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In this study, the effect of seashell utilization as a replacement for calcite on the surface features and optical properties of white ceramic glazes was investigated. As received seashells collected from Black Sea beaches of Samsun, Turkey and purified seashells at 700°C for 1 h were used as calcite replacement by 15 wt.%. Seashell powders were incorporated to white glaze compositions which are applied on the surface of different fired clay bodies such as red clay, chamotte, white and porcelain by dipping technique. Next, the glazed green bodies were sintered at 1100ºC for 8 h. Following to TG-DTA, heating microscope, XRD and optical analysis, the obtained results exhibited that as received seashell powder (SP-1) was composed of calcite (CaCO3), whereas purified seashell powder (SP-2) comprised aragonite (CaCO3) and calcium oxide (CaO). The iron (hematite) content in red clay and the impurities in seashells composition caused specks and crawlings on the surface of glazed red clay bodies and of some glazes containing seashell, respectively. In generally, the higher CaO content in SP-2 enhanced gloss (60°) values, and whiteness values of most glazed surfaces were closed to each other. The color of chamotte bodies increased redness-greenness values. The variations in optical parameters were mainly associated with the difference in body compositions. SP-1 contained glaze, applied on porcelain body, was selected as optimal because that had 33 gloss value, high whiteness (87) and no surface defect. Therefore, the utilization of as received seashells by 15 wt.% as calcite replacement allows eco-friendly and cost-effective production of white ceramic glazes without any additional heat treatment. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the adsorption and desorption isotherms of Tunisian clay product at different temperatures with a water activity varying from 10.95 to 97% using the statistic gravimetric method, which is an important step to evaluate its hygroscopic character. It was found that when temperature increases, clay material becomes less hygroscopic due to physical and/or chemical changes in product. Ten mathematical models were used to fit experimental data of sorption isotherms. The fitting of the model to experimental data was evaluated with the correlation coefficient (R2) and the root mean square error (RMSE). The Oswin model was determined to be the best model for describing experimental data of adsorption and desorption in the investigated ranges of temperature and water activity. The net isosteric heat of sorption determined from sorption isotherms estimated from Oswin model and using Clausius-Clapeyron equation decreased continuously with increasing the equilibrium moisture content. [ABSTRACT FROM AUTHOR]

This study investigates the use of clay-based grout injections for the repair of adobe masonry constructions. Relevant data from the literature is reviewed, whilst the effectiveness of a laboratory-prepared clay-based grout is assessed through an experimental program. A 1:2 scaled adobe model building, previously subjected to a series of lateral loading cycles resulting in significant cracking damage, was injected with the clay-based grout and re-tested. The mix design of the aforementioned grout was based on the use of the same soil composing the earth masonry materials, hence ensuring compatibility between repairing and original materials. Although the grouting repair did not significantly alter the observed damage pattern after re-testing, it generally succeeded in preventing failure propagation through the injected crack paths. Furthermore, the injection of clay-based grout proved to be a repair technique capable of partly restoring the initial stiffness and load-bearing capacity of adobe masonry. The high strength recovery ratios recorded under the tests using static monotonic horizontal loading are particularly encouraging. [ABSTRACT FROM AUTHOR]

The influence of the displacement rate of a T-bar on the remoulded shear strength of a soft, natural, lightly overconsolidated marine clay is investigated. A series of T-bar cyclic tests was carried out in 12 box cores collected from the Gulf of Mexico. One general equation relating the displacement rate to the remoulded strength is presented, which provides insight on rate effects for remoulded clays and which can be used to correct for remoulded penetration resistance data for natural soft clays for a T-bar recorded at displacement rates other than the commonly used displacement rate of 0·020 m/s. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work discusses the mechanical properties of bricks that were made with clay and sludge mixtures. We analyzed 100:0, 99:1, 95:5, 90:10, 80:20 and 60:40 proportions of clay and sludge. Bricks were cooked between 35 ºC to 1100 ºC. The sludge used in this study came from sewage treatment plant of G.M. Colmotors Company. These tests were carried out: Water Absorption and mechanical resistance of bricks compression. The results of this study showed that the best percentage of sludge to mix with clay was 5 % to 10 %. Since, this percentage range meets the quality standards of the product demanded in Colombia.

This article presents results of a pilot study, where metals leaching from ceramic pieces were made with different mixes of slugde and clay from the sewage treatment plant G.M. COLMOTORES in Bogota (Colombia). The slugde have been stabilized and solidified in clays and cook in a Hoffman Furnace oven for the fabrication of bricks. The proportions of mixture of clay and sludge for the fabrication of bricks used were: 99:1, 95:5, 90:10, 80:20 and 60:40. Then, the bricks were burned at temperatures between 50 to 1,100 ° C. Moreover, clays, sludge and bricks were tested by: X ray diffraction (XRD), X-ray Fluorescence X (XRF), Thermogravimetry (TG), Differential Thermal Analysis (DTA), Atomic Absorption Spectroscopy (AA) and Scanning Electron Microscopy (SEM). Finally, other leaching tests were performed in the bricks (Toxicity Characteristic Reaching Procedure - TCLP) for the determination of heavy metals. Results from this study showed that the clay had a high affinity with the sludge and the bricks showed low levels of leaching. Also, it was considered that 95:5 of clay and sludge was the best mixing ratio for all the metals. The metal with lowest removal percentage was selenium and the highest removal percentages were arsenic, nickel, chrome, zinc and cadmium.

Conservation and restoration of cultural heritage are the objects of great interest worldwide. For setting the correct methodology for the procedures of the restoration it is very important to have the right information about the state of the object and the characteristics of the original materials. The basis of our examinations were clay products (samples of bricks, terracotta and clay roof tile) from the middle ages, the fortress in Bač. The following methods were used: x-ray diffraction, classic chemical analysis, SEM-EDS, Hg-porosimetry and dilatometry. Based on the used methods, mineral composition, temperature and regime of firing and textural properties of the examined materials were determined. The degree of destruction of examined materials was also identified, in order to find compatible materials for future techniques of conservation and restoration.

The Cenozoic paleoclimate of the Atacama Desert is not well known. We examined 14 early to mid-Miocene paleosols exposed in the El Tesoro Mine, near Calama, Chile. The paleosols developed on an aggrading alluvial fan system, and lie above the mineralized gravel horizons that host a copper ore body. Soil-forming conditions that oscillated between chemical weathering and clay production (humid: analogous to modern Alfisols) to environments favoring the accumulation of pedogenic carbonate (arid to semi-arid: analogous to modern Aridisols) are indicated. In contrast, the region is presently hyperarid, and soils accumulate sulfates, chlorides, and nitrates. While total chemical analyses clearly show the accumulation of Ca by the carbonate-rich paleosols, none of the soils exhibit significant losses of elements by leaching. The δ 18 O values of the carbonates range from -8.79‰ to − 3.16‰ (VPDB). The O isotope data, when combined with published data from the region, reveal a significant divergence in the O isotope composition of precipitation in the eastern and western margins of the Andean plateau since the early Miocene, suggesting that simple interpretations of declining δ 18 O values of carbonate with increasing elevation may not be appropriate. These paleosols clearly indicate that wetter conditions prevailed in what is now the Atacama Desert during the early to mid-Miocene. [ABSTRACT FROM AUTHOR]

Late Cretaceous and Palaeocene clay deposits of the northern Tunisia were studied for potential valorization in clay product manufacturing. To achieve this goal, physicochemical characterization based on multidisciplinary approaches including mineralogy, geochemistry and thermal analyses was carried out. Clay samples collected from the Bir M'Cherga and Tajerouine study sites have undergone chemical analysis by using atomic absorption spectroscopy. The obtained results showed that the studied samples were mainly composed of silica, alumina, calcium and iron oxide. Mineralogical analysis confirmed the results of chemical analysis; it showed the main peaks of quartz, calcite, kaolinite, smectite and illite. Those clay samples were used as natural resources for manufacturing earthenware tiles. Mixtures of clays and dolomites were prepared from the Late Cretaceous and Palaeocene clays and then heated to the desired temperature to obtain different earthenware products. Finally, the prepared clay products were tested via different geotechnical analyses. It was found that the clay percentage needed to be decreased in the starting mixture to enhance the properties of the final products. Those results also indicated that industrial application of both Late Cretaceous and Palaeocene clays of the northern Tunisia could be done, especially for manufacturing clay products. [ABSTRACT FROM AUTHOR]

In this work, the feasibility of using spent filtration earth (SFE) and spent bleaching earth (SBE), as both pore-forming agent and silica precursor in bricks was reported. Raw materials, clay, SFE and SBE discarded during filtration and bleaching stages in the refining process of vegetable oils and fats, were analysed by X-ray diffraction, fluorescence and thermal analysis. Samples containing (0–30 wt%) SFE or SBE waste were compressed and sintered in air inside an electric furnace (950 °C, for 4 h). The results obtained (firing shrinkage, bulk density, water absorption, mechanical strength and thermal conductivity) show that adding increasing amounts of SFE or SBE waste produced both positive effects (weight loss, bulk density and thermal conductivity decreased and porosity increase) and negative ones (increase of water absorption and mechanical strength decrease). The equilibrium could be reached with the addition of 10 wt% of SFE or SBE waste, reducing the mechanical strength (10% and 24%, respectively), a bulk density reduction of 6.2% and 9.5%, and a decrease in thermal conductivity of 14.1% and 17.7%, respectively to the standard one, due to the good balance between the effect of pore forming and the melting effect of waste, which increases final vitrification in bricks, as indicated by SEM micrographs. The addition of higher amounts of waste, 20 wt% SFE or SBE, shows a predominant effect in pore forming, leading to higher water absorption values with compressive strength around 30–25 MPa, which fall within the range specified by brick standards, and thermal conductivity of 0.77–0.75 W/m•K. Therefore, SFE or SBE waste can be used to obtain bricks with insulating and high mechanical properties using a pore-forming and silica carrier alternative raw material, reducing ceramic raw material consumption and energy, but also production and landfill cost as waste disposal area requirements. [ABSTRACT FROM AUTHOR]

Spent bleaching earth (SBE) is a waste generated by the edible oil industry that currently has limited options for beneficial reuse. In excess of ∼2 million tonnes per year of SBE is generated world-wide with major quantities available in the middle-east where significant volumes of edible oils are produced. Low pressure compaction followed by heat treatment at 150 °C causes polymerisation of the residual organic components in SBE and this produces monolithic samples with high unconfined compressive strengths (54 MPa). SBE can therefore be used to manufacture novel clay blocks for use in construction that are bonded by polymerised vegetable oil. This represents a new, innovative and resource efficient application for SBE. In this research, commercial SBE has been characterised and the effects of key processing variables (temperature and compaction pressure) on the compressive strength, porosity and density of the SBE clay blocks are reported and the mechanisms responsible for strength development are discussed. [ABSTRACT FROM AUTHOR]

Factors influencing final clay brick properties are numerous, since the raw materials are highly heterogeneous. The chemometric approach is rarely used in analysis in this field, although it could significantly improve understanding of the overall system behavior and the quality of products. Principal component analysis (PCA) was used on a group of 139 samples collected in Serbia to discriminate groups of samples according to similarity of chemical composition and fired laboratory products properties. The focus of this study was to determine the importance of parameters that describe clay brick production and quality, depending on final usage of raw material in the clay brick industry. A fuzzy synthetic evaluation, using a membership trapezoidal function with defined optimal interval values for different types of heavy clay products, is chosen for the study. The optimal sample's chemical composition and firing temperature were chosen by the fuzzy synthetic evaluation, regarding the kind of the heavy clay product. [ABSTRACT FROM AUTHOR]

Copyright of Tecnura is the property of Tecnura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Tecnura is the property of Tecnura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Biomimeticorganic–inorganic composite materials were fabricatedvia one-step self-organization on three hierarchical levels. The organiccomponent was a polyoxazoline with pendent cholesteryl and carboxyl(N-Boc-protected amino acid) side chains that wasable to form a chiral nematic lyotropic phase and bind to positivelycharged inorganic faces of Laponite. The Laponite particles formeda mesocrystalline arrangement within the liquid-crystal (LC) polymerphase upon shearing a viscous dispersion of Laponite nanoparticlesand LC polymer in DMF. Complementary analytical and mechanical characterizationtechniques (AUC, POM, TEM, SEM, SAXS, μCT, and nanoindentation)covering the millimeter, micrometer, and nanometer length scales revealthe hierarchical structures and properties of the composite materialsconsisting of different ratios of Laponite nanoparticles and liquid-crystallinepolymer. [ABSTRACT FROM AUTHOR]

Pregnant women in Africa, Asia and Suriname, and some immigrants in Western societies, traditionally consume clay products known by a variety of names such asmabele, calabash chalk,sikorandpimba. Furthermore, clay is used for health purposes in Western societies. Because certain clays can contain high levels of metals and metalloids, the aim of this study was to determine lead, arsenic, mercury and cadmium in clay products for oral use available on the Dutch market. Traditional clays originating from Africa (n = 10) and Suriname (n = 26), and health clays (n = 27) were sampled from 2004 up to and including 2012. Total metal and metalloid contents were measured by ICP-MS and showed maximum levels of lead, arsenic, mercury and cadmium of 99.7, 45.1, 2.2 and 0.75 mg kg–1, respectively. In the absence of maximum limits for these type of clays, the potential exposure was estimated from the determined concentration, the estimated daily use level of the clays, and the estimated bioaccessibility of the different metals and arsenic. The intake estimates were compared with existing health-based guidance values. For lead, the use of 34 of the 36 traditional clays and two of the 27 health clays would result in intake levels exceeding the toxicological limit by up to 20-fold. Use of 15 of the 35 traditional clays and 11 of the 27 health clays would result in intake levels exceeding the toxicological limit for inorganic arsenic by up to 19-fold. Although limited bioaccessibility from the clay may limit the exposure and exceedance of the health-based guidance values, it was concluded that lead and arsenic intakes from some clay products could be of concern also because of their use by pregnant women and the potential developmental toxicity. As a result the use of these products, especially by pregnant women, should be discouraged. [ABSTRACT FROM AUTHOR]

Abstract: Clay products for construction offer durability, thermal and acoustic comfort as well as low cost. Drying is an important stage of the production process of these products, and it was studied herein. Experiments on convective drying of clay slabs with initial moisture content of 0.23 (db) were performed at 50, 60, 70, 80 and 90°C. Drying occurred in two distinct periods: constant and falling rate. In the first period, the process was described by an empirical equation and, in the second one, by the diffusion equation with boundary condition of the third kind. To eliminate some restrictions found in the literature, a three-dimensional numerical approach was used to describe the process. Equations were obtained to express the process parameters as a function of the drying air temperature and local moisture content. A simulation using the values obtained from these equations for the process parameters is coherent with the experimental data. [Copyright &y& Elsevier]

Abstract: As a paper sizing agent, alkenyl succinic anhydride (ASA) emulsion is generally stabilized by cationic starch or synthetic polymer. In this paper, Laponite and urea were employed as particle stabilizer and the modifier of Laponite particle, respectively, to stabilize the ASA emulsion. It is founded that the presence of urea enhances the stability of ASA emulsion, reduces the emulsion droplet size, resulting in improved sizing performance of the ASA emulsion. ASA emulsion with smallest droplet size and best sizing performance on BCTMP is obtained at the urea dosage of 50wt% based on Laponite. The sizing test of ASA emulsion and the infrared spectrum analysis of ASA substances separated from ASA emulsions with different storage time indicate that the introduction of urea in emulsification process can restrain the hydrolytic action of ASA effectively and sustain the sizing performance of ASA emulsion even two hours after its preparation. This is a possible way to solve the problem that paper mills have always encountered: the too rapid hydrolysis of ASA emulsion. [Copyright &y& Elsevier]

Abstract: Geophagy, the practice of consuming clay or soil, is encountered among pregnant women in Africa, Eastern Asia and Latin America, but also in Western societies. However, certain types of clay are known to contain high concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The aim of this study was to determine the PCDD/F contents of orally consumed clays purchased from Dutch and African markets. Congener patterns were compared with those of pooled human milk samples collected in eight African countries, to investigate a possible relationship with clay consumption. From the Dutch market thirteen clay products were examined, seven of African and six of Suriname origin. From seven African countries, twenty clay products were collected. All 33 clay products were screened with a cell-based bioassay and those showing a high response were analyzed by GC/HRMS. High PCDD/F concentrations were measured in three clay products from the Dutch market, ranging from 66 to 103 pg TEQ g-1, whereas clay products from African countries were from 24 to 75 pg TEQ g-1. Patterns and relatively high concentrations of PCDD/Fs in human milk samples from the Democratic Republic of the Congo and Côte d’Ivoire suggest a relationship with the consumption of contaminated clay. Frequent use of PCDD/F contaminated clay products during pregnancy may result in increased exposure of the mother and subsequently the developing fetus and new-born child. The use of these contaminated clays during pregnancy should be carefully considered or even discouraged. [Copyright &y& Elsevier]

Purpose: This paper compares 16 waste lubricant oil (WLO) systems (15 management alternatives and a system in use in Portugal) using a life cycle assessment (LCA). The alternatives tested use various mild processing techniques and recovery options: recycling during expanded clay production, recycling and electric energy production, re-refining, energy recovery during cement production, and energy recovery during expanded clay production. Methods: The proposed 15 alternatives and the actual present day situation were analyzed using LCA software UMBERTO 5.5, applied to eight environmental impact categories. The LCA included an expansion system to accommodate co-products. Results: The results show that mild processing with low liquid gas fuel consumption and re-refining is the best option to manage WLO with regard to abiotic depletion, eutrophication, global warming, and human toxicity environmental impacts. A further environmental option is to treat the WLO using the same mild processing technique, but then send it to expanded clay recycling to be used as a fuel in expanded clay production, as this is the best option regarding freshwater sedimental ecotoxicity, freshwater aquatic ecotoxicity, and acidification. Conclusions: It is recommended that there is a shift away from recycling and electric energy production. Although sensitivity analysis shows re-refining and energy recovery in expanded clay production are sensitive to unit location and substituted products emission factors, the LCA analysis as a whole shows that both options are good recovery options; re-refining is the preferable option because it is closer to the New Waste Framework Directive waste hierarchy principle. [ABSTRACT FROM AUTHOR]

The production of heavy-clay products demands a huge amount of plastic ceramic pastes. During extrusion the clay-compound flow through the extrusion die and this flow mainly show plug flow with extensive wall slip. The viscosity and the thickness of the slipping layer were investigated in this study. Brick-clay from Malyi (Hungary) deposit was applied as a raw material. Clay was characterised by XRPD, BET, SEM and granulometry. By the help of sedimentation of clay minerals content of the clay (d<2μm), the viscosity of suspension with different water content were measured by means of rotational viscositymeter. Based on thickness calculating process from former studies, it was integrated with measurement of viscosity. The thickness values were calculated from viscosity data and from data of former measurements with capillary reometer. The thickness of the slip layer showed a tendency to reach a limit value by increasing the extrusion speed. [ABSTRACT FROM AUTHOR]

Abstract: The effects of ground clay brick (GCB) on alkali-silica reaction (ASR) expansion as well as on mechanical properties of ASR-affected concrete are investigated. Crushed red clay brick originated from demolished masonry was ground in a laboratory ball mill and replaced for portland cement at levels of 15% and 25% by weight in concrete mixes produced with alkali reactive sand. ASR expansion, compressive strength, flexural strength, and modulus of elasticity of the concrete mixes were evaluated. Effect of GCB on ASR gel chemistry was also studied on Pyrex glass-paste specimens using SEM/EDS (scanning electron microscope equipped with energy dispersive X-ray spectroscopy). The results indicate that GCB effectively reduces ASR expansion in concrete: associated cracking and loss on mechanical properties are also significantly reduced. SEM study suggests that GCB alters alkali silica gel chemistry thus resulting in a less expansive product. [Copyright &y& Elsevier]

The agro and industrial activities are currently responsible for the production of large amounts of solid wastes. The use of industrial wastes such as granite, marble, kaolin and pegmatite and agro-industrial rejects into clay products has been widely developed over the last few decades. Clay materials used in the ceramic industry exhibit a large diversification of compositions that allow the addition of different types of waste materials to the clay mixture. Sugar cane bagasse ash (SCBA), a by-product of the sugar process, is exacerbating the environmental problem. Brazil produces an enormous amount of sugar and the lack of adequate landfill areas available for disposal of sugar cane bagasse ash rejects poses a critical problem for the agro-industry. This work describes, for the first time, research carried out on the manufacturing of ceramic tile materials with sugar cane bagasse ash additions. SCBA, consisting basically of potassium oxide, was added to the clay formulations as an alternative to feldspar. Clay with different sugar cane bagasse ash content was mixed and sintered. Sintered specimens were characterized by X-ray diffraction, density, porosity, thermal analysis and strength measurements. The results obtained showed that the sugar cane ash residue can be added to clay materials as an alternative to feldspar, without degrading their properties. [ABSTRACT FROM AUTHOR]

Terracotta figurines of graceful young women discovered in the necropolis at Tanagra and found in many other places in the ancient world attracted great interest among collectors from the 1870s onwards. The simplicity of the processes used to facilitate large-scale production of clay products in the ancient world was exploited by antiquities dealers, who copied them in order to bring significant numbers of forgeries and pastiches onto the market, many of which are pieces now found in many museum collections. Conservation work, backed up by chemical testing, is currently underway to establish the authenticity of such statuettes and to create, from confirmed forgeries, simulations of the original appearance of the true antique with its full polychromy. [ABSTRACT FROM AUTHOR]

The potential shrinkage of eight different geosynthetic clay liners (GCLs) subjected to wetting and drying cycles is examined. It is shown that the initial (e.g, off-the-roll) moisture content may affect the initial shrinkage but did not notably affect the final equilibrium shrinkage. For GCLs with granular bentonite and wetted to a moisture content of about 60% (or greater) in the hydration phase, the actual moisture content did not appear to affect the magnitude of the final equilibrium shrinkage. However, it did affect the rate of shrinkage. Specimens brought to about 100% moisture content in each cycle reached a constant shrinkage value much faster than those brought to about 60% in each wetting cycle. GCLs containing powdered bentonite generally shrank more than those containing granular bentonite. All of the powdered bentonite specimens continued a slow accumulation of strain with increasing cycles, even up to 75 cycles. The shrinkage of a needle-punched GCL with a thermally treated scrim-reinforced nonwoven carrier geotextile and granular bentonite was less than that for a needle-punched GCL with a simple nonwoven carrier and granular bentonite. For some products, there was considerable variability in GCL shrinkage for specimens from the same roll and tested under nominally identical conditions, whereas for other products, the variability was relatively small. The shrinkage strain required to cause the loss of a 150-300 mm panel overlap is shown to be able to be mobilized in about five wet-dry cycles in the experiments reported. [ABSTRACT FROM AUTHOR]

The hydration and subsequent hydraulic performance of geosynthetic clay liners (GCLs) depend on the water-retention curve (WRC) of the GCL. Because of the inherent difficulty in obtaining the WRC for these materials, limited data exists regarding the WRCs of GCLs in the literature. In this study, high-capacity tensiometers and capacitance relative humidity sensors were used to quantify the water-retention behavior of GCLs for four different GCL products that vary both in materials (woven and nonwoven geotextiles) and in fabrication detail (thermal treatment and needle-punching). The water-retention behavior was investigated under wetting and drying paths; we present results in terms of gravimetric and volumetric moisture content and bulk GCL void ratio. The WRCs of the different GCL products showed significant variation among wetting and drying curves, indicating that both needle-punching and thermal treatment have a significant effect on the swelling behavior of the GCL and its WRC. Theoretical equations were fit to the experimental data, establishing the parameters that can be used for numerical modeling of these four GCL products. [ABSTRACT FROM AUTHOR]

The effects on the nature of bentonite, natural sodium, and calcium activated, and of the cation exchange on the diffusive properties of two geosynthetic clay liners (GCLs) were examined. Diffusion laboratory tests were conducted to estimate the diffusion coefficients of 1, 2-dichloroethane (DCA), dichloromethane (DCM), thrichloroethylene (TCE), toluene, and benzene. Both GCLs were needle-punched and came from the same manufacturer. The nature of the bentonite contained in both GCLs was different because a natural sodium bentonite and a calcium activated sodium bentonite were tested. Furthermore, one of the GCLs experienced cation exchange from contact with a synthetic leachate used to generate an increase in its hydraulic conductivity by a factor of 8.5. The objective of this process was to evaluate if an increase in the hydraulic conductivity by cation exchange in a GCL would result in a significant increase in the diffusion coefficients of volatile organic compounds (VOCs). The results obtained for both virgin GCLs were very close to one another. No effect on the nature of the bentonite was observed. An increase in the diffusion coefficient was noticed for the case in which the GCL experienced cation exchange while in contact with a synthetic leachate for DCM, DCA, and TCE at a given bulk GCL void ratio. The largest increase, a factor of 2.6, was observed for TCE. However, this increase in the diffusion coefficient could have been balanced by the decrease in the bulk GCL void ratio from 3.9 to 3. The increase in the diffusion coefficient of VOCs, thus, does not seem to be of concern for the range of GCL hydraulic conductivities generated by cation exchange in this study. [ABSTRACT FROM AUTHOR]

Excavations at two similar but separate prehistoric campsites in south-central Texas have yielded evidence of atypical cooking technologies wherein small, ill-formed clay halls were used in lieu of the more ubiquitous heated rocks. Both sites are on toe-slopes and flood plains of tributaries to the At ascosa River where they were well placed to exploit both floodplain and tributary stream resources. In addition to a predictable complement of fire-cracked rock, midden deposits, lithic debris, and stone tools, both sites contain large quantities of burned clay balls, a cruder form of the type so common at Poverty Point and comparable to the fired clay objects from sites in the Gulf Coastal zone. Radiocarbon dates from fire-cracked rock features, soil humates, and the clay balls themselves place overall occupations of these sites in the Middle Archaic to Late Prehistoric periods in the local chronology (3400 to 570 B.P.). The sequence of dates suggests that burned clay cooking and burned rock cooking were employed at different times, either by different people or for different resources. Ethnographic and archeological models describe the seasonal rounds of coastal people that may explain the overlap of traditional cooking methods in the inland contact zone. [ABSTRACT FROM AUTHOR]

Recent studies have shown that handcrafted glass-clay containers are a health risk because they can be contaminated by heavy metals, which can be transferred to food, thus reaching the human body to potentially cause illness. Therefore, in the present work, we evaluate the leaching of lead, cadmium, and cobalt from glass-clay containers into two types of food: tomato sauce (salsa), and chickpea puree. The containers were obtained from four regions in the Mexican state of Hidalgo. Repetitive extractions from the containers were carried out to quantify the leaching of the heavy metals into the salsa, the chickpea puree, and acetic acid using the technique proposed by the USFDA. The results show that greater use of the containers leads to more leaching of heavy metals into both types of food and into the acetic acid, with the greatest metal extraction recorded for the Ixmiquilpan vessels. These results indicate that the metals present in the glass-clay containers leach into the food and that increased reuse increases the risk to the people who use them in food preparation. [ABSTRACT FROM AUTHOR]

In this article, artist Cecile Johnson Soliz writes about the complexities of using clay, both in her studio and during her experience of working with clay workers at Red Bank Manufacturing for her project,"Skyline?' Tools for making art are of special interest to Johnson Soliz, especially when the very tools she needs do not exist or do they? [ABSTRACT FROM AUTHOR]

Abstract: Friction is one of the most important factors in energy consumption and in the lifetime of machinery used to prepare and produce heavy-clay products such as brick and roof tiles. Production of traditional heavy-clay products often demands additives to change the properties of the clay processed or those of the products. The effects of different additions of organic and non-organic additives on the friction coefficients of clay compounds were investigated. As opening agents sand and ground brick dust, while as pore forming additives sawdust and ground sunflower seed shell were mixed to the clay in 0, 3 and 5wt.%. The water content value was set to 20% and 24% of the compounds. Investigation was performed by a special tribometer up to the plastic deformation of a sample. The sand and brick dust lowered the coefficient of friction to different extents. Raising the amount of sand from 3% to 5% caused some 30% decrease in friction while the effect of brick dust was not so significant. Sunflower seed shell lowered friction at 24% moisture content while increasing it at 20% moisture content. Addition of saw dust resulted in higher friction value as compared to pure clay. The results revealed how additives behaved in the clay matrix. [Copyright &y& Elsevier]

Abstract: The coating of fired clay substrates with various metal oxides, such as anatase, rutile, zinc oxide and tin oxide was achieved using a simple spraying technique followed by a thermal treatment. The photocatalytic activity of the layer was characterized through measurement of the absorption spectrum, in the range 400–800nm, of methylene blue deposited on top of the coating. Results show that the presence of anatase enhances the degradation of methylene blue when it is exposed to ultraviolet light. Thermal treatment at 1050°C transforms anatase crystals into thermodynamically stable rutile. This results in a decrease of the photocatalytic activity, which can be explained by increase of the grain size and by a difference in the crystal structure. Measurements of the photocatalytic activity of ZnO and SnO2 show that these two oxides also exhibit photocatalytic properties. In particular, ZnO is a promising alternative material to anatase. [Copyright &y& Elsevier]

Abstract: Photocatalysis is a very promising method to face most of the problems connected with the increasing environmental pollution. Titanium dioxide in its anatase crystallographic phase is the most investigated photocatalytic material and results to be perfectly compatible with silicate body mixes. The possibility to obtain photocatalytic heavy clays materials, to be used for outdoor applications, such as roof tiles, floor tile and outdoor covering tiles, could represent an important goal. In the present work, several titania powders and a titania nanosuspension were added to a body mix used for heavy clay products and the influence of their morphological characteristics on the photoactivity of the fired materials was studied. The titania powders, characterised by the aid of SEM, X-ray diffraction analysis and surface area measurements, BET, presented particles with different aspect ratio and size, ranging from micrometric to nanoparticles. Besides, the nanosuspension was characterised by FEG, TEM, DLS and XRD on the dried suspension. The photocatalytic activity was assessed in aqueous mixtures, by analysing the degradation of an organic dye with a spectrophotometer. The results were explained taking into account the anatase to rutile phase transformation and its possible reaction, during sintering, with the starting raw materials. [Copyright &y& Elsevier]

An advanced hybrid drug carrier has been developed using porous nanocrystals of a swellable clay mineral conjugated with a block copolymer containing poly (ethylene glycol) and polyamine segments. Synthetic hectorite (Laponite) or silica nanoparticles modified with α-acetal-poly (ethylene glycol)-block-poly[2- (N,N-dimethylamino) ethyl methacrylate] (acetal-PEG-b-PAMA) produced a homogeneous dispersion of an organic-inorganic hybrid in aqueous solution, which showed flocculation-resistive properties with an elevated ionic strength. The zeta-potential measurement revealed that nonionic PEG brush layers are formed on the surface of the clay nanocrystals since the negative charge of the clay surface was completely shielded by the nonionic PEG segment in the block copolymer. This charge neutralization explains the dispersion stability in solutions of high ionic strength. The average particle size of the PEG-modified hybrid was estimated to be 30-120 nm by dynamic light scattering. Pyrene, used as the model compound of a hydrophobic drug, was incorporated into the nanopores of the clay mineral without any remarkable expansion of the basal spacing. On the basis of these results, hybrids of porous inorganic nanoparticles coupled with acetal-PEG-b-PAMA are promising as new drug carrier systems. [ABSTRACT FROM AUTHOR]

Abstract: A series of shear strength tests of needle-punched geosynthetic clay liner (GCL)/textured geomembrane interface were conducted at normal stresses ranging from 10 to 400kPa. The geomembrane was in contact with the woven geotextile of GCL. One half of the tests were carried out on prehydrated GCL samples at low normal stress (about 1kPa), whereas the other half on non-prehydrated samples. The prehydrated samples exposed during shearing to normal stresses of 100kPa and above demonstrated bentonite extrusion to the area in contact with geomembrane, which was visible to the naked eye. The bentonite extruded was quantified by introducing an extrusion coefficient. The quantity of the bentonite extruded increased with an increase in normal stress, and lubrication of the contact area with bentonite resulted in reduced shear strength. Finally, the testing showed that for tests carried out on prehydrated samples at lower shear rates, lower contact shear strengths were obtained and more extensive bentonite extrusion to the contact area was observed. [Copyright &y& Elsevier]

Abstract: The results of long-term hydraulic conductivity test results on two modified bentonite materials, a multiswellable bentonite (MSB) and a dense-prehydrated geosynthetic clay liner (DPH-GCL), permeated with electrolytic chemical solutions are reported. In addition, their chemical compatibilities are discussed in order to investigate the applicability of these compounds as barrier materials at waste containment facilities. Hydraulic conductivity tests with inorganic chemical solutions of NaCl and/or CaCl2 were conducted for a maximum of 7 years. The hydraulic conductivities of MSBs with NaCl solutions, which had a molar concentration of ⩽1.0M, were k≅1.0×10−11 m/s. However, when the molar concentration of the NaCl solution was 2.0M the hydraulic conductivity of the MSB was nearly identical to that of natural bentonite. The hydraulic conductivities of DPH-GCLs with CaCl2 solutions, which had a molar concentration of ⩽1.0M, were k≅1.0×10−12 m/s, regardless of the concentration of the solution tested. Hence, both MSBs and DPH-GCLs exhibit remarkable swelling and chemical resistances, respectively, to electrolytic solutions of NaCl and CaCl2 with a molar concentration of ⩽1.0M. [Copyright &y& Elsevier]

Nanocomposites based on polyamide 6 (PA6) and montmorillonite-type (MMT) commercial clays, either unmodified or organically modified, were prepared by in-situ polymerization of ε-caprolactam (CL). The above materials were characterized in detail by a number of experimental techniques, including transmission electron microscopy (TEM), wide angle X-ray diffraction (WAXD), infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The formation of nanostructured systems was checked not only for the commonly used ω-aminoacid-modified clay, but also for other types of organoclays. In general, a correlation was found between nanoscopic swelling of the clay in molten CL, measured by X-ray diffraction, and level of clay dispersion in PA6. Specifically, with the most swellable clays, completely exfoliated nanocomposites were obtained. However, also layered silicates modified by compatibilizers having carboxy groups, because of the active role of latter in CL polymerization, formed delaminated nanocomposites despite their low degree of swelling in CL monomer. Both molecular mass and crystallinity of the polyamide matrix were found to be strongly influenced by the presence of specific layered silicates. In particular, some characterization techniques (WAXD, FTIR) have evidenced a close relationship between the MMT used and PA6 crystal structure. Namely, PA6 γ-form is promoted by clay with compatibilizer bearing the carboxy group, which is able to induce the polymer to be tethered on the silicate layers, thus provoking conditions of restricted mobility to occur. [ABSTRACT FROM AUTHOR]

Background, Goal and Scope. The ceramic tile industry is one of the most important industries in Spain, with the highest concentration of firms to be found in the province of Castellón on the Mediterranean coast. The basic input material for this industry is red clay. The aim of this study was to carry out an LCA of the process of mining, treating and marketing this clay in order to identify the stages and unit processes that have the greatest impact on the environment. This LCA examines all the stages of the red clay from cradle to the customers gate, including the process of mining and treating the clay in the mining facilities and its later distribution to end users. Methods. Life cycle inventory (LCI): An exhaustive LCI was performed by collecting data from the mine run by Watts Blake Bearne Spain, S.A. (WBB-Spain) in Castellón. Inputs and out- puts were collected for all the unit processes involved in the mining, treatment and marketing of the clay: - Mining the clay, which embraces the unit processes of removing the layer of vegetation covering the chosen area, preparing the area to allow access for the firms vehicles, and boring or blasting the place the clay is to be extracted from. - Treating the clay that is mined to make the finished product, which entails all unit processes required to separate out the waste material and transport it to the tip (which will later be reconditioned), excavating and transporting the clay to the crushing plant and later storing it in heaps before delivery to customers. All the internal transport that takes place between each unit process has also considered. - Distribution of the final product, where the clay is loaded onto dumper trucks and delivered to the customer. Life cycle impact assessment (LCIA): According to ISO 1404X standards, the LCIA is performed at two levels. Firstly, the emissions accounted for in the inventory stage are sorted into impact categories to obtain an indicator for each category (mandatory elements). Secondly, the weighting of environmental data to a single unit is applied (optional elements). In compliance with ISO 14042, a sensitivity analysis is performed and three different impact assessment methods (Eco-Indicator95, Eco- Indicator'99 and EPS'2000) are applied in order to analyse their influence on the results. Results. The processes that involve the movement of clay within the mine (excavation and loading and transport to the crushing facilities and heaps) are the ones that make the greatest contribution to impact categories for pollutant emissions. As weighting methods in LCA remain a controversial issue, a recommendation when robust results are required, can be to use several methods to examine the sensitivity of the results to different values and worldviews. In our application case, in spite of the differences between the three impact assessment methods applied (Eco-Indicator95, Eco-Indicator'99 and EPS'2000), the same conclusions can be established from the environmental point of view and we can conclude that the ultimate results are not sensitive in the transformation of mid-points to end-points. Discussion. Taking into account the characteristics of the product being analysed, in addition to the impact categories for pollutant emissions that are traditionally considered in LCA studies, environmental parameters related to resource use (fuel, electricity and water consumption), waste generation (dangerous and non-dangerous wastes) and land use (natural resource appreciation and land use efficiency) and its later rehabilitation (degree of rehabilitation) have been defined. These parameters can be used as additional criteria for an environmental product declaration or criteria for a future eco-labelling of red clay. Conclusion.… [ABSTRACT FROM AUTHOR]

The method of investigating the crack resistance of a clay semifinished product during drying was examined. A safe duration of drying for articles of complex shape by plotting the diagram of the maximum possible moisture removal as a function of the form factors (reduced thicknesses) of simple parts of the article was proposed. The method was tested on samples of the investigated clay and industrial brick paste. [ABSTRACT FROM AUTHOR]

The disposal of sludge from wastewater treatment presents highly complex problems to any municipality. Most of the sludge disposal methods have varying degrees of environmental impact. Hence, it is necessary to explore potential areas of reuse in order to alleviate sludge disposal problems and to conserve natural resources. Industrial sludge and marine clay are two forms of high-volume wastes. Using these wastes as a resource of raw materials to produce construction aggregates would enable large-scale sludge reuse. The aggregates were produced at various sludge-clay combinations containing 0, 20, 50, 80 and 100% clay contents, respectively. The pelletized aggregates displayed lower particle densities ranged between 1.48 and 2.25 g/cm³, compared to the density of granite at 2.56 g/cm³. Good 28-day concrete compressive strength of 38.5 N/mm² achieved by the 100% sludge aggregate was comparable to the value of 38.0 N/mm² achieved of the granite control specimens. The leachate contamination levels from the aggregates after 150 days were found acceptable when used in concrete, indicating insignificant environmental contamination. The heat flow study showed increases in heat flow at the temperatures of 480°C and between 660°C and 900°C, indicating a need for the extension of heating time around these temperatures. [ABSTRACT FROM AUTHOR]