    Oliveira, Douglas Nunes de; Bourguignon, Lucas Gabriel Garcia; Tolentino, Evandro, E-mail: [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET-MG), Timoteo, MG (Brazil); Costa, Rodrigo Moyses, E-mail: [Universidade de Itauna, Itauna, MG (Brazil); Tello, Cledola Cassia Oliveira de, E-mail: [Centro de Desenvolvimento da Tecnologia Nucelar (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)


    A concrete is durable if it has accomplished the desired service life in the environment in which it is exposed. The durability of concrete materials can be limited as a result of adverse performance of its cement-paste matrix or aggregate constituents under either chemical or physical attack. Among other aggressive chemical exposures, the sulphate attack is an important concern. Water, soils and gases, which contain sulphate, represent a potential threat to the durability of concrete structures. Sulphate attack in concrete leads to the conversion of the hydration products of cement to ettringite, gypsum, and other phases, and also it leads to the destabilization of the primary strength generating calcium silicate hydrate (C-S-H) gel. The formation of ettringite and gypsum is common in cementitious systems exposed to most types of sulphate solutions. The present work presents the application of the neural networks for estimating deterioration of various concrete mixtures due to exposure to sulphate solutions. A neural networks model was constructed, trained and tested using the available database. In general, artificial neural networks could be successfully used in function approximation problems in order to approach the data generation function. Once data generation function is known, artificial neural network structure is tested using data not presented to the network during training. This paper is intent to provide the technical requirements related to the production of a durable concrete to be used in the structures of the Brazilian near-surface repository of radioactive wastes. (author)


    Pustovgar Andrey Petrovich


    Full Text Available The authors considered the gypsum binder obtained in a kettle SMA-158A in the enterprise LLC “MaykopGipsStroy”. The initial gypsum binder burnt at a temperature of 120 °Сwith the following unloading out of the kettle possessed unstable physical, mechanical and operational characteristics, that’s why the grade of gypsum binder was changed from G4-AII to G5-BII for different lots, which greatly reduced its application in the composition of dry mortars. It was stated, that instability of the features of gypsum binder is determined by the essential underburning of the system, which was characterized by residual content of calcium sulfate dihydrate in amount from 2 to 7 % by weight. In frames of the investigation the authors succeeded in raising the grade of the produced gypsum binder (from G4-5 to G6 due to optimization of the technological parameters of the burning process, as well as to stabilize the composition and features, to lay down temperature and time parameters allowing to control the technological process in order to obtain the gypsum binder with specified characteristics.

  12. Estimating gypsum equirement under no-till based on machine learning technique

    Alaine Margarete Guimarães

    Full Text Available Chemical stratification occurs under no-till systems, including pH, considering that higher levels are formed from the soil surface towards the deeper layers. The subsoil acidity is a limiting factor of the yield. Gypsum has been suggested when subsoil acidity limits the crops root growth, i.e., when the calcium (Ca level is low and/or the aluminum (Al level is toxic in the subsoil layers. However, there are doubts about the more efficient methods to estimate the gypsum requirement. This study was carried out to develop numerical models to estimate the gypsum requirement in soils under no-till system by the use of Machine Learning techniques. Computational analyses of the dataset were made applying the M5'Rules algorithm, based on regression models. The dataset comprised of soil chemical properties collected from experiments under no-till that received gypsum rates on the soil surface, throughout eight years after the application, in Southern Brazil. The results showed that the numerical models generated by rule induction M5'Rules algorithm were positively useful contributing for estimate the gypsum requirements under no-till. The models showed that Ca saturation in the effective cation exchange capacity (ECEC was a more important attribute than Al saturation to estimate gypsum requirement in no-till soils.

  13. Room-temperature electrolytic coloration and spectral properties of natural fibrous gypsum using a pointed anode

    Gu, Hongen, E-mail:; Hao, Xiaoqing; Tian, Pin


    Electrolysis experiments can be performed at room temperature and under various voltages using natural fibrous (NF) gypsum with a pointed anode and a flat cathode. The NF gypsum is colored electrolytically. SO{sub 4}{sup −}, SO{sub 3}{sup −}, SO{sub 2}{sup −}, O{sub 3}{sup −} and O{sup −} defect centers are produced in colored NF gypsum. The characteristic absorption bands of the defect centers are observed in the absorption spectra of the colored NF gypsum. The defect centers come mainly from electric-field-induced decomposition and/or direct electron loss of SO{sub 4}{sup 2−} radicals. Current is measured during electrolytic coloration. Electron exchanges from electron and charged radicals to electrodes induce complete current. -- Highlights: • We expanded the traditional electrolysis method. • Electrolysis experiments are performed at room temperature for the first time. • Natural fibrous gypsum is colored electrolytically. • SO{sub 4}{sup −}, SO{sub 3}{sup −}, SO{sub 2}{sup −}, O{sub 3}{sup −} and O{sup −} defect centers are produced in colored gypsum. • Defect centers come from electron transfers and decomposition of SO{sub 4}{sup 2−} radicals.

  14. Oxidation of North Dakota scrubber sludge for soil amendment and production of gypsum. Final report

    Hassett, D.J.; Moe, T.A.


    Cooperative Power`s Coal Creek Station (CCS) the North Dakota Industrial Commission, and the US Department of Energy provided funds for a research project at the Energy and Environmental Research Center. The goals of the project were (1) to determine conditions for the conversion of scrubber sludge to gypsum simulating an ex situ process on the laboratory scale; (2) to determine the feasibility of scaleup of the process; (3) if warranted, to demonstrate the ex situ process for conversion on the pilot scale; and (4) to evaluate the quality and handling characteristics of the gypsum produced on the pilot scale. The process development and demonstration phases of this project were successfully completed focusing on ex situ oxidation using air at low pH. The potential to produce a high-purity gypsum on a commercial scale is excellent. The results of this project demonstrate the feasibility of converting CCS scrubber sludge to gypsum exhibiting characteristics appropriate for agricultural application as soil amendment as well as for use in gypsum wallboard production. Gypsum of a purity of over 98% containing acceptable levels of potentially problematic constituents was produced in the laboratory and in a pilot-scale demonstration.

  15. US cement industry

    Nisbet, M.A.


    This paper describes the cement and concrete industry, and provides data on energy use and carbon dioxide emissions. The potential impact of an energy tax on the industry is briefly assessed. Opportunities identified for reducing carbon dioxide emissions include improved energy efficiency, alternative fuels, and alternative materials. The key factor in determining CO{sub 2} emissions is the level of domestic production. The projected improvement in energy efficiency and the relatively slow growth in domestic shipments indicate that CO{sub 2} emissions in 2000 should be about 5% above the 1990 target. However, due to the cyclical nature of cement demand, emissions will probably be above target levels during peak demand and below target levels during demand troughs. 7 figs., 2 tabs.

  16. Performance of Cement Containing Laterite as Supplementary Cementing Material

    Abbas Bukhari, Z. S.


    Full Text Available The utilization of different industrial waste, by-products or other materials such as ground granulated blast furnace slag, silica fume, fly ash, limestone, and kiln dust, etc. as supplemen- tary cementing materials has received considerable attention in recent years. A study has been conducted to look into the performance of laterite as Supplementary Cementing Materials (SCM. The study focuses on compressive strength performance of blended cement containing different percentage of laterite. The cement is replaced accordingly with percentage of 2 %, 5 %, 7 % and 10 % by weight. In addition, the effect of use of three chemically different laterites have been studied on physical performance of cement as in setting time, Le-Chatlier expansion, loss on ignition, insoluble residue, free lime and specifically compressive strength of cement cubes tested at the age of 3, 7, and 28 days. The results show that the strength of cement blended with laterite as SCM is enhanced. Key words: Portland cement, supplementary cementing materials (SCM, laterite, compressive strength KUI – 6/2013 Received January 4, 2012 Accepted February 11, 2013

  17. Physical, chemical and radioactive characterization of co-products from titanium dioxide industry for valorization in the cement industry; Caracterizacion fisico-quimica y radiactiva de los sub-productos provenientes de la industria de dioxido de titanio para su valorizacion en la industria del cemento: implicaciones radiologicas.

    Gazquez, M.J.; Mantero, J.; Bolivar, J.P.; Garcia-Tenorio, R.; Vaca, F.


    The present study was conducted to characterize the raw materials (ilmenite and slag), waste (red gypsum) and several co-products (sulphate monohydrate and sulphate heptahydrated) form the titanium dioxide industry in relation to their elemental composition (major, minor and trace elements), granulometry, mineralogy, microscopic morphology, physical composition and radioactive content in order to apply this knowledge in the valorization of the co-products in the fields such a as construction, civil engineering, etc. In particular, the main properties of cements produced with different proportions of red gypsum were studied, and the obtained improvements, in relation to Ordinary Portland Cements (OPC) were evaluated. It was also demonstrated that the levels of pollutants and the radioactive content in the produced RG cements, remain within the regulated safety limits. (Author). 38 refs.

  18. Physical, chemical and radioactive characterization of co-products from titanum dioxide industry for valorization in the cement industry; Caracterizacion fisico-quimica y radiactiva de los sub-productos provenientes de la industria de dioxido de titanio para su valorizacion en la industria del cemento: implicaciones radiologicas.

    Gazquez, M.J.; Mantero, J.; Bolivar, J.P.; Garcia-Tenorio, R.; Vaca, F.


    The present study was conducted to characterize the raw materials (ilmenite and slag), waste (red gypsum) and several co-products (sulphate monohydrate and sulphate heptahydrated) form the titanum dioxide industry in relation to their elemental composition (major, minor and trace elements), granulometry, mineralogy, microscopic morphology, physical composition and radioactive content in order to apply this knowledge in the valorization of the co-products in the fields sucha as construction, civil engineering, etc. In particular, the main properties of cements produced with different proportions of red gypsum were studied, and the obtained improvements, in relation to Ordinary Portland Cements (OPC) were evaluated. It was also demonstrated that the levels of pollutants and the radioactive content in the produced RG cements, remain within the regulated safety limits. (Author). 38 refs.

  19. Leachable characteristics of arsenical borogypsum wastes and their potential use in cement production.

    Alp, Ibrahim; Deveci, Haci; Süngün, Y Halil; Yazici, Ersin Y; Savaş, Mehmet; Demirci, Songül


    In this study; the potential use of arsenical borogypsum wastes (ABW) as a set retarder in cement industry was investigated. The comparative performances of arsenical borogypsum wastes (ABW) and natural gypsum samples (NG1 and NG2) at different proportions in the range of 3-8 wt % were tested based on compressive strength over 1, 2, 7, and 28 days and setting times. The use of ABW was observed to lead to a somewhat slower rate of development of strength of the mortar samples than those of NG1 and NG2 during the curing period of 7 days. This is the indication of the effectiveness of ABW as a set retarder. The 28-day compressive strength of mortars tended to decrease with the addition or increasing the proportion of ABW, beyond 5 wt % in particular. The data for setting times of the cement products confirmed set retarding characteristics of ABW with an initial setting time of 90-120 min at 3-5 wt % dosage, which conforms to the desired setting time of > or = 60 min for CEM I (42.5 N) type cement (TS EN 197-1). Leachability tests (TCLP and SPLP) have also shown that ABW can be classified as a nonhazardous waste; but it can readily release metals such as As and Mn, in particular, whereas the mortar samples containing ABW-cement clinker present no environmental concern with its remarkably reduced leachability.

  20. Advances in Glass Ionomer Cements

    KAYA, Dt. Tuğba; TİRALİ, Yard. Doç. Dr. Resmiye Ebru


    In recent years there have been a number of innovations and developments with respect to glass ionomer cements and their applications in clinical dentistry. This article considers some of the recent outstanding studies regarding the field of glass ionomer cement applications, adhesion and setting mechanisms, types, advantage and disadvantages among themselves and also to enhance the physical and antibacterial properties under the title of 'Advances in Glass Ionomer Cements'. As their biologic...

  1. Cement penetration after patella venting.

    Jones, Christopher W; Lam, Li-On; Butler, Adam; Wood, David J; Walsh, William R


    There is a high rate of patellofemoral complications following total knee arthroplasty. Optimization of the cement-bone interface by venting and suction of the tibial plateau has been shown to improve cement penetration. Our study was designed to investigate if venting the patella prior to cementing improved cement penetration. Ten paired cadaver patellae were allocated prior to resurfacing to be vented or non-vented. Bone mineral density (BMD) was measured by DEXA scanning. In vented specimens, a 1.6 mm Kirschner wire was used to breach the anterior cortex at the center. Specimens were resurfaced with standard Profix instrumentation and Versabond bone cement (Smith and Nephew PLC, UK). Cement penetration was assessed from Faxitron and sectioned images by a digital image software package (ImageJ V1.38, NIH, USA). Wilcoxon rank sum test was used to assess the difference in cement penetration between groups. The relationship between BMD and cement penetration was analyzed by Pearson correlation coefficient. There was a strong negative correlation between peak BMD and cement penetration when analyzed independent of experimental grouping (r(2)=-0.812, p=0.004). Wilcoxon rank sum testing demonstrated no significant difference (rank sum statistic W=27, p=0.579) in cement penetration between vented (10.53%+/-4.66; mean+/-std dev) and non-vented patellae (11.51%+/-6.23; mean+/-std dev). Venting the patella using a Kirschner wire does not have a significant effect on the amount of cement penetration achieved in vitro using Profix instrumentation and Versabond cement.

  2. [Haemotoxicity of dental luting cements].

    Anders, A; Welker, D


    A glass ionomer luting cement (AquaCem) shows a relatively low haemolytic activity in comparison with two zinc phosphate cements. Especially the initial irritation by this cement is smaller. Although it is possible that AquaCem particularly, in unfavourable cases, may damage the pulpa dentin system; this is due to the slowly decrease of the haemolytic activity with increasing of the probes. We found that Adhesor showed in dependence of the batches a varying quality.

  3. Petrography of gypsum-bearing facies of the Codó Formation (Late Aptian, Northern Brazil

    Jackson D.S. Paz


    Full Text Available An original and detailed study focusing the petrography of evaporites from the Late Aptian deposits exposed in the eastern and southern São Luís-Grajaú Basin is presented herein, with the attempt of distinguishing between primary and secondary evaporites, and reconstructing their post-depositional evolution. Seven evaporites phases were recognized: 1. chevron gypsum; 2. nodular to lensoidal gypsum or anhydrite; 3. fibrous to acicular gypsum; 4. mosaic gypsum; 5. brecciated gypsum or gypsarenite; 6. pseudo-nodular anhydrite or gypsum; and 7. rosettes of gypsum. The three first phases of gypsum display petrographic characteristics that conform to a primary nature. The fibrous to acicular and mosaic gypsum were formed by replacement of primary gypsum, but their origin took place during the eodiagenesis, still under influence of the depositional setting. These gypsum morphologies are closely related to the laminated evaporites, serving to demonstrate that their formation was related to replacements that did not affect the primary sedimentary structures. The pseudo-nodular anhydrite or gypsum seems to have originated by mobilization of sulfate-rich fluids during burial, probably related to halokinesis. The rosettes of gypsum, which intercept all the other gypsum varieties, represent the latest phase of evaporite formation in the study area, resulting from either intrastratal waters or surface waters during weathering.Neste trabalho, é apresentado um estudo original e detalhado enfocando os aspectos petrográficos dos evaporitos de depósitos aptianos superiores expostos no sul e leste da Bacia de São Luís-Grajaú. O objetivo é o estabelecimento de critérios que permitam distinguir entre evaporitos primários e secundários, além da reconstrução de sua evolução pós-deposicional. Sete fases de evaporitos foram reconhecidas: 1. gipsita em chevron; 2. gipsita ou anidrita nodular a lenticular; 3. gipsita fibrosa a acicular; 4. gipsita em

  4. Feasibility study of the Portland cement industry waste for the reduction of energy consumption

    Bernardo, Ana Carla de Souza Masselli; Junqueira, Mateus Augusto F. Chaib; Jorge, Ariosto Bretanha; Silva, Rogerio Jose da [Universidade Federal de Itajuba (UNIFEI), MG (Brazil). Institute of Mechanical Engineering]. E-mails:;;;


    The Portland cement industry demand a high specific consumption of energy for the production of the clinker. The energy consumption for clinker production varies between 3000 and 5300 kJ/kg of produced clinker. The clinker is produced by blending of different raw materials in order t o achieve precise chemical proportions of lime, silica, alumina and iron in the finished product and by burning them at high temperatures. The Portland cement is a mixture of clinker, gypsum and other materials. Due to need of high temperatures, tradition ally the fuels used in the cement industry are mineral coal, fuel oil, natural gas and petroleum coke. The fuel burning in high temperature leads to the formation of the pollutant thermal NOx. The level of emissions of this pollutant is controlled by environmental law, thus the formation of pollutants in process need be controlled. Moreover, industrial waste has been used by Portland cement industries as a secondary fuel through a technique called co -processing. Materials like waste oils, plastics, waste tyres and sewage sludge are often proposed as alternative fuels for the cement industry. The residues can be introduced as secondary fuel or secondary raw material. For energy conservation in the process, mineralizers are added during the process production of the clinker. The mineralizers promote certain reactions which decrease the temperature in the kiln and improve the quality of the clinker. The adequate quantity of constituents in production process is complex, for maintain in controlled level, the quality of final product, the operational conditions of kiln, and the pollutant emissions. The purpose of the present work is to provide an analysis of an optimal production point through of the optimization technique considering, the introduction of the fuels, industrial wastes as secondary fuels, and raw materials, for the reduction of energy in the process of Portland cement production. (author)

  5. Influence of different levels of gypsum on growth, herb and essential oil yields of lemongrass

    Pandu Sastry Kakaraparthi


    Full Text Available The essential oil obtained from lemongrass (Cymbopogon flexuosus is an industrially important essential oil being used widely for the isolation of citral which can be converted into ionones. Improving the economic yield of the aromatic grass lemongrass is part of the rural development mandate of Central Institute of Medicinal and Aromatic Plants (CSIR-CIMAP. Salt affected soils occupy wide regions scattered all over the world and India has considerable salt-affected soils. The experiment was conducted on a red sandy loam soil at the research farm of CSIR-CIMAP, Hyderabad, India with five levels of gypsum as treatments(0-4 tons/ha.The soils of the experimental site are on the leeward side of an industrial area and the ground water has become saline due to industrial effluents. A field experiment was initiated to study the influence of gypsum in soil remediation and its influence on the growth and herb yield of lemongrass. Due to application of four tons of gypsum /ha a progressive decrease in the soil pH was observed and soil pH also decreased with advancement in time and it decreased from 7.73 to 7.40 at 120 days after planting due to gypsum application. EC increased progressively in all the treatments with time. The increase was less due to gypsum treatments. Similar trend was noticed in case of bicarbonate content of the soil and carbonates were absent in the soil. Gypsum application resulted in increased herb and essential oil yield of lemongrass due to better growth of plants(plant height, number of leaves /plant , number of tillers / clump and weight of plant / clump and the optimum dose of gypsum required is four tons/ha.

  6. Phosphate based oil well cements

    Natarajan, Ramkumar

    The main application of the cement in an oil well is to stabilize the steel casing in the borehole and protect it from corrosion. The cement is pumped through the borehole and is pushed upwards through the annulus between the casing and the formation. The cement will be exposed to temperature and pressure gradients of the borehole. Modified Portland cement that is being used presently has several shortcomings for borehole sealant. The setting of the Portland cement in permafrost regions is poor because the water in it will freeze even before the cement sets and because of high porosity and calcium oxide, a major ingredient it gets easily affected by the down hole gases such as carbon dioxide. The concept of phosphate bonded cements was born out of considerable work at Argonne National Laboratory (ANL) on their use in stabilization of radioactive and hazardous wastes. Novel cements were synthesized by an acid base reaction between a metal oxide and acid phosphate solution. The major objective of this research is to develop phosphate based oil well cements. We have used thermodynamics along with solution chemistry principles to select calcined magnesium oxide as candidate metal oxide for temperatures up to 200°F (93.3°C) and alumina for temperatures greater than 200°F (93.3°C). Solution chemistry helped us in selecting mono potassium phosphate as the acid component for temperatures less than 200°F (93.3°C) and phosphoric acid solution greater than 200°F (93.3°C). These phosphate cements have performance superior to common Portland well cements in providing suitable thickening time, better mechanical and physical properties.

  7. Thermal Shock-resistant Cement

    Sugama T.; Pyatina, T.; Gill, S.


    We studied the effectiveness of sodium silicate-activated Class F fly ash in improving the thermal shock resistance and in extending the onset of hydration of Secar #80 refractory cement. When the dry mix cement, consisting of Secar #80, Class F fly ash, and sodium silicate, came in contact with water, NaOH derived from the dissolution of sodium silicate preferentially reacted with Class F fly ash, rather than the #80, to dissociate silicate anions from Class F fly ash. Then, these dissociated silicate ions delayed significantly the hydration of #80 possessing a rapid setting behavior. We undertook a multiple heating -water cooling quenching-cycle test to evaluate the cement’s resistance to thermal shock. In one cycle, we heated the 200 and #61616;C-autoclaved cement at 500 and #61616;C for 24 hours, and then the heated cement was rapidly immersed in water at 25 and #61616;C. This cycle was repeated five times. The phase composition of the autoclaved #80/Class F fly ash blend cements comprised four crystalline hydration products, boehmite, katoite, hydrogrossular, and hydroxysodalite, responsible for strengthening cement. After a test of 5-cycle heat-water quenching, we observed three crystalline phase-transformations in this autoclaved cement: boehmite and #61614; and #61543;-Al2O3, katoite and #61614; calcite, and hydroxysodalite and #61614; carbonated sodalite. Among those, the hydroxysodalite and #61614; carbonated sodalite transformation not only played a pivotal role in densifying the cementitious structure and in sustaining the original compressive strength developed after autoclaving, but also offered an improved resistance of the #80 cement to thermal shock. In contrast, autoclaved Class G well cement with and without Class F fly ash and quartz flour failed this cycle test, generating multiple cracks in the cement. The major reason for such impairment was the hydration of lime derived from the dehydroxylation of portlandite formed in the autoclaved

  8. Origin of zoning within dedolomite and calcitized gypsum of the Mississippian Arroyo Penasco Group

    Ulmer, D.S.


    The Mississippian Arroyo Penasco Group carbonates are the oldest Paleozoic rocks present in north-central New Mexico. These supratidal to shallow,subtidal sediments exhibit complex diagenetic fabrics produced by periods of pre-Pennsylvanian subaerial exposure. Both extensive recrystallization of the Espiritu Santo carbonates and brecciation of the overlying Macho Member of the Tererro Formation resulted from an extended period of Mississippian subaerial exposure of broad, low-relief tidal flats. Cathodoluminescent petrography indicates that the recrystallized limestones consist of calcite pseudomorphs of dolomite and gypsum. Dedolomite and calcitized gypsum crystals, with /sup 13/C//sup 12/C ratios of -2 to +1.5% PDB, range from highly zoned to uniformly luminescent. Electron microprobe analyses reveals variable Mn and Fe contents across the pseudomorphs which are responsible for differences in observed luminosity. These features are interpreted to reflect a period of subaerial exposure after deposition of Macho Member sediments, which caused dissolution of gypsum and dolomite by sulfate and Mg depleted meteoric fluids and produced the collapse breccia. Preservation of zoning within some pseudomorphs required simultaneous dissolution of gypsum and dolomite and precipitation of calcite. C-isotope data indicates a meteoric to mixed phreatic origin for pore fluids which precipitated calcite; repetitive zoning within dolomite and gypsum pseudomorphs is indicative of interactions between marine and meteoric phreatic fluids in the intertidal environment.

  9. The influence of composition of gypsum plaster on its technological properties

    M. Pawlak


    Full Text Available Gypsum plasters used in art and precision foundry always are the composition of gypsum-silica-cristobalite. It is necessary considering the specifity of plaster during heating stage. Plaster undergoes then, structural transformations causing significant variations of its volume which are nonuniform and proceed with different intensity. The content of silica and cristobalite reduces dimensional variations of setted gypsum plaster what increases dimensional accuracy and significant stresses reduction limiting the possibility of mould cracks occurrence during heating.The influence of cristobalite and silica addition on basic gypsum plaster properties like setting time, dimensional changes after setting, bending strength and permeability in raw and heat treated state are presented in this paper. Experiments were done for mixes containing 30÷70% of the gypsum. It was proven that cristobalite has the biggest influence on the bounding time and expansion of the sandmix and the strength and permeability do not depend on the type of additions and only on theirs total amount in the composition.

  10. Crack Coalescence in Molded Gypsum and Carrara Marble: Part 2—Microscopic Observations and Interpretation

    Wong, L. N. Y.; Einstein, H. H.


    Experimental uniaxial compression loading tests were conducted on molded gypsum and Carrara marble prismatic specimens to study the cracking and coalescence processes between pre-existing artificial flaws. The study showed that material had an influence on the cracking and coalescence processes (see the companion paper in this issue). As reported in the companion paper, one of the pronounced features as observed in the high-speed video recordings was the development of macroscopic white patches prior to the development of observable cracks in marble, but not in gypsum. This paper (part 2) deals with the microscopic aspects of the study. Specifically, the scanning electron microscope (SEM) and the environmental scanning electron microscope (ESEM) imaging techniques were used to study the microscopic development of white patches and their evolution into macroscopic tensile cracks and shear cracks in marble, and the microscopic initiation of hair-line tensile cracks and their evolution into macroscopic tensile cracks in gypsum. The microscopic imaging study in marble showed that the white patches were associated with extensive microcracking zones (process zones), while the extent of process zone development in gypsum was limited. The comparison of the macroscopic and microscopic results indicates that the different extent of microcracking zone development, related to the material textural properties, is a key factor leading to different macroscopic cracking behavior in gypsum and marble.

  11. Magnesium oxychloride cement concrete

    A K Misra; Renu Mathur


    The scope of magnesium oxychloride (MOC) cement in concrete works has been evaluated. MOC cement concrete compositions of varying strengths having good placing and finishing characteristics were prepared and investigated for their compressive and flexural strengths, -values, abrasion resistance etc. The durability of MOC concrete compositions against extreme environmental conditions viz. heating–cooling, freezing–thawing, wetting–drying and penetration and deposition of salts etc were investigated. The results reveal that MOC concrete has high compressive strength associated with high flexural strength and the ratio of compressive to flexural strength varies between 6 and 8. The elastic moduli of the compositions studied are found to be 23–85 GPa and the abrasion losses between 0.11 and 0.20%. While alternate heating–cooling cycles have no adverse effect on MOC concrete, it can be made durable against freezing–thawing and the excessive exposure to water and salt attack by replacing 10% magnesium chloride solution by magnesium sulphate solution of the same concentration.

  12. Cemented total hip arthroplasty with Boneloc bone cement.

    Markel, D C; Hoard, D B; Porretta, C A


    Boneloc cement (WK-345, Biomet Inc, Warsaw, Ind) attempted to improve cement characteristics by reducing exotherm during polymerization, lowering residual monomer and solubility, raising molecular weight, and lowering airborne monomer and aromatic amines. To study the efficacy of this cement, a selected group of 20 patients were prospectively enrolled and followed up after hip arthroplasty. All components were cemented. During the enrollment period, approximately 70 other hip arthroplasties were performed. Clinical evaluation was based on the Harris hip score. Radiographic evaluation was based on assessment of position of the components, subsidence, and/or presence of radiolucencies. Patients had follow-up for an average of 42 months (11 to 58 months); 1 was lost to follow-up. Of these, 7 (35%) had failure at last follow-up. Despite its initial promise, Boneloc cement had an unacceptably high failure rate over a relatively short follow-up period and is not recommended for use. Despite the longevity and odor toxicity problems with conventional bone cement, new cement technologies must be approached with caution.

  13. Natural Radionuclide Contents in Raw Materials and the Aggregate Finished Product from Dangote Cement Plc, Obajana, Kogi State, North Central Nigeria

    J.O. Ajayi


    Full Text Available Assessment of gamma ray activity in raw materials and the end product in Dangote Cement from Dangote Cement Plc, Obajana and Kogi State has been investigated in this study. Gamma ray spectrometry that possesses scintillation detector was used to analyze the samples collected from the company. Samples collected as raw materials are limestone, clay, gypsum and laterite and cement as finished product. The 40K, 238U, 232Th activity concentration were detected. The concentration of 40K range from 4649±366 to 0±65 Bq/Kg with highest value in limestone and lowest in laterite. The 238U concentration is highest in gypsum range from 696±233 to 41±27 Bq/Kg in laterite. 232Th activity is below detectable limit in all the raw materials but it has activity concentration of 40±26 Bq/Kg in the finished product which may be traceable to the fact that some finished additives are present which are not in the basic raw materials of this cement under investigation. It is concluded that the natural radionuclide measured for 40K, 238U and 232Th has mean activities of 2189.75±219.5, 331.25±132.25 and 0±31 Bq/Kg respectively, while its corresponding mean absorbed dose rate in air at 1 m above the ground was calculated to be 235.61 nGy/h or 2.064 mSv/y and the aggregate finished product (cement has absorbed dose rate of 342.22 nGy/h and an effective dose equivalent of 2.998 mSv/y. The calculated absorbed doses in nGy/h and mSv/y shows that Dangote cement under consideration has higher activities of the isotopes than the permissible level suggested by ICRP (80 nGy/h or 0.7 mSv/y

  14. Analysis of cubic and orthorhombic C3A hydration in presence of gypsum and lime

    Kirchheim, A. P.


    Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) have been used to study the microstructural changes and phase development that take place during the hydration of cubic (pure) and orthorhombic (Na-doped) tricalcium aluminate (C3A) and gypsum in the absence and presence of lime. The results demonstrate that important differences occur in the hydration of each C3A polymorph and gypsum when no lime is added; orthorhombic C3A reacts faster with gypsum than the cubic phase, forming longer ettringite needles; however, the presence of lime slows down the formation of ettringite in the orthorhombic sample. Additional rheometric tests showed the possible effects on the setting time in these cementitious mixes.

  15. The effect of magnesium on partial sulphate removal from mine water as gypsum.

    Tolonen, Emma-Tuulia; Rämö, Jaakko; Lassi, Ulla


    The aim of this research was to investigate the effect of magnesium on the removal efficiency of sulphate as gypsum from mine water. The precipitation conditions were simulated with MINEQL + software and the simulation results were compared with the results from laboratory jar test experiments. Both the simulation and the laboratory results showed that magnesium in the mine water was maintaining sulphate in a soluble form as magnesium sulphate (MgSO4) at pH 9.6. Thus magnesium was preventing the removal of sulphate as gypsum (CaSO4·2H2O). However, change in the lime precipitation pH from 9.6 to 12.5 resulted in magnesium hydroxide (Mg(OH)2) precipitation and improved sulphate removal. Additionally, magnesium hydroxide could act as seed crystals for gypsum precipitation or co-precipitate sulphate further enhancing the removal of sulphate from mine water. Copyright © 2015 Elsevier Ltd. All rights reserved.


    CHUMAK Anastasia Gennadievna


    Full Text Available The aim of this work is to carry out a number of studies in the area of nanomodi­fication of gypsum binder matrix and to investigate the influence of multilayer carbon nanotubes on the structure, physical and mechanical properties of obtained compos­ites. The study of the gypsum binders structure formation mechanisms with the use of nanoadditives makes it possible to control the production processes of gypsum materi­als and articles with the given set of properties. The main tasks of the binder nanomodification are: even distribution of carbon nanostructures over the whole volume of material and provision of stability for the nanodimensional modifier during production process of the construction composite.

  17. Compartmentalization of gypsum and halite associated with cyanobacteria in saline soil crusts.

    Canfora, Loredana; Vendramin, Elisa; Vittori Antisari, Livia; Lo Papa, Giuseppe; Dazzi, Carmelo; Benedetti, Anna; Iavazzo, Pietro; Adamo, Paola; Jungblut, Anne D; Pinzari, Flavia


    The interface between biological and geochemical components in the surface crust of a saline soil was investigated using X-ray diffraction, and variable pressure scanning electron microscopy in combination with energy dispersive X-ray spectrometry. Mineral compounds such as halite and gypsum were identified crystallized around filaments of cyanobacteria. A total of 92 genera were identified from the bacterial community based on 16S gene pyrosequencing analysis. The occurrence of the gypsum crystals, their shapes and compartmentalization suggested that they separated NaCl from the immediate microenvironment of the cyanobacteria, and that some cyanobacteria and communities of sulfur bacteria may had a physical control over the distinctive halite and gypsum structures produced. This suggests that cyanobacteria might directly or indirectly promote the formation of a protective envelope made of calcium and sulfur-based compounds.

  18. Grout cement. ; Grout cement to fill ground/grout cement to fill cracks. Chunyuyo cement. ; Jiban chunyuyo cement /hibiware chunyuyo cement

    Okaue, H. (Nittetsu Cement Co. Ltd., Hokkaido (Japan))


    Ground grout cement is grouted into the ground under high pressure in high water ratio (100 to 1000%) in the form of milk differing from concrete in terms of the water-cement ratio. The grouted milk is governed by characteristics of the cement the milk itself possesses, resulting in variable grouting modes, which are divided in fracture grouting, permeation grouting and boundary grouting. Their applications include cutting off of water in dams, ground reinforcement, prevention of water gushing in tunnel excavation, natural ground reinforcement, improvement of sandy soil and prevention of its collapse, and stabilization of ground for urban civil engineering works such as subway, water supply and sewerage constructions. Grout cement to fill cracks in concrete structures is so grouted into cracks that the slurry fills up contiguous cracks to a certain level and goes upward while pushing out air or water existing in the cracks. The slurry filled into the cracks solidifies and hardens while being absorbed into the concrete, and finally integrates with the concrete. The grout cement is used to rework such concrete structures as dams, tunnels, and bridge bases. 6 figs., 4 tabs.

  19. 利用原状脱硫石膏制备高强耐水新型建材%Preparation of High-strength and Water-resistant New Buiding Materials by FGD Gypsum

    林海燕; 阳勇福; 郭献军; 王晓峰


    以原状脱硫石膏、拜尔法赤泥、矿渣等为主要原料,水泥熟料作为激发剂,制备高强耐水建筑试块,研究自然养护和75℃高温养护条件下试块的抗压强度及耐水性.结果表明,水泥熟料的加入促进了石膏胶凝材料的水化速度,自然养护和蒸汽养护下,试块都具有较高强度,14d抗压强度均大于20 MPa; 75℃高温养护明显促进了胶凝材料体系的水化进程.石膏胶凝试块软化系数高,耐水性良好;自然养护条件下,随着水泥熟料用量的增加,二次钙矾石生成量增大,软化系数降低,耐水性变差;高温养护早期水化充分,强度较高,且二次钙矾石生成较少,试块软化系数稳定且保持较高水平.%The high strength and water resistant blocks were produced from FGD gypsum,Bayer red mud,slag and cement clinker,and compressive strength and water resistance under the natural conservation and 75 ℃C steam curing condition were studied.The results showed that the gypsum cementitious material hydration speed was promoted when cement clinker was added.Whether natural or steam maintenance,blocks have higher strength,compressive strength of 14 d is above 20 MPa.The cementitious material hydration process is promoted evidently on steam curing condition.The softening coefficient of gypsum cementitious block is high,and water resistance is very good.On natural curing condition,delayed ettringite formation is increasing with the increase of the content of cement clinker,but softening coefficient and water resistance decreases.On steam curing condition,early hydration is very sufficient,and compressive strength is high,the delayed ettringite formation is less,the softening coefficient is high and stable.

  20. 21 CFR 888.4200 - Cement dispenser.


    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027)...

  1. LCA of Recycling Options for Gypsum from Construction and Demolition Waste

    Butera, Stefania; Møller, Jacob; Christensen, Thomas Højlund


    Large amounts of gypsum waste are annually produced from the construction and demolition sector. Its landfilling is becoming more and more expensive due to stricter EU regulations, while its recycling together with the rest of construction and demolition waste might be hampered due to technical...... restrictions; source separation, however, makes gypsum waste recycling feasible. Different alternatives for recycling exist, but their overall environmental impacts have never been quantified and compared in details. This study investigates from a life cycle perspective the environmental impacts of two...

  2. Gypsum addition to soils contaminated by red mud: implications for aluminium, arsenic, molybdenum and vanadium solubility.

    Lehoux, Alizée P; Lockwood, Cindy L; Mayes, William M; Stewart, Douglas I; Mortimer, Robert J G; Gruiz, Katalin; Burke, Ian T


    Red mud is highly alkaline (pH 13), saline and can contain elevated concentrations of several potentially toxic elements (e.g. Al, As, Mo and V). Release of up to 1 million m(3) of bauxite residue (red mud) suspension from the Ajka repository, western Hungary, caused large-scale contamination of downstream rivers and floodplains. There is now concern about the potential leaching of toxic metal(loid)s from the red mud as some have enhanced solubility at high pH. This study investigated the impact of red mud addition to three different Hungarian soils with respect to trace element solubility and soil geochemistry. The effectiveness of gypsum amendment for the rehabilitation of red mud-contaminated soils was also examined. Red mud addition to soils caused a pH increase, proportional to red mud addition, of up to 4 pH units (e.g. pH 7 → 11). Increasing red mud addition also led to significant increases in salinity, dissolved organic carbon and aqueous trace element concentrations. However, the response was highly soil specific and one of the soils tested buffered pH to around pH 8.5 even with the highest red mud loading tested (33 % w/w); experiments using this soil also had much lower aqueous Al, As and V concentrations. Gypsum addition to soil/red mud mixtures, even at relatively low concentrations (1 % w/w), was sufficient to buffer experimental pH to 7.5-8.5. This effect was attributed to the reaction of Ca(2+) supplied by the gypsum with OH(-) and carbonate from the red mud to precipitate calcite. The lowered pH enhanced trace element sorption and largely inhibited the release of Al, As and V. Mo concentrations, however, were largely unaffected by gypsum induced pH buffering due to the greater solubility of Mo (as molybdate) at circumneutral pH. Gypsum addition also leads to significantly higher porewater salinities, and column experiments demonstrated that this increase in total dissolved solids persisted even after 25 pore volume replacements. Gypsum

  3. Building on previous OSL dating techniques for gypsum: a case study from Salt Basin playa, New Mexico and Texas

    Mahan, Shannon; Kay, John


    The long term stability and reliability of the luminescence signal for gypsum has not been well documented or systematically measured until just recently. A review of the current literature for luminescence dating of gypsum is compiled here along with original efforts at dating an intact and in-situ bed of selenite gypsum at Salt Basin Playa, New Mexico and Texas. This effort differs from other documented luminescence dating efforts because the gypsum is not powdery or redistributed from its original growth patterns within the playa basin but is instead of a crystalline form. Sixteen ages from eight cores were ultimately produced with seven of the ages coming from rare detrital quartz encased in or with the gypsum crystals while the remaining ages are from the crystalline gypsum. As far as can be ascertained, the quartz was measured separately from the gypsum and no contaminants were noted in any of the aliquots. Some basic and preliminary tests of signal stability were measured and found to be mitigated by lessening of pre-heat protocols. Ages ranged from 8 ka to 10 ka in the shallow cores and 16 ka to 22 ka in the deeper cores. These ages will be useful in determining rates of gypsum growth within a sequence of evaporates which, in turn, will help to better document historic rates of evaporation and thus estimate, with more precision, the corresponding annual evaporation rates.

  4. Evaluation of Synthetic Gypsum Recovered via Wet Flue-Gas Desulfurization from Electric Power Plants for Use in Foundries

    R. Biernacki


    Full Text Available This article investigates possible use of waste gypsum (synthetic, recovered via flue-gas desulfurization from coal-fired electric powerplants, in foundries. Energy sector, which in Eastern Europe is mostly composed from coal-fired electric power plants, is one of the largestproducers of sulfur dioxide (SO2.In order to protect the environment and reduce the amount of pollution flue-gas desulfurization (FGD is used to remove SO2 fromexhaust flue gases of fossil-fuel power plants. As a result of this process gypsum waste is produced that can be used in practicalapplications.Strength and permeability tests have been made and also in-depth analysis of energy consumption of production process to investigateways of preparing the synthetic gypsum for casting moulds application. This paper also assesses the chemical composition, strength andpermeability of moulds made with synthetic gypsum, in comparison with moulds made with traditional GoldStar XL gypsum and withceramic molds. Moreover examination of structure of synthetic gypsum, the investigations on derivatograph and calculations of energyconsumption during production process of synthetic gypsum in wet flue-gas desulfurization were made.After analysis of gathered data it’s possible to conclude that synthetic gypsum can be used as a material for casting mould. There is nosignificant decrease in key properties, and on the other hand there is many additional benefits including low energy consumption,decreased cost, and decreased environmental impact.

  5. Cement for Oil Well Cementing Operations in Ghana


    This research evaluates the ... The paper details results of API specification tests and the physical ... Keywords: Compressive strength, Free fluid, Portland cement, Rheology, Thickening time ..... Geothermal Well Cementing” Proceedings of.

  6. The Aspects About of Objectively Appraisals of Modeling Gypsum Quality and Composites of Phonic-Absorbent and Orthopedic on Base of Gypsum

    Pop, P. A.; Ungur, P. A.; Lazar, L.; Marcu, F.


    The EU Norms about of protection environment, outside and inside ambient, and human health demands has lead at obtain of new materials on the base of airborne material, with high thermo and phonic-absorbent properties, porous and lightweight. The α and β-modeling gypsum plaster quality and lightweight depend on many factors as: fabrication process, granulation, roast temperature, work temperature, environment, additives used, breakage, etc. Also, the objectively appraisal of modeling gypsum quality depends of proper tests methods selection, which are legislated in norms, standards and recommendations. In Romanian Standards SR EN 13279-1/2005 and SR EN 13279-2/2005, adaptable from EU Norms EN 13279-1/2004 and EN 13279-2/2004, the characteristics gypsum family tests are well specification, as: granule-metric analysis, determination of water/plaster ratio, setting time, mechanical characteristics, adhesions and water restrain. For plaster with special use (phonic-absorbent and orthopedic materials, etc.) these determinations are not concluding, being necessary more parameters finding, as: elastic constant, phonic-absorbent coefficient, porosity, working, etc., which is imposed the completion of norms and standards with new determinations.

  7. Preliminary investigation of cement materials in the Taif area, Saudi Arabia

    Martin, Conrad


    A preliminary investigation of possible sources of cement rock in the Taft area was made during the latter part of August 1968. Adequate deposits of limestone, clay, quartz conglomerate and sandstone, and pisolitic iron ore, yet no gypsum, were located to support a Cement plant should it prove feasible to establish one in this area. These materials, made up mostly of Tertiary and later sediments, crop out in isolated, inconspicuous low hills in a north- trending belt, 10 to 15 kilometers wide, lying about 90 kilometers to-the east of At Taft. The belt extends for more than 90 kilometers from the vicinity of Jabal 'An in the south to the crushed rock pits at Radwan and beyond in the north. The area is readily accessible either from the Talf-Riyadh highway or from the Taif-Bishah road presently under construction. The limestone, which is quite pure and dense in some localities but dolomitic, argillaceous, and cherty in others, occurs in a variety of colors and would make suitable decorative building stone. The volcanic rocks of the Harrat Hadan, lying directly to the east of the limestone belt, include volcanic ash beds some of which may have been altered to bentonitlc clays. Others may have been lithified and might be suitable for light-weight aggregate. These possibilities remain to be investigated. Precambrian metamorphic rocks lying directly to the south and southeast of Taif were also investigated as possible cement rock sources, but no suitable material was found here.

  8. Durability of Concrete Using Rice Husk Ash as Cement Substitution Exposed To Acid Rain

    I. A. Ahmad


    Full Text Available The acidity of rainfall in major areas of Indonesia is under neutral pH. Average pH of rainfall is between 3 and 5. Free lime within concrete will react with acid and cause a decrease in the strength of concrete. A means to anticipate the damage is to reduce the content of free lime within concrete. Silicon oxide contained in rice husk ash can react with free lime to form a new compound that is harder and denser. It became the basis for the use of rice husk ash in concrete mixtures. The mixtures were prepared by replacing 5% and 10% of cement with rice husk ash and the results were compared with a reference mix with 100% cement. This paper presents the results of an experimental investigation on the mechanical characteristics of concrete specimens as durability parameters. Then to evaluate the mechanical characteristics, microstructure test was conducted. The lower the mechanical properties of the concrete, the higher the level of gypsum contained within concrete. The percentage of 5% rice husk ash of the cement weight has a lower compressive strength decrease than the 10% rice husk ash. In addition, the proposed durability model is a model of polynomial equation with two variables.

  9. Research on flue gas desulphurization gypsum based inorganic thermal insulation mortar%以脱硫石膏为复合胶凝材料基料配制无机保温砂浆

    孙振平; 郑金飚; 蒋正武; 王君若; 洪辉; 黄晖皓; 杨正宏


    The primary properties and changing law of a kind of inorganic thermal insulation mortar taking Flue Gas Desulphurization gypsum (FCD gypsum) as raw material and small expanded and vitrified balls as lightweight aggregate were studied. The cementitious material made up with FCD gypsum,slag powder,and small amount of cement and activator owned excellent hydration and hardening function,and the 28 d compressive strength can be reached above 25 MPa. The results show that the primary properties of such prepared thermal insulation mortar can meet with the requirements of rlated standards. Moreover,the utilization ability of industrial waste brings them good environmental benefit and social benefit,so the market prospects are broad.%研究了一种以脱硫石膏为复合胶凝材料的基料,以玻化微珠为轻质集料配制而成的保温砂浆的性能及其变化规律.复合胶凝材料由脱硫石膏、矿渣粉、少量水泥和激发剂组成,具备优良的水化硬化特性,其28 d抗压强度能达25 MPa以上.结果表明,以这种复合胶凝材料和玻化微珠共同配制的保温砂浆,其各项性能指标均达到相关标准的要求.同时,因原材料中采用了大量工业废弃物,这种保温砂浆产品的环境效益和社会效益极佳,市场前景广阔.

  10. Magnesium substitution in brushite cements.

    Alkhraisat, Mohammad Hamdan; Cabrejos-Azama, Jatsue; Rodríguez, Carmen Rueda; Jerez, Luis Blanco; Cabarcos, Enrique López


    The use of magnesium-doped ceramics has been described to modify brushite cements and improve their biological behavior. However, few studies have analyzed the efficiency of this approach to induce magnesium substitution in brushite crystals. Mg-doped ceramics composed of Mg-substituted β-TCP, stanfieldite and/or farringtonite were reacted with primary monocalcium phosphate (MCP) in the presence of water. The cement setting reaction has resulted in the formation of brushite and newberyite within the cement matrix. Interestingly, the combination of SAED and EDX analyses of single crystal has indicated the occurrence of magnesium substitution within brushite crystals. Moreover, the effect of magnesium ions on the structure, and mechanical and setting properties of the new cements was characterized as well as the release of Ca(2+) and Mg(2+) ions. Further research would enhance the efficiency of the system to incorporate larger amounts of magnesium ions within brushite crystals.

  11. Portland cement-blast furnace slag blends in oilwell cementing applications

    Mueller, D.T.; DiLullo, G.; Hibbeler, J. [and others


    Recent investigations of blast furnace slag cementing technologies. have been expanded to include Portland cement/blast furnace slag blends. Mixtures of Portland cement and blast furnace slag, while having a long history of use in the construction industry, have not been used extensively in oilwell cementing applications. Test results indicate that blending blast furnace slag with Portland cement produces a high quality well cementing material. Presented are the design guidelines and laboratory test data relative to mixtures of blast furnace slag and Portland cements. Case histories delineating the use of blast furnace slag - Portland cement blends infield applications are also included.

  12. Hydrothermal synthesis of calcium sulfate whisker from flue gas desulfurization gypsum

    Chengjun Liu; Qing Zhao; Yeguang Wang; Peiyang Shi; Maofa Jiang


    Plenty of flue gas desulfurization (FGD) gypsum generated from coal-fired power plants for sulfur dioxide se-questration caused many environmental issues. Preparing calcium sulfate whisker (CSW) from FGD gypsum by hydrothermal synthesis is considered to be a promising approach to solve this troublesome problem and uti-lize calcium sulfate in a high-value-added way. The effects of particle size of FGD gypsum, slurry concentration, and additives on CSW were investigated in this work. The results indicated that fine particle size of FGD gypsum and moderately high slurry concentration were beneficial for crystal nucleation and growth. Three additives of magnesium chloride, citric acid, and sodium dodecyl benzene sulfonate (SDBS) were employed in this study. It was found that mean length and aspect ratio of CSW were both decreased by the usage of magnesium chloride, while a small quantity of citric acid or SDBS could improve the CSW morphology. When multi-additives of citric acid-SDBS were employed, the mean length and aspect ratio increased more than 20%. Moreover, surface morphology of CSW went better, and the particle size and crystal shape became more uniform.

  13. Morphology and stability of aggregates of an Oxisol according to tillage system and gypsum application

    Fábio Régis de Souza


    Full Text Available Morphological characterization and aggregate stability is an important factor in evaluating management systems. The aim of this paper is to evaluate the stability and morphology of the aggregates of a dystrophic Oxisol managed with no-tillage and conventional tillage with and without the residual action of gypsum. The experimental design was randomized blocks arranged in split-split plot, where the treatments were two soil management systems (plots with 0 and 2000 kg ha-1 of gypsum (subplots and five depths (0-0.05, 0.05-0.10, 0.10-0.15, 0.15-0.20 and 0.20-0.30 m as the subsubplots, with four replications. The aggregate morphology was determined through images and later evaluated by the Quantporo software. Stability was determined by the wet method. The results showed that the no-tillage system, with or without gypsum residual effect, provided the aggregates with the largest geometric diameters. The combination of no-tillage system and the gypsum residual effect provided rougher aggregates.

  14. Responses to Environmental Stress in Plants Adapted to Mediterranean Gypsum Habitats

    Josep V. LLINARES


    Full Text Available Gypsum areas are stressful environments inhabited by gypsophytes, plants that are exclusive for such habitats, and by plants that grow on gypsum but also on other soil types, the so-called gypsovags. To investigate possible differences between gypsovags and gypsophytes with respect to basic stress response mechanisms, two common osmolytes, glycine betaine and total soluble sugars, as well as monovalent (Na+ and K+ and bivalent (Ca2+ and Mg2+ cations, were quantified, under field conditions, in two Iberian endemic gypsophytes (Gypsophila struthium subsp. hispanica and Ononis tridentata and two common Mediterranean gypsovags (Rosmarinus officinalis and Helianthemum syriacum. Their spatial variation according to a topographic gradient and their temporal variation over a period of three successive seasons were correlated with climatic data and soil characteristics. This analysis confirmed that water stress is the main environmental stress factor in gypsum habitats, whereas the percentage of gypsum in the soil does not seem to play any relevant role in the activation of stress responses in plants. Glycine betaine may contribute to stress tolerance in the gypsophytes, but not in the gypsovags, according to the close correlation found between the level of this osmolyte and the gypsophily of the investigated taxa. Cation contents in the plants did not correlate with those present in the soil, but the gypsophytes have higher levels of Ca2+ and Mg2+ than the gypsovags, under all environmental conditions, which may represent an adaptation mechanism to their specific habitat.

  15. Gypsum plasterboards enhanced with phase change materials: A fire safety assessment using experimental and computational techniques

    Kolaitis Dionysios I.


    Full Text Available Phase Change Materials (PCM can be used for thermal energy storage, aiming to enhance building energy efficiency. Recently, gypsum plasterboards with incorporated paraffin-based PCM blends have become commercially available. In the high temperature environment developed during a fire, the paraffins, which exhibit relatively low boiling points, may evaporate and, escaping through the gypsum plasterboard's porous structure, emerge to the fire region, where they may ignite, thus adversely affecting the fire resistance characteristics of the building. Aiming to assess the fire safety behaviour of such building materials, an extensive experimental and computational analysis is performed. The fire behaviour and the main thermo-physical physical properties of PCM-enhanced gypsum plasterboards are investigated, using a variety of standard tests and devices (Scanning Electron Microscopy, Thermo Gravimetric Analysis, Cone Calorimeter. The obtained results are used to develop a dedicated numerical model, which is implemented in a CFD code. CFD simulations are validated using measurements obtained in a cone calorimeter. In addition, the CFD code is used to simulate an ISO 9705 room exposed to fire conditions, demonstrating that PCM addition may indeed adversely affect the fire safety of a gypsum plasterboard clad building.

  16. Palaeoclimatic significance of gypsum pseudomorphs in the inner shelf sediments off Machalipatnam bay

    Rao, V.P.

    Pseudo-gypsum crystals have been found in the coarse fraction of the sediments from the inner continental shelf off Machilipatnam Bay. They range in size from 3 to 7 mm are elongate and lenticular in shape. Bassanite and calcite are pseudomorphs...

  17. Composting and gypsum amendment of broiler litter to reduce nutrient leaching loss

    Relative to fresh broiler litter, little is known about the dynamics of composted litter derived-nutrient in the ecosystem. In this study, the potential leaching losses of nutrients from compost relative to fresh broiler litter along with flue gas desulfurization (FGD gypsum), as a nutrient immobil...

  18. Study of Fresh and Hardening Process Properties of Gypsum with Three Different PCM Inclusion Methods

    Susana Serrano


    Full Text Available Gypsum has two important states (fresh and hardened states, and the addition of phase change materials (PCM can vary the properties of the material. Many authors have extensively studied properties in the hardened state; however, the variation of fresh state properties due to the addition of Micronal® DS 5001 X PCM into gypsum has been the object of few investigations. Properties in fresh state define the workability, setting time, adherence and shrinkage, and, therefore the possibility of implementing the material in building walls. The aim of the study is to analyze, compare and evaluate the variability of fresh state properties after the inclusion of 10% PCM. PCM are added into a common gypsum matrix by three different methods: adding microencapsulated PCM, making a suspension of PCM/water, and incorporating PCM through a vacuum impregnation method. Results demonstrate that the inclusion of PCM change completely the water required by the gypsum to achieve good workability, especially the formulation containing Micronal® DS 5001 X: the water required is higher, the retraction is lower (50% less due to the organic nature of the PCM with high elasticity and, the adherence is reduced (up to 45% due to the difference between the porosity of the different surfaces as well as the surface tension difference.

  19. Investigation of Parameters Affecting Gypsum Dewatering Properties in a Wet Flue Gas Desulphurization Pilot Plant

    Hansen, Brian Brun; Kiil, Søren


    Wet flue gas desulphurization (FGD) plants with forced oxidation, installed at coal and oil fired power plants for removal of SO2(g), must produce gypsum of high quality. However, quality issues such as an excessive moisture content, due to poor gypsum dewatering properties, may occur from time...... to time. In this work, the particle size distribution, morphology, and filtration rate of wet FGD gypsum formed in a pilot-scale experimental setup, operated in forced oxidation mode, have been studied. The influence of holding tank residence time (10–408 h), solids content (30–169 g/L), and the presence...... of impurities (0.002 M Al2F6; 50 g quartz/L; 0.02 M Al3+, and 0.040 M Mg2+) were investigated. In addition, slurry from a full-scale wet FGD plant, experiencing formation of flat shaped crystals and poor gypsum dewatering properties, was transferred to the pilot plant to test if the plant would now start...

  20. Crack Coalescence in Molded Gypsum and Carrara Marble: Part 1. Macroscopic Observations and Interpretation

    Wong, L. N. Y.; Einstein, H. H.


    Cracking and coalescence behavior has been studied experimentally with prismatic laboratory-molded gypsum and Carrara marble specimens containing two parallel pre-existing open flaws. This was done at both the macroscopic and the microscopic scales, and the results are presented in two separate papers. This paper (the first of two) summarizes the macroscopic experimental results and investigates the influence of the different flaw geometries and material, on the cracking processes. In the companion paper (also in this issue), most of the macroscopic deformation and cracking processes shown in this present paper will be related to the underlying microscopic changes. In the present study, a high speed video system was used, which allowed us to precisely observe the cracking mechanisms. Nine crack coalescence categories with different crack types and trajectories were identified. The flaw inclination angle ( β), the ligament length ( L), that is, intact rock length between the flaws, and the bridging angle ( α), that is, the inclination of a line linking up the inner flaw tips, between two flaws, had different effects on the coalescence patterns. One of the pronounced differences observed between marble and gypsum during the compression loading test was the development of macroscopic white patches prior to the initiation of macroscopic cracks in marble, but not in gypsum. Comparing the cracking and coalescence behaviors in the two tested materials, tensile cracking generally occurred more often in marble than in gypsum for the same flaw pair geometries.

  1. The Thermal Damage Properties of Mudstone, Gypsum and Rock Salt from Yingcheng, Hubei, China

    Jie Chen


    Full Text Available The impacts of temperature on the surface thermal damage of rock salt, gypsum and mudstone from the Yingcheng salt mine, China were investigated by the surface crack growth and propagation tests at different temperatures. We found that: (a high temperature could strengthen the rock salt molecular thermal motion and weaken the cohesion among the rock salt grains, so that the grain boundaries were more prone to slip and thus develop into cracks; (b high temperature could make the water molecules evaporate from rock specimens, which should change the physical properties of gypsum and mudstone; and (c high temperature had a significant effect on the interface between rock salt and gypsum and mudstone, therefore it should be easy to produce cracks with white or light yellow cumulate powder here. The surface crack growth and propagation of the rock salt, gypsum and mudstone have a positive correlation with the temperature by stereo microscope and the method of binary images, which could observe the surface thermal damage properties. Finally, the fractal dimension of the rock salt surface cracks was calculated based on fractal theory, and the evolution of the surface thermal damage was found from 50 to 260 °C.

  2. 40 CFR 436.50 - Applicability; description of the gypsum subcategory.


    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Applicability; description of the gypsum subcategory. 436.50 Section 436.50 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS MINERAL MINING AND PROCESSING POINT SOURCE CATEGORY...

  3. Decreasing phosphorus loss in tile-drained landscapes using flue gas desulfurization gypsum

    Elevated phosphorus (P) loading from agricultural non-point source pollution continues to impair inland waterbodies throughout the world. The application of flue gas desulfurization (FGD) gypsum to agricultural fields has been suggested to decrease P loading because of its high calcium content and P...

  4. Assessment of Mercury in Soils, Crops, Earthworms, and Water when Soil is Treated with Gypsum

    Flue gas desulfurization (FGD) gypsum from fossil fuel combustion has many potential uses in agriculture, but there is concern about the potential environmental effects of its elevated mercury (Hg) concentration. The wet limestone scrubbing process that removes sulfur from flue gas (and produces gyp...

  5. Calcium Orthophosphate Cements and Concretes

    Sergey V. Dorozhkin


    Full Text Available In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone, calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.

  6. Modeling grain size variations of aeolian gypsum deposits at White Sands, New Mexico, using AVIRIS imagery

    Ghrefat, H.A.; Goodell, P.C.; Hubbard, B.E.; Langford, R.P.; Aldouri, R.E.


    Visible and Near-Infrared (VNIR) through Short Wavelength Infrared (SWIR) (0.4-2.5????m) AVIRIS data, along with laboratory spectral measurements and analyses of field samples, were used to characterize grain size variations in aeolian gypsum deposits across barchan-transverse, parabolic, and barchan dunes at White Sands, New Mexico, USA. All field samples contained a mineralogy of ?????100% gypsum. In order to document grain size variations at White Sands, surficial gypsum samples were collected along three Transects parallel to the prevailing downwind direction. Grain size analyses were carried out on the samples by sieving them into seven size fractions ranging from 45 to 621????m, which were subjected to spectral measurements. Absorption band depths of the size fractions were determined after applying an automated continuum-removal procedure to each spectrum. Then, the relationship between absorption band depth and gypsum size fraction was established using a linear regression. Three software processing steps were carried out to measure the grain size variations of gypsum in the Dune Area using AVIRIS data. AVIRIS mapping results, field work and laboratory analysis all show that the interdune areas have lower absorption band depth values and consist of finer grained gypsum deposits. In contrast, the dune crest areas have higher absorption band depth values and consist of coarser grained gypsum deposits. Based on laboratory estimates, a representative barchan-transverse dune (Transect 1) has a mean grain size of 1.16 ??{symbol} (449????m). The error bar results show that the error ranges from - 50 to + 50????m. Mean grain size for a representative parabolic dune (Transect 2) is 1.51 ??{symbol} (352????m), and 1.52 ??{symbol} (347????m) for a representative barchan dune (Transect 3). T-test results confirm that there are differences in the grain size distributions between barchan and parabolic dunes and between interdune and dune crest areas. The t-test results

  7. Investigation on the Permeability Evolution of Gypsum Interlayer Under High Temperature and Triaxial Pressure

    Tao, Meng; Yechao, You; Jie, Chen; Yaoqing, Hu


    The permeability of the surrounding rock is a critical parameter for the designing and assessment of radioactive waste disposal repositories in the rock salt. Generally, in the locations that are chosen for radioactive waste storage, the bedded rock salt is a sedimentary rock that contains NaCl and Na2SO4. Most likely, there are also layers of gypsum ( {CaSO}_{ 4} \\cdot 2 {H}_{ 2} {O)} present in the salt deposit. Radioactive wastes emit a large amount of heat and hydrogen during the process of disposal, which may result in thermal damage of the surrounding rocks and cause a great change in their permeability and tightness. Therefore, it is necessary to investigate the permeability evolution of the gypsum interlayer under high temperature and high pressure in order to evaluate the tightness and security of the nuclear waste repositories in bedded rock salt. In this study, a self-designed rock triaxial testing system by which high temperature and pressure can be applied is used; the μCT225kVFCB micro-CT system is also employed to investigate the permeability and microstructure of gypsum specimens under a constant hydrostatic pressure of 25 MPa, an increasing temperature (ranging from 20 to 650 °C), and a variable inlet gas pressure (1, 2, 4, 6 MPa). The experimental results show: (a) the maximum permeability measured during the whole experiment is less than 10-17 m2, which indicates that the gypsum interlayer has low permeability under high temperature and pressure that meet the requirements for radioactive waste repository. (b) Under the same temperature, the permeability of the gypsum specimen decreases at the beginning and then increases as the pore pressure elevates. When the inlet gas pressure is between 0 and 2 MPa, the Klinkenberg effect is very pronounced. Then, as the pore pressure increases, the movement behavior of gas molecules gradually changes from free motion to forced directional motion. So the role of free movement of gas molecules gradually

  8. 磷石膏作缓凝剂对油井水泥性能的影响%Influence of Phosphogypsum as Retarder on Performance of Oil-well Cement

    陈倛; 张礼华; 周永生


    利用工业废渣磷石膏替代天然石膏作油井水泥的缓凝剂,对不同熟料细度及不同磷石膏掺量对G级高抗油井水泥强度及抗硫酸盐侵蚀等性能的影响进行了研究.结果表明,水泥石强度随着油井水泥熟料细度的增加而增加,当油井水泥熟料的细度达到400m2/kg时,水泥石强度较高;随着磷石膏掺量的增加,水泥石强度呈现缓慢上升趋势,同时表明磷石膏替代天然石膏对水泥石强度影响不大,磷石膏替代天然石膏对高抗油井水泥的抗硫酸盐侵蚀性能未造成不良影响.%By using industrial scrap phosphogypsum instead of natural gypsum as retarder of oil-well cement, the influence of the dosage of phosphogypsum and the clinker fineness on the properties of the oil-well cement including compressive strength and sulphate resistance was studied in this paper. The results show that the compressive strength of cement block increases with the clinker fineness of the oil-well cement. When the fineness is above 400m /kg,the strength of cement is relatively high. The compressive strength of cement block increases slowly with the content of phosphogypsum. Phosphogypsum instead of natural gypsum has little effect upon the compressive strength and the sulfate resistance properties of oil-well cement.

  9. Iron and Sulfur Geochemistry in Class H Wellbore Cements Exposed to CO2 and H2S

    Lopano, C. L.; Webb, S. M.; Kutchko, B. G.; Strazisar, B. R.; Hawthorne, S. B.; Miller, D. J.; Guthrie, G.; Hakala, A.


    potentially amorphous Fe-S. In a similar manner, S was evaluated by collecting multiple energy maps through the S-edge using beamline 14-3 at SSRL. The S ME maps revealed much broader reaction fronts as revealed by the iron mapping alone. Analysis of S XANES spectra is ongoing, but preliminary results indicate that possibly 6 different binding environments are likely in the cements depending on the H2S concentration: FeS, FeS2, S, a sulfite phase, and potentially two different sulfates (gypsum and ettringite). The results indicate that S oxidation state likely grades from S+6 in the core of the cement to S-1 in the rim of the cement, with S oxidation states ranging from S4+ to S0 in zones in between. This work will serve to better understand the geochemical reactions in the cement upon addition of S co-constituents in order to better assess potential impacts on long-term cement integrity.

  10. Effect of the cement type on compatibility with carboxylate superplasticisers

    Bundyra-Oracz, G.


    Full Text Available An empirical study was conducted to gain a fuller understanding of the interactions taking place in cementsuperplasticiser systems. To this end, two clinkers of known chemical and phase composition were prepared in this study to gain insight into such interactions. One contained no tricalcium aluminate (C1, while the other had a 9% C3A content (C2. These clinkers were ground to approximately 340 m2/kg and blended with gypsum only or gypsum and Klein compound (3CaO·3Al2O3·CaSO4 (1, 2. Sufficient compound was added to C1 to ensure the formation of about the same amount of ettringite after 0.5 and 1 h of hydration as found in cement C2 + gypsum. The admixture used was a carboxylate superplasticiser. Rheology measurements showed that while paste yield stress was correlated to ettringite formation, no such simple relationship was observed for plastic viscosity. Plastic viscosity depended on the total hydrates formed, i.e., not only as ettringite but also as C-S-H gel. The findings revealed that in clinkers with very low sulfate and potassium contents, the rheology of carboxylate-containing cement paste is primarily controlled by ettringite formation.

    En el presente trabajo se ha realizado un estudio empírico con el objetivo de profundizar en el conocimiento de las interacciones del sistema cemento-superplastificante. Con este fin, se prepararon dos clínkeres con una composición química y de fases conocida: el primero (C1 sin aluminato tricálcico y el segundo (C2 con un contenido en C3A del 9%. Ambos se molieron hasta obtener una superficie específica aproximada de 340 m2/kg y se emplearon con dos adiciones: yeso y el compuesto de Klein (3CaO·3Al2O3·CaSO4 (1, 2. Se añadió la cantidad necesaria del compuesto de Klein a C1 para garantizar la formación, tras 0,5 y 1ª h. de hidratación, de aproximadamente la misma cantidad de etringita en dicho

  11. Low pH Cements

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)


    The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit {<=} 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio {<=} 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

  12. Low pH Cements

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)


    The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit {<=} 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio {<=} 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

  13. Can isotopic variations in structural water of gypsum reveal paleoclimatic changes?

    Gatti, E.; Bustos, D.; Coleman, M. L.


    Water of crystallization in gypsum can be used as paleo-environmental proxy to study large scale climatic variability in arid areas. This is because changes in the isotopic composition of water of crystallization are due to isotopic variations in the mother brine from which the mineral precipitated, and the brine isotopic composition is linked to evaporation processes and humidity. This is particularly important when the salts are the only traces left of the original water, i.e. in modern arid areas. This study aims to prove that the 2-D/18-O compositions of the water of crystallization extracted from successive precipitates or even different growth zones of natural gypsum (CaSO4·H2O) can reconstruct the evaporation history and paleo-humidity of the source water basin. The method was tested in a laboratory experiment that evaporated CaSO4 brines under controlled temperature and humidity conditions. The brine was left to evaporate for five days at two different humidities (45 and 75 RH%); subsequently, brines and precipitated gypsum were sampled at 24 hour intervals. In this way we simulated zoned growth of gypsum. The samples were then analyzed for oxygen and hydrogen isotopic composition using a Thermo Scientific TC/EA with modified column, coupled to a MAT 253 Thermo Finnigan mass spectrometer at JPL. If preliminary results validate the novel hypothesis that changes in mineral composition can reveal details of paleo-environmental conditions the theory will be tested on natural gypsum collected from selected areas in White Sands National Monument, New Mexico. The study is currently ongoing but the full dataset will be presented at the conference.

  14. Obtaining a sulfoaluminate belite cement by industrial waste

    Elkhadiri, L.


    Full Text Available Sulfoaluminate belite clinkers by burning raw at moderate temperatures near 1250 °C were synthesized. The used mixtures were made by calcium carbonate blended to two industrial wastes: low calcium fly ash and phosphogypsum. The clinkers were characterised by X-Ray Diffraction (XRD, Infrared Spectroscopy (FTIR and free lime. The hydraulic behaviour of the obtained cements, by adequate clinkers with 7% of added gypsum, was followed by XRD, scaning electronic microscopy (SEM, FTIR and NMR.

    Los clínkeres belíticos de sulfoaluminatos se obtienen por cocción de crudos a temperaturas moderadas, hacia 1.250 ºC. Esos crudos se componen de carbonato de calcio mezclados con dos subproductos industriales: cenizas volantes pobres en óxido de calcio y fosfoyeso. Los clínkeres obtenidos se caracterizaron a través de Difracción de Rayos X (DRX, Espectroscopia Infrarroja por Transformada de Fourier (FTIR y por la determinación de CaO libre. El comportamiento hidráulico de los cementos elaborados de los clínkeres con el 7% de yeso se estudió por DRX, Microscopía Electrónica de Barrido (SEM, FTIR y Resonancia Magnética Nuclear (RMN

  15. Contaminant mobility and carbon sequestration downstream of the Ajka (Hungary) red mud spill: The effects of gypsum dosing.

    Renforth, P; Mayes, W M; Jarvis, A P; Burke, I T; Manning, D A C; Gruiz, K


    A number of emergency pollution management measures were enacted after the accidental release of caustic bauxite processing residue that occurred in Ajka, western Hungary in October, 2010. These centred on acid and gypsum dosing to reduce pH and minimise mobility of oxyanion contaminants mobile at high pH. This study assessed the effectiveness of gypsum dosing on contaminant mobility and carbon sequestration through assessment of red mud and gypsum-affected fluvial sediments via elemental analysis and stable isotope analysis. There was a modest uptake of contaminants (notably As, Cr, and Mn) on secondary carbonate-dominated deposits in reaches subjected to gypsum dosing. C and O stable isotope ratios of carbonate precipitates formed as a result of gypsum dosing were used to quantify the importance of the neutralisation process in sequestering atmospheric carbon dioxide. This process was particularly pronounced at sites most affected by gypsum addition, where up to 36% of carbonate-C appears to be derived from atmospheric in-gassing of CO(2). The site is discussed as a large scale analogue for potential remedial approaches and carbon sequestration technologies that could be applied to red mud slurries and other hyperalkaline wastes. The results of this work have substantial implications for the aluminium production industry in which 3-4% of the direct CO(2) emissions may be offset by carbonate precipitation. Furthermore, carbonation by gypsum addition may be important for contaminant remediation, also providing a physical stabilisation strategy for the numerous historic stockpiles of red mud.

  16. 21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.


    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device...: Polymethylmethacrylate (PMMA) Bone Cement.”...

  17. Cementation of Loose Sand Particles based on Bio-cement

    RONG Hui; QIAN Chunxiang


    Loose sand particles could be cemented to sandstone by bio-cement (microbial induced magnesium carbonate). The bio-sandstone was firstly prepared, and then the compressive strength and the porosity of the sandstone cemented by microbial induced magnesium carbonate were tested to characterize the cementation effectiveness. In addition, the formed mineral composition and the microstructure of bio-sandstone were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The experimental results show that the feasibility of binding loose sand particles using microbial induced magnesium carbonate precipitation is available and the acquired compressive strength of bio-sandstone can be excellent at certain ages. Moreover, the compressive strength and the porosity could be improved with the increase of microbial induced magnesium carbonate content. XRD results indicate that the morphology of magnesium carbonate induced by microbe appears as needles and SEM results show that the cementation of loose sand particles to sandstone mainly relies on the microbial induced formation of magnesium carbonate precipitation around individual particles and at particle-particle contacts.

  18. An Experimental Investigation of Partial Replacement of Cement by Various Percentage of Phosphogypsum And Flyash In Cement Concrete

    Suchita R Saikhede


    Full Text Available Over 15 million tons of fly ash (FA and 3 million tons of phospho-gypsum (PG are produced every year. The utilization of these industrial by-product materials is important in terms of environmental and economical issues are concerned. The main purpose of this study is to evaluate the technical possibilities of incorporating FA and PG in production of concrete .In this study Combination of FA and PG is use as a mineral admixture with, phosphogypsum 0%., 5%,10%, 15% and fly ash is constant as 20% , Last proportion was taken PG- 5% and FA- 25%. . The compressive, tensile and flexural strength are studied by casting and testing specimens for 7, 14 and 28 days. It is shown that a part of ordinary Portland cement can be replaced with PG and FA to develop a good and hardened concrete to achieve economy; above 10% replacement of phosphogypsum and 20% replacement of F in concrete lead to drastic reduction not only in the compressive strength but also in Flexural and split tensile strength of concrete.

  19. High Water Content Material Based on Ba-Bearing Sulphoaluminate Cement

    CHANG Jun; CHENG Xin; LU Lingchao; HUANG Shifeng; YE Zhengmao


    A new type of high water content material which is made up of two pastes is prepared, one is made from lime and gypsum, and another is based on Ba-bearing stdphoaluminate cement. It has excellent properties such as slow single paste solidifing,fast double pastes solidifing,fast coagulating and hardening, high early strength, good suspension property at high W/C ratio and low cost. Meanwhile, the properties and hydration mechanism of the material were analyzed by using XRD , DTA- TG and SEM. The hydrated products of new type of high water content material are Ba-bearing ettringite, BaSO4 , aluminum gel and C-S-H gel.

  20. Formation mechanism of authigenic gypsum in marine methane hydrate settings: Evidence from the northern South China Sea

    Lin, Qi; Wang, Jiasheng; Algeo, Thomas J.; Su, Pibo; Hu, Gaowei


    During the last decade, gypsum has been discovered widely in marine methane hydrate-bearing sediments. However, whether this gypsum is an in-situ authigenic precipitate remains controversial. The GMGS2 expedition carried out in 2013 by the Guangzhou Marine Geological Survey (GMGS) in the northern South China Sea provided an excellent opportunity for investigating the formation of authigenic minerals and, in particular, the relationship between gypsum and methane hydrate. In this contribution, we analyzed the morphology and sulfur isotope composition of gypsum and authigenic pyrite as well as the carbon and oxygen isotopic compositions of authigenic carbonate in a drillcore from Site GMGS2-08. These methane-derived carbonates have characteristic carbon and oxygen isotopic compositions (δ13C: -57.9‰ to -27.3‰ VPDB; δ18O: +1.0‰ to +3.8‰ VPDB) related to upward seepage of methane following dissociation of underlying methane hydrates since the Late Pleistocene. Our data suggest that gypsum in the sulfate-methane transition zone (SMTZ) of this core precipitated as in-situ authigenic mineral. Based on its sulfur isotopic composition, the gypsum sulfur is a mixture of sulfate derived from seawater and from partial oxidation of authigenic pyrite. Porewater Ca2+ ions for authigenic gypsum were likely generated from carbonate dissolution through acidification produced by oxidation of authigenic pyrite and ion exclusion during methane hydrate formation. This study thus links the formation mechanism of authigenic gypsum with the oxidation of authigenic pyrite and evolution of underlying methane hydrates. These findings suggest that authigenic gypsum may be a useful proxy for recognition of SMTZs and methane hydrate zones in modern and ancient marine methane hydrate geo-systems.

  1. Soil fertility, nutrition and yield of maize and barley with gypsum application on soil surface in no-till

    Leandro Michalovicz


    Full Text Available Annual crop yield and nutrition have shown differentiated responses to modifications in soil chemical properties brought about by gypsum application. The aim of this study was to evaluate the effect of gypsum application rates on the chemical properties of a Latossolo Bruno (Clayey Oxisol, as well as on the nutrition and yield of a maize-barley succession under no-till. The experiment was set up in November 2009 in Guarapuava, Parana, Brazil, applying gypsum rates of 0.0, 1.5, 3.0, 4.5, and 6.0 Mg ha-1 to the soil surface upon sowing maize, with crop succession of barley. Gypsum application decreased the levels of Al3+ and Mg2+ in the 0.0-0.1 m layer and increased soil pH in the layers from 0.2-0.6 m depth. Gypsum application has increased the levels of Ca2+ in all soil layers up to 0.6 m, and the levels of S-SO4(2- up to 0.8 m. In both crops, the leaf concentrations of Ca and S were increased while Mg concentrations have decreased as a function of gypsum rates. There was also an effect of gypsum rates on grain yield, with a quadratic response of maize and a linear increase for barley. Yield increases were up to 11 and 12 % in relation to control for the maximum technical efficiency (MTE rates of 3.8 and 6.0 Mg ha-1 of gypsum, respectively. Gypsum application improved soil fertility in the profile, especially in the subsurface, as well as plant nutrition, increasing the yields of maize and barley.

  2. Hydration of fly ash cement

    Etsuo Sakai; Shigeyoshi Miyahara; Shigenari Ohsawa; Seung-Heun Lee; Masaki Daimon [Tokyo Institute of Technology, Tokyo (Japan). Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering


    It is necessary to establish the material design system for the utilization of large amounts of fly ash as blended cement instead of disposing of it as a waste. Cement blended with fly ash is also required as a countermeasure to reduce the amount of CO{sub 2} generation. In this study, the influences of the glass content and the basicity of glass phase on the hydration of fly ash cement were clarified and hydration over a long curing time was characterized. Two kinds of fly ash with different glass content, one with 38.2% and another with 76.6%, were used. The hydration ratio of fly ash was increased by increasing the glass content in fly ash in the specimens cured for 270 days. When the glass content of fly ash is low, the basicity of glass phase tends to decrease. Reactivity of fly ash is controlled by the basicity of the glass phase in fly ash during a period from 28 to 270 days. However, at an age of 360 days, the reaction ratios of fly ash show almost identical values with different glass contents. Fly ash also affected the hydration of cement clinker minerals in fly ash cement. While the hydration of alite was accelerated, that of belite was retarded at a late stage.

  3. Seating load parameters impact on dental ceramic reinforcement conferred by cementation with resin-cements.

    Addison, Owen


    Cementation of all-ceramic restorations with resin-cements has been demonstrated to reduce the incidence of fracture in service. The aim was to investigate the influence of loading force and loading duration applied during cementation on the reinforcement conferred by a resin-cement on a leucite reinforced glass-ceramic.

  4. 76 FR 76760 - Gray Portland Cement and Cement Clinker From Japan


    ... Portland Cement and Cement Clinker From Japan Determination On the basis of the record \\1\\ developed in the... antidumping duty order on gray Portland cement and cement clinker from Japan would be likely to lead to... the Commission are contained in USITC Publication 4281 (December 2011), entitled Gray Portland...

  5. In Situ Observation of Gypsum-Anhydrite Transition at High Pressure and High Temperature

    LIU Chuan-Jiang; ZHENG Hai-Fei


    An in-situ Raman spectroscopic study of gypsum-anhydrite transition under a saturated water condition at high pressure and high temperature is performed using a hydrothermal diamond anvil cell (HDAC).The experimental results show that gypsum dissolvs in water at ambient temperature and above 496 MPa.With increasing temperature,the anhydrite (CaSO4) phase precipitates at 250 320℃ in the pressure range of 1.0 1.5 GPa,indicating that under a saturated water condition,both stable conditions of pressure and temperature and high levels of Ca and SO4 ion concentrations in aqueous solution are essential for the formation of anhydrite.A linear relationship between the pressure and temperature for the precipitation of anhydrite is established as P(GPa) =0.0068T - 0.7126 (250℃≤T≤320℃).Anhydrite remained stable during rapid cooling of the sample chamber,showing that the gypsum-anhydrite transition involving both dissolution and precipitation processes is irreversible at high pressure and high temperature.%An in-situ Raman spectroscopic study of gypsum-anhydrite transition under a saturated water condition at high pressure and high temperature is performed using a hydrothermal diamond anvil cell (HDAC). The experimental results show that gypsum dissolvs in water at ambient temperature and above 496 Mpa. With increasing temperature, the anhydrite (CaSO4) phase precipitates at 250-320℃ in the pressure range of 1.0-1.5 Gpa, indicating that under a saturated water condition, both stable conditions of pressure and temperature and high levels of Ca and SO4 ion concentrations in aqueous solution are essential for the formation of anhydrite. A linear relationship between the pressure and temperature for the precipitation of anhydrite is established as P(Gpa) = 0.0068T - 0.7126 (250℃≤T≤320℃). Anhydrite remained stable during rapid cooling of the sample chamber, showing that the gypsum-anhydrite transition involving both dissolution and precipitation processes is

  6. Rheological Behaviour and Microstructures of Natural Gypsum Experimentally Deformed in Simple Shear

    Barberini, V.; Burlini, L.; Rutter, E. H.; Dapiaggi, M.


    Gypsum is an important mineral of evaporitic rocks. Evaporites, interlayered within sedimentary sequences, play an important role in localizing the deformation especially in thrust tectonics (Apennines, Zagros, Gulf of Mexico, etc.) since are generally weaker than the other rocks; in some cases the deformation is accompanied by seismicity as in the Northern Apennines extensional systems. In order to determine the rheological and microstructural evolution of gypsum with strain, a set of experiments was performed on natural gypsum samples from Volterra (Tuscany, Italy). Experimental deformation tests were performed at confining pressures up to 300 MPa, at temperatures up to 130° C and at strain rates ranging between 6x10-4 and 5x10-6 s-1. In order to reach high shear strain values, we deformed gypsum specimens using both the torsion technique in the Paterson apparatus at ETH Zurich (up to γ = 5) and the sawcut-type assembly at 35° in a Heard-type apparatus at Manchester University (up to γ = 1.2). All samples have been studied by optical microscopy, to investigate the evolution of the microstructure with strain, and by XRD analysis, to determine whether and to what extent gypsum dehydrated during deformation. In torsion, the shear stress increased with the strain rate and decreased with the temperature. In general a peak stress was reached at γ between 0.5 and 1 (at higher temperatures is reached sooner). After the peak, a various amount of weakening occurred, and mechanical 'steady state' conditions were never reached. Weakening was up to 30-40%. Most of the times the jacket failure ended prematurely the experiment. The microstructure evolved from a deformation microstructure, where grains changed shape according to the bulk strain imposed, into a recrystallization microstructure, where grains were more aequant. Grain boundary migration recrystallization was very effective in resetting the microstructure after γ of 1 or 2. In the samples deformed using saw

  7. Freezing resistance of high iron phoasphoaluminate cement

    Zhang, S. X.; Lu, L. C.; Wang, S. D.; Zhao, P. Q.; Gong, C. C.


    The influence of freeze-thaw cycle on the mechanical properties of high iron phoasphoaluminate cement was investigated in the present study. The visual examination was conducted to evaluate the surface damage. The deterioration considering the weight loss, modulus loss of relative dynamic elastic and strength loss of mortar were also investigated. The morphology of hydration products were analysed by SEM. Compared with ordinary Portland cement and sulphoaluminate cement, the frost resistance of high iron phosphoraluminate cement is better. Hydration products of high iron phoasphoaluminate cement contain sheet crystals, and a lot of gel form a dense three-dimensional network structure, which results in a lower porosity. Different from ordinary Portland cement, the hydration product of high iron phoasphoaluminate cement does not contain Ca(OH)2, and low alkalinity reduces its osmotic pressure. The lower porosity and osmotic pressure are the two main reasons which causes in the higher frost resistance of high iron phoasphoaluminate cement.

  8. Antibacterial potential of contemporary dental luting cements.

    Daugela, Povilas; Oziunas, Rimantas; Zekonis, Gediminas


    The aims of this investigation were to evaluate the antibacterial activities of different types of dental luting cements and to compare antibacterial action during and after setting. Agar diffusion testing was used to evaluate the antibacterial properties of seven types of dental luting cements (glass ionomer cements (GICs), resin modified GICs, resin composite, zinc oxide eugenol, zinc oxide non-eugenol, zinc phosphate, zinc polycarboxylate cements) on Streptococcus mutans bacteria. Instantly mixed zinc phosphate cements showed the strongest antibacterial activity in contrast to the non-eugenol, eugenol and resin cements that did not show any antibacterial effects. Non-hardened glass ionomer, resin modified and zinc polycarboxylate cements exhibited moderate antibacterial action. Hardened cements showed weaker antibacterial activities, than those ones applied right after mixing.

  9. 76 FR 24519 - Gray Portland Cement and Cement Clinker From Japan; Institution of a Five-Year Review Concerning...


    ... COMMISSION Gray Portland Cement and Cement Clinker From Japan; Institution of a Five-Year Review Concerning the Antidumping Duty Order on Gray Portland Cement and Cement Clinker From Japan AGENCY: United States... determine whether revocation of the antidumping duty order on gray portland cement and cement clinker...

  10. 76 FR 50252 - Gray Portland Cement and Cement Clinker From Japan; Scheduling of an Expedited Five-Year Review...


    ... COMMISSION Gray Portland Cement and Cement Clinker From Japan; Scheduling of an Expedited Five-Year Review Concerning the Antidumping Duty Order on Gray Portland Cement and Cement Clinker From Japan AGENCY: United... cement and cement clinker from Japan would be likely to lead to continuation or recurrence of...

  11. Cementation in adhesive dentistry: the weakest link

    Jongsma, L.A.


    Het succesvol bevestigen van tandrestauraties is een belangrijke en veeleisende procedure. Met behulp van cement wordt het restauratiemateriaal aan de tandstructuur verbonden. Op die manier worden twee hechtvlakken gecreëerd: het raakvlak tussen tand en cement, en het raakvlak tussen cement en resta

  12. 21 CFR 872.3275 - Dental cement.


    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Dental cement. 872.3275 Section 872.3275 Food and... DENTAL DEVICES Prosthetic Devices § 872.3275 Dental cement. (a) Zinc oxide-eugenol—(1) Identification... filling or as a base cement to affix a temporary tooth filling, to affix dental devices such as crowns or...

  13. Characteristics solidified cement waste using heavy concrete and light concrete paste generated from KRR-2 and UCP

    Min, B. Y.; Choi, W. K.; Kim, G. N.; Lee, K. W. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)


    As the number of obsolete research reactors and nuclear facilities increases, dismantling nuclear facilities has become an influential issue. During the decommissioning of nuclear plants and facilities, large quantities of slightly contaminated concrete wastes are generated. In Korea, the decontamination and decommissioning of the retired TRIGA MARK II and III research reactors and a uranium conversion plant at KAERI has been under way. By dismantling KRR-2, more than 260 tons of radioactive concrete wastes were generated among the total 2,000 tons of concrete wastes and more than 60 tons of concrete wastes contaminated with uranium compounds have been generated. Typically, the contaminated layer is only 1{approx}10mm thick because cement materials are porous media, the penetration of radionuclides may occur up to several centimeters from the surface of a material. Concrete is a structural material which generally consists of a binder (cement), water, and aggregate. The binder is typically a portland cement which comprises the four principal clinker phases tricalcium silicate (Ca{sub 3}SiO{sub 5}) and constitutes 50-70%, decalcium silicate (Ca{sub 2}SiO{sub 4}), tricalcium aluminate (Ca{sub 3}Al{sub 2}O{sub 6}), and calcium aluminoferrite (Ca{sub 4}Al{sub 2}Fe{sub 2}O{sub 10}). Cement powder (anhydrous cement) created from the co-grinding of clinkers and gypsum is mixed with waster and hydrate phase are formed. The interaction between highly charged C-S-H particles in the presence of divalent calcium counter ions is strongly attractive because of ion-ion correlations and a negligible entropic repulsion. In the temperature range 100-300 .deg. C, these evolutions are mainly attributed to the loss of the bound water from the C-S-H gel. Similar consequences have been reported for mortars and concretes enhanced sometimes by the appearance of micro-cracks related to the strain incompatibilities between the aggregates and the cement paste. Concrete aggregates are combined




    Using the conventional well cements consisting of the calcium silicate hydrates (CaO-SiO{sub 2}-H{sub 2}O system) and calcium aluminum silicate hydrates (CaO-Al{sub 2}O{sub 3}-SiO{sub 2}-H{sub 2}O system) for the integrity of geothermal wells, the serious concern confronting the cementing industries was their poor performance in mechanically supporting the metallic well casing pipes and in mitigating the pipe's corrosion in very harsh geothermal reservoirs. These difficulties are particularly acute in two geological regions: One is the deep hot downhole area ({approx} 1700 m depth at temperatures of {approx} 320 C) that contains hyper saline water with high concentrations of CO{sub 2} (> 40,000 ppm) in conjunction with {approx} 100 ppm H{sub 2}S at a mild acid of pH {approx} 5.0; the other is the upper well region between the well's surface and {approx} 1000 m depth at temperatures up to 200 C. The specific environment of the latter region is characterized by highly concentrated H{sub 2}SO{sub 4} (pH < 1.5) brine containing at least 5000 ppm CO{sub 2}. When these conventional cements are emplaced in these harsh environments, their major shortcoming is their susceptibility to reactions with hot CO{sub 2} and H{sub 2}SO4, thereby causing their deterioration brought about by CO{sub 2}-catalyzed carbonation and acid-initiated erosion. Such degradation not only reduced rapidly the strength of cements, lowering the mechanical support of casing pipes, but also increased the extent of permeability of the brine through the cement layer, promoting the rate of the pipe's corrosion. Severely carbonated and acid eroded cements often impaired the integrity of a well in less than one year; in the worst cases, casings have collapsed within three months, leading to the need for costly and time-consuming repairs or redrilling operations. These were the reasons why the geothermal well drilling and cementing industries were concerned about using conventional well

  15. The Environmental Impact and Cost Analysis of Concrete Mixing Blast Furnace Slag Containing Titanium Gypsum and Sludge in South Korea

    Tae Hyoung Kim


    Full Text Available This study assessed the environmental effects and cost of the Industrial Waste addictive Blast Furnace Slag (W-BFS using Life Cycle Assessment (LCA and compared it to general BFS. The environmental impacts of W-BFS were as follows: 1.12 × 10−1 kg-CO2 eq/kg, 3.18 × 10−5 kg-Ethylene eq/kg, 4.79 × 10−4 kg-SO2 eq/kg, 7.15 × 10−4 kg-PO43− eq/kg, 7.15 × 10−4 kg-CFC11 eq/kg and 3.94 × 10−3 kg-Antimony eq/kg. Among the environmental impact category, GWP and AP were 9.28 × 10−2 kg-CO2 eq/kg and 3.33 × 10−4 kg-SO2 eq/kg at a raw material stage, accounting for 80% and 70% of total environmental impact respectively. In EP, POCP and ADP, in addition, raw material stage accounted for a great portion in total environmental impact because of “W” among input materials. In ODP, however, compared to the environmental impact of raw materials, oil, which was used in transporting BFS to the W-BFS manufacturing factory, was more influential. In terms of GWP, POCP and ODP, W-BFS was higher than general BFS. In terms of AP, EP and ADP, in contrast, the former was lower than the latter. In terms of cost, W-BFS (41.7 US$/ton was lower than general BFS by about 17% because of the use of waste additives comprised of industrial wastes instead of natural gypsum ,which has been commonly used in general BFS. In terms of GWP and POCP, the W-BFS mixed (30% concrete was lower than plain concrete by 25%. In terms of AP and EP, the former was lower than the latter by 30%. In terms of ADP, furthermore, W-BFS mixed (30% concrete was lower than plain concrete by 11%. In aggregate-related ODP, however, almost no change was found. In terms of cost, when W-BFS was added by 10% and 30%, it was able to reduce cost by 3% and 7% respectively, compared to plain concrete. Compared to BFS-mixed concrete as well, cost could be saved by 1% additionally because W-BFS (US$41.7/ton is lower than common cement (US$100.3/ton by about 60% in terms of production costs.

  16. Arsenic uptake by gypsum and calcite: Modeling and probing by neutron and x-ray scattering

    Fernandez-Martinez, Alejandro; Roman-Ross, Gabriela; Johnson, Mark R; Bardelli, Fabrizio; Turrillas, Xavier; Charlet, Laurent


    Here we report on two structural studies performed on As-doped gypsum (CaSO4 2H2O) and calcite (CaCO3), using neutron (D20-ILL) and x-ray (ID11-ESRF) diffraction data and EXAFS (BM8-ESRF). The aim of this study is to determine whether As gets into the bulk of gypsum and calcite structures or is simply adsorbed on the surface. Different mechanisms of substitution are used as hypotheses. The combined Rietveld analysis of neutron and x-ray diffraction data shows an expansion of the unit cell volume proportional to the As concentration within the samples. DFT-based simulations confirm the increase of the unit cell volume proportional to the amount of carbonate or sulphate groups substituted. Interpolation of the experimental Rietveld data allows us to distinguish As substituted within the structure from that adsorbed on the surface of both minerals.

  17. Two distinctive new species of Commicarpus (Nyctaginaceae) from gypsum outcrops in eastern Ethiopia

    Friis, Ib; Gilbert, Michael G.; Weber, Odile;


    During field trips in 2013 and 2014, two distinctive plants belonging to the genus Commicarpus were collected in the Lele Hills, Bale Zone, eastern Ethiopia, on outcrops of sedimentary rock belonging to the Gorrahei Formation with high contents of gypsum. The plants are here described as two new...... in Commicarpus, being a small self-supporting shrub to 0.8 (– 1) m high. Both new species occur in small populations with restricted distribution; models based on the available information show that the potential distribution is also restricted. C. macrothamnus is here evaluated as Vulnerable (VU), while C....... leleensis, only known from the type, should remain Data Deficient (DD). Outcrops of gypsum with restricted-range species are well known from eastern Ethiopia and Somalia, but the locality with the two new species of Commicarpus is the most north-western and one of the highest sites recorded so far...

  18. Thermal Dehydration Kinetics of Gypsum and Borogypsum under Non-isothermal Conditions

    I.Y.Elbeyli; S.Piskin


    Thermal dehydration of gypsum and borogypsum was investigated under nonisothermal conditions in air by using simultaneous thermogravimetric-differential thermal analyzer. Nonisothermal experiments were carried out at various linear heating rates. Kinetics of dehydration in the temperature range of 373-503 K were evaluated from the DTA (differential thermal analysis)-TGA (thermogravimetric analysis) data by means of Coats-Redfern,Kissinger and Doyle Equations. Values of the activation energy and the pre-exponential factor of the dehydration were calculated. The results of thermal experiments and kinetic parameters indicated that borogypsum is similar to gypsum from dehydration mechanism point of view although it consists of boron and small amount of alkali metal oxides.

  19. Gypsum treated fly ash as a liner for waste disposal facilities

    Baig, A.A.; Sivapullaiah, P.V. [Indian Inst. of Science, Bangalore (India)


    Fly ash is now being used in geotechnical engineering and construction applications as a means of reducing the environmental impacts of fly ash generated in thermal power plants. Various additions are used to improve fly ash properties. This abstract discussed a study conducted to investigate lime and gypsum additions to fly ash. Lime amendments ranged from 0 to 10 per cent, while gypsum additions ranged from 0 to 2.5 per cent. Laboratory experiments were conducted to determine the hydraulic conductivity of compacted samples in moulds. The study showed wide variations in hydraulic conductivity for the various samples. The physico-chemical, chemical, and mineralogical changes in the fly ash amended samples were discussed.

  20. Accuracy of Gypsum Casts after Different Impression Techniques and Double Pouring.

    Silva, Stephania Caroline Rodolfo; Messias, Aion Mangino; Abi-Rached, Filipe de Oliveira; de Souza, Raphael Freitas; Reis, José Maurício Dos Santos Nunes


    This study evaluated the accuracy of gypsum casts after different impression techniques and double pouring. Ten patients were selected and for each one it was obtained 5 partial putty/wash impressions with vinyl polysiloxane (VPS) material from teeth #13 to #16 with partial metal stock trays. The following techniques were performed: (1) one-step; two-step relief with: (2) PVC film; (3) slow-speed tungsten carbide bur and scalpel blade, (4) small movements of the tray and (5) without relief-negative control. The impressions were disinfected with 0.5% sodium hypochlorite for 10 minutes and stored during 110 and 230 minutes for the first and second pouring, respectively, with type IV gypsum. Three intra-oral lateral photographs of each patient were taken using a tripod and a customized radiographic positioner. The images were imported into ImageJ software and the total area of the buccal surface from teeth #13 to #16 was measured. A 4.0% coefficient of variance was criterion for using these measurements as Baseline values. The casts were photographed and analyzed using the same standardization for the clinical images. The area (mm2) obtained from the difference between the measurements of each gypsum cast and the Baseline value of the respective patient were calculated and analyzed by repeated-measures two way-ANOVA and Mauchly's Sphericity test (α = 0.05). No significant effect was observed for Impression technique (P = 0.23), Second pouring (P = 0.99) and their interaction (P = 0.25). The impression techniques and double pouring did not influence the accuracy of the gypsum casts.

  1. Use of textile fibres in the reinforcement of a gypsum-cork based composite material

    Vasconcelos, Graça; Camões, Aires; Fangueiro, Raúl, ed. lit.; Vila-Chã, Nuno; Jesus, Carlos M. G.; Cunha, Fernando Eduardo Macedo


    The study presented herein focus on the analysis of a series of experimental tests aiming at characterizing the performance of distinct textile fibers acting as a reinforcement of a gypsum-cork composite material. Two groups of textile fibers were selected, namely synthetic fibers (glass and basalt) and natural fibers (banana and sisal). The reinforced composite material was submitted to distinct types of loading, namely compression tests, which it was possible to obtain the compressive stren...

  2. The effect of gypsum products and separating materials on the typography of denture base materials.

    Firtell, D N; Walsh, J F; Elahi, J M


    The typography of polymethyl methacrylate processed against various gypsum products coated with various separating materials was studied under an SEM. Tinfoil and two commercial tin foil substitutes were used as separating material during processing, and the surfaces of the resulting acrylic resin forms were studied for topographical differences. Tinfoil and alpha 2 hemihydrates produced the smoothest surfaces. As a practical solution, a good quality tinfoil substitute and alpha 1 hemihydrate could be used when processing polymethyl methacrylate resin.

  3. 用于外墙内侧、分户墙及顶棚补充节能的轻质石膏砂浆%Lightweight gypsum plaster used on exterior wall, party wall and ceiling for additional energy conservation

    叶蓓红; 施嘉霖; 谈晓青; 曹禹


    轻质石膏砂浆作为粉刷石膏的一个新品种,主要用于墙面的找平层,同时对外墙内侧、分户墙及顶棚具有补充节能的作用.配制时宜选择表面玻化率高、密度小的玻化微珠作为轻骨料,其掺量为石膏量的20%~35%;当采用膨胀珍珠岩作为轻骨料时,其掺量为石膏量的15%~25%;纤维素醚掺量一般为石膏量的0.2%~0.4%;引气剂的掺量为粉料总量的0.6%~1.2%.按m(石膏):m(玻化微珠):m(纤维素醚):m(引气剂):m (SC缓凝剂)=770.0:215.0:4.1:5.0:2.3制备的轻质石膏砂浆导热系数为0.12 W/(m·K),通过计算,采用20 mm厚轻质石膏砂浆代替传统水泥砂浆,对200 mm厚混凝土隔墙进行双面抹灰后,保温效果提高38%.%As a new species of plaster, lightweight gypsum plaster is mainly used for wall leveling layer,meanwhile it has additional energy conservation effect when applied on the inside surface of external wall,party wall and ceiling. During preparation,glass beads with high surface vitrify rate and low density are selected as lightweight aggregate,and its dosage is 20%~35% of the gypsum amount;when expanded perlite is as lightweight aggregate,its dosage is 15%~25% of the gypsum amount;the dosage of cellulose ether is generally 0.22%~0.4% of the gypsum amount;the dosage of air-entraining agent (AEA) is 0.6%~1.2% of the total powder quantity. When m (gypsum) ∶m (glass beads) ∶m (cellulose ethers) ∶m (AEA) ∶m (SC retarder) =770.0∶215.0∶4.1∶5,0∶2.3, the prepared lightweight gypsum plaster has thermal conductivity of 0.12 W/(m·K). The calculation results show that the insulating effect will be increased by 38% if 20 mm-thick this type of plaster instead of the ordinary cement mortar is applied on both sides of the 200 mm-thick concrete wall.

  4. Mercury transportation in soil via using gypsum from flue gas desulfurization unit in coal-fired power plant.

    Wang, Kelin; Orndorff, William; Cao, Yan; Pan, Weiping


    The mercury flux in soils was investigated, which were amended by gypsums from flue gas desulphurization (FGD) units of coal-fired power plants. Studies have been carried out in confined greenhouses using FGD gypsum treated soils. Major research focus is uptakes of mercury by plants, and emission of mercury into the atmosphere under varying application rates of FGD gypsum, simulating rainfall irrigations, soils, and plants types. Higher FGD gypsum application rates generally led to higher mercury concentrations in the soils, the increased mercury emissions into the atmosphere, and the increased mercury contents in plants (especially in roots and leaves). Soil properties and plant species can play important roles in mercury transports. Some plants, such as tall fescue, were able to prevent mercury from atmospheric emission and infiltration in the soil. Mercury concentration in the stem of plants was found to be increased and then leveled off upon increasing FGD gypsum application. However, mercury in roots and leaves was generally increased upon increasing FGD gypsum application rates. Some mercury was likely absorbed by leaves of plants from emitted mercury in the atmosphere.

  5. Implications of moisture content determination in the environmental characterisation of FGD gypsum for its disposal in landfills

    Alvarez-Ayuso, E. [Department of Environmental Geology, Institute of Earth Sciences ' Jaume Almera' (CSIC), C/ Lluis Sole i Sabaris s/n, 08028 Barcelona (Spain)], E-mail:; Querol, X. [Department of Environmental Geology, Institute of Earth Sciences ' Jaume Almera' (CSIC), C/ Lluis Sole i Sabaris s/n, 08028 Barcelona (Spain); Tomas, A. [Endesa Generacion, S.A., C/ Ribera de Loira 60, 28042 Madrid (Spain)


    The leachable contents of elements of environmental concern considered in the Council Decision 2003/33/EC on waste disposal were determined in flue gas desulphurisation (FGD) gypsum. To this end, leaching tests were performed following the standard EN-12457-4 which specifies the determination of the dry mass of the material at 105 deg. C and the use of a liquid to solid (L/S) ratio of 10 l kg{sup -1} dry matter. Additionally, leaching tests were also carried out taking into account the dry mass of the material at 60 deg. C and using different L/S ratios (2, 5, 8, 10, 15 and 20 l kg{sup -1} dry matter). It was found that the dry mass determination at 105 deg. C turns out to be inappropriate for FGD gypsum since at this temperature gypsum transforms into bassanite, and so, in addition to moisture content, crystalline water is removed. As a consequence the moisture content is overvalued (about 16%), what makes consider a lower L/S ratio than that specified by the standard EN-12457-4. As a result the leachable contents in FGD gypsum are, in general, overestimated, what could lead to more strict environmental requirements for FGD gypsum when considering its disposal in landfills, specially concerning those elements (e.g., F) risking the characterisation of FGD gypsum as a waste acceptable at landfills for non-hazardous wastes.

  6. Mercury transportation in soil via using gypsum from flue gas desulfurization unit in coal-fired power plant

    Kelin Wang; William Orndorff; Yan Cao; Weiping Pan


    The mercury flux in soils was investigated,which were amended by gypsums from flue gas desulphurization (FGD) units of coalfired power plants.Studies have been carried out in confined greenhouses using FGD gypsum treated soils.Major research focus is uptakes of mercury by plants,and emission of mercury into the atmosphere under varying application rates of FGD gypsum,simulating rainfall irrigations,soils,and plants types.Higher FGD gypsum application rates generally led to higher mercury concentrations in the soils,the increased mercury emissions into the atmosphere,and the increased mercury contents in plants (especially in roots and leaves).Soil properties and plant species can play important roles in mercury transports.Some plants,such as tall fescue,were able to prevent mercury from atmospheric emission and infiltration in the soil.Mercury concentration in the stem of plants was found to be increased and then leveled off upon increasing FGD gypsum application.However,mercury in roots and leaves was generally increased upon increasing FGD gypsum application rates.Some mercury was likely absorbed by leaves of plants from emitted mercury in the atmosphere.

  7. Modelling of Fluidised Geomaterials: The Case of the Aberfan and the Gypsum Tailings Impoundment Flowslides

    Paola Dutto


    Full Text Available The choice of a pure cohesive or a pure frictional viscoplastic model to represent the rheological behaviour of a flowslide is of paramount importance in order to obtain accurate results for real cases. The principal goal of the present work is to clarify the influence of the type of viscous model—pure cohesive versus pure frictional—with the numerical reproduction of two different real flowslides that occurred in 1966: the Aberfan flowslide and the Gypsum tailings impoundment flowslide. In the present work, a depth-integrated model based on the v - p w Biot–Zienkiewicz formulation, enhanced with a diffusion-like equation to account for the pore pressure evolution within the soil mass, is applied to both 1966 cases. For the Aberfan flowslide, a frictional viscous model based on Perzyna viscoplasticity is considered, while a pure cohesive viscous model (Bingham model is considered for the case of the Gypsum flowslide. The numerical approach followed is the SPH method, which has been enriched by adding a 1D finite difference grid to each SPH node in order to improve the description of the pore water evolution in the propagating mixture. The results obtained by the performed simulations are in agreement with the documentation obtained through the UK National Archive (Aberfan flowslide and the International Commission of large Dams (Gypsum flowslide.

  8. Histological Comparison in Rats between Carbonate Apatite Fabricated from Gypsum and Sintered Hydroxyapatite on Bone Remodeling

    Yasunori Ayukawa


    Full Text Available Carbonate apatite (CO3Ap, the form of apatite found in bone, has recently attracted attention. The purpose of the present study was to histologically evaluate the tissue/cellular response toward the low-crystalline CO3Ap fabricated using a dissolution-precipitation reaction with set gypsum as a precursor. When set gypsum was immersed in a 100°C 1 mol/L Na3PO4 aqueous solution for 24 h, the set gypsum transformed into CO3Ap. Both CO3Ap and sintered hydroxyapatite (s-HAp, which was used as a control, were implanted into surgically created tibial bone defects of rats for histological evaluation. Two and 4 weeks after the implantation, histological sections were created and observed using light microscopy. The CO3Ap granules revealed both direct apposition of the bone matrix by osteoblasts and osteoclastic resorption. In contrast, the s-HAp granules maintained their contour even after 4 weeks following implantation which implied that there was a lack of replacement into the bone. The s-HAp granules were sometimes encapsulated with fibrous tissue, and macrophage polykaryon was occasionally observed directly apposed to the implanted granules. From the viewpoint of bone remodeling, the CO3Ap granules mimicked the bone matrix, suggesting that CO3Ap may be an appropriate bone substitute.

  9. Do Ca2+-adsorbing ceramics reduce the release of calcium ions from gypsum-based biomaterials?

    Belcarz, Anna; Zalewska, Justyna; Pałka, Krzysztof; Hajnos, Mieczysław; Ginalska, Grazyna


    Bone implantable materials based on calcium sulfate dihydrate dissolve quickly in tissue liquids and release calcium ions at very high levels. This phenomenon induces temporary toxicity for osteoblasts, may cause local inflammation and delay the healing process. Reduction in the calcium ion release rate by gypsum could be therefore beneficial for the healing of gypsum-filled bone defects. The aim of this study concerned the potential use of calcium phosphate ceramics of various porosities for the reduction of high Ca(2+) ion release from gypsum-based materials. Highly porous ceramics failed to reduce the level of Ca(2+) ions released to the medium in a continuous flow system. However, it succeeded to shorten the period of high calcium level. It was not the phase composition but the high porosity of ceramics that was found crucial for both the shortening of the Ca(2+) release-related toxicity period and intensification of apatite deposition on the composite. Nonporous ceramics was completely ineffective for this purpose and did not show any ability to absorb calcium ions at a significant level. Moreover, according to our observations, complex studies imitating in vivo systems, rather than standard tests, are essential for the proper evaluation of implantable biomaterials.

  10. Surface induced constant composition crystal growth kinetics studies. The brushite gypsum system

    Hina, A.; Nancollas, G. H.; Grynpas, M.


    The possible oriented growth of one crystalline phase on the surface of another is especially important in systems containing both phosphate and sulfate salts of calcium. Whether the overgrowth results from a true epitaxial relationship is dependent on factors such as the thermodynamic driving forces and the free energies of the surfaces. Despite the fact that calcium sulfate dihydrate (CSD, gypsum) and calcium hydrogen phosphate dihydrate (DCPD, brushite) show many crystallographic and structural analogies, their surface reactions are quite different. The nucleation and growth of gypsum on brushite surfaces has been investigated in supersaturated solutions of calcium sulfate dihydrate at 25.0°C using the constant composition (CC) method. During the kinetics experiments, the harvested solid phases were examined by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDS). Induction periods, τ, preceding the initial formation of gypsum crystals at the brushite surfaces, varied markedly with relative supersaturation, σ. A thin layer wicking method was used to investigate the interfacial free energies of the growing phases, and these data were also calculated from the kinetics results. The interfacial free energy, γ, estimated from initial growth rates was 8.4 mJ m -2, while that calculated from the induction times was 8.9 mJ m -2. These values were in agreement with those determined directly using thin layer wicking.

  11. Risk minimisation of FGD gypsum leachates by incorporation of aluminium sulphate

    Alvarez-Ayuso, E. [Department of Environmental Geology, Institute of Earth Sciences ' Jaume Almera' (CSIC), C/ Lluis Sole i Sabaris, s/n, 08028 Barcelona (Spain); Department of Environmental Geochemistry, IRNASA, CSIC, Apto. 257, 37071 Salamanca (Spain)], E-mail:; Querol, X. [Department of Environmental Geology, Institute of Earth Sciences ' Jaume Almera' (CSIC), C/ Lluis Sole i Sabaris, s/n, 08028 Barcelona (Spain); Ballesteros, J.C.; Gimenez, A. [Endesa Generacion, S.A., C/ Ribera de Loira, 60, 28042 Madrid (Spain)


    The incorporation of aluminium sulphate to (flue gas desulphurisation) FGD gypsum before its disposal was investigated as a way to minimise the risk supposed by the high fluoride content of its leachates. Using a bath method the kinetic and equilibrium processes of fluoride removal by aluminium sulphate were studied at fluoride/aluminium molar concentration (F/Al) ratios in the range 1.75 10{sup -2}-1.75 under the pH conditions (about 6.5) of FGD gypsum leachates. It was found that fluoride removal was a very fast process at any of the (F/Al) ratios subject of study, with equilibrium attained within the first 15 min of interaction. High decreases in solution fluoride concentrations (50-80%) were found at the equilibrium state. The use of aluminium sulphate in the stabilization of FGD gypsum proved to greatly decrease its fluoride leachable content (in the range 20-90% for aluminium sulphate doses of 0.1-5%, as determined by the European standard EN 12457-4). Such fluoride leaching minimisation assures the characterization of this by-product as a waste acceptable at landfills for non-hazardous wastes according to the Council Decision 2003/33/EC on waste disposal. Furthermore, as derived from column leaching studies, the proposed stabilization system showed to be highly effective in simulated conditions of disposal, displaying fluoride leaching reduction values about 55 and 80% for aluminium sulphate added amounts of 1 and 2%, respectively.

  12. Numerical modelling and thermal simulation of PCM-gypsum composites with ESP-r

    Heim, D.; Clarke, J.A. [Department of Building Physics and Building Materials, Technical University of Lodz, Lodz (Poland)


    The aim of the present work is to refine the ESP-r system by incorporating phase change materials (PCMs) modelling. The behaviour of PCMs is modelled using ESP-r's special materials facility. The effect of phase transition is added to the energy balance equation as a latent heat generation term according to the so-called effective heat capacity method. Numerical simulations were conducted for a multi-zone, highly glazed and naturally ventilated passive solar building. PCM-impregnated gypsum plasterboard was used as an internal room lining. The air, surface and resultant temperatures were compared with the no-PCM case and the diurnal latent heat storage effect was analysed. While this effect did not cause a considerable reduction in the diurnal temperature fluctuation, the PCMs did effectively store solar energy in the transitions periods. Additionally, the energy requirement at the beginning and end of the heating season was estimated and compared with ordinary gypsum wallboard. Within this comparison, the PCM composite solidification temperature was 22 {sup o}C (i.e. 2 K higher than the heating set-point for the room). The results show that solar energy stored in the PCM-gypsum panels can reduce the heating energy demand by up to 90% at times during the heating season. (author)

  13. Developing biodiversity indicators on a stakeholders' opinions basis: the gypsum industry Key Performance Indicators framework.

    Pitz, Carline; Mahy, Grégory; Vermeulen, Cédric; Marlet, Christine; Séleck, Maxime


    This study aims to establish a common Key Performance Indicators (KPIs) framework for reporting about the gypsum industry biodiversity at the European level. In order to integrate different opinions and to reach a consensus framework, an original participatory process approach has been developed among different stakeholder groups: Eurogypsum, European and regional authorities, university scientists, consulting offices, European and regional associations for the conservation of nature, and the extractive industry. The strategy is developed around four main steps: (1) building of a maximum set of indicators to be submitted to stakeholders based on the literature (Focus Group method); (2) evaluating the consensus about indicators through a policy Delphi survey aiming at the prioritization of indicator classes using the Analytic Hierarchy Process method (AHP) and of individual indicators; (3) testing acceptability and feasibility through analysis of Environmental Impact Assessments (EIAs) and visits to three European quarries; (4) Eurogypsum final decision and communication. The resulting framework contains a set of 11 indicators considered the most suitable for all the stakeholders. Our KPIs respond to European legislation and strategies for biodiversity. The framework aims at improving sustainability in quarries and at helping to manage biodiversity as well as to allow the creation of coherent reporting systems. The final goal is to allow for the definition of the actual biodiversity status of gypsum quarries and allow for enhancing it. The framework is adaptable to the local context of each gypsum quarry.

  14. Thermal testing and numerical simulation of gypsum wallboards incorporated with different PCMs content

    Borreguero, Ana M.; Luz Sanchez, M.; Valverde, Jose Luis; Carmona, Manuel; Rodriguez, Juan F. [Department of Chemical Engineering, University of Castilla - La Mancha, Av. Camilo Jose Cela s/n, 13004 Ciudad Real (Spain)


    A mathematical model based on the Fourier heat conduction equation for one dimension was developed. The complexity of the mathematical solution of this stiff set of differential equations that use boundary conditions that move with the solid-liquid interface was simplified by using an apparent heat capacity (c{sub p}{sup ap}) dependent on temperature and obtained by Modulated Differential Scanning Calorimetry (MDSC). The performance of this model was confirmed by using a home-made experimental installation for the thermal characterization of solid materials. Theoretical curves obtained for gypsum blocks with three different contents of phase change materials (PCMs) were in agreement with experimental ones, indicating that this thermal process can be reproduced theoretically by using the c{sub p}{sup ap} of each block and a unique thermal conductivity of the pure gypsum. The other physical and thermal properties were taken from literature or supplied by the manufacturers. Results also indicated that the higher the PCM content, the higher the energy storage capacity of the wallboard and the lower the wall temperature variation. Furthermore, it was found that a block containing a 5 wt.% of microcapsule allows the reduction of gypsum thickness by 8.5%, maintaining the same insulating effect. Thus, these kind of material can be used to improve comfort, save energy in buildings and even reduce the weight of wallboards. (author)

  15. Thoughts on the Current Cement Industry Development

    Gan Zhihe


    According to the analysis of cement capacity andits relations with macro economy running index, the mainreasons for the present rapid development of cement capacityare the rapid development of economy and the shot up ofwhole society fixed asset investment. According to the presentspeed of economy development, cement still enjoys a po-tential increase, So here has not been an overall excessivepopularity of cement industry. The best way to prevent lowlevel repeated construction is to promote the development ofnew dry- process cement as well as try to get rid of blindness.

  16. CO2 Capture by Cement Raw Meal

    Pathi, Sharat Kumar; Lin, Weigang; Illerup, Jytte Boll


    The cement industry is one of the major sources of CO2 emissions and is likely to contribute to further increases in the near future. The carbonate looping process has the potential to capture CO2 emissions from the cement industry, in which raw meal for cement production could be used...... as the sorbent. Cyclic experiments were carried out in a TGA apparatus using industrial cement raw meal and synthetic raw meal as sorbents, with limestone as the reference. The results show that the CO2 capture capacities of the cement raw meal and the synthetic raw meal are comparable to those of pure limestone...... that raw meal could be used as a sorbent for the easy integration of the carbonate looping process into the cement pyro process for reducing CO2 emissions from the cement production process....

  17. Understanding cement mechanical behavior in SAGD wells

    Xie, J.; Zahacy, T. A. [C-FER Technologies (Canada)


    In the heavy oil industry, the steam assisted gravity drainage process is often used to enhance oil recovery but it can cause cracks in the cement sheath. These cracks are the result of high steam temperatures and thermal expansion. In order to mitigate this risk, improved well designs are required. The aim of this paper is to present the mechanical behavior of the cement sheath during the heating phase. An analysis of the impact of design and operating parameters was conducted through thermal hydraulic and thermal mechanical analyses to assess cement integrity. These analyses were then performed on an example of an SAGD project in the southern part of the Athabasca oilsands region to assess the performance of the cement sheath. Results showed that potential damage to the cement can be reduced by slow heating and a lower Young's modulus cement blend. This paper makes recommendations for optimizing cement design in thermal recovery wells.

  18. Laboratory Salinization of Brazilian Alluvial Soils and the Spectral Effects of Gypsum

    Luis Clenio J. Moreira


    Full Text Available Irrigation-induced salinization is an important land degradation process that affects crop yield in the Brazilian semi-arid region, and gypsum has been used as a corrective measure for saline soils. Fluvent soil samples (180 were treated with increasing levels of salinization of NaCl, MgCl2 and CaCl2. The salinity was gauged using electrical conductivity (EC. Gypsum was added to one split of these samples before they were treated by the saline solutions. Laboratory reflectance spectra were measured at nadir under a controlled environment using a FieldSpec spectrometer, a 250-W halogen lamp and a Spectralon panel. Variations in spectral reflectance and brightness were evaluated using principal component analysis, as well as the continuum-removed absorption depths of major features at 1450, 1950, 1750 and 2200 nm for both the gypsum-treated (TG and non-treated (NTG air-dried soil samples as a function of EC. Pearson’s correlation coefficients of reflectance and the band depth with EC were also obtained to establish the relationships with salinity. Results showed that NTG samples presented a decrease in reflectance and brightness with increasing CaCl2 and MgCl2 salinization. The reverse was observed for NaCl. Gypsum increased the spectral reflectance of the soil. The best negative correlations between reflectance and EC were observed in the 1500–2400 nm range for CaCl2 and MgCl2, probably because these wavelengths are most affected by water absorption, as Ca and Mg are much more hygroscopic than Na. These decreased after chemical treatment with gypsum. The most prominent features were observed at 1450, 1950 and 1750 nm in salinized-soil spectra. The 2200-nm clay mineral absorption band depth was inversely correlated with salt concentration. From these features, only the 1750 and 2200 nm ones are within atmospheric absorption windows and can be more easily measured using hyperspectral sensors.

  19. Theoretical determination of O and S isotope fractionations between gypsum and aqueous sulfate

    Liu, Y.; Bao, H.


    Some non-labile oxyanions, such as sulfate (SO42-) or nitrate (NO3-), do not exchange O atoms readily with O in water at ambient temperatures. They often behave like a single atom during mineral precipitation, dissolution, adsorption, and even microbial transport. Considering the many different isotopologues these oxyanions usually possess, for example, SO42- has 32-16-16-16-16, 34-16-16-16-16, 32-18-16-16-16, 34-18-16-16-16, …, etc., the behaviour of isotope fractionation for different elements in the oxyanions (e.g., O and S) may lead to certain degrees of coupling during different physical, chemical, and biological processes. Here, we use an aqueous sulfate - solid gypsum (CaSO4-2H2O) system to illustrate a first-principle approach to calculating the isotope fractionation factors and their coupling for O and S in sulfate during gypsum precipitation. Using Urey model or Bigeleisen-Mayer equation in combination with quantum chemistry calculations (at B3LYP/6-311+G(2df,p) level), we have calculated equilibrium isotope fractionation factors α18 and α34 for tens of isotopologues of SO42-. We use a time-consuming yet explicit solvent model (i.e. “water-droplet”) to precisely evaluate solvation effects for aqueous sulfate species. A large and partially fixed cluster model is used for simulating gypsum mineral surface. Our results show that the equilibrium fractionations at 25°C between solid gypsum and aqueous sulfate are ~ 2.5 and 1.6 ‰ for the Δδ18O and Δδ34S, respectively. Without considering ion-pair effect on sulfate anion in solution, however, the corresponding Δδ18O and Δδ34S become ~ 4.4 and 2.8 ‰, respectively. Our work presents a new approach to predicting isotope fractionation behaviour for no-labile species at equilibrium and lays the ground for evaluating kinetic effects. The results also shed lights on the mechanism and model for gypsum crystal growth at molecular level.

  20. EXAFS speciation and phytoavailability of Pb in a contaminated soil amended with compost and gypsum.

    Hashimoto, Yohey; Yamaguchi, Noriko; Takaoka, Masaki; Shiota, Kenji


    Due to unregulated uses of lead pellets for hunting purposes in Japan, soils and sediments in some river basins and wetlands have become highly contaminated with Pb. Deterioration of natural vegetation has occurred sporadically in these areas, and therefore revegetation is needed for ecological restoration. The objectives of the present study were to assess the effects of surface applications of compost and gypsum amendments on Pb availability to a watercress plant (Nasturtium officinale W.T. Aiton) and molecular-scale speciation of Pb in soil solid phases. The compost and gypsum amendments significantly decreased dissolved Pb and Sb in pore water. The concentration of Pb in aboveground plant tissues was 190mg kg(-1) in the control soil and was reduced to soils. The concentration of Sb in plants grown in the control soil was 13mg kg(-1), whereas that in the soils receiving compost and gypsum decreased below detectable levels. Redox potential was higher in vegetated soils (ave. 349mV) than in the unvegetated soils (ave. 99mV) due to oxygen introduced by plant roots. Extended X-ray absorption fine structure (EXAFS) spectroscopy illustrated that Pb occurred as Pb sorbed on birnessite and/or ferrihydrite (Pb-Mn/Fe, ~60%) and Pb sorbed on organic matter (Pb-org, ~15%), and galena (PbS, ~10%) in the vegetated and unvegetated control soils. The compost amendment increased the proportion of Pb-org by 2-fold than in the control soils. The amended soils with plant growth decreased the proportion of Pb-Mn/Fe phases by half of that without plant growth. Galena and anglesite (PbSO(4)) were not detected in compost-amended soils and even in gypsum-amended soils since a significant soil reduction to anoxic levels did not occur in the entire soil. The present study indicated that, under flooded conditions, surface applications of compost and gypsum amendments reduced plant Pb uptake from the Pb contaminated soil. Crown Copyright © 2010. Published by Elsevier B.V. All rights

  1. Some durability aspects of hybrid alkaline cements

    Donatello S.


    Full Text Available Blended cements that contain a high content of fly ash and a low content of Portland cement typically suffer from low early strength development and long setting times. Recently, one method of overcoming these problems has been to use an alkali activator to enhance the reactivity of fly ash particles at early ages. Such cements can be grouped under the generic term “hybrid alkaline cements”, where both cement clinker and fly ash, encouraged by the presence of alkalis, are expected to contribute to cementitious gel formation. The work presented here examines some of the durability aspects of high fly ash content hybrid alkaline cement. Specifically, the aspects investigated were: exposure at high temperatures (up to 1000°C, resistance to immersion in aggressive solutions and susceptibility to the alkali aggregate reaction. All tests were repeated with a commercially available sulfate resistant Portland cement for comparison. When exposed to high temperatures, the hybrid alkaline cement showed strikingly different behaviour compared to the control Portland cement, showing fewer micro-cracks and maintaining residual compressive strengths at least equal to original strengths. Beyond 700°C, the hybrid alkaline cement began to sinter, which resulted in shrinkage of around 5% and a 100% increase in residual compressive strengths. No such sintering event was noted in the control Portland cement, which showed a drastic loss in residual compressive strengths upon heating. In immersion tests, the hybrid alkaline cement possessed excellent resistance to sulfate and seawater attack, similar to the control sulfate resistant cement. Both cements were however severely degraded by immersion in 0.1M HCl for 90 days. Both binders complied with the accelerated alkali-aggregate test but when this test was extended, the hybrid alkaline binder showed much greater dimensional stability. Possible reasons for the differences in durability behaviour in both cements

  2. Sulfate Resistance of Alite-barium Calcium Sulphoaluminate Cement%阿利特-硫铝酸钡钙水泥抗硫酸盐侵蚀性能的研究

    李贵强; 芦令超; 王守德; 陈诚; 尹超男


    本文研究了石膏掺量对阿利特-硫铝酸钡钙水泥抗硫酸盐侵蚀性能的影响,并与硅酸盐水泥进行了比较;利用XRD,SEM-EDS等测试方法对侵蚀后水泥水化产物的物相组成和形貌进行了分析.研究结果表明:阿利特-硫铝酸钡钙水泥具有良好的抗硫酸盐侵蚀性能.当石膏掺量为5%时,阿利特-硫铝酸钡钙水泥的抗蚀系数达1.31,而硅酸盐水泥的抗蚀系数仅为0.94.石膏对阿利特-硫铝酸钡钙水泥硬化浆体的致密性有较大影响,进而影响水泥的抗硫酸盐侵蚀性能.同时,对阿利特-硫铝酸钡钙水泥的抗侵蚀机理进行了初步分析.%Effect of gypsum content on the sulfate resistance of alite-barium calcium sulphoaluminate cement was investigated. Portland cement was taken for comparison. The composition and microstructure of hardened cement pastes were analyzed by X-ray diffraction and scanning electron microscope. The results show that alite-barium calcium sulphoaluminate cement has better ability of sulfate resistance. The coefficient of resistance to sulfate attack with 5% gypsum addition in alite-barium calcium sulphoaluminate is 1.31, while that in Portland cement is only 0.94. Gypsum can affect the tightness of alite-barium calcium sulphoaluminate cement hardened pastes and further influence the ability of resistance to sulfate attack. At the same time, the mechanism of sulfate resistance of alite-barium calcium sulphoaluminate cement was discussed in this paper.

  3. Reforestation and landscape reconstruction in gypsum mine area from the semiarid region of NE Brazil

    Bittar, S. M. B.; Straaten, P. V.; de Araujo Vieura Santos, M. de Fatima; Agra Bezerra da Silva, Y. J.; da Silva, M.; Saraiva de Melo Pinheiro, T.; Gusmao Didier de Moraes, F.; de Aguiar Accioly, A. M.; Alves de Santana, S. R.; dos Santos, H. A.; de Carvalho, D. M.; de Lima Ferreira, G.; de Carvalho Santos, C.


    In the Araripe region, Northeast Brazil, exist the world's second largest reserve of gypsum, estimated at over than one billion tons, which accounts for 95% of the Brazilian production and constitutes an important segment of the regional economy. The gypsum deposit occurs in the Lower Cretaceous Santana Formation of the Araripe basin, which is constituted by siltstones, marls, limestones, shales and gypsum layers. The ore extraction is from an open pit, on simple benches with a height of about 15 meters. Activities in mining operations involve stripping, drilling, loading explosives, blast, fragmentation and block loading / transport. Currently, gypsum mining and processing results in major changes in the landscape (pits and wastes heaps sedimentary rocks and soil mixture), deforestation of the "caatinga" ecosystem for use as firewood in small calcinations, dust pollution and changes in hydrology. To promote environmental remediation of this area, a multidisciplinary research has being done with the aim to support reforestation at the wastes heaps. The study involved the following activities: collection and physical, chemical and mineralogical characterization of mine waste materials; a floristic survey around the mines (botanical identification and measuring physical parameters in 16 plots, in order to identify which species are best suited to the conditions of the substrate at the mine site); an experiment (randomized block design) developed in a greenhouse, where seedlings of various native tree species were grown in a "constructed soil" made up of gypsum waste combined with chicken, goat and cattle manure, aimed to select tree species and soil treatment to be used in a waste heap; and an assessment of water quality for irrigation of the reforestation areas. The waste materials consist of large clayey aggregates, which may present physical/chemical properties unfavorable for plant development. The mineralogy of the sand fraction (> 85% quartz, gypsum and

  4. Effect of Fly Ash on TSA Resistance of Cement-based Material

    ZHANG Fengchen; MA Baoguo; WU Shengxing; ZHOU Jikai


    Thaumasite form of sulfate attack (TSA) is a major concern in evaluating durability of concrete structures subjected to sulfate and carbonate ions. By means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM),and energy dispersive spectrum (EDS)as well as Raman spectra of erosion substances, effect of fly ash on TSA resistance of Portland cement-based material were investigated. Immersed in magnesium sulfate solution with 33 800 ppm mass concentration of SO42- at 5±2 ℃ for 15 weeks, ratio of compressive strength loss decreased as binder replacement ratio of fly ash increased. Furthermore, when binder replacement of fly ash was 60%, compressive strength increased. When thaumasite came into being in samples with 0, 15% binder replacement ratio of fly ash, ettringite and gypsum appeared in those with 30%, 45%, 60% binder replacement ratio of fly ash. Results mentioned above showed that fly ash can restrain formation of thaumasite and improve TSA resistance of Portland cement-based material sufficiently.

  5. Bacterial Communities and the Nitrogen Cycle in the Gypsum Soils of Cuatro Ciénegas Basin, Coahuila: A Mars Analogue

    López-Lozano, Nguyen E.; Eguiarte, Luis E.; Bonilla-Rosso, Germán; García-Oliva, Felipe; Martínez-Piedragil, Celeste; Rooks, Christine; Souza, Valeria


    The OMEGA/Mars Express hyperspectral imager identified gypsum at several sites on Mars in 2005. These minerals constitute a direct record of past aqueous activity and are important with regard to the search of extraterrestrial life. Gale Crater was chosen as Mars Science Laboratory Curiosity's landing site because it is rich in gypsum, as are some desert soils of the Cuatro Ciénegas Basin (CCB) (Chihuahuan Desert, Mexico). The gypsum of the CCB, which is overlain by minimal carbonate deposits...

  6. Limestone, gypsum and residual effect of fertilizers in the biomass production and nutrient cycling of millet plants

    Maria da Conceição Santana Carvalho


    Full Text Available Cover crops can provide a higher nutrient cycling. This study aimed to determine the effect of annual applications of gypsum and lime to the soil surface and of fertilizer doses to the previous crop (soybean in the dry biomass production and nutrient accumulation by plants of pearl millet grown in succession, under no-tillage system. The experimental design was randomized blocks, in a 4x4 factorial scheme, with four replications. Treatments consisted of the combination of four types of soil conditioner (lime, lime + gypsum, gypsum and control, split in three parts (2 t ha-1 of lime and 1,0 t ha-1 of gypsum; 2 t ha-1 of lime and 1 t ha-1 of gypsum; and 1 t ha-1 of lime and 0.5 t ha-1 of gypsum, and four fertilizing rates with P (triple and simple superphosphate and K (potassium chloride (0%, 50%, 100% and 150% of the recommended fertilizing, applied at the sowing of the previous crop (soybean. Liming provided increments in the dry biomass production and in the accumulation of nutrients (N, P, K, Ca, Mg and S by millet plants. The application of gypsum did not increase the millet dry biomass yield. The use of increasing rates of fertilizers in the previous crop (soybean increased the biomass dry matter, density and accumulation of nutrients by millet plants. The intercropping of millet as a cover crop, with the residual effect of the fertilizer applied in the summer crop, provided a nutrient cycling that can be used by the following crops.

  7. Research of magnesium phosphosilicate cement

    Ding, Zhu

    Magnesium phosphosilicate cement (MPSC) is a novel phosphate bonded cement, which consists mainly of magnesia, phosphate and silicate minerals. The traditional magnesium phosphate cements (MPCs) usually composed by ammonium phosphate, and gaseous ammonia will emit during mixing and in service. There is no noxious ammonia released from MPSC, furthermore, it can recycle a large volume of the non-hazardous waste. The goal of this research is to investigate the composition, reaction products, reaction mechanism, microstructure, properties, durability and applications of the MPSC. MPSC sets rapidly and has high early strength. It reacts better with solid industrial waste when compared to Portland cement. Many solid industrial wastes, such as fly ash, steel slag, coal gangue, red coal gangue, red mud, barium-bearing slag, copper slag, silica fume, and ground granulated blast furnace slag, have been used as the main component (40% by weight) in MPSC. The research has found that these aluminosilicate (or ironsilicate, or calciumsilicate) minerals with an amorphous or glass structure can enhance the performance of MPSC. The disorganized internal structure of amorphous materials may make it possess higher reactivity compared to the crystalline phases. Chemical reaction between phosphate and these minerals may form an amorphous gel, which is favorable to the cementing. Borax, boric acid and sodium tripolyphosphate have been used as retardants in the MPSC system. It is found that boric acid has a higher retarding effect on the setting of cement, than borax does. However, sodium polyphosphate accelerates the reaction of MPSC. The hydration of MPSC is exothermic reaction. The heat evolution may prompt hydrates formation, and shorten the setting process. Modern materials characterization techniques, XRD, DSC, TG-DTA FTIR, XPS, MAS-NMR, SEM, TEM, MIP, etc. were used to analyze the phase composition, micro morphology, and microstructure of hardened MPSC. The main hydration product

  8. Occupational hand dermatitis among cement workers in Taiwan

    Bour-Jr Wang


    Conclusion: We conclude that occupational cement hand dermatitis among cement workers is an important and severe issue in Taiwan, and the most common allergens among cement workers are potassium dichromate, thiuram mix, fragrance mix and cobalt chloride. The high positive rate of chromium hypersensitivity among cement workers reflects the urgency to regulate the addition of ferrous sulfate to cement in Taiwan.

  9. Alternative Fuels in Cement Production


    Substitutionen af fossilt med alternativt brændsel i cement produktionen er steget betydeligt i den sidste dekade. Af disse nye alternative brændsler, udgør de faste brændsler p.t. den største andel, hvor kød- og benmel, plastic og dæk i særdeleshed har været de alternative brændsler der har bidraget med mest alternativ brændsels energi til den tyske cement industri. De nye alternative brændsler er typisk karakteriseret ved et højt indhold af flygtige bestanddele og adskiller sig typisk fra t...

  10. Alkaline cement mortars. Chemical resistance to sulfate and seawater attack

    Puertas, F.


    Full Text Available The durability and chemical resistance of alkali activated slag and fly ash/slag mortars in contact with sulfates and seawater media have been studied. Two methods were used in the evaluation of such durability: Kock-Steinegger and ASTM C1012. A mineralogical and a microstructural characterization of mortars were done at different ages of their conservation in aggressive media through XRD, SEM/ EDX and mercury porosimetry. Results showed a high durability of activated cement mortars in sulfates and seawater media. NaOH activated mortars are the most sensitive to environment attack with formation of expansive products as gypsum and ettringite, although in very low proportion.

    Se ha estudiado la estabilidad química en medios sulfáticos y de agua de mar de morteros de escorias activadas alcalinamente y morteros de mezclas de escoria y cenizas volantes activadas alcalinamente. Se han empleado dos métodos para evaluar dicha estabilidad: Kock-Steinegger y la norma ASTM C1012. Se ha realizado una caracterización mineralógica y micro estructural de los morteros (a diferentes edades de permanencia en los medios agresivos a través de DRX, SEM/EDX y porosimetría de mercurio. Los resultados obtenidos han demostrado la elevada durabilidad de todos los morteros de cementos activados estudiados frente a la agresividad de los sulfatos y del agua de mar Los morteros de escoria activada con NaOH son los más susceptibles al ataque por esos medios, conformación de productos expansivos como el yeso y la etringita, aunque en proporciones muy bajas.

  11. A Twofold Comparison between Dual Cure Resin Modified Cement and Glass Ionomer Cement for Orthodontic Band Cementation

    Attar, Hanaa El; Elhiny, Omnia; Salem, Ghada; Abdelrahman, Ahmed; Attia, Mazen


    AIM: To test the solubility of dual cure resin modified resin cement in a food simulating solution and the shear bond strength compared to conventional Glass ionomer cement. MATERIALS AND METHOD: The materials tested were self-adhesive dual cure resin modified cement and Glass Ionomer (GIC). Twenty Teflon moulds were divided into two groups of tens. The first group was injected and packed with the modified resin cement, the second group was packed with GIC. To test the solubility, each mould was weighed before and after being placed in an analytical reagent for 30 days. The solubility was measured as the difference between the initial and final drying mass. To measure the Shear bond strength, 20 freshly extracted wisdom teeth were equally divided into two groups and embedded in self-cure acrylic resin. Four mm sections of stainless steel bands were cemented to the exposed buccal surfaces of teeth under a constant load of 500 g. Shear bond strength was measured using a computer controlled materials testing machine and the load required to deband the samples was recorded in Newtons. RESULTS: GIC showed significantly higher mean weight loss and an insignificant lower Shear bond strength, compared to dual cure resin Cement. CONCLUSION: It was found that dual cure resin modified cement was less soluble than glass ionomer cement and of comparable bond strength rendering it more useful clinically for orthodontic band cementation. PMID:28028417

  12. Influence of the temperature on the cement disintegration in cement-retained implant restorations.

    Linkevicius, Tomas; Vindasiute, Egle; Puisys, Algirdas; Linkeviciene, Laura; Svediene, Olga


    The aim of this study was to estimate the average disintegration temperature of three dental cements used for the cementation of the implant-supported prostheses. One hundred and twenty metal frameworks were fabricated and cemented on the prosthetic abutments with different dental cements. After heat treatment in the dental furnace, the samples were set for the separation to test the integration of the cement. Results have shown that resin-modified glass-ionomer cement (RGIC) exhibited the lowest disintegration temperature (pcement (ZPC) and dual cure resin cement (RC) (p>0.05). Average separation temperatures: RGIC - 306 ± 23 °C, RC - 363 ± 71 °C, it could not be calculated for the ZPC due to the eight unseparated specimens. Within the limitations of the study, it could be concluded that RGIC cement disintegrates at the lowest temperature and ZPC is not prone to break down after exposure to temperature.



    The article presents results of research of rotary-screw systems in relation to the creation of rotary kilns for the annealing of-cuttings in the preparation of cement clinker. Using the proposed design, in comparison with known designs of similar purpose, it significantly improves performance, reduces size and power consumption through the use of rotary screw systems in the form of screw rotors and drums made hollow with sidewalls assembled from separate strips or plates of different geometr...

  14. Center for Cement Composite Materials


    pastes have shown that the matrix is microporous; mesopores are absent unless the material is allowed to dry out. This results in water adsorption at low...only to water. When subsequently dried a portion of3 the porosity is converted to larger mesopores . • Only about one third of the cement reacts in a...Frictional sliding, in this case was characterized by a decreasing slope in the loading curve followed by hysteresis in the unload/reloading curves

  15. Long-term erosion rate measurements in gypsum caves of Sorbas (SE Spain) by the Micro-Erosion Meter method

    Sanna, Laura; De Waele, Jo; Calaforra, José Maria; Forti, Paolo


    The present work deals with the results of long-term micro-erosion measurements in the most important gypsum cave of Spain, the Cueva del Agua (Sorbas, Almeria, SE Spain). Nineteen MEM stations were positioned in 1992 in a wide range of morphological and environmental settings (gypsum floors and walls, carbonate speleothems, dry conduits and vadose passages) inside and outside the cave, on gypsum and carbonate bedrocks and exposed to variable degree of humidity, different air flow and hydrodynamic conditions. Four different sets of stations have been investigated: (1) the main cave entrance (Las Viñicas spring); (2) the main river passage; (3) the abandoned Laboratory tunnel; and (4) the external gypsum surface. Data over a period of about 18 years are available. The average lowering rates vary from 0.014 to 0.016 mm yr- 1 near the main entrance and in the Laboratory tunnel, to 0.022 mm - 1 on gypsum floors and 0.028 mm yr- 1 on carbonate flowstones. The denudation data from the external gypsum stations are quite regular with a rate of 0.170 mm yr- 1. The observations allowed the collecting of important information concerning the feeding of the karst aquifer not only by infiltrating rainwater, but under present climate conditions also by water condensation of moist air flow. This contribution to the overall karst processes in the Cueva del Agua basin represents over 20% of the total chemical dissolution of the karst area and more than 50% of the speleogenetically removed gypsum in the cave system, thus representing all but a secondary role in speleogenesis. Condensation-corrosion is most active along the medium walls, being slower at the roof and almost absent close to the floor. This creates typical corrosion morphologies such as cupola, while gypsum flowers develop where evaporation dominates. This approach also shows quantitatively the morphological implications of condensation-corrosion processes in gypsum karst systems in arid zones, responsible for an




    Full Text Available India is one among the fast developing countries in the world in the areas of Infrastructure. Now a day, Carbon monoxide (CO and carbon dioxide (CO2 are the temporary atmospheric pollutants in the environment chiefly emitted from the fuel burning vehicles and street lights which lead to global warming and pose a major threat tothe survival and sustainable development. This paper deals with the principal purpose of use of white cement in pavement design which will take care of the Green house gases (i.e., CO and CO2 and also saves lot of money in the long run process. A small amount of these gases in environment can cause major problems over time. Use of white cement in composite pavement design where there is heavy traffic loads are acting as well as number of vehicles are more such as junctions, bus stops, check posts etc., can perform better and acts asenvironment friendly. Its light colour reflects more than bituminous pavement so that it can be easily identified and avoid accidents to some extent. White cement helps to lower the average bus stop, junction temperature providing comfort to the people because it has high solar reflectance there by reducing “urban heat island” effect. In addition to this it has some more advantages which increase the sustainability, durability and workability of the pavements.

  17. Visualization of the structural changes in plywood and gypsum board during the growth of Chaetomium globosum and Stachybotrys chartarum.

    Lewinska, Anna M; Hoof, Jakob B; Peuhkuri, Ruut H; Rode, Carsten; Lilje, Osu; Foley, Matthew; Trimby, Patrick; Andersen, Birgitte


    Fungal growth in indoor environments is associated with many negative health effects. Many studies focus on brown- and white-rot fungi and their effect on wood, but there is none that reveals the influence of soft-rot fungi, such as Stachybotrys spp. and Chaetomium spp., on the structure of building materials such as plywood and gypsum wallboard. This study focuses on using micro-computed tomography (microCT) to investigate changes of the structure of plywood and gypsum wallboard during fungal degradation by S. chartarum and C. globosum. Changes in the materials as a result of dampness and fungal growth were determined by measuring porosity and pore shape via microCT. The results show that the composition of the building material influenced the level of penetration by fungi as shown by scanning electron microscopy (SEM). Plywood appeared to be the most affected, with the penetration of moisture and fungi throughout the whole thickness of the sample. Conversely, fungi grew only on the top cardboard in the gypsum wallboard and they did not have significant influence on the gypsum wallboard structure. The majority of the observed changes in gypsum wallboard occurred due to moisture. This paper suggests that the mycelium distribution within building materials and the structural changes, caused by dampness and fungal growth, depend on the type of the material.

  18. GyPSuM: A Detailed Tomographic Model of Mantle Density and Seismic Wave Speeds

    Simmons, N A; Forte, A M; Boschi, L; Grand, S P


    GyPSuM is a tomographic model fo mantle seismic shear wave (S) speeds, compressional wave (P) speeds and detailed density anomalies that drive mantle flow. the model is developed through simultaneous inversion of seismic body wave travel times (P and S) and geodynamic observations while considering realistic mineral physics parameters linking the relative behavior of mantle properties (wave speeds and density). Geodynamic observations include the (up to degree 16) global free-air gravity field, divergence of the tectonic plates, dynamic topography of the free surface, and the flow-induced excess ellipticity of the core-mantle boundary. GyPSuM is built with the philosophy that heterogeneity that most closely resembles thermal variations is the simplest possible solution. Models of the density field from Earth's free oscillations have provided great insight into the density configuration of the mantle; but are limited to very long-wavelength solutions. Alternatively, simply scaling higher resolution seismic images to density anomalies generates density fields that do not satisfy geodynamic observations. The current study provides detailed density structures in the mantle while directly satisfying geodynamic observations through a joint seismic-geodynamic inversion process. Notable density field observations include high-density piles at the base of the superplume structures, supporting the fundamental results of past normal mode studies. However, these features are more localized and lower amplitude than past studies would suggest. When we consider all seismic anomalies in GyPSuM, we find that P and S-wave speeds are strongly correlated throughout the mantle. However, correlations between the high-velocity S zones in the deep mantle ({approx} 2000 km depth) and corresponding P-wave anomalies are very low suggesting a systematic divergence from simplified thermal effects in ancient subducted slab anomalies. Nevertheless, they argue that temperature variations are

  19. Sustainable Development of the Cement Industry and Blended Cements to Meet Ecological Challenges

    Konstantin Sobolev


    The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA) cement helps to improve its ecologi...

  20. Water dynamics in glass ionomer cements

    Berg, M. C.; Jacobsen, J.; Momsen, N. C. R.; Benetti, A. R.; Telling, M. T. F.; Seydel, T.; Bordallo, H. N.


    Glass ionomer cements (GIC) are an alternative for preventive dentistry. However, these dental cements are complex systems where important motions related to the different states of the hydrogen atoms evolve in a confined porous structure. In this paper, we studied the water dynamics of two different liquids used to prepare either conventional or resin-modified glass ionomer cement. By combining thermal analysis with neutron scattering data we were able to relate the water structure in the liquids to the materials properties.

  1. Pulmonary Cement Embolism following Percutaneous Vertebroplasty

    Ümran Toru


    Full Text Available Percutaneous vertebroplasty is a minimal invasive procedure that is applied for the treatment of osteoporotic vertebral fractures. During vertebroplasty, the leakage of bone cement outside the vertebral body leads to pulmonary cement embolism, which is a serious complication of this procedure. Here we report a 48-year-old man who was admitted to our hospital with dyspnea after percutaneous vertebroplasty and diagnosed as pulmonary cement embolism.

  2. 常压盐溶液脱硫石膏转化生成α-半水石膏%Transformation of Flue-Gas-Desulfurization Gypsum to α-Hemihydrated Gypsum in Salt Solution at Atmospheric Pressure

    吴晓琴; 童仕唐; 官宝红; 吴忠标


    Direct phase transformation of flue gas desulfurization gypsum in hot salt solution at atmospheric pressure was investigated. The effects of temperature, salt species, salt concentration, solids content, pH and modifier were examined. The crystals obtained under different conditions and solubility of calcium sulfate in contact with solid gypsum were also determined. α-Calcium sulfate hemihydrate crystals of stubby columnar shape and regular pentahedral sides were obtained under the following conditions: salt concentration 20%-30%, operation temperature 95-100 ℃, solids mass content in the slurry 10%-30% and neutral pH. Thermodynamic analysis revealed that phase transformation of calcium sulfate dihydrate to α-calcium suffate hemihydrate occurs because of the difference in solubilities between the two solid gypsum phases in this system.

  3. Climatic control on the growth of gigantic gypsum crystals within hypogenic caves (Naica mine, Mexico)?

    Garofalo, Paolo S.; Fricker, Mattias B.; Günther, Detlef; Forti, Paolo; Mercuri, Anna-Maria; Loreti, Mara; Capaccioni, Bruno


    Three hypogenic caves within the Naica mine of Mexico ( Cueva de los Cristales — CLC, Ojo de la Reina — OR, and Cueva de las Velas — CLV) host spectacular gypsum crystals up to 11 m in length. These caves are close to another shallow cave of the area ( Cueva de las Espadas — CLE), with which they cover a 160 m-deep vertical section of the local drainage basin. Similar to other hypogenic caves, all these caves lack a direct connection with the land surface and should be unrelated with climate. A record of multi-technique fluid inclusion data and pollen spectra from cave and mine gypsum indicates surprisingly that climatic changes occurring at Naica could have controlled fluid composition in these caves, and hence crystal growth. Microthermometry and LA-ICP-Mass Spectrometry of fluid inclusions indicate that the shallow, chemically peculiar, saline fluid (up to 7.7 eq. wt.%NaCl) of CLE could have formed from evaporation, during a dry and hot climatic period. The fluid of the deep caves was instead of low salinity (˜ 3.5 eq. wt.% NaCl) and chemically homogeneous, and was poorly affected by evaporation. We propose that mixing of these two fluids, generated at different depths of the Naica drainage basin, determined the stable supersaturation conditions for the gigantic gypsum crystals to grow. Fluid mixing was controlled by the hydraulic communication between CLE and the other deep caves, and must have taken place during cycles of warm-dry and fresh-wet climatic periods, which are known to have occurred in the region. Pollen grains from a 35 ka-old gypsum crystal of CLC corresponds to a fairly homogenous catchment basin made of a mixed broadleaf wet forest, which suggests precipitation during a fresh-wet climatic period and confirms our interpretation of the fluid inclusion data. The unusual combination of geological and geochemical factors of Naica suggests that other hypogenic caves found elsewhere may not host similar crystals. However, this work shows that

  4. Utilization of the gypsum from a wet limestone flue gas desulfurization process

    Chou, I.-Ming; Patel, V.; Lytle, J.M.; Chou, S.J.; Carty, R.H.


    The authors have been developing a process which converts FGD-gypsum to ammonium sulfate fertilizer with precipitated calcium carbonate as a by-product during the conversion. Preliminary cost estimates suggest that the process is economically feasible when ammonium sulfate crystals are produced in a granular size (1.2 to 3.3 mm), instead of a powder form. However, if additional revenue from the sale of the PCC for higher-value commercial application is applicable, this could further improve the economics of the process. Ammonium sulfate is known to be an excellent source of nitrogen and sulfur in fertilizer for corn and wheat production. It was not known what impurities might co-exist in ammonium sulfate derived from scrubber gypsum. Before the product could be recommended for use on farm land, the impurities and their impact on soil productivity had to be assessed. The objectives of this phase of the study were to evaluate the chemical properties of ammonium sulfate made from the FGD-gypsum, to estimate its effects on soil productivity, and to survey the marketability of the two products. The results of this phase of the study indicated that the impurities in the ammonium sulfate produced would not impose any practical limitations on its use at application levels used by farmers. The market survey showed that the sale price of solid ammonium sulfate fertilizer increased significantly from 1974 at $110/ton to 1998 at $187/ton. Utilities currently pay $16 to $20/ton for the calcium carbonate they use in their flue gas scrubber system. The industries making animal-feed grade calcium supplement pay $30/ton to $67/m-ton for their source of calcium carbonate. Paper, paint, and plastic industries pay as much as $200 to $300/ton for their calcium carbonate filers. The increased sale price of solid ammonium sulfate fertilizer and the possible additional revenue from the sale of the PCC by-product could further improve the economics of producing ammonium sulfate from FGD-gypsum.

  5. Perimbangan Gypsum Bonded Investment terhadap Penysutan Logam Paduan Emas pada Saat Pengecoran

    Ronnie Rusli


    Full Text Available Gypsum bonded investment is usually used for dental gold alloys casting procedure. Casting alloys shrink during solidified from melting temperature to room temperature. In order to obtain an accurate restoration, the shrinkage of the alloy should be compensated by the expansion of the investment at the time of casting procedure. Ideally, the shrinkage of the alloy is equal to the expansion of the investment. However, no investment material fulfills this ideal condition properly. In this paper, how the investment material compensated the shrinkage of the casting alloys will be described briefly.

  6. Constraints from sulfur isotopes on the origin of gypsum at concrete/claystone interfaces

    Lerouge, Catherine; Claret, Francis; Tournassat, Christophe; Grangeon, Sylvain; Gaboreau, Stéphane; Boyer, Bernard; Borschnek, Daniel; Linard, Yannick

    Two in situ concrete/claystone interfaces were sampled at the laboratory level in the Andra Meuse/Haute Marne (France) Underground Research Laboratory (URL) in order to study five years of interactions between Callovian-Oxfordian (COx) claystone and two cementitious materials (concrete bottom slab and shotcrete on the walls of the main gallery), with a specific focus on sulfur. Combined mineralogical, chemical and sulfur isotopic investigations were carried out to define the degree of the perturbation of the sulfur system in the claystone and in both the cementitious materials. At both interfaces, results show that the main perturbation on the claystone side is the formation of scarce μm-sized gypsum, the sulfur content of which is essentially derived from pyrite oxidation. The distribution of gypsum is highly correlated with the fissure network of the damaged zone due to excavation of the gallery. Its presence is also often associated with a loss of cohesion of the concrete/claystone interface. Due to the small amounts of gypsum and its μm-size, measurements were performed by ion microprobe. Adaptations were needed on account of the reactivity of gypsum and sulfates in general under the beam. The use of ion microprobe analysis provided evidence of high local isotopic heterogeneity that could be attributed to kinetic fractionation effects. Some analyses suggest a minor contribution of dissolved sulfates in pore water of claystone and possibly of concrete. The perturbation on the concrete side is marked by a significant increase in the bulk sulfur content within three millimeters of the interface with the claystone, showing a sulfur gradient from claystone to concrete. The main objective of this work was to define the extent of the chemical and mineralogical perturbations, taking into account in situ URL conditions, i.e. hydrodynamic conditions (shotcrete sprayed on the gallery walls and subjected to ventilation of the galleries), damaged zone of claystone induced

  7. Glomalin Production and Microbial Activity in Soils Impacted by Gypsum Mining in a Brazilian Semiarid Area

    Adalia C.E.S. Mergulhao


    Full Text Available Problem statement: Mining activities involve the removal of the vegetal cover and the soil organic layer, causing a severe environmental impact. In Northeast Brazil, 40% of the worlds crude gypsum is found in a semiarid area, making this region responsible for 95% of the gypsum demand in the national market. Although economically important, this activity is harmful to the environment. Studies of soil microbiological and biochemical attributes can help in the identification of the limitations of impacted ecosystems, providing data to define strategies for sustainability of such environments. Approach: To evaluate and compare the biological state of preserved and mining degraded semiarid soils, a native preserved area and areas impacted by gypsum mining were selected at the Araripina Experimental Station, located in the semiarid region of Pernambuco State, Northeast Brazil. The four sampling areas included: (1 A native, preserved �caatinga� area with spine bearing trees and shrubs and some characteristic xerophytic plants (AN; (2 An area surrounding the mine, presenting the same type of vegetation although already degraded (AM; (3 A waste deposit area (AR; (4 Interface area between the waste deposit and a mining degraded area (AI. Samples were taken in each area (1000 m2 during two periods: wet (December/2003, Rainfall = 28.7 mm and dry (September/2004, Rainfall = 1.3 mm. Results: Fluorescein diacetate hydrolysis values, microbial biomass C and basal respiration were higher in the preserved caatinga than in the impacted areas. The gypsum mining activity reduced the concentration of easily extractable glomalin in relation to the native caatinga area in both sampling periods. Higher deposits of total glomalin also occurred in the native area, however, mainly during the wet period. Conclusion: The mining activity produced a negative impact on the soil microbiota, reducing the total enzymatic activity. The microbial

  8. Physical and mechanical characterization of gypsum boards containing phase change materials for latent heat storage

    Oliver-Ramírez, A.


    Full Text Available This article describes the design and manufacture of a gypsum board which, despite its 45 % wt content of phase change materials, meets the minimum physical and mechanical requirements laid down in the legislation on gypsum plasters (Spanish and European standard UNE EN 13279 and Spanish specifications for gypsum acceptance, RY 85. Under this design, a one-metre square, 1.5-cm thick board contains 4.75 kg of PCM, much more than in any prior drylining (the maximum attained to date is 3 kg per m2. The mechanical and physical characteristics of this new composite were previously improved with two joint-action additives: polypropylene fibres and melamine formaldehyde as a dispersing agent. In the 20-30 ºC temperature range, a gypsum board 1.5 cm thick containing this percentage of PCMs can store five times more thermal energy than conventional plasterboard of the same thickness, and the same amount of energy as half-foot hollow brick masonry.

    En esta investigación se ha diseñado y fabricado un panel de escayola que incorpora un 45% en peso de material de cambio de fase, manteniendo las propiedades físicas y mecánicas exigidas en la normativa de aplicación para yesos de construcción (UNE EN 13279 y referencias a la RY 85. Así, un panel de 1,0 m2 y 1,5 cm de espesor, contiene 4,75 kg de PCM, cantidad muy superior a la conseguida hasta la fecha (3 kg/m2. Para ello se ha mejorado previamente sus prestaciones mecánicas y físicas mediante adiciones binarias: fibras de polipropileno y dispersión de melanina formaldehído. Este porcentaje es capaz de almacenar en 1,5 cm de espesor cinco veces la energía térmica de un panel de cartón yeso con el mismo espesor y la misma cantidad que una fábrica de 1/2 pie de ladrillo hueco, en el rango de temperaturas próximas a la de confort (20-30 ºC.

  9. Effects of cement flue dusts from a Nigerian cement plant on air, water and planktonic quality.

    Olaleye, Victor F; Oluyemi, Emmanuel A


    Effects of cement flue dust from Ewekoro cement Kilns were monitored at some aquatic receptor locations. High levels of total suspended particulates (TSPs) and atmospheric deposition rates (ADRs) were recorded within the factory compared to ancillary locations outside the factory. The TSP and ADR levels which were location dependent were significantly higher (P cement factory catchment areas.

  10. The mechanical effects of different levels of cement penetration at the cement-bone interface.

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.


    The mechanical effects of varying the depth of cement penetration in the cement-bone interface were investigated using finite element analysis (FEA) and validated using companion experimental data. Two FEA models of the cement-bone interface were created from micro-computed tomography data and the p

  11. The influence of ultrasound on removal of prefabricated metal post cemented with different resin cements

    Atiyeh Feiz


    Conclusion: Ultrasonic energy did not decrease the retention of posts cemented with Panavia or Maxcem Elite cements. Furthermore, it seems that there is no significant difference between removal force of self-etch (Panavia and the self-etch self-adhesive (Maxcem Elite resin cements.

  12. Frozen delivery of brushite calcium phosphate cements.

    Grover, Liam M; Hofmann, Michael P; Gbureck, Uwe; Kumarasami, Balamurgan; Barralet, Jake E


    Calcium phosphate cements typically harden following the combination of a calcium phosphate powder component with an aqueous solution to form a matrix consisting of hydroxyapatite or brushite. The mixing process can be very important to the mechanical properties exhibited by cement materials and consequently when used clinically, since they are usually hand-mixed their mechanical properties are prone to operator-induced variability. It is possible to reduce this variability by pre-mixing the cement, e.g. by replacing the aqueous liquid component with non-reactive glycerol. Here, for the first time, we report the formation of three different pre-mixed brushite cement formulations formed by freezing the cement pastes following combination of the powder and liquid components. When frozen and stored at -80 degrees C or less, significant degradation in compression strength did not occur for the duration of the study (28 days). Interestingly, in the case of the brushite cement formed from the combination of beta-tricalcium phosphate with 2 M orthophosphoric acid solution, freezing the cement paste had the effect of increasing mean compressive strength fivefold (from 4 to 20 MPa). The increase in compression strength was accompanied by a reduction in the setting rate of the cement. As no differences in porosity or degree of reaction were observed, strength improvement was attributed to a modification of crystal morphology and a reduction in damage caused to the cement matrix during manipulation.

  13. Substantial global carbon uptake by cement carbonation

    Xi, Fengming; Davis, Steven J.; Ciais, Philippe; Crawford-Brown, Douglas; Guan, Dabo; Pade, Claus; Shi, Tiemao; Syddall, Mark; Lv, Jie; Ji, Lanzhu; Bing, Longfei; Wang, Jiaoyue; Wei, Wei; Yang, Keun-Hyeok; Lagerblad, Björn; Galan, Isabel; Andrade, Carmen; Zhang, Ying; Liu, Zhu


    Calcination of carbonate rocks during the manufacture of cement produced 5% of global CO2 emissions from all industrial process and fossil-fuel combustion in 2013. Considerable attention has been paid to quantifying these industrial process emissions from cement production, but the natural reversal of the process--carbonation--has received little attention in carbon cycle studies. Here, we use new and existing data on cement materials during cement service life, demolition, and secondary use of concrete waste to estimate regional and global CO2 uptake between 1930 and 2013 using an analytical model describing carbonation chemistry. We find that carbonation of cement materials over their life cycle represents a large and growing net sink of CO2, increasing from 0.10 GtC yr-1 in 1998 to 0.25 GtC yr-1 in 2013. In total, we estimate that a cumulative amount of 4.5 GtC has been sequestered in carbonating cement materials from 1930 to 2013, offsetting 43% of the CO2 emissions from production of cement over the same period, not including emissions associated with fossil use during cement production. We conclude that carbonation of cement products represents a substantial carbon sink that is not currently considered in emissions inventories.

  14. Hidration kinetics study of tlie mixed cements

    Duque Fernández, Gabriel . L; Díaz Quintanilla, David; Zapata Sierra, Manuel; Rubio Frías, Ester


    A study of the hydration process of cements with 10% and 20% addition of a tuff from "Las Carolinas" quarry (Cienfuegos, Cuba) by different methods was done. The results obtained by different methods showed a good agreement. It was proved an increment of the hydration products, an acceleration of alite hydration and a swelling of the fixed water in mixed cements. The resistance of the cement with 10% addition is similar to that of the pure cement for ages of 28 days, whereas with 20% addition...

  15. Determining cement ball mill dosage by artificial intelligence tools aimed at reducing energy consumption and environmental impact

    Julio R. Gómez Sarduy


    Full Text Available Energy management systems can be improved by using artificial intelligence techniques such as neural networks and genetic algorithms for modelling and optimising equipment and system energy consumption. This paper proposes modelling ball mill consumption as used in the cement industry from field variables. The regression model was based on artificial neural networks for predicting the electricity consumption of the mill’s main drive and evaluating established consumption rate performance. This research showed the influence of the amount of pozzolanic ash, gypsum and clinker on a mill’s power consumption; the dose determined according to the model ensured minimum energy consumption using a simple genetic algorithm. The estimated savings potential from the proposed dose was 36 600 kWh / year for mill number 1, representing $5,793.78 / year and a 33,708 kg CO2 / year reduction in the environmental impact of gas left to escape.

  16. A study on provisional cements, cementation techniques, and their effects on bonding of porcelain laminate veneers.

    Vinod Kumar, G; Soorya Poduval, T; Bipin Reddy; Shesha Reddy, P


    Minimal tooth preparation is required for porcelain laminate veneers, but interim restorations are a must to protect their teeth against thermal insult, chemical irritation, and to provide aesthetics. Cement remaining after the removal of the provisional restoration can impair the etching quality of the tooth surface and fit and final bonding of the porcelain laminate veneer. This in vitro study examined the tooth surface for remaining debris of cement after removal of a provisional restoration. Determine the presence of cement debris on prepared tooth surface subsequent to the removal of provisional restoration. Determine the cement with the least residue following the cleansing procedures. Determine the effect of smear layer on the amount of residual luting cement. Eighty-four extracted natural anterior teeth were prepared for porcelain laminate veneers. For half of the teeth, the smear layer was removed before luting provisional restorations. Veneer provisional restorations were fabricated and luted to teeth with six bonding methods: varnish combined with glass ionomer cement (GIC), varnish combined with resin modified GIC, varnish, spot etching combined with dual-cure luting cement, adhesive combined with GIC, adhesive combined with resin modified GIC, and adhesive, spot etching combined with dual-cure luting cement. After removal of provisional restorations 1 week later, the tooth surface was examined for residual luting material with SEM. Traces of cement debris were found on all the prepared teeth surfaces for all six groups which were cemented with different methods. Cement debris was seen on teeth subsequent to the removal of provisional's. Dual-cure cement had the least residue following the cleansing procedures. Presence of smear layer had no statistical significance in comparison with cement residue. With the use of adhesive the cement debris was always found to be more than with the use of varnish. GIC showed maximum residual cement followed by dual-cure.

  17. Study on witherite as admixture of cement%毒重石作水泥混合材的研究

    刘煦; 吕淑珍; 霍冀川


    结合毒重石质量优、易加工、生产成本低及吸收X射线、γ射线等特点,制备了以普通硅酸盐水泥熟料为主要原料,毒重石作水泥混合材,辅以适量石膏的水硬性胶凝材料.考察了毒重石掺量对水泥标准稠度用水量、凝结时间、安定性、不同龄期机械强度以及辐射屏蔽能力的影响.结果表明:毒重石对普通硅酸盐水泥熟料具有一定的缓凝作用;毒重石本身参与水化的能力很差,在水泥中基本上是作为非活性掺和材料,主要起填料的作用;毒重石水泥具有一定的辐射屏蔽能力,且随着毒重石掺量的增加,水泥的屏蔽效果增强.%Combining witherite's characteristics,such as high quality,easy-processing,low production cost,absorbing X ray and y ray etc.,hydraulic cementing material was prepared by using ordinary portland cement clinker as main material, witherite as admixture,and proper amount of gypsum as excipients.Influences of different witherite doping contents on water requirement of normal consistency, setting time, soundness, mechanical strength, and radiation shield performance of the cement were investigated.Results showed that witherite had some retarding effect on the Portland cement clinker.However.the ability of witherite to participate in hydration of cement clinker was so poor that it was basically being an inactive admixture and played a role of filler in cement.Cement based materials with witherite as admixture had certain radiation shield ability, and the radiation shielding effect was more apparent as the content of witherite increased.

  18. Influence of clinker grinding-aids on the intrinsic characteristics of cements and on the behaviour of mortars

    Fernández Luco, L.


    Full Text Available In the production of portland cement, grinding aids are used to improve the grinding stage and reduce the energy required to achieve the required fineness. These additives remain in the final product and they might influence the characteristics and properties of the cement, and thus, mortar and concrete. This paper presents an evaluation of two grinding-aid additives used in the production of portland cement ground in a ball mill at a laboratory stage, with suitable proportions of portland cement clinker and gypsum. A control cement mix was also produced without using any admixture and the results are shown on a comparative basis. Conclusions indicate that grinding-aids additives have some influence on the characteristics of portland cement produced, increasing their specific surface and modifying microstructure and its packing ability. Mortars and concretes made with cements ground with the addition of gringing-aids exhibit higher strength at any age and a reduced water demand. Special attention should be taken to consider any interaction with water-reducing admixture in concretes and mortars.

    En la fabricación de cemento portland es una práctica creciente la utilización de aditivos para optimizar el proceso de molienda; éstos quedan incorporados en el producto final y pueden influir sobre las características y propiedades del cemento, morteros y hormigones. En este trabajo se presenta la evaluación de dos aditivos comerciales en la molienda conjunta de clínker de cemento portland y yeso comercial, tratados en un molino a bolas a escala de laboratorio, en forma comparativa con un cemento sin aditivo producido en forma equivalente. Las conclusiones indican que los aditivos de molienda tienen influencia en las características del cemento resultante, incrementando su superficie y modificando su microestructura y estado de agregación; los morteros mejoran sus prestaciones mecánicas a todas las edades y se reduce la demanda de agua

  19. A win/win solution for FGD-gypsum: researches discover beneficial applications for by-product in agriculture

    Ramsier, C.; Norton, D. [AG Spectrum Co. (United States)


    Research at the Ohio State University and the USDA-ARS National Soil Erosion Research Lab at Purdue University has uncovered some viable new reasons for using FGD-gypsum as a regular part of production agriculture. Work has centered on FGD gypsum or calcium sulfite and to a much lesser extent on fly ash. Researchers have found three agronomically valuable functions of these materials. First, and most obvious, is the fertilizer value of these materials. Gypsum applications to the soil surface provide the rainfall with an alternative source of electrolyte which prevents soil crushing, thus keeping the soil open and permeable to rainwater and air. Gypsum is more effective than liming materials atremediation of sub-soil acidity by detoxifying the excess exchangeable aluminium, which causes low pH. One proven way to sequester carbon is to fix it as organic matter in soil. 90% of the carbon in roots is converted to soil organic matter, whereas 90% of surface residue is oxide and the carbon returned to the atmosphere. Therefore, more carbon is sequestered by increasing root growth. Improved soil water management also reduces nitrous oxide emissions from soils. The utility's world is improved since the highest quality and lowest cost material is generated by an emission control scrubber as FGD-gypsum. There are more than 175 million crop acres in the US alone. Each acre would require 0.5 ton per year to prevent surface sealing. This means that the potential for FGD-gypsum use is more than 80 million tons per year. 4 photos.

  20. Biogeochemical oxidation of calcium sulfite hemihydrate to gypsum in flue gas desulfurization byproduct using sulfur-oxidizing bacteria.

    Graves, Duane; Smith, Jacques J; Chen, Linxi; Kreinberg, Allison; Wallace, Brianna; White, Robby


    Flue gas desulfurization (FGD) is a well-established air treatment technology for coal and oil combustion gases that commonly uses lime or pulverized limestone aqueous slurries to precipitate sulfur dioxide (SO2) as crystalline calcium salts. Under forced oxidation (excess oxygen) conditions, FGD byproduct contains almost entirely (>92%) gypsum (CaSO4·2H2O), a useful and marketable commodity. In contrast, FGD byproduct formed in oxygen deficient oxidation systems contains a high percentage of hannebachite (CaSO3·0.5H2O) to yield a material with no commercial value, poor dewatering characteristics, and that is typically disposed in landfills. Hannebachite in FGD byproduct can be chemically converted to gypsum; however, the conditions that support rapid formation of gypsum require large quantities of acids or oxidizers. This work describes a novel, patent pending application of microbial physiology where a natural consortium of sulfur-oxidizing bacteria (SOB) was used to convert hannebachite-enriched FGD byproduct into a commercially valuable, gypsum-enriched product (US Patent Assignment 503373611). To optimize the conversion of hannebachite into gypsum, physiological studies on the SOB were performed to define their growth characteristics. The SOB were found to be aerobic, mesophilic, neutrophilic, and dependent on a ready supply of ammonia. They were capable of converting hannebachite to gypsum at a rate of approximately five percent per day when the culture was applied to a 20 percent FGD byproduct slurry and SOB growth medium. 16S rDNA sequencing revealed that the SOB consortium contained a variety of different bacterial genera including both SOB and sulfate-reducing bacteria. Halothiobacillus, Thiovirga and Thiomonas were the dominant sulfur-oxidizing genera. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Antibacterial activity of selected glass ionomer cements

    Elżbieta Łuczaj-Cepowicz


    Full Text Available Introduction: The aim of the paper was to determine the antibacterial activity of four glass ionomer cements against bacteria of the genera Streptococcus and Lactobacillus.Material and methods: Four capsulated glass ionomer cements were applied in the study: Fuji Triage (GC, Fuji IX (GC, Ketac Molar (3M Espe and Ketac Silver (3M Espe. Four standard bacterial strains were used to assess the antibacterial activity of the studied cements: Streptococcus mutans, S. sanguis, S. salivarius and Lactobacillus casei. The antibacterial activity was determined by the agar diffusion method. The bacterial suspension was spread with a cotton swab on TSA plates. For each material six wells (7 mm diameter, 5 mm deep were made with a cork borer. Each well was then filled with freshly prepared cements. The results were obtained by measuring the bacterial growth inhibition zone after 1, 2, 3 and 7 days. Results: Fuji Triage cement inhibited the growth of all bacterial strains. Fuji IX cement demonstrated the most potent antibacterial activity against S. sanguis. Ketac Molar showed antibacterial activity against S. sanguis and S. salivarius, whereas Ketac Silver was efficient against S. mutans as well. Neither of the Ketac cements inhibited growth of the standard L. casei strain. Discussion: Antibacterial activity of glass ionomer cements has attracted the interest of scientists in recent years. Most authors, including us, carried out experiments using the agar diffusion method and demonstrated antibacterial activity of glass ionomer cements. Different antibacterial activity of glass ionomer cements, observed in our study and studies of other authors, depended on the evaluated cement, bacterial strain and period of evaluation.

  2. Antibacterial activity of selected glass ionomer cements.

    Luczaj-Cepowicz, Elżbieta; Marczuk-Kolada, Grażyna; Zalewska, Anna; Pawińska, Małgorzata; Leszczyńska, Katarzyna


    The aim of the paper was to determine the antibacterial activity of four glass ionomer cements against bacteria of the genera Streptococcus and Lactobacillus. Four capsulated glass ionomer cements were applied in the study: Fuji Triage (GC), Fuji IX (GC), Ketac Molar (3M Espe) and Ketac Silver (3M Espe). Four standard bacterial strains were used to assess the antibacterial activity of the studied cements: Streptococcus mutans, S. sanguis, S. salivarius and Lactobacillus casei. The antibacterial activity was determined by the agar diffusion method. The bacterial suspension was spread with a cotton swab on TSA plates. For each material six wells (7 mm diameter, 5 mm deep) were made with a cork borer. Each well was then filled with freshly prepared cements. The results were obtained by measuring the bacterial growth inhibition zone after 1, 2, 3 and 7 days. Fuji Triage cement inhibited the growth of all bacterial strains. Fuji IX cement demonstrated the most potent antibacterial activity against S. sanguis. Ketac Molar showed antibacterial activity against S. sanguis and S. salivarius, whereas Ketac Silver was efficient against S. mutans as well. Neither of the Ketac cements inhibited growth of the standard L. casei strain. Antibacterial activity of glass ionomer cements has attracted the interest of scientists in recent years. Most authors, including us, carried out experiments using the agar diffusion method and demonstrated antibacterial activity of glass ionomer cements. Different antibacterial activity of glass ionomer cements, observed in our study and studies of other authors, depended on the evaluated cement, bacterial strain and period of evaluation.

  3. Effect of burnout temperature on strength of gypsum-bonded investments.

    Luk, W K; Darvell, B W


    To investigate the variation of the strength of gypsum-bonded dental investments with burnout temperature. The disc-rupture test was employed at burnout temperatures ranging from 450 to 800 degrees C for four products (Beauty Cast, Cristobalite, Novocast (all WhipMix) and Deguvest California (Degussa)). In this test, an investment disc is created inside an investment mold such that it forms a diaphragm across the mold space, being an integral part of the mold. Copper was cast into molds of this type, and whether the disc had ruptured or not was determined by inspection when cold. The amount of copper cast in successive tests was varied in staircase fashion up and down depending on whether the disc survived or failed. The strength of the investment was represented by the 50% point of the transition from survival to rupture. The strength of gypsum-bonded investment is temperature sensitive, there being marked differences between the products tested. Overall, the strength ranking (temperature range average/MPa) was: Cristobalite (10.1)>Beauty Cast (7.8)>Novocast (5.1)>Deguvest California (3.4). The strength ranking at high temperatures differs from that known for the room temperature values. The use by manufacturers of room-temperature strength data conveys no information about high temperature behavior. Investment properties should be optimized by reference to behavior under casting conditions.

  4. Potential Agricultural Uses of Flue Gas Desulfurization Gypsum in the Northern Great Plains

    DeSutter, T.M.; Cihacek, L.J. [North Dakota State University, Fargo, ND (United States). Department of Soil Science


    Flue gas desulfurization gypsum (FGDG) is a byproduct from the combustion of coal for electrical energy production. Currently, FGDG is being produced by 15 electrical generating stations in Alabama, Florida, Indiana, Iowa, Kentucky, Ohio, North Carolina, South Carolina, Tennessee, Texas, and Wisconsin. Much of this byproduct is used in the manufacturing of wallboard. The National Network for Use of FGDG in Agriculture was initiated to explore alternative uses of this byproduct. In the northern Great Plains (North Dakota, South Dakota, and Montana), FGDG has the potential to be used as a Ca or S fertilizer, as an acid soil ameliorant, and for reclaiming or mitigating sodium-affected soils. Greater than 1.4 million Mg of FGDG could initially be used in these states for these purposes. Flue gas desulfurization gypsum can be an agriculturally important resource for helping to increase the usefulness of problem soils and to increase crop and rangeland production. Conducting beneficial use audits would increase the public awareness of this product and help identify to coal combustion electrical generating stations the agriculturally beneficial outlets for this byproduct.


    Daniel Tao


    The objective of this research program is to develop a novel integrated process to eliminate millions of tons of gypsum and pyrite wastes generated annually by the U.S. energy industries and reduce the emission of millions of tons of greenhouse gas carbon dioxide. This was accomplished by converting gypsum and pyrite wastes to marketable products such as lime, direct reduced iron (DRI), and sulfur products and obviating the need to calcine millions of tons of limestone for use in utility scrubbers. Specific objectives included: (1) Develop a novel, integrated process for utilizing two major wastes generated by mining and energy industries to produce lime for recycling and other marketable products. (2) Study individual chemical reactions involved in pyrite decomposition, DRI production, and Muller-Kuhne process for lime regeneration to determine optimum process variables such as temperature, time, and reactant composition. (3) Investigate techniques for effective concentration of pyrite from tailing waste and methods for effective separation of DRI from calcium sulfide.

  6. The production of hydroxyapatite prototypes from solid bodies of Gypsum/Polyvinyl Alcohol composites

    Barbosa, Amanda Alves; Ferraz, Andrea de Vasconcelos; Dantas, Alan Christie; Olivier, Nelson Cardenas, E-mail: [Universidade Federal do Vale do Sao Francisco (UNIVASF), Juazeiro, BA (Brazil)


    Prototypes of porous hydroxyapatite (HAp) were produced from Gypsum/PVA composite, using a mass proportion of 15% polymer. The material was obtained by means of chemical conversion in (NH{sub 4}){sub 2}HPO{sub 4} 0.5 mol.L{sup -1} solution and NH{sub 4}OH 6.0 mol.L{sup -1} alkaline medium for pH control, maintained between 6.0 and 9.0. The reaction occurred at a temperature of 100°C at different test times. The obtained HAp was characterized by several techniques, such as FTIR, which identified the SO{sub 4}{sup 2-} groups characteristic for the Gypsum block, and the PO{sub 4}{sup 2-} groups that are attributed to the biomaterial HAp, besides XRD and SEM, which made it possible to confirm a successful conversion of the material. Tests for mechanical resistance to compression (σ{sub c}) were carried out for both materials as well. (author)

  7. Seepage Analysis of Upper Gotvand Dam Concerning Gypsum Karstification (2D and 3D Approaches)

    Sadrekarimi, Jamshid; Kiyani, Majid; Fakhri, Behnam;


    Upper Gotvand Dam is constructed on the Karun River at the south west of Iran. In this paper, 2D and 3D models of the dam together with the foundation and abutments were established, and several seepage analyses were carried out. Then, the gypsum veins that are scattered throughout the foundation...... ground were included in the models, and the seepage pattern, considering the dissolution law of gypsum, was analyzed. It was disclosed that the discharge fluxes obtained from 2D and 3D analyses are not similar, and the discharge flux in 3D model is about four times that of the 2D model. Also, the 3D...... model locates the phreatic surface somewhat higher than the 2D model. This means that the 2D model estimates lower pore water pressure pattern in comparison with the 3D model. These may be attributed to the fact that with 2D model the lateral components of vectors of seepage velocity are ignored...

  8. Gypsum bonded investment for micro-structure casting of ZnAl4

    Yang Chuang; Li Bangsheng; Ren Mingxing; Fu Hengzhi


    The effects of sintering temperature on the surface roughness of gypsum bonded investments were investigated to find the appropriate sintering temperature applied for micro-investment casting. The surface roughness tests were carried out at sintering temperatures ranging from room temperature to 1,000 ℃for investment compounds mixed from calcium sulphate α-hemihydrate and quartz powder (wt.%, 6:4; 5:5, 4:6, 3:7). In this experiment, each investment compound was prepared by pouring the investment materials into a plastic bottle with the good surface roughness (Ra ~0.2 urn). DTA-TG curves were measured using a thermal analyzer to investigate the difference of surface roughness at different temperatures. The results show that the surface roughness of gypsum bonded investment is temperature sensitive. The preheating temperature of the mold should be up to 600 ℃, but not over 700 ℃, and the investment compound with 60 % plaster and 40 % quartz powder is applicable for preparing the micro-structures. The micro-structures with 100 Mm diameter were produced in the present studies. The results show that the surface roughness of the casting is only Ra ~0.51 urn, slightly rougher than that of the investment mold.

  9. Breakdown development in cover beds, and landscape features induced by intrastratal gypsum karst

    Andrejchuk V.


    Full Text Available Intrastratal karst is by far the predominant gypsum karst type. Its development may begin in deep-seated settings within rocks already buried by younger strata, and it proceeds increasingly rapidly as uplift brings gypsum sequences into progressively shallower positions. Such development commonly occurs under confined (artesian hydrogeological conditions, that subsequently change to open conditions (phreatic-water table-vadose. The general evolutionary line of intrastratal karst is typified by progressive emergence of a sequence into a shallower position, activation of groundwater circulation and development of cave systems within karst units, commencement of gravitational breakdown and its upward propagation through overlying beds, and development of a karst landscape. These processes and phenomena progress through the directed evolution of karst types as follows: deep-seated intrastratal karst (1K to subjacent 1K to entrenched 1K to denuded karst. One of the main characteristics of intrastratal karst is that it induces gravitational breakdown in cover beds. With the aid of processes other then simple breakdown, such effects may propagate upwards and may, or may not, reach the surface, depending upon the thickness and structure of the overburden. A karst landscape evolves when such features reach the surface. This paper considers the conditions and mechanisms of such development.

  10. A Method for Optimizing Lightweight-Gypsum Design Based on Sequential Measurements of Physical Parameters

    Vimmrová, Alena; Kočí, Václav; Krejsová, Jitka; Černý, Robert


    A method for lightweight-gypsum material design using waste stone dust as the foaming agent is described. The main objective is to reach several physical properties which are inversely related in a certain way. Therefore, a linear optimization method is applied to handle this task systematically. The optimization process is based on sequential measurement of physical properties. The results are subsequently point-awarded according to a complex point criterion and new composition is proposed. After 17 trials the final mixture is obtained, having the bulk density equal to (586 ± 19) kg/m3 and compressive strength (1.10 ± 0.07) MPa. According to a detailed comparative analysis with reference gypsum, the newly developed material can be used as excellent thermally insulating interior plaster with the thermal conductivity of (0.082 ± 0.005) W/(m·K). In addition, its practical application can bring substantial economic and environmental benefits as the material contains 25 % of waste stone dust.

  11. Crystallisation of Gypsum and Prevention of Foaming in Wet Flue Gas Desulphurisation (FGD) Plants

    Hansen, Brian Brun

    of reliability of operation and consistency of the gypsum quality obtained. This work may furthermore be of interest to other industrial systems in which foaming or gypsum crystallisation may take place. FGD is an industrial process, which removes sulphur dioxide (SO2) from flue gasses generated by fossil fuel...... combustion at power plants and other heavy industries, thereby abating the detrimental effects known as “acid rain”. The majority of the 680 FGD-plants installed at power plants worldwide in 1999 (2.41•105 MWe) were using the wet FGD-technology. This process absorbs ~ 99 % of the SO2 by an alkaline slurry....... Experiments in a falling film wet FGD pilot plant have shown a strong non-linear behaviour (in a ln(n(l)) vs. l plot) at the lower end of the particle size range, compared to the well-known linear “mixed suspension mixed product removal (MSMPR)” model. A transient population balance model, fitted...

  12. Experimental Study of Stabilized Soil Utilizing Circulating Fluidized Bed Combustion Desulfurization Ash with Carbide Slag and Desulfurization Gypsum


    This paper discusses the feasibility of preparing soil stabilizer which is circulating fluidized bed combustion ash-based, supplemented with carbide slag and desulfurization gypsum, composed entirely of complete industrial wastes. The results show that CFBC ash has better pozzolanic activity than fly ash. When stabilizer total content is 10% and the ratio of CFBC ash : carbide slag : desulfurization gypsum is 7.2 : 1.8 : 1, compressive strength of stabilized soil can reach the maximum of 2.12...

  13. Gypsum-based biomaterials: Evaluation of physical and mechanical properties, cellular effects and its potential as a pulp liner.

    Low, Amy; Mohd Yusof, Hamidah; Reza, Fazal; Abdullah Nurul, Asma; Sritharan, Shaminea; Haania Zain Ali, Niswathul; Subhi Azeez, Hasan; Husein, Adam


    This in vitro study aimed to evaluate setting time and compressive strength of gypsum-based chitosan biomaterials and its effect on proliferation of stem cells from human exfoliated deciduous teeth (SHED) and alkaline phosphatase (ALP) activity. Pure-GYP was mixed with water (2.5 g: 1.9 mL); Gyp-CHT was prepared with gypsum, chitosan, and water (2.5 g: 0.285 g: 1.9 mL). Cell viability and ALP activity were assessed at different periods. Data were analyzed using SPSS (pbiomaterials for its pulp protective potentialities.

  14. Populations of some molds in water-damaged homes may differ if the home was constructed with gypsum drywall compared to plaster

    Starting in the 1940s, gypsum drywall began replacing plaster and lathe in the U.S. home construction industry. Our goal was to evaluate whether some mold populations differ in water- damaged homes primarily constructed with gypsum drywall compared to plaster. The dust samples fr...

  15. Populations of some molds in water-damaged homes may differ if the home was constructed with gypsum drywall compared to plaster

    Starting in the 1940s, gypsum drywall began replacing plaster and lathe in the U.S. home construction industry. Our goal was to evaluate whether some mold populations differ in water- damaged homes primarily constructed with gypsum drywall compared to plaster. The dust samples fr...

  16. Evaluating the fate of mercury and other metals across the life-cycle stages from the use of FGD gypsum for wallboard production

    In 2007, 12.3 million tons of flue gas desulfurization (FGD) gypsum was produced due to air emission controls at coal-fired power plants. With increasing use of wet scrubbers in response to more stringent air pollution control requirements, FGD gypsum production is expected to in...

  17. Microbial analysis of biofilms on cement surfaces: An investigation in cement-associated peri-implantitis.

    Korsch, Michael; Walther, Winfried; Marten, Silke-Mareike; Obst, Ursula


    The cementation of implant-supported restorations always poses the risk of excess cement retained in the peri-implant sulcus despite careful clinical control. Excess cement can become the basis of colonization by oral microorganisms. As a result of the biofilm formation peri-mucositis or peri-implantitis may develop. Complications were observed in the routine prosthetic restoration of implants when a methacrylate-based cement was used. These developed a few weeks after cementation of the suprastructure and caused bleeding on probing as well as suppuration from the peri-implant tissue. In the revision therapy, excess cement in the peri-implant sulcus was found in many cases. This excess cement was sampled from ten patients and investigated for biofilm formation. For this purpose, the cement samples were collected and analyzed for bacterial in situ colonization by 16S rDNA-based methods. In laboratory experiments, the methacrylate-based cement and two other dental cements were then investigated for their proneness to form biofilm. The results of the in situ and in vitro investigations revealed a strong tendency towards bacterial invasion of the methacrylate-based cement by opportunistic species and pathogens.

  18. Copper Slag Blended Cement: An Environmental Sustainable Approach for Cement Industry in India

    Jagmeet Singh


    Full Text Available Indian cement industry is facing environmental issue of emission of carbon dioxide (CO2, a greenhouse gas. Blended cements including supplementary cementitious materials are substitute of Portland cement to reduce CO2 emission. The present paper investigates theappropriateness of copper slag (CS as supplementary cementitious material. Strength properties and hydration of mixes were determined at different replacement levels of CS with cement. Compressive, flexural and tensile strength of each mix was found out at different curing periods. The hydration of cement was investigated through X-ray diffraction (XRD. The strength test results showed that substitution of up to 20% of CS can significantly replace Portland cement.XRD test results were corresponding to strength test results. The present study encourages the utilization of CS as supplementary cementitious material to make economical and environmentally sustainable blended cement

  19. The influence of cement type and temperature on chloride binding in cement paste

    Jensen, Ole Mejlhede; Korzen, Migge Sofie Hoffmann; Skibsted, Jørgen


    This paper describes effects of cement type and temperature on chloride binding in cement paste, which is an important subject in relation to life-time modelling of reinforced concrete structures. The influence of cement type on chloride binding is investigated by substituting cement with pure...... cement clinker. Both theoretical considerations and experimental data for chloride binding in cement pastes are presented. A physico-chemically based model to describe the influence of temperature on physical binding of chloride is presented. Solid-state 27Al and 29Si magic-angle spinning (MAS) nuclear...... magnetic resonance (NMR) spectroscopy has been used for quantification of the anhydrous and hydrated aluminate and silicate phases in the chloride exposed cement pastes. The 27Al isotropic chemical shift and nuclear quadrupole coupling is reported for a synthetic sample of Friedel's salt, Ca2Al(OH)6Cl×2H2O....

  20. A Pause for China's Cement Industry

    Li Zhen


    @@ Cement industry suffers excess productionWith the advent of global financial crisis,the Chinese government has laid out a stimulus package on infrastructure construction.Driven by the investment spree,China's cement makers are flocking to expand output capacity,which is now leading the industry into a much-higher-thanneeded state.

  1. Contact dermatitis in cement workers in Isfahan

    Iraji Fariba


    Full Text Available BACKGROUND: Due to recent industrialization and inadequately protected workers or in other words poor supervision on constructive workers habits in our large city of Isfahan cement contact dermatitis is relatively high especially among cement factory workers and constructive personnel. PURPOSES: To investigate the prevalence rate of cement contact dermatitis in cement factory workers in Isfahan. METHODS: A case-control clinical study was carried out by randomly selecing 150 factory workders and 150 official clerks in a cement factory in Isfahan in 2001. After a complete physical examination, data was recorded in observational checklists. FINDINGS: The percentages of contact dermatitis prevalences in the first and the second groups were 22% and 5.3% respectively. About 60% of cement workers with contact dermatitis were between 30-40 years of age. There was a direct relationship with age in both groups of the workers. In the high-exposure group, the hand eczema along was 70% but in the other group the percentage of involvement was the same in exposed and unexposed anatomical areas. CONCLUSIONS: There was a direct relationship between occurrence and the severity of involvement and duration of contact in the first group. Cent percent of cement workers had contact dermatitis after 10 or less years, but the percentage among the other group was 35%. LIMITATION: Irritant contact dermatitis to cement has not been detected.

  2. Basic Chemistry for the Cement Industry.

    Turner, Mason

    This combined student workbook and instructor's guide contains nine units for inplant classes on basic chemistry for employees in the cement industry. The nine units cover the following topics: chemical basics; measurement; history of cement; atoms; bonding and chemical formulas; solids, liquids, and gases; chemistry of Portland cement…

  3. Investigation of a Hardened Cement Paste Grout

    Esteves, Luis Pedro; Sørensen, Eigil Verner

    This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S.......This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S....

  4. Chloride ingress in cement paste and mortar

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben; Coats, Alison M.


    In this paper chloride ingress in cement paste and mortar is followed by electron probe microanalysis. The influence of several paste and exposure parameters on chloride ingress are examined (e.g., water-cement ratio, silica fume addition, exposure time, and temperature), The measurements...




  6. A note on cement in asteroids

    Bilalbegovic, G


    Cement mineral tobermorite was formed in hydrothermal experiments on alternation of calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrite meteorites. Unidentified bands at 14 microns were measured for CAIs and the matrix of the Allende meteorite sample, as well as for Hektor and Agamemnon asteroids. The presence of cement nanoparticles may explain the feature at 14 microns.

  7. A note on cement in asteroids

    Bilalbegović, G.


    Cement mineral tobermorite was formed in hydrothermal experiments on alternation of calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrite meteorites. Unidentified bands at 14 μm were measured for CAIs and the matrix of the Allende meteorite sample, as well as for Hektor and Agamemnon asteroids. The presence of cement nanoparticles may explain the feature at 14 μm.

  8. Effect of hydrogen sulfide emissions on cement mortar specimens

    Idriss, A. F. [Alberta Environment, Science and Technology Branch, Edmonton, AB (Canada); Negi, S. C.; Jofriet, J. C.; Haywoard, G. L. [Guelph Univ., Guelph, ON (Canada)


    Six different cement mortar specimens used in animal buildings, where they were exposed to hydrogen sulfide generated from anaerobic fermentation of manure during a period of one year, were investigated. Primary interest was on comparing the corrosion resistance of different cement mortar specimens under long term exposure to hydrogen sulfide. The impressed voltage technique was used to test the specimens in the laboratory. Results revealed that test specimens made with eight per cent silica fume cement replacement performed best and similar Portland cement mortar specimens with a water-cement ratio of 0.55 (PC55) the poorest. All other treatments, (Portland cement with a water to cement ratio of 045, Portland cement Type 50, Portland cement with fibre mesh and Portland cement Type 10 coated with linseed oil) all with water-cement ratios of 0.45, were less effective in preventing corrosion than silica fume replacement.

  9. Energetically Modified Cement (EMC) - Performance Mechanism

    Ronin, Vladimir; Elfgren, Lennart [Luleaa Univ. of Technology (Sweden). Centre for High Performance Cement


    Energetically Modified Cements, EMC, made of intensively milled cement (50%) and fillers (50%) of quartz or fly ash have been compared to blends of Ordinary Portland Cement, OPC, and fillers. The EMCs have better properties than other blends and are comparable to unblended OPC. This remarkable fact can probably be explained as follows. The grinding process reduces the size of both cement grains and fillers. This combined with the creation of micro defects gives the ground cement a very high degree of hydration. The increased early hydration and a better distribution of hydration products results in an extensive pore size refinement of the hardened binder. This pore size refinement leads to a favorably reduced permeability and diffusivity and very good mechanical properties.

  10. Shrinkage Properties of Cement Stabilized Gravel

    Lund, Mia Schou Møller; Hansen, Kurt Kielsgaard


    Cement stabilized gravel is an attractive material in road construction because its strength prop-erties are accommodating the increasingly higher requirements to the bearing capacity of a base course. However, reflection cracking of cement stabilized gravel is a major concern. In this pa......-per the shrinkage properties of cement stabilized gravel have been documented under various temperature and relative humidity conditions. Two cement contents corresponding to a 28-days compressive strength of 6.2 MPa and 12.3 MPa have been tested and compared. It is found that the coefficient of linear expansion...... for the two cement contents is 9.9 × 10-6 ⁰C-1 and 11.3 × 10-6 ⁰C-1, respectively. Furthermore, it is found that reflecting cracking can mainly be explained by temperature dependent shrinkage rather than moisture dependent shrinkage....

  11. Energetically Modified Cement (EMC) - Performance Mechanism

    Ronin, Vladimir; Elfgren, Lennart [Luleaa Univ. of Technology (Sweden). Centre for High Performance Cement


    Energetically Modified Cements, EMC, made of intensively milled cement (50%) and fillers (50%) of quartz or fly ash have been compared to blends of Ordinary Portland Cement, OPC, and fillers. The EMCs have better properties than other blends and are comparable to unblended OPC. This remarkable fact can probably be explained as follows. The grinding process reduces the size of both cement grains and fillers. This combined with the creation of micro defects gives the ground cement a very high degree of hydration. The increased early hydration and a better distribution of hydration products results in an extensive pore size refinement of the hardened binder. This pore size refinement leads to a favorably reduced permeability and diffusivity and very good mechanical properties.

  12. CO2 Capture by Cement Raw Meal

    Pathi, Sharat Kumar; Lin, Weigang; Illerup, Jytte Boll


    The cement industry is one of the major sources of CO2 emissions and is likely to contribute to further increases in the near future. The carbonate looping process has the potential to capture CO2 emissions from the cement industry, in which raw meal for cement production could be used...... as the sorbent. Cyclic experiments were carried out in a TGA apparatus using industrial cement raw meal and synthetic raw meal as sorbents, with limestone as the reference. The results show that the CO2 capture capacities of the cement raw meal and the synthetic raw meal are comparable to those of pure limestone....... The CO2 capture capacity of limestone in the raw meal is lower than for pure limestone. The difference in the CO2 capture capacity decreases with an increase in cycle number. The calcination conditions and composition are major factors that influence the CO2 capture capacity of limestone. At 850 °C in N2...

  13. Simultaneous determination of lfuorine and chlorine in gypsum and gypsum products by ion chromatography%离子色谱法同时测定石膏及石膏制品中的氟和氯

    徐丹华; 梅一飞; 刘实华


    建立了离子色谱法同时测定石膏及石膏制品中氟和氯的方法。实验结果表明:采用离子色谱法一次进样可准确测定石膏及石膏制品中的氟和氯的含量。流动相采用20/30mM KOH溶液,流速为0.8/1.0mL/min。方法有较好的准确度和回收率。%Method to establish the ion chromatography method for the simultaneous determination of fluoride and chloride in gypsum and gypsum products.The experimental results show that: Using ion chromatography can be accurate determination of fluorine and chlorine in gypsum and gypsum products.The mobile phase is the 20/30mM KOH solution,the flow rate was 0.8/1.0mL/min. Method has better accuracy and recovery rate.


    D. V. Rudenko


    Full Text Available Purpose. The article considers definition of the bond types occurring in a modified cement concrete matrix, and the evaluation of the quality of these links in a non-uniform material to determine the geometrical and physical relationships between the structure and the cement matrix modifiers. Methodology. To achieve this purpose the studies covered the microstructure of dispersed modified concrete cement matrix, the structure formation mechanism of the modified cement concrete system of natural hardening; as well as identification of the methods of sound concrete strength assessment. Findings. The author proposed a model of the spatial structure of the concrete cement matrix, modified by particulate reinforcement crystal hydrates. The initial object of study is a set of volume elements (cells of the cement matrix and the system of the spatial distribution of reinforcing crystallohydrates in these volume elements. It is found that the most dangerous defects such as cracks in the concrete volume during hardening are formed as a result of internal stresses, mainly in the zone of cement matrix-filler contact or in the area bordering with the largest pores of the concrete. Originality. The result of the study is the defined mechanism of the process of formation of the initial strength and stiffness of the modified cement matrix due to the rapid growth of crystallohydrates in the space among the dispersed reinforcing modifier particles. Since the lack of space prevents from the free growth of crystals, the latter cross-penetrate, forming a dense structure, which contributes to the growth of strength. Practical value. Dispersed modifying cement matrix provides a durable concrete for special purposes with the design performance characteristics. The developed technology of dispersed cement system modification, the defined features of its structure formation mechanism and the use of congruence principle for the complex of technological impacts of physical

  15. Pack cementation coatings for alloys

    He, Yi-Rong; Zheng, Minhui; Rapp, R.A. [Ohio State Univ., Columbus, OH (United States)


    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on a Cr-Cr{sub 2}Nb alloy in a single processing step. The morphology and composition of the coating depended both on the composition of the pack and on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi{sub 2} and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. In cyclic and isothermal oxidation in air at 700 and 1050{degrees}C, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation by the formation of a Ge-doped silica film. The codeposition and diffusion of aluminum and chromium into low alloy steel have been achieved using elemental Al and Cr powders and a two-step pack cementation process. Sequential process treatments at 925{degrees}C and 1150{degrees}C yield dense and uniform ferrite coatings, whose compositions are close to either Fe{sub 3}Al or else FeAl plus a lower Cr content, when processed under different conditions. The higher content of Al in the coatings was predicted by thermodynamic calculations of equilibrium in the gas phase. The effect of the particle size of the metal powders on the surface composition of the coating has been studied for various combinations of Al and Cr powders.

  16. Cements with low Clinker Content

    García-Lodeiro, I.; Fernández-Jiménez, A.; Palomo, A.


    Hybrid alkaline cements are multi-component systems containing a high percentage of mineral additions (fly ash, blast furnace slag), low proportions (clinker and scarce amounts of alkaline activators. The substantially lower amount of clinker needed to manufacture these binders in comparison to ordinary Portland cement is both economically and ecologically beneficial. Their enormous versatility in terms of the raw materials used has made them the object of considerable interest. The present study explored the mechanical strength of binary blends mixes; B1= 20% clinker (CK) + 80% fly ash (FA) and B2=20% clinker + 80% blast furnace slag (BFS), both hydrated in the presence and absence of an alkaline activator specifically designed for this purpose. The use of the activator enhanced the development of early age strength considerably. All the hydrated matrices were characterised with XRD, SEM/EDX and (29Si and 27Al) NMR. The use of the alkaline activator generated reaction products consisting primarily of a mix of gels ((N,C)-A-S-H and C-A-S-H) whose respective proportions were found to depend upon system composition and initial reactivity.

  17. Dentin-cement Interfacial Interaction

    Atmeh, A.R.; Chong, E.Z.; Richard, G.; Festy, F.; Watson, T.F.


    The interfacial properties of a new calcium-silicate-based coronal restorative material (Biodentine™) and a glass-ionomer cement (GIC) with dentin have been studied by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), micro-Raman spectroscopy, and two-photon auto-fluorescence and second-harmonic-generation (SHG) imaging. Results indicate the formation of tag-like structures alongside an interfacial layer called the “mineral infiltration zone”, where the alkaline caustic effect of the calcium silicate cement’s hydration products degrades the collagenous component of the interfacial dentin. This degradation leads to the formation of a porous structure which facilitates the permeation of high concentrations of Ca2+, OH-, and CO32- ions, leading to increased mineralization in this region. Comparison of the dentin-restorative interfaces shows that there is a dentin-mineral infiltration with the Biodentine, whereas polyacrylic and tartaric acids and their salts characterize the penetration of the GIC. A new type of interfacial interaction, “the mineral infiltration zone”, is suggested for these calcium-silicate-based cements. PMID:22436906

  18. Cement compositions for cementing wells, allowing pressure gas-channeling in the cemented annulus to be controlled

    Parcevaux, P.A.; Piot, B.M.; Vercaemer, C.J.


    The invention relates to cement compositions for cementing oil and geothermal wells. These compositions allow pressure gas-channeling to be effectively controlled up to more than about 485/sup 0/F. The compositions according to the invention comprise four essential constituents: a cement, a styrene-butadiene latex, a latex stabilizer, and water. The cement is a hydraulic cement belonging to any class among those currently used for cementing oil wells. The useful stabilizers according to the invention are anionic polyelectrolytes such as lignosulfanates and their desulfonated and/or resulfonated derivatives; sulfonated lignin-Kraft products; melamine-formaldehyde resins modified by a sulfonic acid or sulfite; formaldehyde/sulfonated naphthalene resins; or the condensation products of bi-nuclear sulfonated phenols and of formaldehyde. Preferred are the sodium salts of the condensation product of mononaphthalenesulfonic acid and of formaldehyde. The patent also includes a description of tests of various cement compositions of the invention, plus scanning electron microscope observations. 10 figs., 7 tabs.

  19. Lipid and Phylogenetic Analysis of a Gypsum-hosted Endoevaporitic Microbial Community

    Turk, K. A.; Jahnke, L. L.; Green, S. J.; Kubo, M. D.; Vogel, M. B.; Des Marais, D. J.


    Gypsum evaporites host diverse, productive and volumetrically significant microbial communities and are relevant modern-day analogs to both Precambrian sabkha deposits and, potentially, Martian evaporites. Extensive evaporites form in subaqueous environments of high salinity ponds (>150 permil) maintained by the Exportadora de Sal, S. A. (ESSA) in Guerrero Negro, B.C.S., Mexico. A gypsarenite (reworked clastic gypsum) crust found along the southeast margin of ESSA's Pond 9 was collected in February 2004 and each vibrantly colored layer in the top centimeter was sampled. Extant microbial communities from each layer were characterized using complementary culture-independent molecular techniques, lipid biomarker analysis, and compound specific isotopic analysis. Coupling molecular analysis with lipid biomarker analysis revealed that oxygenic photosynthetic organisms dominate the surface layers (top 3 mm). Polar lipids from the surface layers consisted predominantly of glycolipids, which are characteristic of algae, cyanobacteria and green anoxygenic photosynthetic bacteria. Consistent with prior analyses of gypsum evaporites, 16S rRNA gene clone libraries indicate that cyanobacterial populations belong primarily to the genus Cyanothece. The bacterial community below the surface layers is more diverse and dominated by anaerobic organisms. Phototrophic purple sulfur bacteria, sulfate-reducing bacteria (SRB), and Bacteroidetes were particularly abundant. The relative abundances of SRB increased with depth; Desulfobacteraceae clones were distributed throughout the crust, but not at the surface, while Desulfovibrionaceae clones were found predominantly in the deepest layers. These molecular results are consistent with fatty acid biomarker analysis. δ13C values of major lipid classes in the crust and sediment range from 14 to 36‰, which is considerably lower than corresponding values for benthic Microcoleus-dominated cyanobacterial mats found at lower salinities at ESSA

  20. Permeability control on transient slip weakening during gypsum dehydration: Implications for earthquakes in subduction zones

    Leclère, Henri; Faulkner, Daniel; Wheeler, John; Mariani, Elisabetta


    A conflict has emerged from recent laboratory experiments regarding the question of whether or not dehydration reactions can promote unstable slip in subduction zones leading to earthquakes. Although reactions produce mechanical weakening due to pore-fluid pressure increase, this weakening has been associated with both stable and unstable slip. Here, new results monitoring strength, permeability, pore-fluid pressure, reaction progress and microstructural evolution during dehydration reactions are presented to identify the conditions necessary for mechanical instability. Triaxial experiments are conducted using gypsum and a direct shear sample assembly with constant normal stress that allows the measurement of permeability during sliding. Tests are conducted with temperature ramp from 70 to 150 °C and with different effective confining pressures (50, 100 and 150 MPa) and velocities (0.1 and 0.4 μm s-1). Results show that gypsum dehydration to bassanite induces transient stable-slip weakening that is controlled by pore-fluid pressure and permeability evolution. At the onset of dehydration, the low permeability promoted by pore compaction induces pore-fluid pressure build-up and stable slip weakening. The increase of bassanite content during the reaction shows clear evidence of dehydration related with the development of R1 Riedel shears and P foliation planes where bassanite is preferentially localized along these structures. The continued production of bassanite, which is stronger than gypsum, provides a supporting framework for newly formed pores, thus resulting in permeability increase, pore-fluid pressure drop and fault strength increase. After dehydration reaction, deformation is characterized by unstable slip on the fully dehydrated reaction product, controlled by the transition from velocity-strengthening to velocity-weakening behaviour of bassanite at temperature above ∼140 °C and the localization of deformation along narrow Y-shear planes. This study

  1. Preparation of pure calcium carbonate by mineral carbonation using industrial byproduct FGD gypsum

    Song, K.; Kim, W.; Bang, J. H.; Park, S.; Jeon, C. W.


    Mineral carbonation is one of the geological approaches for the sequestration of anthropogenic CO2 gas. Its concept is based on the natural weathering processes in which silicate minerals containing divalent cations such as Ca or Mg are carbonated to CaCO3 or MgCO3 in the reaction with CO2gas. Raw materials for the mineral carbonation have been extended to various industrial solid wastes such as steel slag, ashes, or FGD (flue gas desulfurization) gypsum which are rich in divalent cations. These materials have economic advantages when they are produced in CO2 emission sites. Flue gas desulfurization (FGD) gypsum is such a byproduct obtained in at coal-fired power plants. Recently, we carried out a research on the direct mineral carbonation of FGD gypsum for CO2sequestration. It showed high carbonation reactivity under ambient conditions and the process can be described as follows: CaSO4·2H2O + CO2(g) + 2NH4OH(aq) → CaCO3(s) + (NH4)2SO4(aq) (1) At the early stage of the process, calcium carbonate (CaCO3) exists as a dissolved ion pair during the induction period. High-purity CaCO3 could be precipitated from dissolved calcium carbonate solution extracted during the induction period. The effect of experimental parameters on pure CaCO3 was evaluated: CO2 flow rate (1-3 L/min), ammonia content (4-12%), and solid-to-liquid (S/L) ratio (5-300 g/L). FE-SEM (field-emission scanning electron microscopy) and XRD (X-ray diffraction) study revealed that the precipitated CaCO3 was round-shaped vaterite crystals. The induction time was inversely proportional to the CO2 flow rate and the yield for pure CaCO3 increased with the ammonia content. The formation efficiency for pure CaCO3 decreased with S/L (solid/liquid) ratio. It was 90% (mol/mol) when the S/L ratio was 5 g/L. However, S/L ratio didn't affect the maximum solubility limit of dissolved CaCO3.

  2. Clinical Evaluation of Indirect Composite Resin Restorations Cemented with Different Resin Cements.

    Marcondes, Maurem; Souza, Niélli; Manfroi, Fernanda Borguetti; Burnett, Luiz Henrique; Spohr, Ana Maria


    To clinically evaluate the performance of indirect composite resin restorations cemented with conventional and self-adhesive resin cements over a 12-month period. Ten patients fulfilled all the inclusion criteria. Twenty-four composite resin restorations were performed using an indirect technique and cemented with a resin cement (RelyX ARC) or a self-adhesive resin cement (RelyX U100). Two independent evaluators analyzed the restorations using modified USPHS criteria after periods of two weeks and 6 and 12 months. Statistical significance between the cements at each timepoint was evaluated with the Wilcoxon test and between timepoints with the Mann-Whitney test, both at a significance level of 5%. Fisher's exact test was used to assess the occurrence of absolute failures. No statistically significant differences were found between the groups at the same timepoint nor between groups at different timepoints. The only significant difference was found for color match for both groups after 12 months. After 12 months, indirect composite resin restorations cemented with self-adhesive resin cement performed similarly to those cemented with conventional resin cement.

  3. Influence of gypsum on efflorescence in ceramic tiles; Influence da gipsita no surgimento de eflorescencia em telhas ceramicas

    Monteiro, C.M.O.L. [Servico Nacional de Aprendizagem Industrial (SENAI), Teresina, PI (Brazil); Nascimento, R.M.; Martinelli, A.E. [Universidade Federal do Rio Grande do Norte (PPgCEM/UFRN), Natal, RN (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais


    The red ceramic industry is recognized as of major importance in Piaui State. The State capital, Teresina, is the greatest producer of this material, which is used mainly for masonry sealing blocks. One of the most frequent problems in this kind of products is the efflorescence.This paper has the main objective of studying the influence of gypsum on tiles, using the local industry production standards. The raw materials were characterized by FRX, DRX, thermal analysis and sulfates. Extruded test specimens were made with the addition of 1%, 3% and 5% of gypsum in the ceramic paste, burned at 850 deg C, 950 deg C and 1050 deg C and submitted to further technological and analysis for MEV. The reference ceramic paste did not show tendency to efflorescence formation after burning for samples with 1% gypsum added to the paste. The reference ceramic paste showed tendency to efflorescence formation after drying and consolidated efflorescence after burning for samples with 5% gypsum added to the paste. (author)

  4. Gypsum (CaSO42H2O) scaling on polybenzimidazole and cellulose acetate hollow fiber membranes under forward osmosis

    Chen, Si Cong


    We have examined the gypsum (CaSO42H2O) scaling phenomena on membranes with different physicochemical properties in forward osmosis (FO) processes. Three hollow fiber membranes made of (1) cellulose acetate (CA), (2) polybenzimidazole (PBI)/polyethersulfone (PES) and (3) PBI-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) were studied. For the first time in FO processes, we have found that surface ionic interactions dominate gypsum scaling on the membrane surface. A 70% flux reduction was observed on negatively charged CA and PBI membrane surfaces, due to strong attractive forces. The PBI membrane surface also showed a slightly positive charge at a low pH value of 3 and exhibited a 30% flux reduction. The atomic force microscopy (AFM) force measurements confirmed a strong repulsive force between gypsum and PBI at a pH value of 3. The newly developed PBI-POSS/PAN membrane had ridge morphology and a contact angle of 51.42 14.85 after the addition of hydrophilic POSS nanoparticles and 3 min thermal treatment at 95 C. Minimal scaling and an only 1.3% flux reduction were observed at a pH value of 3. Such a ridge structure may reduce scaling by not providing a locally flat surface to the crystallite at a pH value of 3; thus, gypsum would be easily washed away from the surface. 2013 by the authors; licensee MDPI, Basel, Switzerland.

  5. Flue-Gas Desulfurization Gypsum Effects on Urea-Degrading Bacteria and Ammonia Volatilization From Broiler Litter

    A major concern of the broiler industry is the volatilization of ammonia (NH3) from the mixture of bedding material and broiler excretion that covers the floor of broiler houses. Gypsum has been proposed as a litter amendment to reduce NH3 volatilization, but reports of NH3 abatement vary among stu...

  6. Three annual flue gas desulfurization gypsum applications on macronutrient and micronutrient losses in runoff from bermudagrass fertilized with poultry litter

    Considerable amounts of flue gas desulfurization (FGD) gypsum are being produced as a by-product of generating electricity. As a result, beneficial reuse of this by-product is being sought to reduce landfilling and its associated cost. The use of this byproduct as a low-cost soil amendment for suppl...

  7. Characterization of gypsum crystals exposed to a high CO{sub 2} concentration fog using x-ray

    Carreño-Márquez, I. J. A.; Castillo-Sandoval, I.; Esparza-Ponce, H. E.; Fuentes-Cobas, L.; Montero-Cabrera, M. E., E-mail: [Centro de Investigación en Materiales Avanzados (CIMAV), Miguel de Cervantes 120, Chihuahua, Chih. 31136 (Mexico)


    In Chihuahua State, a little town called Naica has the largest gypsum single crystals in the world. The growth of these structures has been described as a long and stable process developed over thousands of years. Due to the change in the environmental conditions, these crystals could suffer alterations on their surface. In this project we study the cause of possible deterioration of the giant crystals and intend to suggest measures for their preservation. For this sake, our first experiment consists on several gypsum crystals that have been subjected in a climate chamber to a fog at high CO{sub 2} concentration and 51 °C for a period of time of six months, extracting two crystals every 15 days. Then the crystals have been characterized through Grazing Incidence X-Ray Diffraction using a diffractometer PanAlytical X’PertPro with two different detectors; Xe-filled proportional detector and a Pixel 3D detector. The results were compared to determine which technique is the most suitable to study the degradation of gypsum single crystals. In the two cases, we have identified only the gypsum phase, but with different crystal plane orientations.

  8. Dehydration kinetics of Portland cement paste at high temperature

    Zhang, Q.; Ye, G.


    Portland cement paste is a multiphase compound mainly consisting of calcium-silicate-hydrate (CSH) gel, calcium hydroxide (CH) crystal, and unhydrated cement core. When cement paste is exposed to high temperature, the dehydration of cement paste leads to not only the decline in strength, but also

  9. Dehydration kinetics of Portland cement paste at high temperature

    Zhang, Q.; Ye, G.


    Portland cement paste is a multiphase compound mainly consisting of calcium-silicate-hydrate (CSH) gel, calcium hydroxide (CH) crystal, and unhydrated cement core. When cement paste is exposed to high temperature, the dehydration of cement paste leads to not only the decline in strength, but also th

  10. Environmental Assessment of Different Cement Manufacturing ...

    Due to its high environmental impact and energy intensive production, the cement industry needs to adopt more energy efficient technologies to reduce its demand for fossil fuels and impact on the environment. Bearing in mind that cement is the most widely used material for housing and modern infrastructure, the aim of this paper is to analyse the Emergy and Ecological Footprint of different cement manufacturing processes for a particular cement plant. There are several mitigation measures that can be incorporated in the cement manufacturing process to reduce the demand for fossil fuels and consequently reduce the CO2 emissions. The mitigation measures considered in this paper were the use of alternative fuels and a more energy efficient kiln process. In order to estimate the sustainability effect of the aforementioned measures, Emergy and Ecological Footprint were calculated for four different scenarios. The results show that Emergy, due to the high input mass of raw material needed for clinker production, stays at about the same level. However, for the Ecological Footprint, the results show that by combining the use of alternative fuels together with a more energy efficient kiln process, the environmental impact of the cement manufacturing process can be lowered. The research paper presents an analysis of the sustainability of cement production , a major contributor to carbon emissions, with respect to using alternative fuels and a more efficient kiln. It show

  11. Dermatoses in cement workers in southern Taiwan.

    Guo, Y L; Wang, B J; Yeh, K C; Wang, J C; Kao, H H; Wang, M T; Shih, H C; Chen, C J


    Construction workers are known to have occupational dermatoses. The prevalence of such dermatoses was unknown in Taiwanese construction workers. The objective of this study was to determine the work exposure, prevalence of skin manifestations, and sensitivity to common contact allergens in cement workers of southern Taiwan. A total of 1147 current regular cement workers were telephone-interviewed about skin problems during the past 12 months, work exposure, and personal protection. Among those interviewed, 166 were examined and patch tested with common contact allergens. A high % of cement workers reported skin problems in the past 12 months. More men (13.9%) reported skin problems possibly related to work than women (5.4%). Prevalence was associated with lower use of gloves, duration of work as cement worker, and more time in jobs involving direct manual handling of cement, especially tiling. A high % of dermatitis was noted in the 166 workers examined, which correlated with reported skin problems. On patch testing, construction workers had a high frequency of sensitivity to chromate. Sensitivity to chromate or cobalt was associated with reported skin problems, or dorsal hand dermatitis on examination. These workers' dermatitis was under-diagnosed and inadequately managed. It is concluded that cement workers in southern Taiwan had a high prevalence of skin problems related to cement use. Protective measures, work practice, and physician education should be improved to prevent or manage such problems.

  12. 利用磷石膏制备低热、微膨胀复合水泥的研究%Preparation of Low Hydration Heat, Micro-expansive Blended Cements Using Phosphogypsum

    石正国; 郭辉


    To utilize phosphogypsum more efficiently in building materials, low hydration heat, micro-expansive blended cements were prepared by adding phosphogypsum and alkali activator in blended cements. Hydration properties of the blended cements were characterized by DSC, XRD, SEM and isothermal calorimetry. The results show the hydration process of blended cement can be delayed by phosphogypsum. Through adding alkali activator and/or larger amount of phosphogypsum, the setting time of blended cement can be reduced significantly and the compressive strength can also be improved. When the addition of phosphogypsum exceeded 10% , the hardened cement pastes exhibited micro-expansive behavior due to the generation of AFt ( perhaps gypsum dihydrate). The expansion ratio of hardened cement pastes can be controlled by adjusting the addition of phosphogypsum.%为大量利用磷石膏,本文采用在复合水泥中掺加磷石膏的方法,开展了制备低热、微膨胀复合水泥的试验研究,并采用DSC、XRD、SEM及等温水化热仪表征了该复合水泥的水化特征.研究结果表明:磷石膏具有显著的缓凝效果,通过掺加Na2SO4和提高磷石膏掺量的方法,可大幅度缩短水泥的凝结时间、提高水泥的早期强度.当磷石膏掺量超过10%时,水泥水化产物中钙矾石量显著增加,并出现二水石膏,硬化水泥浆体呈现出微膨胀性.通过调整磷石膏的掺量,可控制复合水泥的膨胀率.

  13. Effect of Ammonium Chloride Solution on the Growth of Phosphorus Gypsum Whisker and Its Modification

    Shouwei Jian


    Full Text Available Phosphogypsum is the by-product of phosphate of fertilizer or phosphate which causes serious environmental pollution. In this work, a series of phosphogypsum whiskers were prepared using phosphogypsum as raw materials and NH4Cl as additive through the atmospheric water solution method. The results showed that the ammonium chloride solution has a great influence on phosphogypsum whiskers growth and the solubility. The best whisker aspect ratio of phosphogypsum was preferred in 1 mol/L NH4Cl solution, in which the solubility achieved 6.434 mg/mL and the aspect ratio reached 69.29. Besides, NH4Cl was found to have a modified effect on gypsum whiskers’ growth and it can be used to get mesh or dendritic whiskers.

  14. Age and speleogenesis of epigenic gypsum caves in the northern Apennines (Italy)

    Columbu, Andrea; Chiarini, Veronica; De Waele, Jo; Drysdale, Russell; Forti, Paolo; Hellstrom, John; Woodhead, Jon


    Triassic and Messinian gypsum beds host the majority of the caves in the eastern flank of the northern Apennines. To date, more than six hundreds voids have been mapped, including the longest known epigenic gypsum cave system in the world (Spipola-Acquafredda, ~11 km of tunnels) (De Waele et al., 2013). Superimposed caves are typically sub-horizontal (Klimchouk, 2000) and connected through vertical shafts, reflecting the palaeo base-level variations. When preserved, river terraces at the surface lie at the same palaeo altitude of the base level and horizontal cave passages. Notwithstanding the well-known geology of the area known (Vai and Martini, 2001), the age of these caves has been greatly underestimated in the past. Considering the rapid dissolution of the gypsum and uplifting of the area, the start of speleogenesis activity was considered to have occurred during the last glacial age. The age of karst voids can be only indirectly estimated by the dating of the infilling sediments. U-Th dating on carbonate speleothems provides high-precision and accurate ages (Hellstrom, 2003; Scholz and Hoffmann, 2008). We thus applied this methodology to 20 speleothems coming from 14 different caves belonging to the Monte Tondo, Spipola Acquafredda, Castelnuovo, Stella-Rio Basino and Brisighella systems. The results show that: i) caves were forming since at least ~300 ka; ii) the peak of speleogenesis was reached during relatively cold climate stages, when rivers formed terraces at the surface and aggradation caused paragenesis in the stable cave levels (Columbu et al., 2015). Besides the significant contribution to the understanding of the Apennines evaporite karst evolution, this study (and its further advancement) may also refine knowledge of the local vs regional uplifting rates and base-level variations since the late Pleistocene (Wegmann and Pazzaglia, 2009). References Columbu, A., De Waele, J., Forti, P., Montagna, P., Picotti, V., Pons-Branchu, E., Hellstrom, J

  15. SO/sub 2/ scrubbing downstream of combustion systems with raw gypsum as final product

    Hoelter, H.; Igelbuescher, H.; Gresch, H.; Dewert, H.


    This flue gas purification method first purifies the crude gas from HCl and HF in the prescrubber and from SO/sub 2/ and/or NO/sub x/ in the main scrubber. The CaSO/sub 3//CaSO/sub 4/ product occurring in the main scrubber is, according to the invention, pumped through a pipe into the prescrubber. In this process a well-oxidized CaSO/sub 4/ product with adequate content of calcium chloride develops in the scrubber liquid because of the high quantity of excess atmospheric oxygen in the crude gas. In this way raw gypsum is enriched by chlorides and can be directly used as building material, e.g. in mines. Thus, the salt load in the prescrubber is reduced.

  16. Calibration of a hysteretic model for glass fiber reinforced gypsum wall panels

    Janardhana, Maganti; Robin Davis, P.; Ravichandran, S. S.; Prasad, A. M.; Menon, D.


    Glass fiber reinforced gypsum (GFRG) wall panels are prefabricated panels with hollow cores, originally developed in Australia and subsequently adopted by India and China for use in buildings. This paper discusses identification and calibration of a suitable hysteretic model for GFRG wall panels filled with reinforced concrete. As considerable pinching was observed in the experimental results, a suitable hysteretic model with pinched hysteretic rule is used to conduct a series of quasi-static as inelastic hysteretic response analyses of GFRG panels with two different widths. The calibration of the pinching model parameters was carried out to approximately match the simulated and experimental responses up to 80% of the peak load in the post peak region. Interestingly, the same values of various parameters (energy dissipation and pinching related parameters) were obtained for all five test specimens.

  17. International development trends in low-energy cements

    Stark, J.; Mueller, A.


    Besides the currently dominant tendency to increase the proportion of interground additive in cement, the following development trends are internationally emerging in the material composition of so-called low-energy cements with a view to minimizing energy input for cement manufacture: (1) active belite cement with the principal clinker minerals a'C/sub 2/S and C/sub 3/S; (2) belite sulphoaluminate cement (..beta.. C/sub 2/S, C/sub 4/A/sub 3/S); (3) belite sulphoferrite cement (..beta.. C/sub 2/S, C/sub 4/AF, C/sub 4/A/sub 3/S); (4) NTS cement (alinite).

  18. Effect Of Coir Fibres On The Compaction And Unconfined Compressive Strength Of Bentonite-Lime-Gypsum Mixture

    Tilak B. Vidya


    Full Text Available This paper presents the effect of coir fibres on the compaction and unconfined compressive strength of a bentonite-lime-gypsum mixture. The coir fiber content varied from 0.5 to 2 %. The results indicated that the dry unit weight and the optimum moisture content of a bentonite – lime mix increased with the addition of gypsum. The unconfined compressive strength of the bentonite increased with the increase in the lime content up to 8 %. Beyond 8 %, the unconfined compressive strength decreased. The dry unit weight of the reference mix decreased, and the optimum moisture content increased with the addition of coir fibre. The unconfined compressive strength of the bentonite + 8 % lime mix increased up to 4 % with the gypsum. Beyond 4 %, the unconfined compressive strength decreased. The unconfined compressive strength of the reference mix increased with the addition of coir fibre up to a fibre content of 1.5 %. The unconfined compressive strength of the reference mix-coir fibre composite was less in comparison to the reference mix. The unconfined compressive strength of the bentonite increased with the addition of lime and gypsum and with the increase in the curing period. The improvement in the post-peak region was better for the reference mix with reinforced coir fibres as compared to the unreinforced reference mix. The improved post-peak behaviour of the bentonite-lime-gypsum-coir fibre mixture could boost the construction of temporary roads on such problematic soils. Further, its use will also provide an environmental motivation for providing a means of consuming large quantities of coir fibres.

  19. Holocene cemented beach deposits in Belize

    Gischler, Eberhard; Lomando, Anthony J.


    Two types of cemented beach deposits occur on reef islands off the coast of Belize. These are (1) intertidal beachrock that is dominantly cemented by marine aragonite and high-magnesium-calcite cements, and (2) supratidal cayrock that is cemented mainly by vadose low-magnesium-calcite cements. Besides differences in position relative to present sea level and resulting early diagenesic features, beachrock and cayrock can be distinguished on the basis of differences in composition, texture, geographical position, and age. Whereas the composition of beachrock is similar to that of the adjacent marginal reef sediments, cayrock is enriched in benthic foraminifera. Intertidal beachrock is moderately to well sorted and well cemented, while supratidal cayrock is very well sorted, poorly cemented and friable. Beachrock occurs preferentially on windward beaches of sand-shingle Gays on the middle and southern barrier reefs and on the isolated platforms Glovers and Lighthouse Reefs. Cayrock only occurs on larger mangrove-sand Gays of the isolated platforms Turneffe Islands, Lighthouse Reef, and the northern barrier reef. 14C-dating of ten whole-rock and mollusk shell samples produced calibrated dates between AD 345 and AD 1435 for beachrock and between BC 1085 and AD 1190 for cayrock. The large-scale distribution of beachrock in Belize supports the contention that physical processes such as water agitation rather than biological processes control beachrock formation and distribution. Only on windward sides of cays that are close to the reef crest, where large amounts of seawater flush the beaches, considerable amounts of cements can be precipitated to produce beachrock. Cayrock forms due to cementation in the vadose zone and is only preserved on larger, stable mangrove-sand cays.

  20. Hydration effects on gypsum dissolution revealed by in situ nanoscale atomic force microscopy observations

    Burgos-Cara, A.; Putnis, C. V.; Rodriguez-Navarro, C.; Ruiz-Agudo, E.


    Recent work has suggested that the rates of mineral dissolution in aqueous solutions are dependent on the kinetics of dehydration of the ions building the crystal. Dehydration kinetics will be ultimately determined by the competition between ion-water and water-water interactions, which can be significantly modified by the presence of background ions in solution. At low ionic strength, the effect of electrolytes on ion-water (electrostatic) interactions will dominate (Kowacz et al., 2007). By performing macroscopic and in situ, microscopic (atomic force microscopy) dissolution experiments, the effect of background electrolytes on the dissolution kinetics of gypsum (CaSO4·2H2O) {0 1 0} cleavage surfaces is tested at constant, low ionic strength (IS = 0.05) and undersaturation (saturation index, SI = -0.045). Dissolution rates are systematically lower in the presence of 1:1 background electrolytes than in an electrolyte-free solution, regardless of the nature of the electrolyte tested. We hypothesize that stabilization of the hydration shell of calcium by the presence of background ions can explain this result, based on the observed correlations in dissolution rates with the ionic surface tension increment of the background ion in solution. Stabilization of the cation hydration shell should favor dissolution. However, in the case of strongly hydrated ions such as Ca2+, this has a direct entropic effect that reduces the overall ΔG of the system, so that dissolution is energetically less favorable. Overall, these results provide new evidence that supports cation dehydration being the rate-controlling step for gypsum dissolution, as proposed for other minerals such as barite, dolomite and calcite.

  1. Carbon and sulfur cycling by microbial communities in a gypsum-treated oil sands tailings pond.

    Ramos-Padrón, Esther; Bordenave, Sylvain; Lin, Shiping; Bhaskar, Iyswarya Mani; Dong, Xiaoli; Sensen, Christoph W; Fournier, Joseph; Voordouw, Gerrit; Gieg, Lisa M


    Oil sands tailings ponds receive and store the solid and liquid waste from bitumen extraction and are managed to promote solids densification and water recycling. The ponds are highly stratified due to increasing solids content as a function of depth but can be impacted by tailings addition and removal and by convection due to microbial gas production. We characterized the microbial communities in relation to microbial activities as a function of depth in an active tailings pond routinely treated with gypsum (CaSO(4)·2H(2)O) to accelerate densification. Pyrosequencing of 16S rDNA gene sequences indicated that the aerobic surface layer, where the highest level of sulfate (6 mM) but no sulfide was detected, had a very different community profile than the rest of the pond. Deeper anaerobic layers were dominated by syntrophs (Pelotomaculum, Syntrophus, and Smithella spp.), sulfate- and sulfur-reducing bacteria (SRB, Desulfocapsa and Desulfurivibrio spp.), acetate- and H(2)-using methanogens, and a variety of other anaerobes that have been implicated in hydrocarbon utilization or iron and sulfur cycling. The SRB were most abundant from 10 to 14 mbs, bracketing the zone where the sulfate reduction rate was highest. Similarly, the most abundant methanogens and syntrophs identified as a function of depth closely mirrored the fluctuating methanogenesis rates. Methanogenesis was inhibited in laboratory incubations by nearly 50% when sulfate was supplied at pond-level concentrations suggesting that in situ sulfate reduction can substantially minimize methane emissions. Based on our data, we hypothesize that the emission of sulfide due to SRB activity in the gypsum treated pond is also limited due to its high solubility and oxidation in surface waters.

  2. Analysis of naturally-occurring radionuclides in coal combustion fly ash, gypsum, and scrubber residue samples.

    Roper, Angela R; Stabin, Michael G; Delapp, Rossane C; Kosson, David S


    Coal combustion residues from coal-fired power plants can be advantageous for use in building and construction materials. These by-products contain trace quantities of naturally occurring radionuclides from the uranium and thorium series, as well as other naturally occurring radionuclides such as K. Analysis was performed on samples of coal fly ash, flue gas desulfurization, gypsum and scrubber sludges, fixated scrubber sludges, and waste water filter cakes sampled from multiple coal-fired power plants in the United States. The radioactive content of U and Th decay series nuclides was determined using gamma photopeaks from progeny Pb at 352 keV and Tl at 583 keV, respectively; K specific activities were determined using the 1,461 keV photopeak. The samples were hermetically sealed to allow for secular equilibrium between the radium parents and the radon and subsequent progeny. Samples were analyzed in a common geometry using two high purity germanium photon detectors with low energy detection capabilities. The specific activities (Bq kg) were compared to results from literature studies including different building materials and fly ash specific activities. Fly ash from bituminous and subbituminous coals had U specific activities varying from 30-217 Bq kg (mean + 1 s.d. 119 ± 45 Bq kg) and 72-209 Bq kg (115 ± 40 Bq kg), respectively; Th specific activities from 10-120 Bq kg (73 ± 26 Bq kg) and 53-110 Bq kg (81 ± 18 Bq kg), respectively; and K specific activities from 177 to 928 Bq kg (569 ± 184 Bq kg) and 87-303 Bq kg (171 ± 69 Bq kg), respectively. Gypsum samples had U, Th, and K specific activities approximately one order of magnitude less than measured for fly ash samples.

  3. Comparison of Temperature Field Distribution between Cement Preclinkering Technology and Cement Precalcining Technology

    XU Xun; WANG Lan


    Through the comparison of calcination conditions between cement preclinkering technology and cement precalcining technology, we studied the characteristics of temperature ifeld distribution of cement preclinkering technology systems including cyclone preheater, preclinkering furnace, and rotary kiln. We used numerical simulation method to obtain data of temperature ifeld distribution.Some results are found by system study. The ratio of tail coal of cement preclinkering technology is about 70%, and raw meal temperature can reach 1070℃. ShorterL/D kiln type of preclinkering technology can obtain more stable calcining zone temperature. The highest solid temperature of cement preclinkering technology is higher than 80℃, and high temperature region (>1450℃) length is 2 times, which is beneifcial for calcining clinker and higher clinker quality. So cement preclinkering technology can obtain more performance temperature ifled, which improves both the solid-phase reaction and liquid-phase reaction.

  4. The behavior of the micro-mechanical cement-bone interface affects the cement failure in total hip replacement

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.


    In the current study, the effects of different ways to implement the complex micro-mechanical behavior of the cement-bone interface on the fatigue failure of the cement mantle were investigated. In an FEA-model of a cemented hip reconstruction the cement-bone interface was modeled and numerically im

  5. Effect of cementing technique and cement type on thermal necrosis in hip resurfacing arthroplasty - a numerical study

    Janssen, D.; Srinivasan, P.; Scheerlinck, T.; Verdonschot, N.J.J.


    Femoral fractures within resurfacing implants have been associated with bone necrosis, possibly resulting from heat generated by cement polymerization. The amount of heat generated depends on cement mantle volume and type of cement. Using finite element analysis, the effect of cement type and volume

  6. Synthesis of pure Portland cement phases

    Wesselsky, Andreas; Jensen, Ole Mejlhede


    Pure phases commonly found in Portland cement clinkers are often used to test cement hydration behaviour in simplified experimental conditions. The synthesis of these phases is covered in this paper, starting with a description of phase relations and possible polymorphs of the four main phases...... in Portland cement, i.e. tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium alumino ferrite. Details of the The process of solid state synthesis are is described in general including practical advice on equipment and techniques. Finally In addition, some exemplary mix compositions...


    A.Karamberi; E.Chaniotakis; D.Papageorgiou; A.Moutsatsou


    The present study investigates glass and cement compatibility with a view to use glass as a cement replacement. Amber, flint and green glasses were chosen due to their prevalence in the Greek market as packaging materials. The factors under investigation were the pozzolanicity of the glass cullet, the hydration rate and the mechanical strength development of the cement pastes, as well as the expansion of the specimens due to alkali-silica reaction.Moreover, the potential enhancement of glass pozzolanic activity was examined. The results of the study were encouraging to show the potentiality of utilising glass cullet in cementitious products.

  8. Seasonal variation of gypsum in aerosol and its effect on the acidity of wet precipitation on the Japan sea side of Japan

    Zhou, Guoping; Tazaki, Kazue

    Variations of mineral concentrations in aerosols collected weekly for a 1 yr period (from October 1992 to September 1993) on Matsue, Shimane Prefecture, Japan, were investigated by X-ray powder diffraction (XRD) analysis. Major elemental concentrations were measured by energy dispersive X-ray analysis (EDX). Sulfate minerals in aerosol include gypsum, ferricopiapite, metavoltine and glauberite. Gypsum showed two high concentration peaks during spring and early winter, which was consistent with that of clay minerals and quartz. The ratios of gypsum to clay minerals, quartz and calcite, respectively, showed an increase of gypsum in spring. A non-agreement of concentration distribution between calcite and other soil minerals during spring implies a conversion of calcite to gypsum during transport. Individual particle analyses by EDX revealed large amounts of S-rich submicrometer particles coated on the surface of minerals. A sequence favorable to be attached by S constituents was calcite (83%) > clay minerals (68%) > fly ash (55) > quartz and feldspars (36%) The reaction between calcite and simulated acid rain solution with pHs of 3, 4 and 5 showed a formation of gypsum in 12 h, indicating that the conversion of calcite to gypsum is possible in the presence of sulfuric acid or (NH 4) 2 SO 4 aerosols during transport from the Asian continent to the Japan Islands.

  9. Alternative Fuels in Cement Production

    Larsen, Morten Boberg

    The substitution of alternative for fossil fuels in cement production has increased significantly in the last decade. Of these new alternative fuels, solid state fuels presently account for the largest part, and in particular, meat and bone meal, plastics and tyre derived fuels (TDF) accounted...... of the fuel heating value. In addition, the devolatilization time of alternative fuels cannot be neglected in kiln system process analyses, as these fuels are typically in the cm-size with devolatilization times in the order of minutes. The devolatilization characteristics of large particles of tyre rubber...... time, where increased particle size increased the devolatilization time. Model analyses demonstrated that the overall devolatilization kinetics of large particles of tyre rubber is mainly controlled by heat transfer and intrinsic pyrolysis kinetics, whereas mass transfer has negligible influence...

  10. Cement Manufacturing Plant Guidelines: An Approach to Reconciling the Financing of Cement with Climate Change Objectives


    Cement manufacturing is an energy-intensive process, requiring high fuel consumption to operate cement kilns, which in turn generates carbon dioxide (CO2). These Guidelines aim to provide clear and quantitative Minimum Climate Change Performance Criteria necessary for IDB to support projects, as well as guidance on assessing and reducing the greenhouse gas (GHG) emissions of projects. The purpose of the Cement Manufacturing Plant guidelines is to set forth an approach for the financing of new...

  11. Chromium content in human skin after in vitro application of ordinary cement and ferrous-sulphate-reduced cement

    Fullerton, A; Gammelgaard, Bente; Avnstorp, C


    The amount of chromium found in human skin after in vitro application of cement suspensions on full-thickness human skin in diffusion cells was investigated. Cement suspensions made from ordinary Portland cement or Portland cement with the chromate reduced with added ferrous sulphate were used....... The cement suspensions were either applied on the skin surface under occlusion for 48 h or applied repeatedly every 24 h for 96 h. No statistically significant difference in chromium content of skin layers between skin exposed to ordinary Portland cement, skin exposed to cement with added ferrous sulphate...

  12. A biological process for the reclamation of flue gas desulfurization gypsum using mixed sulfate-reducing bacteria with inexpensive carbon sources.

    Kaufman, E N; Little, M H; Selvaraj, P


    A combined chemical and biological process for the recycling of flue gas desulfurization (FGD) gypsum into calcium carbonate and elemental sulfur is demonstrated. In this process, a mixed culture of sulfate-reducing bacteria (SRB) utilizes inexpensive carbon sources, such as sewage digest or synthesis gas, to reduce FGD gypsum to hydrogen sulfide. The sulfide is then oxidized to elemental sulfur via reaction with ferric sulfate, and accumulating calcium ions are precipitated as calcium carbonate using carbon dioxide. Employing anaerobically digested municipal sewage sludge (AD-MSS) medium as a carbon source, SRBs in serum bottles demonstrated an FGD gypsum reduction rate of 8 mg/L/h (10(9) cells)(-1). A chemostat with continuous addition of both AD-MSS media and gypsum exhibited sulfate reduction rates as high as 1.3 kg FGD gypsum/m(3)d. The increased biocatalyst density afforded by cell immobilization in a columnar reactor allowed a productivity of 152 mg SO(4) (-2)/Lh or 6.6 kg FGD gypsum/m(3)d. Both reactors demonstrated 100% conversion of sulfate, with 75-100% recovery of elemental sulfur and chemical oxygen demand utilization as high as 70%. Calcium carbonate was recovered from the reactor effluent on precipitation using carbon dioxide. It was demonstrated that SRBs may also use synthesis gas (CO, H(2), and CO(2) in the reduction of gypsum, further decreasing process costs. The formation of two marketable products-elemental sulfur and calcium carbonate-from FGD gypsum sludge, combined with the use of a low-cost carbon source and further improvements in reactor design, promises to offer an attractive alternative to the landfilling of FGD gypsum.

  13. Radiographic appearance of commonly used cements in implant dentistry.

    Pette, Gregory A; Ganeles, Jeffrey; Norkin, Frederic J


    Cement-retained restorations allow for a conventional fixed partial denture approach to restoring dental implants. However, inadequate removal of excess cement at the time of cementation may introduce a severe complication: cement-induced peri-implantitis. Radiopaque cements are more easily detected on radiographs and should improve the recognition of extravasated cement at the time of insertion. The purpose of this study was to evaluate the radiopacity of commercially available cements in vitro. Eighteen different cements commonly used for luting restorations to implants were tested at both 0.5- and 1.0-mm thicknesses. The cements examined were zinc oxide eugenol, zinc oxide, zinc polycarboxylate, zinc phosphate, resin-reinforced glass ionomer, urethane resin, resin, and composite resin. Two samples of each cement thickness underwent standardized radiography next to an aluminum step wedge as a reference. The mean grayscale value of each of the nine 1-mm steps in the step wedge were used as reference values and compared to each of the cement samples. Temp Bond Clear (resin), IMProv (urethane resin), Premier Implant Cement (resin), and Temrex NE (resin) were not radiographically detectable at either sample thickness. Cements containing zinc were the most detectable upon radiographic analysis. There are significant differences in the radiopacity of many commonly used cements. Since cementinduced peri-implantitis can lead to late implant failure, cements that can be visualized radiographically may reduce the incidence of this problem.

  14. Slagment Cement Improve the Cement Resistance Toward Acids Attack During Acidizing Treatment

    Nik Khairul Irfan Bin Nik Ab. Lah.


    Full Text Available Acidizing treatment in past experience shows several zonal isolation problems after the treatment. This study presents the effect of the acid treatment toward class G cement and slagment cement as the improvement method to improve the cement resistance toward the acid. Lab experiments were conducted by immerge the respective cement cubes into 12% HCl/3% HF solution for 40 min before several analysis were conducted. Based on the result, the mass loss and compressive strength loss of the cement cubes decrease as the curing temperature and pressure increase due to more evenly distributed cement chemical composition crystal in high curing condition as shown in Scanning Electron Microscopy (SEM analysis. From X-Ray Diffraction (XRD and X-Ray Fluorescence (XRF analysis, only the first layer of the cement cubes shows chemical component change due to the reaction between the acid. This study found that, replacing class G cement to slagment cement can reduce the mass loss and compressive strength loss up to 72% and 82%, respectively.

  15. Effect of Cement Type on Autogenous Deformation of Cement-Based Materials

    Pietro, Lura; Ye, Guang; van Breugel, Klaas


    (BFS) cement pastes. Self-desiccation shrinkage of the BFS cement paste was modeled based on the RH measurements, following the capillary-tension approach. The main findings of this study are: 1) self-desiccation shrinkage can be related to self-desiccation both for Portland and for BFS cement pastes......, taking into account the influence of the dissolved salts in the pore solution, 2) the BFS cement paste studied shows pronounced self-desiccation and self-desiccation shrinkage, mainly caused by its very fine pore structure....

  16. Laboratory development and field application of novel cement system for cementing high-temperature oil wells

    Wan, X.; Zhang, H.; Li, Y.; Yang, Y. [SINOPEC, Beijing (China); Shan, H.; Xiao, Z. [OPT, Beijing (China)


    The challenges that oil and gas well engineers face when cementing mid-to-high temperature exploration oil and gas wells were discussed. A newly developed cement system with an effective laminar-flow spacer was presented along with case histories that document the system's effectiveness for cementing high temperature exploration wells. The problems associated with cementing high temperature exploration wells include high bottom hole static temperature; very low pump rates; and very long job times. These challenges contribute to the operational risks during cement slurry placement in the wellbore as well as during cement sheath setting during the life of the well. The new cement formulation presented in this paper addresses these challenges. Eight jobs have been completed in the field with much success. The combination of a new retarder and fluid loss control additive improves the system performance considerably in terms of low fluid loss rate, minimal free water, proper rheology, predictable thickening time, high resistance to salt contaminations and no adverse effect on set cement strength. The drilling muds are effectively displaced by the laminar flow spacer, thus improving the cementing bond. 9 refs., 5 tabs., 6 figs.


    Nediljka Gaurina-Međimurec


    Full Text Available Adaptation of commercial types of domestic cements for use in cementing the deep wells is a process by which Yugoslav oil industry tends to solve problems of completion of those wells independently. In order to design a domestic, cheep and effective retarder, tests of applicability of wine acid on cement slurries have been carried out. Besides examining the necessary wine acid content to achieve desirable Theological properties, the influence of this additive on properties of hardened cement samples has been tested too (the paper is published in Croatian.

  18. Technology status of production of SA integrated with cement from phosphogypsum%磷石膏制硫酸联产水泥的技术现状



    介绍石膏制硫酸联产水泥技术的发展背景、技术现状和鲁北磷石膏制硫酸联产水泥装置的工艺流程、主要设备、原材料要求、中间产品控制、产品质量、稳定操作要点、成本及效益情况,提出推广磷石膏制硫酸联产水泥意义重大。%The development background and technology status of the production of SA integrated with cement from gypsum are introduced. The process, main equipment, demand of raw material, middling product control, product quality, stable operation points, costs and benefits situation for production of SA integrated with cement from phosphogypsum in Lubei Group are introduced, the important significance of popularizing production of SA integrated with cement from phosphogypsum is proposed.

  19. Assessment of Comprehensive Effects and Optimization of a Circular Economy System of Coal Power and Cement in Kongtong District, Pingliang City, Gansu Province, China

    Suocheng Dong


    Full Text Available The idea of a circular economy (CE, which differs from traditional linear economy with a high consumption of natural resources and pollution, has captured much interest and attention. This paper uses a CE system of coal power and cement in Kongtong District, Pingliang City, Gansu Province, China as a case study to analyze the comprehensive effects of CE paradigm. Our simulation results, based on system dynamics (SD modeling, infer that the transformation of manufacturing towards a CE system can prominently help coal power and cement enterprises reduce waste emission and increase economic profits. Through solid waste exchanges, a power plant can achieve over RMB 80 million of additional revenue per year at the highest level. CE also contributes to the reduction of regional pollution, saves mineral resources, and improves the atmospheric environment, an accumulated total of 14.11 million t of natural gypsum and 22.67 million t of coal can be saved. This sets a promising example for coal power and cement plants worldwide. Effective regulatory measures and further optimization towards a circular economy system are essential in maintaining the stable development of a CE system due to the risk of surplus production of upstream industries and other defects.

  20. Basalt waste added to Portland cement

    Thiago Melanda Mendes


    Full Text Available Portland cement is widely used as a building material and more than 4.3 billion tons were produced in 2014, with increasing environmental impacts by this industry, mainly through CO2 emissions and consumption of non-removable raw materials. Several by-products have been used as raw materials or fuels to reduce environmental impacts. Basaltic waste collected by filters was employed as a mineral mixture to Portland cement and two fractions were tested. The compression strength of mortars was measured after 7 days and Scanning Electron Microscopy (SEM and Electron Diffraction Scattering (EDS were carried out on Portland cement paste with the basaltic residue. Gains in compression strength were observed for mixtures containing 2.5 wt.% of basaltic residue. Hydration products observed on surface of basaltic particles show the nucleation effect of mineral mixtures. Clinker substitution by mineral mixtures reduces CO2 emission per ton of Portland cement.

  1. The Setting Chemistry of Glass Ionomer Cement

    CHENG Hanting; LIU Hanxing; ZHANG Guoqing


    The setting chemistry of glass ionomer cement was investigated by using mechanical determination of compressive strength at predetermined intervals, and measurement of structure changes of corresponding fracture sample by means of IR spectra and differential scanning calorimetry ( DSC). Zinc polycarboxylate cement was used as a comparison sample. The compressive strength of glass ionomer cement (GIC) increases with aging. IR spectra and DSC of corresponding fracture sample show the structure changes of the matrix and interface layer comprising of silica gel during the predetermined intervals studied, however, no significant changes occur in the zinc polycarxyolate cement. Hence the structure changes of the matrix and/or interface layer are responsible for compressive strength increasing with aging. The structure changes include the crosslink density, the ratio of complex form to ionic form, the content ratio of Al-PAA to Ca-PAA, the forming and mauring process of the interface layer comprising of silica gel.

  2. Dicalcium phosphate cements: brushite and monetite.

    Tamimi, Faleh; Sheikh, Zeeshan; Barralet, Jake


    Dicalcium phosphate cements were developed two decades ago and ever since there has been a substantial growth in research into improving their properties in order to satisfy the requirements needed for several clinical applications. The present paper presents an overview of the rapidly expanding research field of the two main dicalcium phosphate bioceramics: brushite and monetite. This review begins with a summary of all the different formulae developed to prepare dicalcium phosphate cements, and their setting reaction, in order to set the scene for the key cement physical and chemical properties, such as compressive and tensile strength, cohesion, injectability and shelf-life. We address the issue of brushite conversion into either monetite or apatite. Moreover, we discuss the in vivo behavior of the cements, including their ability to promote bone formation, biodegradation and potential clinical applications in drug delivery, orthopedics, craniofacial surgery, cancer therapy and biosensors.

  3. The case of Mugher cement facto


    based on emission test and mass balance performed. Yet it accounts for ... Hydraulic (chiefly portland) cement, the binding agent in concrete and most .... phenolphthalein were used for end-point detection of the acid-base titration. Materials.

  4. Considerations on the mechanical behavior and hydration process supersulphated cement (CSS) formulated with phosphogypsum; Consideracoes sobre a resistencia mecanica e o processo de hidratacao de cimentos supersulfatados (CSS) formulados com fosfogesso

    Gracioli, Bruna; Varela, Maxwell Vinicius Favero; Beutler, Cheila Sirlene; Frare, Andreza; Luz, Caroline Angulski da; Pereira Filho, Jose Ilo, E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Universidade Tecnologica Federal do Parana (UTFPR), Pato Branco, PR (Brazil)


    Supersulfated Cements (SSC) are composed from blast furnace slag (90%), calcium sulfate (10-20%) and a small amount of alkali activator (up 5%). Gypsum is a conventional source of calcium sulfate, however, it can be replaced by phosphogypsum (PG), a byproduct from the production of phosphoric acid (H{sub 3}PO{sub 4}) with similar chemical and mineralogical composition of the gypsum. In Brazil, the production of this material is about 4.5 million tons per year. Because the SSC contains a higher calcium sulfate content (20%) in relation to Portland cement, a higher consumption of phosphogypsum is possible. The goal of this study was to investigate the phosphogypsum (PG) as an alternative source of calcium sulfate in order to obtain CSS. In addition to use of PG, the effects of both calcium sulfate and alkali activator content on the process of hydration were investigated. The results showed that SSC made with phosphogypsum met the minimum compressive strength required by the European standard for SSC (EN 15743/2010). Low heat of hydration rates mainly influenced by the low alkali activator content was observed. The excess of alkali activator (KOH) had different influences according to calcium sulfate content. In pastes made with low content (10%), 0.8% of KOH reduced the compressive strength, while in those with a high calcium sulfate content (20%) the high alkaline content resulted in the instability of ettringite. (author)

  5. Low-cycle fatigue of surgical cements

    A. Balin


    Full Text Available Purpose: In case when surgical cement is used to fix endoprostheses of joints the fatigue character of mechanicalinterraction in the cement seems to be a significant importance. The paper suggests to adapt the research methodof low cycle fatigue for modelling the loads on surgical cements in an artificial hip joint. Surgical cements havealso been modified in order to improve their functional properties.Design/methodology/approach: Low cycle fatigue tests were conducted on samples made from Palamedcement without an addition and on samples modified with glassy carbon and titanium. The tests were conductedon a servohydraulic fatigue testing machine, MTS-810, with displacement control.Findings: Fatigue tests proved viscoelastic character of all the tested materials. During the fatigue tests, thephenomenon of stress cyclic relaxation was observed.Research limitations/implications: Modelling the loadings of cement in endoprostheses of joints with the lowcycle fatigue method takes into account all high value stresses, while cement is being used for endoprosthesesfor many years in the conditions of random stress and deformation courses. Therefore the obtained stress anddeformation values are bigger than those which would have been obtained in real conditions in the same time.Practical implications: The low cycle fatigue tests carried out showed how important is the factor of timefor the behavior of surgical cement in the conditions of changeable loadings. This fact is essential to assessits usability for endoprosthesoplasty of joints, specially of a hip joint. Post deformation return which is acharacteristic feature for material viscoelasticity enables its regeneration conditioning expected durability ofendoprosthesis of joints.Originality/value: Low cycle fatigue testing method for modelling of loads on surgical cement in artificial hipjoint enables to carry out the tests in a shorter period of time.

  6. Continued stabilization of Triathlon cemented TKA

    Molt, Mats; Ryd, Leif; Toksvig-Larsen, Sören


    Background and purpose There is a general call for phased introduction of new implants, and one step in the introduction is an early evaluation of micromotion. We compared the micromotion in the Triathlon and its predecessor, the Duracon total knee prosthesis, concentrating especially on continuous migration over 5 years of follow-up. Patients and methods 60 patients were randomized to receive either a cemented Triathlon total knee prosthesis or a cemented Duracon total knee prosthesis. 3-D t...

  7. Cement stratigraphy: Image probes of cathodoluminescent facies.

    Vuillemin, Aurèle; Ndiaye, Mapathe; Martini, Rossana; Davaud, Eric Jean


    Cement stratigraphy of carbonates aims to establish the chronology of processes involved in the rock diagenesis. Regional cement stratigraphy allows correlations and understanding of the petrological heterogeneities in reservoirs and aquifers, but is a long and rigorous approach. This article exposes a methodology of image analysis that facilitates the spatial correlation of diagenetic events in carbonate rocks. Based on the statistical comparison of signals extracted from the red spectrum em...

  8. Physical Properties of Acidic Calcium Phosphate Cements


    The gold standard for bone replacement today, autologous bone, suffers from several disadvantages, such as the increased risk of infection due to the need for two surgeries. Degradable synthetic materials with properties similar to bone, such as calcium phosphate cements, are a promising alternative. Calcium phosphate cements are suited for a limited amount of applications and improving their physical properties could extend their use into areas previously not considered possible. For example...

  9. Dynamic properties of composite cemented clay

    蔡袁强; 梁旭


    In this work,the dynamic properties of composite cemented clay under a wide range of strains were studied considering the effect of different mixing ratio and the change of confining pressures through dynamic triaxial test. A simple and practical method to estimate the dynamic elastic modulus and damping ratio is proposed in this paper and a related empirical normalized formula is also presented. The results provide useful guidelines for preliminary estimation of cement requirements to improve the dynamic properties of clays.

  10. VNIR reflectance spectra of gypsum mixtures for comparison with White Sands National Monument, New Mexico (WSNM) dune samples as an analog study of the Olympia Undae region of Mars

    King, S. J.; Bishop, J. L.; Fenton, L. K.; Lafuente, B.; Garcia, G. C.; Horgan, B. H.


    Dunes at WSNM are being used as an analog study area for gypsum-rich dunes near the northern polar region of Mars. Samples were collected from 4 dunes at WSNM for this study. In order to determine abundances of the gypsum, quartz and dolomite present in the dune sand, size separates (250 μm) were prepared for gypsum, quartz and dolomite, mixtures were prepared using the 90-150 μm size fraction, and all samples were characterized in the lab. Analyses of the VNIR spectral data are presented here (Figs. 1-2) and analyses of the XRD data are presented in a companion abstract [1]. The majority of the dune sand is dominated by gypsum, while the coarse grains at some ripples are largely dolomite. Mid-IR spectra will be evaluated as well. Gypsum/Dolomite Mixtures (Fig. 1) There is a clear progression of albedo and band strength in these mixture spectra as one mineral is increased and the other decreased. The mixture spectra are dominated by the gypsum bands for mixtures that are gypsum rich (≥50wt.% gypsum) including a triplet at 1.446-1.535 μm, plus bands at 1.749, 1.945, 2.217 and 2.267 μm. When mixtures become predominantly dolomite (10/90 & 20/80 mixtures), the gypsum bands are significantly weaker, while the dolomite band at 2.322 becomes much more visible. Gypsum/Quartz Mixtures (Fig. 2) The gypsum/quartz mixture spectra are dominated to an even greater extent by gypsum, resulting in readily observable gypsum features for spectra of samples with only 10 wt.% gypsum. [1] Lafuente et al. (2013) AGU, submitted.

  11. Case Study of the California Cement Industry

    Coito, Fred; Powell, Frank; Worrell, Ernst; Price, Lynn; Friedmann, Rafael


    California is the largest cement producing state in theU.S., accounting for between 10 percent and 15 percent of U.S. cementproduction and cement industry employment. The cement industry inCalifornia consists of 31 sites that consume large amounts of energy,annually: 1,600 GWh of electricity, 22 million therms of natural gas, 2.3million tons of coal, 0.25 tons of coke, and smaller amounts of wastematerials, including tires. The case study summarized in this paperfocused on providing background information, an assessment ofenergy-efficiency opportunities and barriers, and program recommendationsthat can be used by program planners to better target products to thecement industry. The primary approach to this case study involvedwalk-through surveys of customer facilities and in depth interviews withcustomer decision makers and subsequent analysis of collected data. Inaddition, a basic review of the cement production process was developed,and summary cement industry energy and economic data were collected, andanalyzed. The analysis of secondary data provides background informationon the cement industry and identification of potential energy-efficiencyopportunities. The interviews provide some understanding of the customerperspective about implementation of energy-efficiencyprojects.

  12. Influence of Cellulose Ethers on Hydration Products of Portland Cement

    MA Baoguo; OU Zhihua; JIAN Shouwei; XU Rulin


    Cellulose ethers are widely used to mortar formulations, and it is significant to understand the interaction between cellulose ethers and cement pastes. FT-IR spectra, thermal analysis and SEM are used to investigate hydration products in the cement pastes modified by HEMC and HPMC in this article. The results show that the hydration products in modified cement pastes were finally identical with those in the unmodified cement paste, but the major hydration products, such as CH (calcium hydroxide), ettringite and C-S-H, appeared later in the modified cement pastes than in the unmodified cement paste. The cellulose ethers decrease the outer products and increase inner products of C-S-H gels. Compared to unmodified cement pastes, no new products are found in the modified cement pastes in the present experiment. The HEMC and HPMC investigation shows almost the same influence on the hydration products of Portland cement.

  13. Investigation of Possible Wellbore Cement Failures During Hydraulic Fracturing Operations

    Kim, Jihoon; Moridis, George


    We model and assess the possibility of shear failure, using the Mohr-Coulomb model ? along the vertical well by employing a rigorous coupled flow-geomechanic analysis. To this end, we vary the values of cohesion between the well casing and the surrounding cement to representing different quality levels of the cementing operation (low cohesion corresponds to low-quality cement and/or incomplete cementing). The simulation results show that there is very little fracturing when the cement is of high quality.. Conversely, incomplete cementing and/or weak cement can causes significant shear failure and the evolution of long fractures/cracks along the vertical well. Specifically, low cohesion between the well and cemented areas can cause significant shear failure along the well, but the same cohesion as the cemented zone does not cause shear failure. When the hydraulic fracturing pressure is high, low cohesion of the cement can causes fast propagation of shear failure and of the resulting fracture/crack, but a high-quality cement with no weak zones exhibits limited shear failure that is concentrated near the bottom of the vertical part of the well. Thus, high-quality cement and complete cementing along the vertical well appears to be the strongest protection against shear failure of the wellbore cement and, consequently, against contamination hazards to drinking water aquifers during hydraulic fracturing operations.

  14. 低温施工用快硬水泥的配方及性能试验研究%Low-temperature construction with rapid hardening cement formulations and performance test study

    莫富治; 肖展瑜


      通过试验确定了一种以硫铝酸盐水泥熟料为主要成分的低温施工用快硬水泥的配方,在5℃的低温环境下试验,结果表明该配方水泥不需添加任何外加剂,按普通混凝土常温施工方法进行施工养护,不需实施任何冬期施工措施,1d抗压强度可达拆除模板要求,后期强度能继续增长。该配方水泥在低温下正常快速硬化主要机理为:硅酸盐水泥熟料和生石灰能快速释放出Ca(OH)2,天然二水石膏能快速释放出CaSO4, Ca(OH)2和CaSO4与硫铝酸盐水泥熟料中的主要矿物4(CaO)・3(Al2O3)・SO3(无水硫铝酸钙)迅速反应生成大量的钙矾石,加上硫铝酸盐水泥低温水化硬化专用催化剂——亚硝酸钠的作用,水泥奖体快速硬化。天然硬石膏溶解速度比天然二水石膏缓慢,在天然二水石膏用尽之后与无水硫铝酸钙等继续发生水化反应,使水泥硬化体后期强度不断增长。%Determined a formula of which a sulfur aluminate cement clinker as the main ingredient and low temperature construction with rapid hardening cement by experiment. At 5 ° C low-temperature environment test, the results show that the formulation of cement don’t need to add any admixtures, Construction maintenance is used by Ordinary concrete construction method at room temperature, Don’t need to implement any winter construction measures, 1d compressive strength up to the removal of the template requirements and the late strength can continue to grow. The main mechanism of the formulation normal and rapid hardening cement at low temperatures:Portland cement clinker and quicklime rapid release of Ca (OH) 2, Natural dihydrate gypsum quick release CaSO4, Ca (OH) 2 and CaSO4 sulphoaluminate cement clinker mineral 4 (CaO) 3 (Al2O3) SO3 (anhydrous calcium sulphoaluminate) rapid responsegenerate large amounts of ettringite, Plus sulfur the aluminate cement hypothermia hydration hardened special catalyst-the role of sodium

  15. 用废铝渣制备膨胀和自应力硫铝酸盐水泥的研究%Preparation of Expansive and Self-stressing Sulphoaluminate Cement Using Bauxite Waste

    冯庆革; 邱树恒; 杨义; 陈明源; 程伟


    In this study, bauxite waste was used instead of bauxite to produce sulphoaluminate clinker. With orthogonal design the technical parameters, for production of sulphoaluminate clinker were studied. Expansive and self-stressing sulphoaluminate cements were prepared using the clinkers produced by varying the added amount of gypsum. The results show that: (1) Using bauxite waste to make sulphoaluminate cement is feasible;(2) The optimum condition for the production of clinker are N= 3.9, P= 2.8, Cm= 0.99 and Tb =1350 ℃;(3) The physical properties of the prepared cement conform to the standard of self-stressing and expansive cement.%通过正交试验设计,研究了用废铝渣替代铝矾土制备硫铝酸盐水泥熟料,调整石膏掺量制备膨胀和自应力水泥.研究结果表明:①用废铝渣替代铝矾土制备硫铝酸盐水泥熟料是可行的;②最佳熟料煅烧条件为N = 3.9, P = 2.8, Cm = 0.99 和煅烧温度 Tb =1350 ℃;③制备的水泥物理性能符合膨胀和自应力水泥国家标准.

  16. Acid attack on hydrated cement — Effect of mineral acids on the degradation process

    Gutberlet, T.; Hilbig, H.; Beddoe, R.E., E-mail:


    During acid attack on concrete structural components, a degraded layer develops whose properties as a protective barrier are decisive for durability. {sup 29}Si NMR spectroscopy and {sup 27}Al NMR spectroscopy were used with XRD to investigate the degraded layer on hardened cement paste exposed to HCl and H{sub 2}SO{sub 4}. The layer comprises an amorphous silica gel with framework silicates, geminate and single silanol groups in which Si is substituted by Al. Amorphous Al(OH){sub 3} and Fe(OH){sub 3} are present. The gel forms by polycondensation and cross-linking of C-A-S-H chains at AlO{sub 4} bridging tetrahedra. In the transition zone between the degraded layer and the undamaged material, portlandite dissolves and Ca is removed from the C-A-S-H phases maintaining their polymer structure at first. With HCl, monosulphate in the transition zone is converted into Friedel's salt and ettringite. With H{sub 2}SO{sub 4}, gypsum precipitates near the degradation front reducing the thickness of the transition zone and the rate of degradation.

  17. Utilization of municipal solid waste incineration fly ash for sulfoaluminate cement clinker production.

    Wu, Kai; Shi, Huisheng; Guo, Xiaolu


    The feasibility of partially substituting raw materials with municipal solid waste incineration (MSWI) fly ash in sulfoaluminate cement (SAC) clinker production was investigated by X-ray diffraction (XRD), compressive strength and free expansion ratio testing. Three different leaching tests were used to assess the environmental impact of the produced material. Experimental results show that the replacement of MSWI fly ash could be taken up to 30% in the raw mixes. The good quality SAC clinkers are obtained by controlling the compositional parameters at alkalinity modulus (C(m)) around 1.05, alumina-sulfur ratio (P) around 2.5, alumina-silica ratio (N) around 2.0~3.0 and firing the raw mixes at 1250 °C for 2h. The compressive strengths of SAC are high in early age while that develop slowly in later age. Results also show that the expansive properties of SAC are strongly depended on the gypsum content. Leaching studies of toxic elements in the hydrated SAC-based system reveal that all the investigated elements are well bounded in the clinker minerals or immobilized by the hydration products. Although some limited positive results indicate that the SAC prepared from MSWI fly ash would present no immediate thread to the environment, the long-term toxicity leaching behavior needs to be further studied.

  18. Characterization of cement minerals, cements and their reaction products at the atomic and nano scale

    Skibsted, Jørgen; Hall, Christopher


    Recent advances and highlights in characterization methods are reviewed for cement minerals, cements and their reaction products. The emphasis is on X-ray and neutron diffraction, and on nuclear magnetic resonance methods, although X-ray absorption and Raman spectroscopies are discussed briefly...

  19. Color difference of composite resins after cementation with different shades of resin luting cement.

    Cengiz, Esra; Kurtulmus-Yilmaz, Sevcan; Karakaya, Izgen; Aktore, Huseyin


    The purpose of this study was to evaluate the color difference of nanohybrid and ormocer-based composite resins with different thicknesses when 4 different shades of resin luting cement were used. 56 disc specimens of each composite resin (Aelite aesthetic enamel, Ceram-X mono) with 0.5 and 1 mm thicknesses were fabricated. Baseline color measurements were performed using a clinical spectrophotometer. The specimens of each thicknesses of each resin were randomly divided into 4 groups according to the shades of resin luting cement (white/A1, yellow/universal/A3, transparent and white opaque) (n = 7). Mixed resin cement was applied onto the resin specimens using a Teflon mold in 0.1 mm thickness. Color measurements of cemented composite resin specimens were repeated and color difference (∆E) between baseline and after cementation measurements was calculated. ANOVA and Tukey's test were used for statistical analysis. The opaque shade had significantly increased ∆E values as compared to the other shades (p resins in terms of ∆E values. The shade of resin cement and the type of the resin affected the final color; however, the thickness of composite resin had no influence on the final color of restoration. Selecting the shade of resin luting cement before cementation of indirect composite laminate restoration is important to achieve final color match.

  20. Revision Total Hip Arthroplasty Using the Cement-in-Cement Technique.

    Amanatullah, Derek F; Pallante, Graham D; Floccari, Lorena V; Vasileiadis, George I; Trousdale, Robert T


    The cement-in-cement technique is useful in the setting of revision total hip arthroplasty (THA), especially to gain acetabular exposure, change a damaged or loose femoral component, or change the version, offset, or length of a fixed femoral component. The goal of this retrospective study was to assess the clinical and radiographic characteristics of revision THA using the cement-in- cement technique. Between 1971 and 2013, a total of 63 revision THAs used an Omnifit (Osteonics, Mahwah, New Jersey) or Exeter (Howmedica, Mahwah, New Jersey) stem and the cement-in-cement technique at the senior author's institution. Aseptic loosening (74%) was the predominant preoperative diagnosis followed by periprosthetic fracture (14%), instability (8%), and implant fracture (6%). Mean clinical follow-up was 5.5±3.8 years. The Harris Hip Score had a statistically significant increase of 18.5 points (Pfracture, or circumferential lucent lines at final follow-up. The patients who underwent cement-in-cement revision THA at the senior author's institution had good restoration of function but a high complication rate. [Orthopedics. 2017; 40(2):e348-e351.]. Copyright 2016, SLACK Incorporated.

  1. Study of the Effect of Gypsum and Rice Straw Extract on the Control of Earthy-Musty Odor in Tilapia Culture Pond

    Supannee SUWANPAKDEE


    Full Text Available The effect of gypsum and rice straw extract to reduce the levels of earthy-musty odor in tilapia earthen ponds was determined. Three treatments with 3 replicates in a completely randomized design were performed as follows: T1 - control; T2 - gypsum at 200 ppm, and T3 - rice straw tannin extract at 1 ppm. The results show that rice straw tannin extract treatment in tilapia ponds was the most effective method in reducing off-flavor in pond water. The use of 200 ppm gypsum in reducing off-flavor in ponds was also more effective than the control. Both rice straw extract and gypsum-treated ponds had increased fish biomass and %FCE. These methods have potential as alternative methods for the reduction of off-flavor, as well as the control of phytoplankton, turbidity, and TSS in tilapia ponds.

  2. [Burns caused by cement mortar (based on expert opinion)].

    Kleinhans, D


    A 35-year-old farmer with scars on his right arm, following erosion obviously due to wet cement (case of an expert opinion), was examined. Cement water had continuously soaked his shirt while he was planing a freshly applied wet cement ceiling with his right arm upwards. The cement did not contain special additives, so the normal alkalinity of wet cement and occlusion effects caused the erosion. The farmer sued the manufacturer of the cement for damages because of missing warning notices. The court decided in his favor.

  3. A Blended Cement Containing Blast Furnace Slag and Phosphorous Slag


    Blended cement containing blast furnace slag(BFS) and phosphorous slag(PS) is a new kind of cement.The total content of blended materials could increase if two additives were used. Using the same admixtures, the properties of the blended cement with 70% additives could reach the standard of 525-grade slag cement according to GB.The strength of cement with 80% additives could reach the standard of 425-grade slag cement.The tests of strength, pore structure,hydration products,inhibiting alkali-aggregate reaction, resistance to sulfate corrosion of BFS-PSC were performed.

  4. Carbonation Resistance of Sulphoaluminate Cement-based High Performance Concrete

    ZHANG Decheng; XU Dongyu; CHENG Xin; CHEN Wen


    The influences of water/cement ratio and admixtures on carbonation resistance of sulphoaluminate cement-based high performance concrete(HPC)were investigated.The experimental results show that with the decreasing water/cement ratio,the carbonation depth of sulphoaluminate cement-based HPC is decreased remarkably,and the carbonation resistance capability is also improved with the adding admixtures.The morphologies and structure characteristics of sulphoaluminate cement hydration products before and after carbonation were analyzed using SEM and XRD.The analysis results reveal that the main hydration product of sulphoaluminate cement,that is ettringite(AFt),de-composes after carbonation.

  5. Quantifying mold biomass on gypsum board: Comparison of ergosterol and beta-N-acetylhexosaminidase as mold biomass parameters

    Reeslev, M.; Miller, M.; Nielsen, Kristian Fog


    Two mold species, Stachybotrys chartarum and Aspergillus versicolor, were inoculated onto agar overlaid with cellophane, allowing determination of a direct measurement of biomass density by weighing. Biomass density, ergosterol content, and beta-N-acetylhexosaminidase ( activity were...... monitored from inoculation to stationary phase. Regression analysis showed a good linear correlation to biomass density for both ergosterol content and beta-N-acetylhexosaminidase activity. The same two mold species were inoculated onto wallpapered gypsum board, from which a direct biomass measurement...... density from ergosterol content and beta-N-acetylhexosaminidase activity were determined. The CFs were used to estimate the biomass density of the molds grown on gypsum board. The biomass densities estimated from ergosterol content and beta-N-acetylhexosaminidase activity data gave similar results...

  6. Precise timing of lacustrine gypsum in Luobubo, Xinjiang using the thermal ionization mass spectrometry U-series method


    Dating techniques including gypsum dissolu tion in water, iron hydroxide co-precipitation with uranium and thorium and mass spectrometric determination have been investigated in this note. The ages of the gypsum sam ples in a CK core from Luobubo lacustrine sediments are in the range of (12.85 ± 0.21) kaBP (4 m distance from the top core) to (153.2± 7.2) kaBP (49 m distance from the top core) with the relative errors of ± 1.6%-± 4.7%. It indicates that the sedimental environment of the CK core was situated in the middle-late Pleistocene and Holocene periods, corre sponding to 1--6 stages of oxygen isotopes in the abyssal sediments and included much information from last inter glacial to Holocene warm periods.

  7. Alternative Fuel for Portland Cement Processing

    Schindler, Anton K; Duke, Steve R; Burch, Thomas E; Davis, Edward W; Zee, Ralph H; Bransby, David I; Hopkins, Carla; Thompson, Rutherford L; Duan, Jingran; ; Venkatasubramanian, Vignesh; Stephen, Giles


    The production of cement involves a combination of numerous raw materials, strictly monitored system processes, and temperatures on the order of 1500 °C. Immense quantities of fuel are required for the production of cement. Traditionally, energy from fossil fuels was solely relied upon for the production of cement. The overarching project objective is to evaluate the use of alternative fuels to lessen the dependence on non-renewable resources to produce portland cement. The key objective of using alternative fuels is to continue to produce high-quality cement while decreasing the use of non-renewable fuels and minimizing the impact on the environment. Burn characteristics and thermodynamic parameters were evaluated with a laboratory burn simulator under conditions that mimic those in the preheater where the fuels are brought into a cement plant. A drop-tube furnace and visualization method were developed that show potential for evaluating time- and space-resolved temperature distributions for fuel solid particles and liquid droplets undergoing combustion in various combustion atmospheres. Downdraft gasification has been explored as a means to extract chemical energy from poultry litter while limiting the throughput of potentially deleterious components with regards to use in firing a cement kiln. Results have shown that the clinkering is temperature independent, at least within the controllable temperature range. Limestone also had only a slight effect on the fusion when used to coat the pellets. However, limestone addition did display some promise in regards to chlorine capture, as ash analyses showed chlorine concentrations of more than four times greater in the limestone infused ash as compared to raw poultry litter. A reliable and convenient sampling procedure was developed to estimate the combustion quality of broiler litter that is the best compromise between convenience and reliability by means of statistical analysis. Multi-day trial burns were conducted

  8. 掺高 fCaO物料的水泥抗硫酸盐性的初步研究%Preliminary study on the property of sulfate resistance of cement with the addition of high f- CaO materials

    范付忠; 冯涛; 施惠生; 赖振宇


    测试了掺入不同量的高钙粉煤灰、高 fCaO熟料、钢渣及石膏的试样抗蚀系数、质量增量和强度,结果表明,掺高 fCaO物料的水泥抗硫酸盐性与引入的 fCaO量、浸渍的硫酸盐种类和浓度有关,掺高 fCaO熟料和钢渣的水泥抗硫酸盐性优于掺高钙粉煤灰的水泥,适量石膏的掺入可改善试样的抗硫酸盐性,在实际应用中可通过控制引入的 fCaO量和掺入适量石膏来提高掺高 fCaO物料的水泥抗硫酸盐性。%Parameters as corrosion resistance ratio, the increment in quantity and strength of cement with different addition of high calcium pfa, high fCaO clinker, steel slag and gypsum were tested. The results indicate that the property of sulfate resistance of cement is associated with the amount of fCaO and the type and concentration of sulfate in the corrosive agent. The addition of high fCaO clinker and steel slag in cement possesses higher performance in the sulfate resistance compared with the addition of pfa. The introduction of proper quantity of gypsum can improve the sulfate resistance property. This property can be improved in practice through the proper introduction of fCaO and gypsum.

  9. Evaluation of surface detail reproduction, dimensional stability and gypsum compatibility of monophase polyvinyl-siloxane and polyether elastomeric impression materials under dry and moist conditions

    Vadapalli, Sriharsha Babu; Atluri, Kaleswararao; Putcha, Madhu Sudhan; Kondreddi, Sirisha; Kumar, N. Suman; Tadi, Durga Prasad


    Objectives: This in vitro study was designed to compare polyvinyl-siloxane (PVS) monophase and polyether (PE) monophase materials under dry and moist conditions for properties such as surface detail reproduction, dimensional stability, and gypsum compatibility. Materials and Methods: Surface detail reproduction was evaluated using two criteria. Dimensional stability was evaluated according to American Dental Association (ADA) specification no. 19. Gypsum compatibility was assessed by two crit...

  10. Isotopic composition of gypsum hydration water in deep Core SG-1, western Qaidam basin (NE Tibetan Plateau), implications for paleoclimatic evolution

    Li, Jiao; Li, Minghui; Fang, Xiaomin; Zhang, Gengxin; Zhang, Weilin; Liu, Xiaoming


    The oxygen and hydrogen isotopic compositions of gypsum hydration water can be useful for determining the isotopic composition of the original brine from which gypsum precipitated. However, relatively few long-term and continuous records of the stable isotope geochemistry of gypsum hydration water in arid regions have been reported. We measured the δ18O and δD of primary gypsum hydration water from a 938.5 m-long deep core (SG-1) in the western Qaidam Basin to study the mechanisms that contributed to gypsum formation and to reconstruct potential paleoclimatic change. The measured δ18O and δD ranged from - 4.21‰ to 8.69‰ and from - 72.77‰ to 49.73‰, respectively. The linear relationship between δ18O and δD indicates that meteoric water was the original source of the gypsum hydration water. The gradient of 5.39 for the δ18O and δD plots is lower than that of global meteoric water, suggesting that paleo-lakewater evaporated and became a CaSO4-rich brine leading to gypsum deposition. The evaporation/precipitation (E/P) ratio played an important role in determining δ18O and δD. The oscillations noted in the δ18O and δD of the gypsum hydration water imply that: (a) there was a long-term and stepwise aridification after 2.2 Ma in the western Qaidam Basin; and (b) there were three increasingly dry phases at 2.2-1.2 Ma, 1.2-0.6 Ma, and 0.6-0.1 Ma, with two cold and dry events at 1 Ma and 0.6 Ma. Global cooling, especially during the Mid Pleistocene Climate Transition event (MPT), may have been the primary cause of the aridification recorded in core SG-1 in the Asian inland.

  11. Thermal reactions of brushite cements.

    Bohner, M; Gbureck, U


    The thermal reactions of a brushite cement made of beta-tricalcium phosphate (beta-TCP), monocalcium phosphate monohydrate (MCPM), and an aqueous solution were followed in situ with an isothermal calorimeter at 37 degrees C. The investigated parameters were the beta-TCP/MCPM weight ratio, the liquid-to-powder ratio, the synthesis route and milling duration of the beta-TCP powder, as well as the presence of sulfate, citrate, and pyrophosphate ions in the mixing liquid. The thermograms were complex, particularly for mixtures containing an excess of MCPM or additives in the mixing solution. Results suggested that the endothermic MCPM dissolution and the highly exothermic beta-TCP dissolution occurred simultaneously, thereby leading to the formation of a large exothermic peak at early reaction time. Both reactions were followed by the exothermic crystallization of brushite and in the presence of an excess of MCPM by the endothermic crystallization of monetite. Additives generally widened the main exothermic reaction peak, or in some cases with pyrophosphate ions postponed the main exothermic peak at late reaction time. Generally, the results could be well explained and understood based on thermodynamic and solubility data.

  12. Inorganic contaminants attenuation in acid mine drainage by fly ash and fly ash-ordinary Portland cement (OPC) blends : column experiments

    Gitari, W.M. [Venda Univ., Thohoyandou (South Africa). Dept. of Ecology and Resources Management, School of Environmental Studies; Petrik, L.F.; Etchebers, O. [Western Cape Univ., Bellville (South Africa). Environmental and Nanosciences Group, Dept. of Chemistry; Key, D.L. [Western Cape Univ., Bellville (South Africa). Dept. of Chemistry; Okujeni, C. [Western Cape Univ., Bellville (South Africa). Dept. of Earth Sciences


    The infiltration of acid mine drainage (AMD) material into mine voids is one of the environmental impacts of underground coal mining. In this study, the mitigation of AMD in a mine void was simulated in laboratory conditions. Various mixtures of fly ash, solid residues, and Portland cement were added to packed columns over a 6-month period. The fly ash additions generated near-neutral to alkaline pH levels, which in turn induced precipitation, co-precipitation, and adsorption contaminant attenuation mechanisms. A modelling study demonstrated that the precipitation of ferrihydrite, Al-hydroxides, Al-oxyhydroxysulphates, gypsum, ettringite, manganite, and rhodochrosite lowered contaminant levels. Results of the study indicated that the pH regime and acidity level of the AMD strongly influenced both the leaching of the toxic trace elements as well as the attenuation of the AMD. 3 refs., 2 figs.

  13. Fly and bottom ashes from biomass combustion as cement replacing components in mortars production: rheological behaviour of the pastes and materials compression strength.

    Maschio, Stefano; Tonello, Gabriele; Piani, Luciano; Furlani, Erika


    In the present research mortar pastes obtained by replacing a commercial cement with the equivalent mass of 5, 10, 20 and 30 wt.% of fly ash or bottom ash from fir chips combustion, were prepared and rheologically characterized. It was observed that the presence of ash modifies their rheological behaviour with respect to the reference blend due to the presence, in the ashes, of KCl and K2SO4 which cause precipitation of gypsum and portlandite during the first hydration stages of the pastes. Hydrated materials containing 5 wt.% of ash display compression strength and absorption at 28 d of same magnitude as the reference composition; conversely, progressive increase of ash cause a continuous decline of materials performances. Conversely, samples tested after 180 d display a marked decline of compression strength, as a consequence of potassium elution and consequent alkali-silica reaction against materials under curing.

  14. Quality control of cemented waste forms

    Slate, L.J.


    To insure that cemented radwaste remains immobilized after disposal, certain standards have been set in Europe by the Commission of the European Communities. One such standard is compressive strength. If the compressive strength can be predicted during the early curing stages, time and money can be saved and the quality of the final waste form guaranteed. It was determined that the 7- and 28-day compressive strength from radwaste cementation can be predicted during the mixing and early curing stages by at least three methods. The three that were studied were maturity, rheology, and impedance. Maturity is a temperature-to-time measurement, rheology is a shear stress-to-shear rate measurement, and impedance is the opposition offered to the flow of alternating current. These three methods were employed on five different cemented radwaste concentrations with three different water-to-cement ratios; thus, a total of 15 different mix designs were considered. The results showed that the impedance was the easiest to employ for an on-line process. The results of the impedance method showed a very good relationship between impedance and water-to-cement ratio; therefore, an accurate prediction of compressive strength of cemented radwaste can be drawn from this method. The results of the theology method were very good. The method showed that concrete conforms to the Bingham plastic rheologic model, and the theology method can be used to predict the compressive strength of cemented radwaste, but may be too cumbersome. The results of the maturity method were shown to be limited in accuracy for determining compressive strength.

  15. Shaking table model test and engineering practice of a new gypsum-adobe walls dwelling in Xinjiang autonomous region, China

    ZHOU Tie-gang; HU Xin; YU Chang-xia


    The paper introduces a new type of green building which suits for the construction of rural dwellings in Xinjiang, China. Results of the shaking table test on building model show that the single-layer gypsum-adobe structure has better seismic performance. And it also analyzes the construction features and engineering practice, which means that it is significant to extend this type of building to the drier regions in China.

  16. Estimates of inhalation doses resulting from the possible use of phospho-gypsum plaster-board in Australian homes.

    O'Brien, R S; Peggie, J R; Leith, I S


    Current materials used as internal lining in Australian buildings are based on natural gypsum of low radium content. A study was carried out to estimate the contribution to the annual effective dose due to airborne contamination from chemical by-product gypsum plaster-board of higher radium content if it were used as an internal lining. The 226Ra content and 222Rn exhalation rate were measured for several samples of the plaster-board, and the behavior of 222Rn and its progeny (218Po, 214Pb, 214Bi, and 214Po) in a typical building was modeled numerically, using the results of the exhalation rate measurements as input. For building ventilation rates greater than approximately 0.5 air changes per hour, the contribution to the total annual effective dose from inhalation of 222Rn and its progeny exhaled from the phospho-gypsum plaster-board is estimated to be below 1 mSv. This contribution is reduced if the surface of the plaster-board is coated with paint or cardboard, or if the very fine particles are removed from the phospho-gypsum during manufacture of the plaster-board. The effective doses arising from dust generation during the installation of the plaster-board are also estimated to be below 1 mSv. The recommended action level of 200 Bq m-3 for radon in air in Australia corresponds to an annual effective dose of approximately 6 mSv. The study indicates that the suggested acceptable level of 185 Bq kg-1 for the 226Ra concentration in the plaster-board may be too restrictive under Australian conditions.

  17. Hydrochemical features of groundwater in a coastal gypsum karst (Marina di Lesina, Gargano, Southern Italy) in relation to tides

    Fidelibus, Maria Dolores; Campana, Claudia


    As part of a complex monitoring aimed at collecting suitable data for conceptual and numerical modelling of the coastal gypsum karst of Marina di Lesina (Gargano, Southern Italy), 64 groundwater samples were collected during three surveys at different depths from 9 monitoring wells aligned along two transects. The transects, perpendicular to the Acquarotta canal, are less of 1 Km long. The canal is directly connected to the sea and to the Lesina Lagoon and behaves as an oscillating border following sea tides. The sampling campaigns were carried out concurrently to phases of increasing, decreasing, and low tide and provide different frameworks of the chemical composition of ground waters. TDS (Total Dissolved Solids) of ground water samples ranges from 0.2 g/l to 35 g/l and increases generally along the flow lines towards the canal, and downward. The concentrations of the major ions deviate from theoretical ones defined by non-reactive mixing lines, which have as saline end-member either standard seawater or local seawater sampled offshore.Owing to the multi-component character of the hydrochemical system, the cation concentrations are controlled by competition among concurrent water-rock interaction processes that overlap to non-reactive freshwater-saltwater (FW-SW) mixing, being even triggered and/or enhanced by the same mixing, with feedback loops: gypsum and calcite dissolution, ion exchange (with direction depending on hydrodynamic conditions mainly driven by tides, and justified due to the presence of clay in the gypsum bedrock), and dedolomitization. The geochemical study also highlights the involvement of saline ground waters belonging to regional circuits that develop in the huge Mesozoic carbonate basement. The study highlights that in the saturated thickness of the gypsum coastal aquifer closer to the coast, the hydrochemical system is extremely reactive and strongly influenced by the different groundwater hydraulic conditions induced by the tide phases.

  18. Synthesis of Fluorite (CaF2 Crystal from Gypsum Waste of Phosphoric Acid Factory in Silica Gel

    Mohammad Misbah Khunur


    Full Text Available This paper report the synthesis and characterization of fluorite single crystal prepared from gypsum waste of phosphoric acid production in silica gel. Instead of its high calcium, gypsum was used to recycle the waste which was massively produces in the phosphoric acid production. The gypsum waste, the raw material of CaCl2 supernatant, was dissolved in concentrated HCl and then precipitated as calcium oxalate (CaC2O4 by addition of ammonium oxalate. The CaCl2 was obtained by dissolving the CaC2O4 with HCl 3M. The crystals were grown at room temperature in silica gel and characterized by AAS, FTIR and powder XRD. The optimum crystal growth condition, which is pH of gel, CaCl2 concentration and growth time, were investigated. The result shows that at optimum condition of pH 5.80, CaCl2 concentrations of 1.2 M, and growth time of 144 hours, colorless crystals with the longest size of 3 mm, were obtained (72.57%. Characterization of the synthesized crystal by AAS indicates that the obtained crystal has high purity. Meanwhile, analysis by FTIR spectra shows a Ca–F peak at 775 cm-1, and powder-XRD analysis confirms that the obtained crystal was fluorite (CaF2. © 2012 BCREC UNDIP. All rights reservedReceived: 11st April 2012; Revised: 4th June 2012; Accepted: 13rd June 2012[How to Cite: M.M. Khunur, A. Risdianto, S. Mutrofin, Y.P. Prananto. (2012. Synthesis of Fluorite (CaF2 Crystal from Gypsum Waste of Phosphoric Acid Factory in Silica Gel. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (1: 71-77.  doi:10.9767/bcrec.7.1.3171.71-77 ][How to Link / DOI: ] | View in 

  19. Microbial diversity in the deep-subsurface hydrothermal aquifer feeding the giant gypsum crystal-bearing Naica Mine, Mexico

    Marie eRagon; Alexander ES Van Driessche; Juan Manuel eGarcia Ruiz; David eMoreira; Purificacion eLopez-Garcia


    The Naica mine in Northern Mexico is famous for its giant gypsum crystals, which may reach up to 11 m long and contain fluid inclusions that might have captured microorganisms during their formation. These crystals formed under particularly stable geochemical conditions in cavities filled by low salinity hydrothermal water at 54-58°C. We have explored the microbial diversity associated to these deep, saline hydrothermal waters collected in the deepest (ca. 700-760 m) mineshafts by amplif...

  20. Flue gas desulfurization gypsum: implication for runoff and nutrient losses associated with broiler litter use on pastures on ultisols.

    Endale, Dinku M; Schomberg, Harry H; Fisher, Dwight S; Franklin, Dorcas H; Jenkins, Michael B


    Gypsum has been shown to reduce runoff on soils prone to crust formation in the southeastern United States. Increased infiltration from gypsum applications could therefore help reduce runoff P and other nutrient losses from application of broiler litter (BL), a nutrient-rich fertilizer. In rainfall simulation experiments in June 2009 and May 2011, runoff and nutrient (N, P, Ca, Mg) losses in runoff were compared among treatments consisting of 0, 2.2, 4.5, and 9.0 Mg ha flue gas desulfurization gypsum (FGDG) combined with 13.5 Mg ha of BL and two control treatments of (0-0) and (9.0-0.0) Mg ha (FGDG-BL). A randomized block design with three replications was set up on a Cecil (Typic Kanhapludult) soil growing Coastal bermudagrass ( L.) for hay near Watkinsville, Georgia. Amendments were applied each April from 2009 to 2011. A reduction in runoff of 30% each year from the (9.0-13.5) compared with the (0-0) treatment was not statistically significant. Gypsum was effective in reducing concentration and load in one of the two study years: P and NH-N in 2009 (up to 83%) and NO-N in 2011 (up to 73%). A combination of factors related to weather extremes, timing of FGDG and BL applications, and their implication on soil and vegetation responses at different landscape positions might have caused the different responses between years. Additional studies focused on isolating the impacts of such factors would be helpful to ascertain the effectiveness of multiyear applications of FGDG as a best management practice to reduce P and other nutrient losses in soils of the southeastern United States. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  1. Possible utilization of flue-gas desulfurization gypsum and fly ash for citrus production: Evaluation of crop growth response

    Alva, A.K. (Univ. of Florida, Lake Alfred, FL (United States). Citrus Research and Education Center)


    The application of industrial by-products to agricultural land has been a topic of considerable interest during recent years. For the industries, this is an attractive avenue to utilize the by-products rather than land filling. Agriculturists/horticulturists are faced with a new challenge to evaluate the potential advantages of this practice in terms of crop growth, production, and quality as well as effects of such practices on environmental quality. Fly ash and flue-gas desulfurization (FGD) gypsum are by-products produced from coal-fired electric power generation plants. There is a growing interest in evaluation of potential benefits of land application of coal combustion by products mixed with organic by-products. The objective of this study was to investigate the effects of application of FGD gypsum, fly ash or chicken manure,, or application of the former two in combination with the latter, on soil properties as well as on growth and mineral nutrition of Cleopatra mandarin and Swingle citrumelo rootstock seedlings grown on a Myakka sand. The growth of seedlings of either rootstock improved significantly in soils amended with either FGD gypsum, fly ash, or chicken manure, individually or in combination of either by-product with chicken manure. However, the ranking of various amendments in relation to growth response differed between the two rootstocks. The combined application of all three amendments decreased the growth of both rootstock seedlings significantly as compared to that of seedlings in unamended soil. The application of either FGD gypsum, fly ash, or chicken manure each at 2 g/kg soil increased the concentration of Ca, Ca and K, and Ca and P in the leaves of seedlings, respectively.

  2. Assessment of Natural Radioactivity Levels of Cements and Cement Composites in the Slovak Republic

    Adriana Eštoková


    Full Text Available The radionuclide activities of 226Ra, 232Th and 40K and radiological parameters (radium equivalent activity, gamma and alpha indices, the absorbed gamma dose rate and external and internal hazard indices of cements and cement composites commonly used in the Slovak Republic have been studied in this paper. The cement samples of 8 types of cements from Slovak cement plants and five types of composites made from cement type CEM I were analyzed in the experiment. The radionuclide activities in the cements ranged from 8.58–19.1 Bq·kg−1, 9.78–26.3 Bq·kg−1 and 156.5–489.4 Bq·kg−1 for 226Ra, 232Th and 40K, respectively. The radiological parameters in cement samples were calculated as follows: mean radium equivalent activity Raeq = 67.87 Bq·kg−1, gamma index Iγ = 0.256, alpha index Iα = 0.067, the absorbed gamma dose rate D = 60.76 nGy·h−1, external hazard index Hex = 0.182 and internal hazard index Hin was 0.218. The radionuclide activity in composites ranged from 6.84–10.8 Bq·kg−1 for 226Ra, 13.1–20.5 Bq·kg−1 for 232Th and 250.4–494.4 Bq·kg−1 for 40K. The calculated radiological parameters of cements were lower than calculated radiological parameters of cement composites.

  3. Heuristic economic assessment of the Afghanistan construction materials sector: cement and dimension stone production

    Mossotti, Victor G.


    Over the past decade, the U.S. Government has invested more than $106 billion for physical, societal, and governmental reconstruction assistance to Afghanistan (Special Inspector General for Afghanistan Reconstruction, 2012a). This funding, along with private investment, has stimulated a growing demand for particular industrial minerals and construction materials. In support of this effort, the U.S. Geological Survey released a preliminary mineral assessment in 2007 on selected Afghan nonfuel minerals (Peters and others, 2007). More recently, the 2007 mineral assessment was updated with the inclusion of a more extensive array of Afghan nonfuel minerals (Peters and others, 2011). As a follow-up on the 2011 assessment, this report provides an analysis of the current use and prospects of the following Afghan industrial minerals required to manufacture construction materials: clays of various types, bauxite, gypsum, cement-grade limestone, aggregate (sand and gravel), and dimension stone (sandstone, quartzite, granite, slate, limestone, travertine, marble). The intention of this paper is to assess the: Use of Afghan industrial minerals to manufacture construction materials, Prospects for growth in domestic construction materials production sectors, Factors controlling the competitiveness of domestic production relative to foreign imports of construction materials, and Feasibility of using natural gas as the prime source of thermal energy and for generating electrical energy for cement production. The discussion here is based on classical principles of supply and demand. Imbedded in these principles is an understanding that the attributes of supply and demand are highly variable. For construction materials, demand for a given product may depend on seasons of the year, location of construction sites, product delivery time, political factors, governmental regulations, cultural issues, price, and how essential a given product might be to the buyer. Moreover, failure on the

  4. Potential of soil amendments (Biochar and Gypsum) in increasing water use efficiency of Abelmoschus esculentus L. Moench.

    Batool, Aniqa; Taj, Samia; Rashid, Audil; Khalid, Azeem; Qadeer, Samia; Saleem, Aansa R; Ghufran, Muhammad A


    Water being an essential component for plant growth and development, its scarcity poses serious threat to crops around the world. Climate changes and global warming are increasing the temperature of earth hence becoming an ultimate cause of water scarcity. It is need of the day to use potential soil amendments that could increase the plants' resistance under such situations. Biochar and gypsum were used in the present study to improve the water use efficiency (WUE) and growth of Abelmoschus esculentus L. Moench (Lady's Finger). A 6 weeks experiment was conducted under greenhouse conditions. Stress treatments were applied after 30 days of sowing. Plant height, leaf area, photosynthesis, transpiration rate (Tr), stomatal conductance and WUE were determined weekly under stressed [60% field capacity (F.C.)] and non-stressed (100% F.C.) conditions. Stomatal conductance and Tr decreased and reached near to zero in stressed plants. Stressed plants also showed resistance to water stress upto 5 weeks and gradually perished at sixth week. On the other hand, WUE improved in stressed plants containing biochar and gypsum as compared to untreated plants. Biochar alone is a better strategy to promote plant growth and WUE specifically of A. esculentus, compared to its application in combination with gypsum.

  5. Potential of Soil Amendments (Biochar and Gypsum in increasing Water Use Efficiency of Abelmoschus esculentus L. Moench

    Aniqa eBatool


    Full Text Available Water being an essential component for plant growth and development, its scarcity poses serious threat to crops around the world. Climate changes and global warming are increasing the temperature of earth hence becoming an ultimate cause of water scarcity. It is need of the day to use potential soil amendments that could increase the plants’ resistance under such situations. Biochar and gypsum were used in the present study to improve the water use efficiency and growth of Abelmoschus esculentus L. Moench (Lady’s Finger. A six weeks experiment was conducted under greenhouse conditions. Stress treatments were applied after thirty days of sowing. Plant height, leaf area, photosynthesis, transpiration rate, stomatal conductance and water use efficiency were determined weekly under stressed (60% field capacity and non-stressed (100% field capacity conditions. Stomatal conductance and transpiration rate decreased and reached near to zero in stressed plants. Stressed plants also showed resistance to water stress upto five weeks and gradually perished at sixth week. On the other hand, water use efficiency improved in stressed plants containing biochar and gypsum as compared to untreated plants. Biochar alone is a better strategy to promote plant growth and WUE specifically of Abelmoschus esculentus, compared to its application in combination with gypsum.

  6. Simulation and Prediction of Ion Transport in the Reclamation of Sodic Soils with Gypsum Based on the Support Vector Machine

    Jinman Wang


    Full Text Available The effect of gypsum on the physical and chemical characteristics of sodic soils is nonlinear and controlled by multiple factors. The support vector machine (SVM is able to solve practical problems such as small samples, nonlinearity, high dimensions, and local minima points. This paper reports the use of the SVM regression method to predict changes in the chemical properties of sodic soils under different gypsum application rates in a soil column experiment and to evaluate the effect of gypsum reclamation on sodic soils. The research results show that (1 the SVM soil solute transport model using the Matlab toolbox represents the change in Ca2+ and Na+ in the soil solution and leachate well, with a high prediction accuracy. (2 Using the SVM model to predict the spatial and temporal variations in the soil solute content is feasible and does not require a specific mathematical model. The SVM model can take full advantage of the distribution characteristics of the training sample. (3 The workload of the soil solute transport prediction model based on the SVM is greatly reduced by not having to determine the hydrodynamic dispersion coefficient and retardation coefficient, and the model is thus highly practical.

  7. Uptake of Nutrients in Vegetables Grown on FGD-Gypsum-Amended Soils

    Yutdanai Yodthongdee


    Full Text Available This research evaluated the effects of using flue gas desulphurization gypsum (FGDG for growing of some agronomic crops. The FGDG was added to soil at 0, 2.5, 5.0 and 7.5% by weight. The test plants, Chinese kale and green bean, were grown and harvested after 45 days and 60 days, respectively. Application of FGDG at all ratios significantly increased pH of the soil, due to the lime containing in FGDG. The heavy metals content in plants grown in the FGDG treated tanks were not significantly different from those of the control tank. From the ten studied elements in Chinese kale and green bean seed tissues (As, Ca, Cd, Cr, Cu, K, Mg, Na, Pb, and Zn, the content of five toxic elements (As, Cd, Cr, Cu, and Pb were very low and not significantly influenced by FGDG, while the content of some nutrient elements (K, Ca, Mg in the plant tissues growing in FGDG treated soil were higher than the control. Concentration of some micronutrients (Cu and Zn in plants decreased with increasing dose of FGDG. There has not been any negative effect from applying up to 5.0% FGDG in soil. The results showed possibility of using FGDG as soil amendment in terms of agricultural production and safety.


    S. Z. M. NOR


    Full Text Available In this study, several formulations of gypsum bonded investment (GBI as a mould for copper alloy casting has been developed and their properties had been investigated. The mould was developed using Terengganu local silica sand with the average particle size of 220–250 µm, acted as a refractory and Plaster of Paris (POP as a binder. The formulations used were 75% local silica, 25% plaster and various amounts (31–37% of water. The compressive strength, tensile strength, porosity, core hardness and mould hardness properties of the prepared GBI were studied. It has been found that both compressive strength and tensile strength reduced with a water content due to an increment of mould porosity which was confirmed via Scanning Electron Microscopy analysis. The mould hardness was found unchanged, but the core hardness was slightly reduced with the increment of water. The compressive strength of GBI moulds developed in this work was in the range of 600–1100 kN/m2, which was sufficient for copper alloy casting.

  9. Problems and possible remedies concerning NORM in by-Product gypsum produced by the phosphate industry

    Burnett, W.C.; Hull, C.D [Florida State Univ., Tallahassee, FL (United States). Dept. of Oceanography


    Large quantities ({approx} 30 million tons/year) of phosphogypsum are produced as a by-product of fertilizer production in Florida. The sedimentary phosphate rock, used as the raw material for phosphoric acid production, is enriched in uranium and daughter products. Relatively high concentrations of some of these U-series daughters, particularly {sup 226} Ra (av. = 910 Bq.Kg{sup -1}), prevent use of the by-product gypsum for construction or other purposes. The material is thus stockpiled on huge stacks which are unsightly and a potential threat to the surrounding air and especially groundwater resources. It is estimated that {approx} 10{sup 9} tons of this material will be on Florida stacks by the turn of the century. We have been investigating the detailed radiochemistry of phosphogypsum in the hope that can understanding of how these radionuclides are fixed in the material may lead to cost-effective purification schemes. Our work has focused on the distribution of {sup 226} Ra but has also included {sup 210} Pb and {sup 210} Po (av. = 860 Bq.Kg{sup -1}) which are also enriched in phosphogypsum. This paper summarizes the problems associated with this material and reviews its radiochemistry as elucidated by sequential extraction and other methodologies. We also present some possible alternatives to long-term storage as a solution to the phosphogypsum problem. (author) 4 figs., 1 tab.

  10. Combination of simvastatin, calcium silicate/gypsum, and gelatin and bone regeneration in rabbit calvarial defects

    Zhang, Jing; Wang, Huiming; Shi, Jue; Wang, Ying; Lai, Kaichen; Yang, Xianyan; Chen, Xiaoyi; Yang, Guoli


    The present study was performed to determine whether simvastatin improves bone regeneration when combined with calcium silicate/gypsum and gelatin (CS-GEL). The surface morphology was determined using field-emission scanning electron microscopy (FSEM). Degradation in vitro was evaluated by monitoring the weight change of the composites soaked in phosphate buffered saline (PBS). Drug release was evaluated using high-performance liquid chromatography (HPLC). Cytotoxicity testing was performed to assess the biocompatibility of composites. Four 5 mm-diameter bone defects were created in rabbit calvaria. Three sites were filled with CS-GEL, 0.5 mg simvastatin-loaded CS-GEL (SIM-0.5) and 1.0 mg simvastatin-loaded CS-GEL (SIM-1.0), respectively, and the fourth was left empty as the control group. Micro-computed tomography (micro-CT) and histological analysis were carried out at 4 and 12 weeks postoperatively. The composites all exhibited three-dimensional structures and showed the residue with nearly 80% after 4 weeks of immersion. Drug release was explosive on the first day and then the release rate remained stable. The composites did not induce any cytotoxicity. The results in vivo demonstrated that the new bone formation and the expressions of BMP-2, OC and type I collagen were improved in the simvastatin-loaded CS-GEL group. It was concluded that the simvastatin-loaded CS-GEL may improve bone regeneration.

  11. New design options with gypsum-based cooling ceilings; Neue Gestaltungsmoeglichkeiten mit Gipskuehldecken

    Bringmann, A.


    The Sulzer administrative building at Winterthur, Switzerland, was constructed in 1928/'29 by the architect Lebrecht Voelkli. It was now modernized by the Zuerich architects, Marianne Burkhalter and Christian Sumi. The technical facilities, with a traditional heating system and modern air conditioning, was planned and constructed by Axima. As new elements, there are gypsum-based cooling ceilings which have the advantages of easy integration in the building design, high economic efficiency, and user-friendliness. The emphasis during modernisation was on architectural aspects, i.e. modern interior design, colour schemes, acoustics and flexible use of rooms. [German] 1928/29 erstellte der Architekt Lebrecht Voelkli einen Neubau fuer die Sulzer-Konzernleitung in Winterthur (Schweiz) in Gestalt eines neoklassischen Wuerfels mit vier oberirdischen Geschossen. Dessen komplette Sanierung realisierten die Zuercher Architekten Marianne Burkhalter und Christian Sumi. Die von Axima geplante und ausgefuehrte Gebaeudetechnik mit traditioneller Heizung und modernen Luftaufbereitungsanlagen weist als Novum neu konzipierte Gipskuehldecken auf. Sie erfuellen die Architektenansprueche in Bezug auf unauffaellige Integration, Wirtschaftlichkeit und Benutzerfreundlichkeit, denn im Vordergrund standen Forderungen nach moderner Innenraumgestaltung, akzentuierter Farbgebung, guter Akustik und flexibler Flaechennutzung. (orig.)

  12. Kinetic and morphological differentiation of ettringites in plain and blended Portland cements with metakaolin and the ASTM C 452-68 test. Part II: Morphological differentiation by SEM and XRD analysis

    Talero, R.


    Full Text Available The same cementitious materials (OPCs, SRPCs and matekaolin, MK, the same blended cements and the same ASTM C 452-68 test than in Part I, were used. Other complementary determinations were: chemical analysis of cementing materials, SEM and XRD analysis of ettringites and specific properties of some cement tested and of their pastes.The experimental results have also demonstrated that when 7.0% SO3, equivalent to 15.05% of gypsum, was added to the M pozzolan-containing Portland cement and tested with the ASTM C 452-68 method, it was not found to behave aggressively but rather as “setting regulator ”, because the increase in mechanical strengths over time and setting times in these mixes were, therefore, similar to the pattern observed in any PC. However, when the gypsum content was raised to triple than that amount (21.0% SO3, it behaved aggressively. In both cases, logically, ettringite from both origins were involved in the resulting beneficial or adverse behavior.En esta Parte II se utilizaron los mismos materiales cementíceos (CPO, CPRS, y metakaolín, MK, los mismos cementos de mezcla y el mismo método de ensayo ASTM C 452-68 que en la Parte I. Otras determinaciones complementarias fueron: análisis químico de los materiales cementíceos, análisis por DRX y SEM de ettringitas y propiedades específicas de algunos cementos ensayados y de sus pastas.Los resultados experimentales obtenidos han demostrado también que, el 7.0% de SO3 presente en los 30 cementos de mezcla con MK, ensayados conforme el método ASTM C 452-68, no se comporta como agresivo sino como ”regulador de fraguado”, porque los tiempos de fraguado y el aumento de resistencias mecánicas fueron como los de cualquier CP. De aquí que algunos de esos cementos de mezcla puedan ser considerados “cementos hidráulicos expansivos”, el resto, no. Sin embargo, cuando la cantidad de yeso aportada fue el triple (21,0% SO3, se comportó como agresivo, motivo por el cual

  13. Chemical and Physical Reactions of Wellbore Cement under CO2 Storage Conditions: Effects of Cement Additives

    Kutchko, B. G.; Strazisar, B. R.; Huerta, N.; Lowry, G. V.; Dzombak, D. A.; Thaulow, N.


    Sequestration of CO2 into geologic formations requires long-term storage and low leakage rates to be effective. Active and abandoned wells in candidate storage formations must be evaluated as potential leakage points. Wellbore integrity is an important part of an overall integrated assessment program being developed at NETL to assess potential risks at CO2 storage sites. Such a program is needed for ongoing policy and regulatory decisions for geologic carbon sequestration. The permeability and integrity of the cement in the well is a primary factor affecting its ability to prevent leakage. Cement must be able to maintain low permeability over lengthy exposure to reservoir conditions in a CO2 injection and storage scenario. Although it is known that cement may be altered by exposure to CO2, the results of ongoing research indicate that cement curing conditions, fluid properties, and cement additives play a significant role in the rate of alteration and reaction. The objective of this study is to improve understanding of the factors affecting wellbore cement integrity for large-scale geologic carbon sequestration projects. Due to the high frequency use of additives (pozzolan) in wellbore cement, it is also essential to understand the reaction of these cement-pozzolan systems upon exposure to CO2 under sequestration conditions (15.5 MPa and 50°C). Laboratory experiments were performed to determine the physical and chemical changes, as well as the rate of alteration of commonly used pozzolan-cement systems under simulated sequestration reservoir conditions, including both supercritical CO2 and CO2-saturated brine. The rate of alteration of the cement-pozzolan systems is considerably faster than with neat cement. However, the alteration of physical properties is much less significant with the pozzolanic blends. Permeability of a carbonated pozzolanic cement paste remains sufficiently small to block significant vertical migration of CO2 in a wellbore. All of the

  14. 湿法脱硫系统“石膏雨”问题的成因及解决对策%Origin and solution of the“gypsum rain”problem of limestone-gypsum WFGD system

    翁卫国; 张军; 李存杰


    “石膏雨”现象已逐渐引起社会各界的关注,研究合理、有效的解决方法已成为当前燃煤烟气污染物控制的重要课题之一。本文对影响“石膏雨”形成的因素进行了分析,湿法脱硫系统取消烟气换热器致使排烟温度降低是“石膏雨”产生的主要原因,其主要影响因素包括设备设计及运行、操作参数变化及外界环境。综述了“石膏雨”检测方法:“石膏雨”的主要成分(浆滴、细颗粒物及 SO3酸雾)的检测手段主要分为采样后化学分析法及电荷或光学物理化学法。针对“石膏雨”的现象提出除尘设备及脱硫系统的设计运行优化、尾部烟道设计优化及增设湿式静电除尘器三种主要的解决措施。面对日益严峻的“石膏雨”问题,政府应当尽快颁布相关规章制度,同时积极开展“石膏雨”的监督检查工作。%The problem of“gypsum rain”has gradually aroused the concern of the society,and the study of reasonable and effective solution has become one of the most important topics in the research of coal-fired flue gas pollution control. In this paper,the factors affecting the formation of“gypsum rain” were analyzed. The main reason for “gypsum rain” was canceling gas gas heater (GGH) in the wet flue gas desulfurization (WFGD) system which lowered exhaust temperature,and other influence factors included equipment design,operation parameters and external environment. The measurement methods of “gypsum rain” were reviewed. Measurement of the main composition of “gypsum rain”(slurry drops,fine particulate matter and SO3 acid mist) could be classified into chemical analysis after sampling,and electric charge or optical physical chemistry method. Three solutions of design and operation optimization of dust removal equipment and FGD system,design optimization of tail flue gas duct,and additional wet electrostatic precipitator (WESP) were proposed

  15. The fluid-compensated cement bond log

    Nayfeh, T.H.; Leslie, H.D.; Wheelis, W.B.


    An experimental and numerical wave mechanics study of cement bond logs demonstrated that wellsite computer processing can now segregate wellbore fluid effects from the sonic signal response to changing cement strength. Traditionally, cement logs have been interpreted as if water were in the wellbore, without consideration of wellbore fluid effects. These effects were assumed to be negligible. However, with the increasing number of logs being run in completion fluids such as CaCl/sub 2/, ZnBr/sub 2/, and CaBr/sub 2/, large variations in cement bond logs became apparent. A Schlumberger internal paper showing that bond log amplitude is related to the acoustic impedance of the fluid in which the tool is run led to a comprehensive study of wellbore fluid effects. Numerical and experimental models were developed simulating wellbore geometry. Measurements were conducted in 5-, 7-, and 95/8-in. casings by varying the wellbore fluid densities, viscosities, and fluid types (acoustic impedance). Parallel numerical modeling was undertaken using similar parameters. The results showed that the bond log amplitude varied dramatically with the wellbore fluid's acoustic impedance; for example, there was a 70 percent increase in the signal amplitude for 11.5-lb/ gal CaCl/sub 2/ over the signal amplitude in water. This led to the development of a Fluid-Compensated Bond log that corrects the amplitude for acoustic impedance of varying wellbore fluids, thereby making the measurements more directly related to the cement quality.




    Full Text Available Concrete is considered as brittle materials and widely used due to high compressive strength but unfortunately having and has low tensile strength that has a numerous negative impacts on the lifespan of concrete made structures. Therefore, mechanical properties of cement mortar have been investigated experimentally using different types and ratios of nano material to improve the properties. Since the strength of the concrete is of high importance, different materials have been used to enhance the compressive and the tensile characteristics of the cement mortar compressive and tensile strength. Mainly, this objective has been implemented through using micro cement, micro sand, nano silica, and nano clay in developing a nano-cement mortar which can to improve the concrete for the constructional applications. The samples were prepared and tested under tensile and compressive mode according to ASTM-2011 regulations for concrete. The parameters that are taken consideration during the investigation were micro sand, micro cement, nano silica, developed nano clay, and naphthalene sulphonate as super- plasticizers. In general, it has been observed that the results showed a significant increase in both compressive and tensile strength of the mortar at early stages of hardening, where a maximum increase of 22% in the compressive strength was achieved , whereas 3.7 time increase in the compressive strength was recorded over the tradition levels of the concrete strength.

  17. Clinical applications of glass-ionomer cements.

    McLean, J W


    The use of glass-ionomer cements in clinical dentistry is now well established. They have a number of unique properties, including adhesion to moist tooth structure, biological compatibility, and anticariogenic properties due to their fluoride release. Their use in treating early carious or erosion lesions has been widely investigated. Established techniques include fissure filling and sealing, restoration of class 5 erosion lesions without cavity preparation, and the internal occlusal fossa or tunnel restoration. The "sandwich" technique using glass-ionomer cements as "dentin substitutes" has enabled composite restorations to be used with greater safety where pulpal damage may occur. The future probably lies in using a laminate technique where materials that attach to dentin and form a biological seal can be covered by tougher and harder enamel veneers, thus mimicking the structure of the tooth. The deficiencies of glass-ionomer cements are well known, including lack of toughness, early water sensitivity, low abrasion resistance, and porosity leading to poor surface polish. Solving these problems is formidable, since inherently the strength of these cements is related to their water content. The clinician should be aware of these deficiencies and stay within the parameters of the techniques outlined in this paper. In particular, clinical success depends upon early protection of the cement from hydration or dehydration, and the current use of light-cured bonding agents has largely solved this problem.

  18. Stimuli-responsive cement-reinforced rubber.

    Musso, Simone; Robisson, Agathe; Maheshwar, Sudeep; Ulm, Franz-Josef


    In this work, we report the successful development of a cement-rubber reactive composite with reversible mechanical properties. Initially, the composite behaves like rubber containing inert filler, but when exposed to water, it increases in volume and reaches a stiffness that is intermediate between that of hydrogenated nitrile butadiene rubber (HNBR) and hydrated cement, while maintaining a relatively large ductility characteristic of rubber. After drying, the modulus increases even further up to 400 MPa. Wet/drying cycles prove that the elastic modulus can reversibly change between 150 and 400 MPa. Utilizing attenuated total reflection Fourier transform infrared spectroscopy), we demonstrate that the high pH produced by the hydration of cement triggers the hydrolysis of the rubber nitrile groups into carboxylate anions. Thus, the salt bridges, generated between the carboxylate anions of the elastomer and the cations of the filler, are responsible for the reversible variations in volume and elastic modulus of the composite as a consequence of environmental moisture exposure. These results reveal that cement nanoparticles can successfully be used to accomplish a twofold task: (a) achieve an original postpolymerization modification that allows one to work with carboxylate HNBR (HXNBR) not obtained by direct copolymerization of carboxylate monomers with butadiene, and (b) synthesize a stimuli-responsive polymeric composite. This new type of material, having an ideal behavior for sealing application, could be used as an alternative to cement for oil field zonal isolation applications.

  19. Assessment of radiological hazards of naturally occurring radioactive materials in cement industry.

    Aslam, Muhammad; Gul, Rahmat; Ara, Tauseef; Hussain, Manzur


    A study on the radiological hazard in Portland cement due to the presence of naturally occurring radioactive materials is being carried out. The Portland cement manufactured in the Islamabad/Rawalpindi region of Pakistan, intermediate products (clinker) and the various raw materials which compose the product have been analysed for (226)Ra, (232)Th and (40)K using a gamma spectrometry system with a N-type high-purity germanium detector of 80 % relative efficiency. From the measured gamma ray spectra, specific activities were determined. The mean values of the total specific activity of (226)Ra, (232)Th and (40)K are 34.2±11.9, 29.1±3.6 and 295.1±66.9 Bq kg(-1), respectively in Portland cement, 28.4±8.7, 11.3±1.7 and 63.1±17.3 Bq kg(-1), respectively in lime stone, 8.2±1.9, 16.2±3.9 and 187.7±53.2 Bq kg(-1), respectively in gypsum, 34.7±13.1, 41.2±6.7 and 187.6±17.2 Bq kg(-1), respectively in clay, 41.1±11.8, 39.3±6.9 and 195.1±29.2 Bq kg(-1), respectively in latrite and 51.1±18.2, 23.2±1.2 and 258.4±15.3 Bq kg(-1), respectively in clinker. The radium equivalent activities (Ra(eq)), external hazard index (H(ex)), internal hazard index (H(in)), absorbed dose rate in air (D) and annual effective dose rate (E(eff)) were also determined. The measured activity concentrations for these radio nuclides and radiological indices were compared with the reported national and international data. All these measured values are comparable with the worldwide data reported in UNSCEAR publications.

  20. Mechanism of Hg(II) Immobilization in Sediments by Sulfate-Cement Amendment.

    Serrano, Susana; Vlassopoulos, Dimitri; O'Day, Peggy A


    Reactive amendments such as Portland and super-sulfate cements offer a promising technology for immobilizing metalloid contaminants such as mercury (Hg) in soils and sediments through sequestration in less bioavailable solid forms. Tidal marsh sediments were reacted with dissolved Hg(II) in synthetic seawater and fresh water solutions, treated with Portland cement and FeSO4 amendment, and aged for up to 90 days. Reacted solids were analyzed with bulk sequential extraction methods and characterized by powder X-ray diffraction (XRD), electron microscopy, and synchrotron X-ray absorption spectroscopy at the Hg LIII- and S K-edge. In amended sediments, XRD, SEM and sulfur K-edge XANES indicated formation of gypsum in seawater experiments or ettringite-type (Ca6Al2(SO4)3(OH)12(.)26H2O) phases in fresh water experiments, depending on the final solution pH (seawater ∼8.5; freshwater ∼10.5). Analysis of Hg EXAFS spectra showed Cl and Hg ligands in the first- and second-coordination shells at distances characteristic of a polynuclear chloromercury(II) salt, perhaps as a nanoparticulate phase, in both seawater and fresh water experiments. In addition to the chloromercury species, a smaller fraction (∼20-25%) of Hg was bonded to O atoms in fresh water sample spectra, suggesting the presence of a minor sorbed Hg fraction. In the absence of amendment treatment, Hg sorption and resistance to extraction can be accounted for by relatively strong binding by reduced S species present in the marsh sediment detected by S XANES. Thermodynamic calculations predict stable aqueous Hg-Cl species at seawater final pH, but higher final pH in fresh water favors aqueous Hg-hydroxide species. The difference in Hg coordination between aqueous and solid phases suggests that the initial Hg-Cl coordination was stabilized in the cement hydration products and did not re-equilibrate with the bulk solution with aging. Collectively, results suggest physical encapsulation of Hg as a polynuclear