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The high amount of carbon dioxide produced by using cement as a component in concrete has led to environmental issues. Additionally, the amount of cement used in high-performance concrete (HPC) is considerable. As an alternative, slag is being used to reduce cement consumption. This study presents the development of HPC with minimal use of cement without significant strength reduction. The cementitious materials comprise 85% slag, 5% hydrated lime, and 10% ordinary Portland cement (OPC). Replacing cement with slag at high percentages always reduces the strength of concrete. Therefore, appropriate additives were used to achieve the strength of conventional concrete made of OPC. Calcium chloride was used as the most well-known accelerator of hydration, as well as ocher (red clay) due to its Fe2O3 content. Compressive strength and four-point flexural tests at the ages of 7 and 28 days, and Thermogravimetric Analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests were performed. The results showed that the mixture which included 2% calcium chloride with 2% ocher, provided the highest compressive and flexural strengths of 93.2 and 8.1 MPa, respectively. These values were 99% of the compressive strength and 96% of the flexural strength of the concrete sample made of OPC only. The microstructural analysis showed that this mixing design had the highest content of calcium-silicate-hydrate (C–S–H) and other vital phases. Also, due to the role of chloride ions in steel corrosion, the electrical resistance test was performed on the sample that contained 2% calcium chloride and the sample with OPC only. The results showed that calcium chloride used as an accelerator will not cause corrosion of steel bars in the concrete. [ABSTRACT FROM AUTHOR]

The use of ochre has been documented in many Middle Stone Age sites of Southern Africa. However, the literature on the exploitation of ochre within the archaeological contexts of Later Stone Age (LSA) rock art sites is scarce. Despite the discovery of several painted shelters within the Erongo Mountains (Namibia), no archaeological study of ochre assemblages has been conducted in the region. Here, we present the archaeological ochre assemblage recovered from a LSA sequence at the rock art shelter of Leopard Cave (Erongo, Namibia), spanning ca. 5,700 to 2,100 cal. BP. The use-wear traces present on some ochre fragments and the stone tools bearing red residues are indicative of different stages of ochre processing at the site. The presence of other artifacts, such as ostrich eggshell and bone beads with red residues, and the existence of rock paintings in the cave are pointers to the importance of ochre for understanding the sociocultural behaviors of the LSA populations in central Namibia. [ABSTRACT FROM AUTHOR]

The Filanthropinon monastery church is regarded the birthplace of the "Epirus/NW Greece School" of painting as it bears the oldest wall paintings of this very school. Surviving inscriptions bear no painter name(s), yet they testify that the murals were executed in three phases between 1531/2 and 1560. The bulk of the technical and typological characteristics of the latter paintings are typical of post-Byzantine religious art, while OM, SEM-EDX, and micro-Raman probing reveals the existence of a number of idiomorphic characteristics that might be viewed as part of the microscopic fingerprint of the "Epirus school." A microscopic fingerprint of the school is important because current attributions of relevant works to specific painters are mostly stylistic ones, as pertinent signatures are rare. The latter characteristics include the application of a "charcoal plus blue smalt" substrate in the paintings' background and the employment of a possibly local (: Epirus), unusual ochre pigment. Sophisticated segregation of pigment grains, employment of glauconite, and the extensive use of San Giovanni white were also documented. Analytical data support the following scheme as regards artistic identities: the 1531/2 nave paintings were executed by a single painter, possibly assisted by a pupil who also contributed to the 1542 paintings. The paintings of the 1542 and 1560 phases are apparently the outcome of another—yet related to the nave painter—workshop; there are clues which indicate employment of Georgios and Frangos Kontaris in both of these commissions. Finally, remnants of four different overpaintings were also revealed: pertinent pigments indicate successive interventions during an extended period of time, which reflect the will of Filanthropinon votaries to retain the murals vivid. [ABSTRACT FROM AUTHOR]

Upper Palaeolithic yellow and red ochre samples recovered in the last 40 years at Tagliente rock-shelter in the Lessini Mountains (Verona, NE Italy) were analysed by means of conventional X-Ray Powder Diffraction (XRPD) and compared with goethite- and hematite-based natural geomaterials coming from geological deposits within a distance of approximately 20 km from the archaeological site. XRPD allowed the yellow ochre sourcing area to be focused on the basis of characteristic and distinctive mineral assemblages. In addition, several samples clearly demonstrated that archaeological red ochre was obtained by thermal treatment of yellow ochre as shown by characteristic peak intensities, shape and the presence of maghemite (γ-FeO). XRPD was a very powerful tool for a preliminary discrimination and grouping of a large quantity of archaeological ochre, in order to outline a preliminary hypothesis on the provenance area and to narrow down the number of samples to be studied in the next future through geochemical and structural analysis in order to confirm the proposed interpretation. [ABSTRACT FROM AUTHOR]

With the aim to obtain iron tubular microstructures attractive for various applications, we have used a natural biogenic iron ochre as a raw material and explore various procedures and experimental conditions to achieve our goal. Our experiments included reduction, nitridation and characterization of microtubes derived from biogenic iron ochre. Various temperatures of reduction under streams of H/N or NH were tested. Our results show that the tubular structure is maintained after reduction of the natural material under H/N. In addition, ammonia was not produced under our experimental conditions, and as expected, hydrogen reduced the material. However, the treatment under NH reduces the material and allows the incorporation of nitrogen into the structure of the solid yielding iron nitride microtubes. Reduced and nitrided microstructures were successfully obtained from natural biogenic iron ochre. A temperature of 500 °C seems to be suitable to expose the calcined biogenic iron ochre under H/N for 4 h or under ammonia for 8 h to obtain reduced or nitrided microtubes, respectively. The stability of the tubular structure during reduction/reduction-nitridation is maintained under both treatments. Further interesting applications of this natural biomaterial could be envisaged. [ABSTRACT FROM AUTHOR]

The archaeological site Pedra do Cantagalo I is a sandstone shelter displaying rupestrian inscriptions. It is located in the rural area of the municipality of Piripiri, in the northern region of the Piauí state, Brazil. The site was found as being originally decorated with more than 1,900 prehistoric rupestrian paintings, along with engravings, lithics, ceramic fragments and mineral pigments forming reddish and yellowish ochres. Materials of these ochres, collected from recent excavations in this archaeological site, were analyzed by energy dispersive X-ray fluorescence (EDXRF); backscattering and transmission Fe-Mössbauer spectroscopy at 298 K and 25 K and powder X-ray diffraction (XRD), in an effort to assess the chemical and mineralogical characteristics of these sources of pigments that composed the ancient paint materials of the site. The iron contents (expressed as Fe O ) for the reddish ochres were found to range from ∼60 to ∼68 mass%; for the yellowish ochres the corresponding content was ∼34 mass%, as determined by EDXRF. From the Mössbauer spectra for these red ochre samples, hematite ( αFe O ) or a mixture of hematite and goethite ( αFeOOH) were identified. Actually, the spectra at room temperature for the yellow ochres are rather complex, as it is usual for most soil clay materials. At least part of the intense central doublet was assumed to be from superparamagnetic iron oxides in very small particles. The Mössbauer patterns at 25 K allowed confirming this assumption, as the superparamagnetic relaxation effects were virtually suppressed; the spectral contributions due to goethite could be thus more easily separated. [ABSTRACT FROM AUTHOR]

The treatment of mine drainage-impacted waters generates considerable amounts of sludge, which raises several concerns, such as storage and disposal, stability, and potential social and environmental impacts. To alleviate the storage and management costs, as well as to give the mine sludge a second life, recovery and reuse have recently become interesting options. In this review, different recovery and reuse options of sludge originating from active and passive treatment of mine drainage are identified and thoroughly discussed, based on available laboratory and field studies. The most valuable products presently recovered from the mine sludge are the iron oxy-hydroxides (ochre). Other by-products include metals, elemental sulfur, and calcium carbonate. Mine sludge reuse includes the removal of contaminants, such as As, P, dye, and rare earth elements. Mine sludge can also be reused as stabilizer for contaminated soil, as fertilizer in agriculture/horticulture, as substitute material in construction, as cover over tailings for acid mine drainage prevention and control, as material to sequester carbon dioxide, and in cement and pigment industries. The review also stresses out some of the current challenges and research needs. Finally, in order to move forward, studies are needed to better estimate the contribution of sludge recovery/reuse to the overall costs of mine water treatment. [ABSTRACT FROM AUTHOR]

The water is suspected of remobilizing pigments of prehistoric painting into small worm-like heaps named vermiculations. To preserve these artworks, the moisture content of pigments must be monitored. Due to the fragility of the paintings and the technical constraints on the in-situ measurements, colour measurement is proposed as a non-invasive way to access humidity. This study aims at characterizing more precisely the influence of the moisture content on the optical behaviour of yellow ochre. The light reflected by the surface of drying ochre is measured with a gonio-spectroradiometer. A scenario is proposed: the water saturation at high moisture contents is connected to the presence of a specular radiation which brings a loss of chromatic information. The evaporation of water brings the disappearance of the specular radiation and the augmentation of the diffuse radiation. These first results are promising for the development of a non-destructive in situ method of moisture measurement. [ABSTRACT FROM AUTHOR]

The ability of ochre to remove Pb(II) and Cu(II) from aqueous media has been studied by batch sorption studies varying the contact time, initial metal concentration, initial solution pH and temperature to understand the adsorption behaviour of these metals through adsorption kinetics and isotherms. The pH of the solution and the temperature controlled the adsorption of metal ions by ochre and rapid uptake occurred in the first 30 min of reaction. The kinetics of adsorption followed a pseudo-second-order rate equation ( R > 0.99) and the isotherms are well described by the Freundlich model. Adsorption of metals onto ochre is endothermic in nature. Between the two metals, Pb(II) showed more preference towards the exchangeable sites on ochre than Cu(II). This study indicates that ochre is a very effective adsorbent in removing Pb(II) and Cu(II) from the aqueous environment with an adsorptive capacity of 0.996 and 0.628 mg g and removal efficiency of 99.68 and 62.80 %, respectively. [ABSTRACT FROM AUTHOR]

Metal concentrations from stream waters in two geological blocks in Northern Ireland were compared to determine the contributions of catchment characteristics and in-stream conditions. One block is composed of metamorphosed schist and unconsolidated glacial drift with peat or peaty podzol (mainly humic) soils, while the other block consists of tertiary basalt with brown earth and gley soils. Water samples were collected from 52 stream sites and analysed for iron (Fe), manganese (Mn) and aluminium (Al) as well as a range of other chemical determinands known to affect metal solubility. Densities of metal-rich ochre deposit were determined for stream bed stone samples. Higher conductivities and concentrations of bicarbonate, alkalinity, calcium and magnesium occurred on basalt than on schist. Despite higher Fe and Mn oxide concentrations in basalt-derived non-humic soils, stream water concentrations were much lower and ochre deposit densities only one-third of those on schist overlain by humic soils. Neither rock nor soil type predicted Al concentrations, but pH and dissolved oxygen did. Peat-generated acidity and the limited acid neutralising capacity of base-poor metamorphosed schist have resulted in elevated concentrations of metals and ochre deposit in surface waters. [ABSTRACT FROM AUTHOR]

This study examines the phosphorus attenuation capacity of acid mine drainage (AMD) floc (also called ocher or sludge)-generated by neutralizing AMD with ammonia, lime, and sodium hydroxide-in the face of competition from two major organic companions, citrate and oxalate, of phosphorus in manure. Lime-treated floc (LF) was the least effective of the three flocs in attenuating both inorganic phosphorus and organic phosphorus (OP: represented by inositol hexaphosphate or phytate). Out of the remaining two flocs, ammonia-treated floc (AF) attenuated more inorganic phosphorus and less organic phosphorus than did sodium hydroxide-treated floc (SF). Increasing citrate:phosphorus molar ratio in the solution from 0:1 to 1:1 decreased the inorganic P attenuation capacity (IPAC) from 53 to 29 % in AF, 33 to 16 % in LF, and from 49 % to 27 % in SF at pH 4. The corresponding figures for organic P attenuation capacity (OPAC) were from 73 to 54 % in AF, 58 to 45 % in LF, and from 76 to 58 % in SF. Increasing oxalate:phosphorus molar ratio from 0:1 to 1:1 decreased IPAC and OPAC similarly, but to a lesser extent. The competitive influence of citrate and oxalate went on weakening with increase in pH. A likely increase in pH following prolonged manure application may undermine the competitive ability of citrate and oxalate. The study shows that manure P attenuation potential of waste of AMD treatment, notwithstanding the peer anion competition to P, warrants its effectiveness in controlling buildup of P in heavily manured soils. [ABSTRACT FROM AUTHOR]

Incidental losses of dissolved reactive phosphorus (DRP) to a surface waterbody originate from direct losses during land application of fertilizer, or where a rainfall event occurs immediately thereafter. Another source is the soil. One way of immobilising DRP in runoff before discharge to a surface waterbody, is to amend soil within the edge of field area with a high phosphorus (P) sequestration material. One such amendment is iron ochre, a by-product of acid mine drainage. Batch experiments utilising two grassland soils at two depths (topsoil and sub-soil), six ochre amendment rates (0, 0.15, 1.5, 7.5, 15 and 30 g kg mass per dry weight of soil) and five P concentrations (0, 5, 10, 20 and 40 mg L) were carried out. A proportional equation, which incorporated P sources and losses, was developed and used to form a statistical model. Back calculation identified optimal rates of ochre amendment to soil to ameliorate a specific DRP concentration in runoff. Ochre amendment of soils (with no further P inputs) was effective at decreasing DRP concentrations to acceptable levels. A rate of 30 g ochre kg soil was needed to decrease DRP concentrations to acceptable levels for P inputs of ≤10 mg L, which represents the vast majority of cases in grassland runoff experiments. However, although very quick and sustained metal release above environmental limits occurred, which makes it unfeasible for use as a soil amendment to control P release to a waterbody, the methodology developed within this paper may be used to test the effectiveness and feasibility of other amendments. [ABSTRACT FROM AUTHOR]

The archaeological site known as Toca do Enoque (geographical coordinates, 09° 14′ 65.3″ S 43° 55′ 62.5″ W) is a rock shelter located in the Serra das Andorinhas (Serra das Confusões National Park), rural area of the city of Guaribas, state of Piauí, Brazil. Several rupestrian paintings (anthropomorphic and zoomorphic motifs along with some pure graphisms), predominantly in red, are found on the sandstone walls. Charcoals, lithic materials, necklaces with teeth, animal bones, gastropod shells, ochres and human skeletons (dated from 6,220 ± 40 to 6,610 ± 40 years before present, BP) were identified in recent excavations in this shelter. Red and yellow ochre samples were collected from prehistoric funeral structures and analyzed with powder X-ray diffractometry, Fourier-transform infrared spectroscopy and Fe transmission Mössbauer spectroscopy at 298 K and 80 K. Mössbauer data indicate that the red ochre do contain predominantly hematite ( α-FeO) whereas goethite ( α-FeOOH) is the major mineral in the yellow ochre. [ABSTRACT FROM AUTHOR]

TR-FTIR spectroscopy is used to analyze the interaction of yellow ochre with a binding medium (linseed oil) and other pigments (orpiment and azurite). Spectra of four different samples of ochre are compared. Variations in the IR spectra of ochre resulting from drying it on various substrates are detected. Changes in spectra of the linseed oil upon its drying are analyzed. [ABSTRACT FROM AUTHOR]

The potential of thermogravimetric analysis (TG) as a tool for the characterisation of ochre paint used in indigenous Australian bark paintings has been investigated. TG has been combined with differential scanning calorimetry (DSC) and mass spectrometry (MS) to identify and quantify the main inorganic and organic components present in the paints. The results obtained were supported by comparison with infrared spectra and XRD data obtained for the same specimens. The potential of thermal methods for the characterisation ochres has been demonstrated, with subtle differences between small samples being able to be identified. [ABSTRACT FROM AUTHOR]

Behaviour of metals like Cu and Co was studied in nearly neutral (pH ≥ 6.4) mine drainage seepage in a stream downgradient of a tailing dam at Chambishi site in the Copperbelt of Zambia. They are attenuated by precipitation of ferruginous ochres that incorporate significant quantities of metals. Using chemical analysis, X-ray powder diffraction and Mössbauer spectroscopy, we show that the ochres are composed mostly of amorphous ferric hydroxide. Close to the seepage face, the total Fe content of ochres increases due to precipitation of amorphous ferric hydroxide, but total Fe in sediment decreases further downstream. The stream then flows through wetland (dambo) where the remaining fraction of metals is removed. During rainy periods, increased flow rate may result in re-suspension of ochres, increasing thus the mobility of metals. Major ions like sulphate are conservative at the start of the dry period (May), but gypsum may probably precipitate later at the end of the dry period. Sequential extractions of bulk sediments indicate that Mn behaves differently to Fe, with a trend of increasing Mn with distance from the tailing dam. There is much more Fe than Mn in residual (Aqua Regia) fraction, indicating that amorphous ferric hydroxides are transformed to more crystalline phases deeper in sediment. Environmental impact of mine drainage is relatively limited due to its neutral character. [ABSTRACT FROM AUTHOR]

Different analytical techniques were used for microstructural and compositional analysis of the ochre-coloured patinas that appear on the calcarenite substrate of monuments in the historical settings of Úbeda and Baeza (Spain). Optical microscopy, scanning electron microscopy–energy dispersive x-ray spectrometry (SEM-EDX), x-ray diffraction, Raman spectroscopy and attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR) were employed and a critical comparison of their experimental requirements, strengths and weaknesses is presented. The study focussed on two churches in Úbeda where patinas were widespread in ornamental elements. These films contained calcite as the principal component, and traces of dolomite and feldspars. Clear identification of calcium oxalate, mainly in the form of whewellite, was achieved by infrared and Raman spectroscopic studies. Results from texture, distribution and composition of the patinas in ornamental elements suggest that ancient treatments were applied for protection of Renaissance façades and consolidation of weathered older façades. The patinas were seldom found on supporting elements. Their different composition, apatite was found together with oxalates, and location may suggest a biogenic origin here. Gypsum crusts were sometimes found over the patinas. [ABSTRACT FROM AUTHOR]

As evident from archaeological excavation, ochre was widely used for ceremonial, mortuary, and other purposes around the world. However, the ancient meaning and procurement practices of ochre are not well understood. This study examines the variation in the major, minor and trace element patterns of ochre from iron oxide sources in southeastern Missouri to better understand the differences that may occur within and between sources. Samples were analyzed by instrumental neutron activation analysis (INAA), X-ray fluorescence spectroscopy (XRF), and the data were interpreted by Pearson’s linear correlation and multivariate analysis. The data indicate geochemical trends in ochre that satisfy the provenance postulate. [ABSTRACT FROM AUTHOR]

The article attempts to elucidate the composition and origin of the orange patina on the surfaces of the West-Porch of Salisbury Cathedral by comparison to other known patinas. It concludes that the patina of the Salisbury's Cathedral is a variant of the Greco-Latin empirical protective treatment that included bone as a hardening material. Nevertheless, it is also thought that the presence of the bones in the paste could be related to an aesthetical intention: gaining a warm tone for the original stone through the ochre colour of the bones.