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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 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]

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]

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]

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]

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]

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]