Calcareous Content Research Articles

Correlation of Geotechnical and Mineralogical Properties of Lithomargic Clays in Uttara Kannada Region of South India

The present study explores the intricate relationship between the geotechnical and mineralogical properties of lithomargic clays in the Uttara Kannada region of south India. Lithomargic clays, characterized by their unique composition of clay minerals and calcareous content, play a crucial role in the geotechnical behavior of soils. The study aims to provide a comprehensive understanding of the interplay between the mineralogical composition and engineering characteristics of lithomargic clays, shedding light on their suitability for various construction and infrastructure projects. The research methodology involves a systematic analysis of lithomargic clay samples collected from different locations in the Uttara Kannada region. Geotechnical investigations, including particle size distribution, Atterberg limits, unconfined compressive strength (UCS), California bearing ratio (CBR) and triaxial tests, are conducted to assess the engineering properties of the clays. Concurrently, mineralogical analyses, such as X-ray diffraction (XRD) and scanning electron microscopy (SEM), are employed to identify and quantify the clay mineral constituents within the samples. The findings of this study reveal correlations between specific mineralogical features and geotechnical behaviors of lithomargic clays. Understanding these relationships is crucial for predicting the response of these clays to different engineering applications, including slope stability, foundation design and embankment construction. The research contributes valuable insights to the scientific and engineering communities, aiding in the informed utilization of lithomargic clays in geotechnical projects in the Uttara Kannada region and beyond. The outcomes of this investigation, such as the correlation of geotechnical properties with the variation in minerals in various sample locations, enhance our understanding of the complex nature of lithomargic clays, providing a foundation for more sustainable and effective engineering practices in the geologically diverse landscapes of south India.

Short- to Medium-Term Corrosion of Mild Steel in Highly Calcareous Seawaters: Effects of Calcium Carbonate Concentration, Coupon Orientation, and Nutrient Addition

Mild steels exposed to marine immersion conditions in which carbonate solubilities are exceeded, leading to deposition of calcareous material, have been shown to exhibit much-reduced corrosion rates compared with corrosion under conditions in which there is no exceedance of solubility limits and therefore no calcareous deposition. However, the differences in corrosion including the potential effect of microbiologically influenced corrosion (MIC) in these conditions have not been examined systematically in the literature. The study reported herein involves short- to medium-term marine immersion exposures (up to 18 month) of mild steel coupons in natural seawater (control) and in environments using the same seawater source dosed with (1) CaCO3, acting as an inorganic particulate suspension representative of that encountered in seawater with elevated calcareous content; and (2) a nitrate salt, acting as an industrial pollutant and bacterial nutrient source. The results show the extent to which the deposition of particulate CaCO3 from suspension in seawater onto and into the rusts reduces the rate of corrosion of mild steel; a rate that was found to be dependent on the coupon orientation within the seawater. Coupons that were permanently buried beneath a cap of settled CaCO3 particles exhibited a 70% reduction in corrosion rate compared with the representative control coupons. The results also show that for these exposure durations and conditions, while iron-related bacteria and sulfate-reducing bacteria populations were identified in high concentrations (respectively ∼1 × 106 cfu/g and ∼1 × 102 to 4 × 106 cfu/g, depending on coupon orientation) within the rust products themselves after 18 month of exposure, there was no clear evidence of MIC. These findings indicate that short and medium-term (nonaccelerated) studies of MIC for mild steel are insufficient or even misleading for the prediction of long-term corrosion rates in these environments.

Rubble Mines in the Environs of Veszprém (Bakony Region, Hungary)

In the Bakony Region, in the mines of dolomite (dolostone) surfaces between the settlements of Márkó and Pétfürdő (Várpalota), in rubble beds exposed by them and with the consideration of these, the process of rubble formation is studied here in order to interpret the characteristics of rubble beds (different thicknesses and vertical changes in grain size) in the studied area. The mines in the area (differentiated between old-school/traditional mining or mechanical mining) were classified with the consideration of mining methods. Rubble varieties were differentiated, the bedding of rubble beds was studied along profiles, and the elevation difference between mines of mechanical mining and Stream Séd was determined. The calcareous content and structure compactness of 124 samples originating from dolomite, rubble, and non-rubble in the Bakony Region were compared. The data prove that the rubble developed by dissolution. Dissolution might have been caused by both meteoric water and karstwater. The rubble of mines excavated by traditional mining mainly developed to the effect of the dissolution effect of meteoric water (the rubble beds are of coarser and coarser grain size downwards), while the mines excavated by mechanical mining were formed to the dissolution effect of karstwater (the rubble beds are coarser and coarser upwards). The formation of rubble by karstwater origin has not been mentioned in the literature yet. However, dissolution of meteoric water origin may also take place in the case of the latter, and dissolution of karstwater origin also plays a role in the development of mines excavated by traditional mining.

X-ray fluorescence (XRF) fingerprinting of Palaeogene deposits in Denmark

In this study, we test if cost-efficient X-ray fluorescence (XRF) analyses can be used to fingerprint Palaeogene clay and marl deposits in Denmark. A total of 67 samples from key sites in Denmark have been analysed. Our preliminary results indicate that it is possible locally within 10–30 km to distinguish between most of the Palaeogene units, but on a regional scale across Denmark, the units are not unique, and this probably reflects variations in clay mineralogy, grain size and calcareous content. Accordingly, we suggest that a comprehensive reference database is now needed if the full potential of the method is to be utilised, and this will ultimately result in more reliable geological models.

Stratigraphic Modelling of the Lower/Middle Oxfordian (Upper Jurassic) Outer Ramp Deposits from the NE Paris Basin (France)

We investigate herein the lateral and vertical lithological heterogeneities of the Lower/Middle Oxfordian deposits (“Terrain à Chailles” and “Marnes des Eparges” formations) in the north-eastern Paris Basin. This new detailed stratigraphic framework documents the evolution at high resolution of an outer ramp based on regional correlations in order to constrain the evolution of petrological properties between the clayey “Argiles de la Woëvre” Formation and the more calcareous “Marnes et Calcaires à Coraux de Foug Formation. The “Argiles de la Woëvre” Formation is targeted for the deep storage of nuclear waste in north-eastern France. Nine wells are correlated over the “Zone of Interest for Further Research” (ZIRA), defined by the French agency for radioactive waste management (Andra), with a resolution of 0.5–1.0 m. The architecture and the age control of these formations have been refined, revealing that the “Terrain à Chailles” Formation is characterised by a regular slightly inclined sedimentation gently deeping in the SW direction and shows a lithological evolution from silty claystones to an increased occurrence of its calcareous content towards the top (Lower Oxfordian, uppermost mariae and cordatum ammonite zones). The above “Marnes des Eparges” Formation, characterised by claystone limestone alternations, is assigned to the Middle Oxfordian (plicatilis ammonite zone), deposited during a slightly enhanced subsidence phase in the SE part of the basin and documented and associated with onlaps geometries on the more proximal areas. However, this change in geometry does not affect petrological properties over ZIRA, as this is not accompanied by lithological changes. The environmental factors controlling petrological heterogeneities over ZIRA are also discussed. The stepwise increase in the carbonate content and the decrease in the detrital content towards the Lower to Middle Oxfordian deposits was likely triggered by a climate change towards drier conditions, modulated by sea level changes on a ramp morphology. A major condensation phase encompassing most of the Lower Oxfordian cordatum ammonite zone is also highlighted. The occurrence of a maximum regressive surface associated with gentle slope topography is a probable trigger for condensation. Changes in geometries are, however, associated with the activity of the Metz Fault, which potentially had an influence on the subsidence rates of the basin at that time.

Foraminiferal Distribution Pattern and its Ecological Implications in the Koswari and Van Islands of the Tuticorin Group of Islands

Objectives: The present investigation attempts to map the foraminiferal distribution pattern, its ecological significance, and the elemental composition of the Koswari and Van islands. Methods: Foraminiferal distribution patterns (both planktic and benthic) were recorded, and textural and geochemical analyses were carried out in the present study. Findings: The coastal environments are generally highly dynamic regions of the earth that possess imprints of global climatic variations. The islands of the Gulf of Mannar emerged during the last interglacial period. These islands are getting eroded due to the long-term impact of coral mining and climatic changes. The excess removal of corals from Koswari Island adversely affected the live coral cover of the Island. The Van island is in proximity to the Tuticorin coastal city and one-fourth of the Island has already become submerged due to several natural and anthropogenic factors. Both the islands are affected by the world coral bleaching event witnessed from 2014-2017. This study is an attempt to record how the foraminiferal assemblages of Koswari and Van islands responded to the world coral bleaching event. In the present investigation, we identified fifteen benthic foraminiferal species and two planktic foraminiferal species from both islands. The foraminiferal assemblages mark the abundance of Neorotalia calcar, Quinqueloculina seminulum, Elphidium crispum, Amphistegina lessonii, and Rotalidium annectens. The main ecological parameters which govern the foraminiferal distribution in these islands are coral reef flats, carbonate environments, and shallow coastal waters. Neorotalia calcar and Quinqueloculina seminulum are recorded as the most abundant species of both Koswari and Van islands. N. calcar prefers macroalgal mat as substratum,while the frequent occurrence of deformed tests and stress-tolerant species such as Q. seminulum indicate the influence of pollution in the coastal area. These recorded species are considered characteristic reef benthic foraminifers which prefer coarse sandy substratum. The other abundant species are Elphidium crispum, Amphistegina lessonii, and Rotalidium annectens, which are widely distributed in the inner shelf sediments of Tamil Nadu and Kerala coasts. Textural attributes of the Koswari and Van islands reflect its high energy environment, and the geochemical signature shows the high calcareous content with typical coral reef foraminifera associated with such sediment nature. Novelty: The study tried to map the effect of the global coral bleaching event of 2016 on Koswari and Van islands of the Tuticorin group of Islands in the Gulf of Mannar using foraminifera as a proxy. Keywords: Foraminifera; Coral reefs; Ecology; Coral bleaching; Gulf of Mannar

Influence of calcareous nodules content on scaling effect in shear strength of cohesive soil containing calcareous nodules

The difference in the shear strength and other characteristics of the cohesive soil containing calcareous nodules (CSCN) between samples with large size and corresponding scaling size, which is called scaling effect, is significantly affected by its calcareous nodule content (CNC) of the gradation composition. However, current researches rarely reveal the influence of the CNC on the scaling effect in shear strength of samples. In this study, how and why the CNC affects the scaling effect in shear strength were explored. Then a method to reduce the scaling effect based on the reason for influence was proposed. Results show that the correlation between the scaling effect in shear strength and the CNC presents a step curve. This is attributed to that it is easier to form a skeleton effect in samples with scaling size for the same CNC. Considering the skeleton effect, a calculation model for the shear strength parameters of CSCN samples with large size is proposed to reduce the scaling effect. This paper demonstrates that the proposed calculation model provides an access to obtain calculated shear strength parameters of CSCN samples with large size by using measured results of samples with corresponding scaling size.

Suitability of calibrated X-ray fluorescence core scanning for environmental geochemical characterisation of heterogeneous sediment cores

Multi-element analysis of discrete samples via X-Ray fluorescence or inductively coupled plasma spectrometry is commonly used to characterise the composition of solid geo-materials for environmental geochemical characterisation. Conventional geochemical analysis of individual samples is time consuming and costly, which often results in low-resolution sampling with the danger of missing crucial information. X-ray fluorescence Core Scanning (XCS) provides an alternative method to obtain elemental information, which can be potentially used quantitatively when combined with the Multivariate Log-ratio Calibration (MLC) approach. The suitability of the XCS-MLC method was tested for environmental geochemical characterisation on four terrestrial Holocene-Pleistocene sediment cores that have a variable lithology (clay, sand, peat, with variable calcareous content), were stored at ambient room conditions and scanned post sampling. Element contents based on XCS-MLC and conventional geochemical analysis proved to be comparable (R2 > 0.5) for Al, Ca, Cr, Fe, K, Sr, Mn, Ni, Pb, Rb, S, Si, Ti, Zn, Zr, and also for Br as proxy for organic matter. For As, Cu and Ba the correlations were less satisfactory (R2 < 0.4) partially due to the low concentration ranges present in these sediments. For some samples aberrant high values for Ca, Fe, S, and Zn were introduced by application of the MLC method due to extrapolation outside the MLC-calibrated range. Similar to the conventional element analyses the XCS-MLC approach has the ability to retrieve quantitative element contents and enable the calculation of mineral phases such as calcium carbonate and reactive iron species. Both conventional and XCS-MLC methods reproduced the average contents per sediment layer and mostly their ranges. Nevertheless, local features such as diagenetic enrichments were not always evident from the discrete samples. Thus, a better understanding of the spatial heterogeneity in geochemical and mineralogical contents within the sediment layers was obtained with the additional XCS-MLC data. Our study shows that also cores stored under unfavourable conditions can be reliably re-analysed with XCS to generate high resolution records.

Root Morphological Adjustments of Crops to Improve Nutrient Use Efficiency in Limited Environments

ABSTRACT A large portion of applied phosphorus fertilizer undergoes adsorption/fixation due to high pH and calcareous content of soils and becomes unavailable for plant uptake. Plants undergo many morphological and physiological adaptations to overcome the low phosphorus availability. Many plants modify their root morphology and biomass in low phosphorus environments by exploring a greater more soil volume. This study measured plant root morphological and biomass adaptation at different levels of applied phosphorus and its effect on phosphorus use efficiency. Results showed that phosphorus use efficiency, root volume, number of root tips, root surface area, root length, and root length were higher at a low levels of phosphorus with average root diameter and root phosphorus were reduced at lower levels of applied phosphorus. Maize performed better in case of root adaptation; however, phosphorus use efficiency was higher for wheat. Both plant species responded to low phosphorus application by enhancing their root morphology and root production with an increase in phosphorus use efficiency. A significant correlation (r2 ≥ 60%) was observed between root morphology and phosphorus use efficiency. Plants that explore more soil volume by modifying root morphology were found to have low critical phosphorus requirements by efficiently utilizing phosphorus and amount of phosphorus fertilizer application is reduced.

A new perspective of the forming of calcareous layers above oil sand through the analysis of paleo-environment

Lithology and architecture of alluvial fans can become too complicated, influenced by rapid deposition of sediments near the provenance. The paleo-environment of oil sand can be often better observed through drilling cores and well loggings, rather than outcrops and seismic attributes, for the outcrops are usually covered by modern deposition and not allowed to be exploited while seismic waves often cannot detect layers too shallow above 200m. Reservoirs are mostly buried at extremely shallow depths from 0 to 500m. Oil is mostly found within a mixture of oil sand and carbonates. The calcareous layer, which is steady and widespread with a thickness of 0.5∼2m, is found above the oil sand layer in all wells. The limestone above oil sand layer shows a significant change of facies and paleo-environment. Only sandstone with abundant oil can easily form the carbonates above oil sand, which means the calcareous content is a result of temp and pressure change at the edge of oil layers. As a vivid description, the calcareous content is similar to the environment of calculus, which also underwent a change of pressure&temp with a concentration of CO2. These phenomena can also be observed in micro-level or use chemical reactions to explain why both calculus and calcareous can form after they underwent temp and pressure change accompanied with oil.

The Early Silurian Sedimentary Environment of Middle-Upper Yangtze: Lithological and Palaeontological Evidence and Impact on Shale Gas Reservoir

The organic-enriched thick shale at the bottom of Longmaxi Formation is laterally continuous distributed and has been proven to be of good production capability in Fuling of Upper Yangtze. Uplifts that developed during the sedimentation influenced the reservoir characteristics by taking control of the sedimentary environment and provenance. The sedimentary environments are mainly deep-water shelf, shallow-water shelf, and tidal flat. By analyzing reservoir characteristic of these three environments, the deep-water shelf, which dominated the early stage of sedimentation, formed a high-quality reservoir with high TOC (Total Organic Carbon) content, porosity, and brittleness, while the environment was maintained around the basin centre until the Early Silurian. The shales deposited under the shallow-water environment were of low porosity because of the increasing calcareous and argillaceous contents. Sediments which formed on the tidal flat were arenaceous and of the lowest TOC content as the organic preservation conditions deteriorated. The good correlation of graptolite abundance and TOC content, and high porosity within graptolite fossils emphasize the importance of palaeontological development. The argillaceous cap over the Longmaxi shale is of good sealing capability, and the continuous sedimentation zone along southern Sichuan–eastern Chongqing is the best optimized hydrocarbon-bearing system. However, a weak interface on the discontinuity is the potential lateral pathway for gas diffusion at Northern Guizhou and Western Hunan, but on the southeast margin where the dark shale and the tidal sandstone contact, it promises to form a tight gas reservoir.

Recycling of sludge from drinking water treatment as ceramic material for the manufacture of tiles

Currently, the main destination for sludge from Drinking Water Treatment Plants (DWTP) is its disposal in sanitary landfills. However, its chemical composition and physical properties make it suitable for use as a building material. In this work, the use of spray-dried DWTP sludge on the manufacture of cladding ceramic material for the production of tiles as an alternative to the final disposal of sludge is analysed. The work is based on an experimental study carried out on a laboratory scale. Clay and spray-dried DWTP sludge (average humidity of 3 wt%) were mixed with different percentages of sludge (from 0 to 70 wt%) to form a slurry to be extruded. Specimens were then fired up to 980 °C. Chemical and mineralogical composition of raw materials was analysed. Technical properties of the ceramic samples were determined. The results obtained showed that the DWTP sludge became a powder with low organic content and a high-micronised calcareous content (14.4 wt% calcium oxide). The ceramic samples had a high open porosity, which increases with the increase in sludge addition percentage. They also had a high dilatometric coefficient. Taking into account these two properties, a possible application of this material would be the manufacture of glazed tiles. The resulting ceramic material does not pose any environmental problem, far surpassing the NEN-7345 leaching test and accelerated degassing tests (outgassing PSS-01-702 and offgassing PSS-01-729 standards of the European Space Agency).

Prospect analysis of the deep marine shale gas exploration and development in the Sichuan Basin, China

The shale gas exploration and development in Sichuan Basin had achieved a major breakthrough remarkably. However, the business development focused on the marine shale gas in shallow layers (vertical depth < 3500 m) of the Wufeng Formation-Longmaxi Formation alone. Therefore, the deep shale gas (vertical depth > 3500 m) business development in Wufeng Formation-Longmaxi Formation is the key to the rapid growth of shale gas production in the Sichuan Basin. In the literature, authors analyzed the geological characteristics of the deep shale gas of the Wufeng Formation - Longmaxi Formation in southern Sichuan Basin through particular dissection and analysis of deep wells in comparison to the shallow layers. The thickness of organic-rich shale in the deep region of southern Sichuan Basin measures to be more than 120 m, which is larger than that of the shallow layers in Fuling area. The vertical TOC change remains constant whereas the thickness of high-quality shale is approximately forty meters in both regions. Nevertheless, the RO is higher in the deep region of southern Sichuan Basin. The calcareous content of the organic shale increases while the silicon content decreases from the Fuling area down as it gets deeper into the region in southern Sichuan Basin. It is quite evident in research that the shales in the Wufeng Formation – Longmaxi Formation of the deep to shallow layers of southern Sichuan that there are not many differences in depositional environment, lithology, TOC, etc. However, there are four major differences: (1) The porosity of shale in the deep region of southern Sichuan Basin is higher than that in Fulin gas field due to the corrosion pore. (2) The gas-bearing properties are better in the deep regions of southern Sichuan Basin because they have better preservation condition compared to that of the shallow region of Fuling. (3) However, gas-bearing properties are worse in the local region of stronger structure deformation and the basin boundary fault zone. (4) The shale gas resources in the deep regions of southern Sichuan Basin are great and have wide prospects for exploration and development. In order for a breakthrough to be generated in deep shale gas commercial development in the soonest possible time, authors propose the following: utilize strengthening evaluation of small layer contrasting so as to explain fine structure and predict fracture; strengthen the research on drilling and fracturing technology for deep shale gas; strengthen research on wells column; and support technology for efficient production of shale gas.

Lithostratigraphy and physical properties of lacustrine sediments of the last ca. 150 kyr from Chalco basin, central México

The recognition of past climatic fluctuations in sedimentary sequences in central Mexico is relevant for understanding the forcing mechanisms and responses of climatic system in the northern American tropic. Moreover, in this active volcanic setting the sedimentary record preserves the history of past volcanic activity. Climatic and environmental variability has been documented for the last tenths of thousands of years from the upper lacustrine sediments in Chalco basin. A series of cores drilled down to 122 m depth in this basin offer a long, continuous and high resolution record of past climatic changes of the last ca. 150 kyr in this region. Here we present the detailed lithostratigraphy and some physical properties (magnetic susceptibility and density) of the master sequence. Sedimentary components and their abundance were identified and quantified in smear slides and direct core observations. Age model is based on 13 14C and one 230Th/U dates. Based on their facies association seven lithostratigraphic units were defined, which reflect the main stages of lake Chalco evolution. These phases closely match the marine isotopic stages. The data reveal that at the end of MIS6 Chalco was a relatively deep and stratified freshwater lake. During MIS5 the depositional environment fluctuated between low lake stands to marshy and marginal playa settings with sporadic flooding events, and severe arid periods resulted in aerial exposure of lake sediments. Low lake stands persisted during MIS4 and MIS3, with minor fluctuations towards slightly deeper phases. The Last Glacial Maximum (LGM) and the deglacial period (21-13 kyr) are characterized by intense volcanism. The early and mid-Holocene high calcareous content and alkaline-subsaline lake suggest dry conditions. The fluctuations of lake levels inferred provide the basis for future paleoclimatic works.

Correlation of Spatial Variability of Soil Macronutrients with Crop Performance by Using Satellite and Remote Sensing Indices for Site Specific Agriculture: Chakwal Region

Site-specific agriculture includes the application of soil on variable areas rather than the whole field and requires the knowledge of spatial variability of soil nutrients in the area. A survey was conducted to find out the spatial variation of soil macronutrient, to prepare the soil fertility maps and to correlate soil nutrients with NDVI values, at University Research Farm, Koont, Chakwal. Soil samples were collected and analyzed for soil macronutrient (NO3- N, P, K, SO4-S and CaCO3) concentration through standard procedures. Obtained data were analyzed by using GIS and ordinary statistics to predict the spatial variability and preparation of digital maps of the soil macronutrients. NDVI values were calculated by acquiring the cloud free landsat images of study area to correlate with soil macronutrients. The results showed that, NO3-N and Available P were deficient in study area and were having the mean value of 7.54 mg kg-1 and 6.64 mg kg-1 respectively. K and SO4-S were in satisfactory ranges and were having average values of 130.3 mg kg-1 and 8.69 mg kg-1 respectively. Study area was classified as moderately calcareous soil and lime content were having the mean value of 7.88%. Geostatistical analysis showed that NO3-N and available P were strongly spatial dependent while K, SO4-S and CaCO3 were moderately spatial dependent. Pearson correlation analysis among NDVI values and soil parameters showed that NO3-N, P, K and CaCO3 were significantly positively correlated with NDVI values whereas SO4-S showed non-significant positive correlation with NDVI values. Study recommended that spatial variability of soil properties should be taken in account in decision making processes regarding farm operations such as fertilizer application, more studies on different spatial scale should be conducted and use of such techniques in profitable and sustainable site-specific agriculture should be promoted.

Using change-point models to estimate empirical critical loads for nitrogen in mountain ecosystems

To protect ecosystems and their services, the critical load concept has been implemented under the framework of the Convention on Long-range Transboundary Air Pollution (UNECE) to develop effects-oriented air pollution abatement strategies. Critical loads are thresholds below which damaging effects on sensitive habitats do not occur according to current knowledge. Here we use change-point models applied in a Bayesian context to overcome some of the difficulties when estimating empirical critical loads for nitrogen (N) from empirical data. We tested the method using simulated data with varying sample sizes, varying effects of confounding variables, and with varying negative effects of N deposition on species richness. The method was applied to the national-scale plant species richness data from mountain hay meadows and (sub)alpine scrubs sites in Switzerland. Seven confounding factors (elevation, inclination, precipitation, calcareous content, aspect as well as indicator values for humidity and light) were selected based on earlier studies examining numerous environmental factors to explain Swiss vascular plant diversity. The estimated critical load confirmed the existing empirical critical load of 5–15 kg N ha−1 yr−1 for (sub)alpine scrubs, while for mountain hay meadows the estimated critical load was at the lower end of the current empirical critical load range. Based on these results, we suggest to narrow down the critical load range for mountain hay meadows to 10–15 kg N ha−1 yr−1.

Phosphorus Adsorption Isotherm: A Key Aspect for Effective Use and Environmentally Friendly Management of Phosphorus Fertilizers in Calcareous Soils

ABSTRACTCrop response to the phosphorus (P) application is often erratic in most soil types in the world. In Algeria, there is no information on the P behavior in calcareous soils. The purposes of this work were to investigate the degree of P fixing capacity and to predict P fertilizer requirements of crops according to calcareous levels in the soil. Soil samples (at 0–30 cm depth) were collected and spiked with 0, 25 and 50% of lime (CaCO3). Phosphate sorption curves were well fitted to the Freundlich equation. Results indicated that the calcareous level was predominantly controlled the P sorption indices [sorption capacity (a), and P sorption energy (n)] to affect the estimation of external d P requirement (EPR0.2) and P fertilizer rates. The understanding of P sorption and desorption by soils and extrapolating the developed relationship between soil calcareous contents and P fertilizer rates would be quite promising and accurate approach for the economic and effective use of P fertilizers in calcareous soils of Algeria.

Caracterização de argilas calcárias utilizadas na produção de revestimentos cerâmicos no Estado de Sergipe - Brasil

Resumo O presente trabalho tem por objetivo caracterizar quatro argilas diferentes utilizadas na produção de revestimento cerâmico do tipo BIIb no Estado de Sergipe, Brasil. As argilas foram caracterizadas por difração de raios X, fluorescência de raios X, análise termogravimétrica, análise térmica diferencial, distribuição de tamanho de partículas, limites de Atterberg e dilatometria. A partir dos resultados obtidos foi possível detectar concentrações de calcita entre 1,1 e 13,7%, a depender da origem da argila. Esta informação é determinante para ajustes no ciclo de queima e previsão da energia mínima para que a sinterização ocorra. Foram produzidos corpos de prova por prensagem uniaxial em matriz retangular de 120 mm x 56 mm x 6 mm a uma pressão de 28 MPa, os quais foram queimados a 1130 oC com ciclo de queima de 23 min e patamar de 3 min. Os corpos de prova foram caracterizados quanto à absorção de água e módulo de ruptura à flexão, e sua microestrutura foi investigada por microscopia eletrônica de varredura. Através dos resultados, foi possível confirmar a correlação entre a formação de fase líquida e redução de porosidade nos corpos cerâmicos sinterizados a 1150 oC. As energias de ativação para o processo de sinterização foram determinadas a partir dos ensaios dilatométricos e os resultados mostraram que, à medida que se diminui o teor de calcário combinado com o aumento do teor de materiais fundentes, a sinterização ocorre em temperaturas mais baixas, resultando em menores gastos energéticos no processo de produção.

Effect of Incubation Period of Phosphorus Fertilizer on some Properties of Sandy Soil with Low Calcareous Content, Southern Algeria

Effect of Incubation Period of Phosphorus Fertilizer on some Properties of Sandy Soil with Low Calcareous Content, Southern Algeria

A Comparative Study on Production of Autoclaved Aerated Concrete by Coal Gangue Fly Ash

In this paper, compared with common fly ash, the low-silicon coal gangue fly ash is used to produce fly ash autoclaved aerated concrete. The influences of water binder ratio, coal gangue fly ash content, calcareous content and conditioning agents on the compressive strength of the autoclaved aerated concrete are investigated. The results indicate the coal gangue fly ash has different properties from the common fly ash such as its granule appearance and the activity as AAC siliceous raw material. It is noting that the coal gangue fly ash can also be used to prepare AAC blocks by optimizing the raw material formulation and procedure and its B05 product can reach the China top industrial standard.