An Experimental Study on Clay and Sand Mixes to Develop a Non-Linear Homogenized Model for Earth Construction Materials

Due to its ecological interest and large availability, a renewed attention is paid to earth as building material. Indeed, raw earth consumes CO2 only during its processing and transportation, and it provides a natural hygrothermal comfort. However, its mechanical properties are highly linked to its composition, which causes an important variability of performances. That is why any soil has to be characterized before being used as a building material. The aim of this study is to propose a model able to predict the hydromechanical behavior of a reconstituted soil according to its composition. As earth is a heterogeneous material, the model is based on homogenization procedures. The sand is considered as spherical inclusions inside a clay matrix. The particularity of the model stands to consider both positive and negative effects of volume variation and mechanical properties of clay under hydric variations. The model parameters are determined according to an original experimental campaign, which is conducted on various mixes of a single type of clay (kaolinite) and of sand, and water. The experimental study provides some mechanical properties of the mixes versus water content and sand content to test the ability of the homogenization model to assess the main properties of this material.

The Control of Diagenesis and Mineral Assemblages on Brittleness of Mudstones

The variation in mineral composition will affect the rock brittleness, thus the change of mineral assemblages during diagenesis has a potential control on the brittleness of mudstones. In this study, thin section, X-ray diffraction (XRD), and Scanning Electron Microscope (SEM) analyses were used to investigate compositional and microscopic features of mudstones. With the enhancement of diagenesis, three mineral assemblages were divided due to the diagenetic evolution of minerals. Quartz, feldspar, dolomite, chlorite, and illite were regarded as brittle minerals and (quartz + feldspar + dolomite + illite + chlorite)/(detrital mineral + carbonate + clay mineral) was defined as the brittleness evaluation index The mudstone brittleness changed slightly during early diagenesis but increased gradually with enhancement of diagenesis in the late diagenesis stage. Quartz and feldspar were scattered above the clay matrix and the contact of grains was limited, therefore, the contribution of detrital minerals to the brittleness was affected by the properties of clay minerals. The diagenetic transformation of clay minerals resulted in the reduction of ductile components (smectite/I-Sm and kaolinite) and increase of brittle components (illite and chlorite), leading to the enhancement of integral rigidity of the mudstones. Meanwhile, the improved crystallization of carbonate in late diagenesis stage enlarged the carbonate grains which resulted in rigid contact between grains. These results highlighted the influence of diagenesis on mudstone brittleness. Therefore, for evaluation of mudstone brittleness, attention should be paid to the diagenesis process besides mineral composition.

Volcanic Tuff as Secondary Raw Material in the Production of Clay Bricks

The present work examines an innovative manufacturing technique for fired clay bricks, using tuff as a secondary raw material. Samples were made of clay and tuff (0–30 wt.%) fired at 900 to 1100 °C. The chemical and mineralogical compositions and physical and thermal analyses of raw materials were investigated by using SEM-EDS, RX and DTA-TG curves. The samples were analysed from the mineralogical, technological and mechanical points of view. The result show that the tuff’s presence in the clay mixtures considerably reduced the shrinkage of the product during the firing process, and the manufactured samples were of excellent quality. The compressive strength of the bricks varied from 5–35.3MPa, being influenced by the tuff content, clay matrix properties and firing temperatures. Finally, the heat demand for increasing the temperature from room to the firing temperature of the sample with 10% tuff content was 22%.

The Aztec Siltstone: an Upper Devonian Alluvial Plain Red Bed Sequence, Southern Victoria Land, Antarctica

<p>The Aztec Siltstone (late Devonian) crops out for 150 km along the Transantarctic Mountains, between the Mawson and Mulock Glaciers of southern Victoria Land, Antarctica. It is the uppermost formation of the Taylor Group, the lower of the two subdivisions of the Beacon Supergroup of southern Victoria Land. The formation consists largely of fine to medium-grained sandstone, and greyish red (10R 4/2), grey (N5), and greenish grey (5G 6/1) siltstone and claystone. Other lithologies include carbonaceous siltstone and claystone, limestone and intraformational conglomerate. Conchostracans, fish fossils, plant fragments, and gypsum lenses are present also. Cross-stratification, horizontal stratification, channelling, and "fining-upwards" cycles indicate deposition from shallow, high sinuosity (tortuous), meandering streams that migrated laterally across a broad alluvial plain. The sandstone beds are laterally accreted channel deposits, whereas the siltstone and claystone beds represent overbank deposition by vertical accretion in the interchannel areas of the floodbasin. Other floodbasin deposits include lacustrinal sediments from pluvial ponds and ox-bow lakes, and palustrinal sediments from the backswamps. Overbank deposition of bed load material formed levees, and stream avulsion and crevassing during flood stage produced crevasse-splay deposits. The sandstone beds are quartzarenites, with detrital grains consisting largely of plutonic quartz; other grains include chert, feldspar, metamorphic quartz and a trace of heavy minerals. Sandstone textures average fine-grained and well sorted, although sandstone with textural inversion is common. Compositional and textural characteristics indicate that the sandstone is a product of the reworking of older quartzarenite in the source area. Subaerial exposure was a feature of the fine-grained floodbasin sediments; the evidence includes the abundance of mudcracks, and a variety of soil features. The latter include extensive kankar ('calichea') horizons, pseudo- or wavey bedding structures, a compositional and textural similarity to modern soils, vein networks (considered to be a product of deep cracking in the unconsolidated. substratum), burrowing, and root horizons with in some cases associated plant fragments. The kankar ('calichea') suggests that there was a period of prolonged subaerial exposure and soil development which followed the deposition of fine-grained, fine member lithologies of the "fining upwards" cycles. This period was probably in the range 5,000 to 50,000 years. The Aztec Siltstone is a typical "variegated" red-bed sequence, containing interbedded red and drab fine-grained lithologies. The fine-grained drab lithologies consist of quartz grains set in a matrix of green illitic and chloritic clay. The colour in the interbedded red and grey siltstone and claystone results from a haematite pigment, which in the red samples is present in a concentration sufficient to completely mask the green colour of the clay matrix. The reddening is believed to have been a penecontemporaneous process that took place in the floodbasin sediments during their prolonged subaerial exposure under a hot and seasonally wet and dry (savanna) climate. The haematitic pigment was derived from the in situ and progressive dehydration of detrital amorphous and poorly crystalline brown hydrated ferric oxide in those sediments which maintained an oxidizing environment and were above the ground-water table during the dehydration process. Sediments which remained in a water-logged state, below the water table, and in association with organic matter, were invariably reduced and lost their iron oxide in solution. Later post-depositional reduction of some red lithologies produced reduction spheres and channels, reduced burrows and vein networks, and the reduced layers immediately underlying the scoured surface at the base of the channel sandstones. Some chemical redistribution of iron contributed to the variegated and mottled horizons of the formation. The mineral composition of adjacent red and drab lithologies is essentially the same except for the haematite constituent. The red average 5.86 ([delta] = 1.09) percent total Fe (as Fe2O3), of, which 3.01 ([delta] = 0.63) percent is as haematite pigment, 1.57 percent Fe2O3 is in a combined form (probably as ferric silicates), and 1 14 ([delta] = 0.57) percent is as FeO. The green average 3.65 ([delta] = 1.81) percent total Fe (as Fe2O3) of which approximately 0.27 percent is as haematite pigment, approximately 1.4 percent Fe2O3 is in a combined form, and 1.77 ([delta] = 1.37) percent is as FeO. In the majority of the green lithologies the free ferric oxide (as haematite or hydrated ferric oxide) was removed in solution during reduction, and at the same time minor amounts of clay matrix were also leached out.</p>

The Aztec Siltstone: an Upper Devonian Alluvial Plain Red Bed Sequence, Southern Victoria Land, Antarctica

<p>The Aztec Siltstone (late Devonian) crops out for 150 km along the Transantarctic Mountains, between the Mawson and Mulock Glaciers of southern Victoria Land, Antarctica. It is the uppermost formation of the Taylor Group, the lower of the two subdivisions of the Beacon Supergroup of southern Victoria Land. The formation consists largely of fine to medium-grained sandstone, and greyish red (10R 4/2), grey (N5), and greenish grey (5G 6/1) siltstone and claystone. Other lithologies include carbonaceous siltstone and claystone, limestone and intraformational conglomerate. Conchostracans, fish fossils, plant fragments, and gypsum lenses are present also. Cross-stratification, horizontal stratification, channelling, and "fining-upwards" cycles indicate deposition from shallow, high sinuosity (tortuous), meandering streams that migrated laterally across a broad alluvial plain. The sandstone beds are laterally accreted channel deposits, whereas the siltstone and claystone beds represent overbank deposition by vertical accretion in the interchannel areas of the floodbasin. Other floodbasin deposits include lacustrinal sediments from pluvial ponds and ox-bow lakes, and palustrinal sediments from the backswamps. Overbank deposition of bed load material formed levees, and stream avulsion and crevassing during flood stage produced crevasse-splay deposits. The sandstone beds are quartzarenites, with detrital grains consisting largely of plutonic quartz; other grains include chert, feldspar, metamorphic quartz and a trace of heavy minerals. Sandstone textures average fine-grained and well sorted, although sandstone with textural inversion is common. Compositional and textural characteristics indicate that the sandstone is a product of the reworking of older quartzarenite in the source area. Subaerial exposure was a feature of the fine-grained floodbasin sediments; the evidence includes the abundance of mudcracks, and a variety of soil features. The latter include extensive kankar ('calichea') horizons, pseudo- or wavey bedding structures, a compositional and textural similarity to modern soils, vein networks (considered to be a product of deep cracking in the unconsolidated. substratum), burrowing, and root horizons with in some cases associated plant fragments. The kankar ('calichea') suggests that there was a period of prolonged subaerial exposure and soil development which followed the deposition of fine-grained, fine member lithologies of the "fining upwards" cycles. This period was probably in the range 5,000 to 50,000 years. The Aztec Siltstone is a typical "variegated" red-bed sequence, containing interbedded red and drab fine-grained lithologies. The fine-grained drab lithologies consist of quartz grains set in a matrix of green illitic and chloritic clay. The colour in the interbedded red and grey siltstone and claystone results from a haematite pigment, which in the red samples is present in a concentration sufficient to completely mask the green colour of the clay matrix. The reddening is believed to have been a penecontemporaneous process that took place in the floodbasin sediments during their prolonged subaerial exposure under a hot and seasonally wet and dry (savanna) climate. The haematitic pigment was derived from the in situ and progressive dehydration of detrital amorphous and poorly crystalline brown hydrated ferric oxide in those sediments which maintained an oxidizing environment and were above the ground-water table during the dehydration process. Sediments which remained in a water-logged state, below the water table, and in association with organic matter, were invariably reduced and lost their iron oxide in solution. Later post-depositional reduction of some red lithologies produced reduction spheres and channels, reduced burrows and vein networks, and the reduced layers immediately underlying the scoured surface at the base of the channel sandstones. Some chemical redistribution of iron contributed to the variegated and mottled horizons of the formation. The mineral composition of adjacent red and drab lithologies is essentially the same except for the haematite constituent. The red average 5.86 ([delta] = 1.09) percent total Fe (as Fe2O3), of, which 3.01 ([delta] = 0.63) percent is as haematite pigment, 1.57 percent Fe2O3 is in a combined form (probably as ferric silicates), and 1 14 ([delta] = 0.57) percent is as FeO. The green average 3.65 ([delta] = 1.81) percent total Fe (as Fe2O3) of which approximately 0.27 percent is as haematite pigment, approximately 1.4 percent Fe2O3 is in a combined form, and 1.77 ([delta] = 1.37) percent is as FeO. In the majority of the green lithologies the free ferric oxide (as haematite or hydrated ferric oxide) was removed in solution during reduction, and at the same time minor amounts of clay matrix were also leached out.</p>

Study on Sulfide Oxidation in a Clay Matrix by the Hyphenated Method

The requirement of a ceramic product with high technical and aesthetic performance makes it necessary to select and control raw materials to avoid losses caused by low-quality products. Many defects have their origin in impurities present in clay minerals such as sulfides and sulfates. It is important to study the oxidation, decomposition, and pyrolysis reactions that affect these minerals and their dependence on environment conditions (humidity and temperature) during the extraction and beneficiation of clay minerals in an open pit mine. The development of hyphenated techniques coupling mass spectrometry with a thermal analysis instrument provides information that is not available from either technique alone, such as decomposition behavior and the determination of emissions with a lower limit of detection. The evolution of sulfur dioxide from the oxidation of different sulfides provides information on the in situ oxidation and decomposition reactions that happen when a thermal treatment is applied. The results obtained show important differences in the reactions that take place in sulfides when they are stored under different environmental conditions. Specifically, the general tendency is that the sulfurs stored under high relative humidity show a decrease in the intensity of the emission as well as changes in the onset of the peak emission.

Contrasting Genesis of Lateritic Bauxite on Granodioritic and Andesitic Rocks of Mempawah Area, West Kalimantan

The lateritic bauxite deposits in the Mempawah area, West Kalimantan, were formed by the chemical weathering of Cretaceous granodioritic and andesitic rocks. They occurred locally on the low hills surrounded by swampy areas. Detailed surface geological mapping, test pits, mineralogical and geochemical analyses were performed to determine the characteristics and genesis of bauxite from different parent rocks. From bottom upward, the deposits are composed of fresh parent rocks, clay or pallid zone, bauxite zone with a few sparse ferricrete at the top of the bauxite zone, and soil. Bauxite derived from granodiorite exhibits brownish-red, massive, boulder to gravel-sized concretion in clay matrix and is composed of predominant gibbsite with subordinate kaolinite, quartz, goethite, and a minor amount of magnetite and hematite. In contrast, bauxite derived from andesitic rocks exhibits reddish-brown and is composed of predominant goethite. During the leaching process, SiO2 as a mobile compound decreased significantly in neutral pH, while Al2O3 and Fe2O3 precipitated as residual materials to form bauxite concretion. The enrichment anomaly of bauxite derived from andesitic rocks is caused by physio-chemical changes from hydrothermal alteration. Bauxite was formed by indirect bauxitization through the leaching of primary minerals under a tropical-humid climate.

Sedimentology, petrography, and deposition of the Upper Cretaceous Codell Sandstone in the Denver Basin

We integrate new and previous stratigraphic and petrographic data for the mid-Turonian Codell Sandstone to interpret its provenance, depositional characteristics, and environments. Our focus is on sedimentologic, X-ray diffraction, and X-ray fluorescence analyses of cores and thin sections spread throughout the Denver Basin, augmented by interpretation and correlation of well logs, isopach maps, outcrops, and provenance data. Although we treat the Codell as a single mappable unit, it actually consists of two geographically disjunct sandstone packages separated by a southwest-northeast-trending gap, the NoCoZo, short for No Codell Zone. The Codell is everywhere capped by a significant unconformity and across much of the northern Denver Basin rests unconformably on the underlying shales of the Carlile Shale. In the southern Denver Basin, the Codell commonly contains two parasequences, each of which becomes less muddy upward. Biostratigraphic and geochonologic data suggest that the unit represents deposition over a relatively brief time, spanning ~0.4 Ma from ~91.7 to ~91.3 Ma. The Codell is predominantly a thin (<50 ft) sheet-like package of pervasively bioturbated coarse siltstone and very fine-grained sandstone dominated by quartz and chert grains 50 to 100 μm in diameter. The unit is more phosphatic than the underlying members of the Carlile Shale, and its grain size coarsens to medium-grained in the northern part of the basin. An unusual aspect of the Codell across our study area is the generally excellent grain sorting despite the presence of an intermixed clay matrix. This duality of well sorted grains in a detrital clay matrix is due to the bioturbation that dominates the unit. Such burrowing created a textural inversion that obscures most of the unit’s primary sedimentary structures, except for thin intervals dominated by interlaminated silty shale and very fine sandstone. A relatively widespread and unburrowed example of this bedded facies is preserved in a thin (<10 ft) interval that extends across most of the northern Denver Basin where it is informally called the middle Codell bedded to laminated lithofacies. Sparse beds with hummocky or swaley cross-stratified and ripple cross-laminated fine-grained sandstone are present locally in this bedded facies. We hypothesize that Codell sediments were derived from a major deltaic source extending into the Western Interior Seaway from northwestern Wyoming, and that the Codell was deposited and reworked southward on the relatively flat floor of the Seaway by waxing and waning shelf currents as well as storms and waves. Codell sediments were spread across an area of more than 100,000 mi2 in this epeiric shelf system that spans eastern Colorado, southeastern Wyoming, western Kansas, parts of Nebraska and beyond.

To be or not to be local: a provenance study of archaeological ceramics from Shahr-i Sokhta, eastern Iran

Findings from the archaeological site of Shahr-i Sokhta in eastern Iran include a wide range of undecorated, monochrome, and polychrome ceramics with gray, red, and buff-colored bodies that date back to a period spanning from 3200 to 1800 B.C.E. Given the large number and variety of ceramics unearthed from Shahr-i Sokhta, the provenance of these wares has remained a subject of controversy. Based on compositional data obtained from quantitative wavelength dispersive X-ray fluorescence (WDXRF) spectroscopy studies and petrographic observations, findings from this study provide information that can be used to determine whether the ceramics from Shahr-i Sokhta were manufactured locally or were imported from elsewhere. We show here that the chemical components of a large group of ceramics with gray, red, and buff-colored bodies are similar to those found in local clay sources and kiln wasters, suggesting local production of these wares. However, one group of red and gray-colored wares demonstrated entirely different chemistry, suggesting a different origin. In support of the quantitative WDXRF data, petrofabric analysis of the first group of buff, gray, and red wares revealed poorly sorted basaltic clasts similar to those found randomly distributed in the matrix of local clays. By contrast, the non-local gray and red wares exhibited fine-grained clay bodies with sorted distribution of fine-grained quartz within the clay matrix.