Combined Water Content Research Articles

Thermogravimetry on calcined mass basis — hydrated cement phases and pozzolanic activity quantitative analysis

When cement hydrated compositions are analyzed by usual initial mass basis TG curves to calculate mass losses, the higher is the amount of additive added or is the combined water content, the higher is the cement ‘dilution’ in the initial mass of the sample. In such cases, smaller mass changes in the different mass loss steps are obtained, due to the actual smaller content of cement in the initial mass compositions. To have a same mass basis of comparison, and to avoid erroneous results of initial components content there from, thermal analysis data and curves have to be transformed on cement calcined basis, i.e. on the basis of cement oxides mass present in the calcined samples or on the sample cement initial mass basis.

Estimation of the spatial variability of root water uptake of maize and sorghum at the field scale by electrical resistivity tomography

Saving water for crop production is an old, but ongoing, challenge which requires a better understanding of the in situ functioning of root systems. In particular, this requires a better quantification and understanding of the spatial and temporal variability of the root water uptake at the field scale. Electrical Resistivity Tomography (ERT) is a non-destructive soil imaging technique, related to water content, which could help in spatializing active zones of water uptake. In this article, we evaluate ERT as an alternative method for quantifying and spatializing root water uptake at the field scale. To this aim, an experimental field study with maize and sorghum submitted to different water supply levels (Fully, Moderately or Poorly Irrigated treatments—FI, MI, PI zones) was conducted for 3 months with concomitant conventional, local, water balance measurements and 2D ERT imaging. ERT images showed an heterogeneous depletion of soil water by the crops, particularly, in the MI and PI zones with patches of high/low electrical resistivity (and thus water content) variations. This heterogeneity was greatest in the MI zone and points to spatial variations in rooting pattern and/or root efficiency. The 5-days difference in electrical resistivity could be quantitatively related to root uptake in the surface layer (down to 60 cm) but the relationship depends on the mean soil water content. At greater soil depth, in the water stressed zones, the water extraction front progressing downwards could not be assessed with the ERT surface setting used in this study. As a conclusion, ERT can be a useful, unique, technique for monitoring and estimating field water uptake by plant roots and its variability if combined water content measurements are available for in situ calibration and if the sensitivity/resolution of the technique is improved for estimation over the whole root zone.

Lowering Reduction Temperature of Iron Ore and Carbon Composite by Using Ores with High Combined Water Content

The steel industry is facing two difficult and urgent tasks to reduce CO2 emissions and to use low-grade iron resources effectively. The utilization of an iron ore–carbon composite is one of the promising methods to solve the former. The latter is concerning to goethite ores such as Australian Marra Mamba and pisolite ores, which contain high concentration of combined water. In this study, the effect of combined water on the reduction behavior of the iron ore–coal composites at elevating temperature was examined under inert gas flow.Below 1200 K, the reduction of iron oxide in Marra Mamba ore–coal and pisolite ore–coal composites proceeded faster than that in hematite ore–coal composite. It can be attributed to the larger specific surface area of the ores after decomposition of the combined water. Metallic iron also formed at lower temperature in the composites containing Marra Mamba and pisolite ores. The generation rate of CO gas from these composites showed the maximum value at approximately 1170 K; however, that from the hematite-coal composite gave no peak, because formed metallic iron could act as a catalyst for the gasification of carbon. These results indicate that the reduction of ores with high combined water concentration can proceed at lower temperature. Above 1373 K, however, the reduction rate of these ores in the composite significantly decreased due to a drastic decrease in the specific surface area of the ores and the formation of slag.

A moss “canopy” – Small-scale differences in microclimate and physiological traits in Tortula ruralis

We studied vertical changes in light regime and water content (WC) in combination with vertical gradients in several physiological response variables, i.e. net CO 2 uptake, chlorophyll content and nitrogen content in the moss species, Tortula ruralis. The rate of light attenuation within the moss turf, which was determined with a custom-made optical microprobe system, was strongly dependent on plant WC. Curling movements of the upper leaves associated with the beginning desiccation of the uppermost parts of a turf allowed increased penetration of light to greater depth with decreasing WC. The capacity to fix carbon declined steeply with depth: below ca. 9 mm no net CO 2 uptake occurred, even when removing the shading parts above. The potential rates of photosynthesis in different depths were highly correlated with chlorophyll content, but not nitrogen content.

Changes in Key Odorants of Raw Coffee Beans during Storage under Defined Conditions

During storage of raw coffee beans (green coffee) atypical odors may develop, which are suggested to influence the aroma of particularly the coffee beverage. To gain insight into the aroma compounds responsible for such odor changes, a comparative aroma extract dilution analysis was applied on unstored, raw Arabica coffee beans from Colombia (water content=11.75%) and on the same beans with a water content of 13.5%, which were stored for 9 months at 40 degrees C. In combination with the flavor dilution (FD) factors, the results of the identification experiments showed strong increases in (E)-beta-damascenone (cooked apple-like), 2-methoxy-4-vinylphenol (clove-like), and methyl 2-methyl- and methyl 3-methylbutanoate (fruity), whereas others, such as the earthy smelling 3-isopropyl-2-methoxypyrazine as well as 2-phenylethanol and 3-methoxyphenol, remained unchanged during storage. In addition, the previously unknown coffee odorant 2-methoxy-5-vinylphenol (intense smoky odor) increased significantly during storage. Quantitative measurements performed on raw coffee samples stored at various temperatures, water contents, and oxygen availabilities indicated that the significant increase of, in particular, the methyl esters of 2- and 3-methylbutanoic acid were responsible for the pronounced and fruity odor quality perceived in the stored green coffee, whereas the higher concentrations of 2-methoxy-4-vinylphenol and 2-methoxy-5-vinylphenol led to the more pronounced smoky, clove-like odor quality. On the basis of the results obtained, in particular the reduction of the water content in combination with lower temperatures can be suggested to avoid aroma changes in raw coffee beans caused by storage.

Influence of thermally treated phosphogypsum on the properties of Portland slag cement

In this study, thermal treatment of phosphogypsum (PG) at different temperatures 200, 400, 600 and 800 °C were attempted to purify PG and improve its quality to make it fit for the manufacture of Portland slag cement (PSC). PG is a waste of phosphoric acid manufacturing by dehydrate process in Egypt. It is a fine powder with high calcium sulphate content. This waste causes various environmental problems when discharged directly to the environment. The thermally treated PG was found to have lesser amount of impurities of phosphates, fluorides and organic matter than the impure material. In this investigation, preparation of Portland slag cement (PSC) in laboratory was carried out by mixing Portland cement clinker (PCC) and blast furnace slag (BFS) with thermally treated PG at different temperatures instead of raw gypsum (RG). The characteristics of prepared mortars were investigated by determination of compressive strength, bulk density and total porosity. The hydration kinetics of cement mortars was evaluated by determination free lime and chemically combined water contents. IR spectroscopic analysis was used for investigate the change in structure of mortars after curing. The change in morphology and microstructure of some hardened pastes were investigated by scanning electron microscopy (SEM) tests. The results show that, Portland slag cement produced using 6% thermally treated PG at 800 °C improves its hydraulic properties.

Characterization and Utilization of Polystyrene and Polyacrylamide-Graft-Methoxypolyethylene as Cement Admixtures

A series of polystyrene-g-methoxypolyoxyethylene (PS-g-MPOE) was prepared by solution polymerization technique using benzoyl peroxide as an initiator and another series of polyacrylamide-g-methoxypolyoxyethylene (PAM-g-MPOE) was prepared by using potassium persulfate initiator. The prepared grafted copolymers were characterized by infrared (IR), thermogravimetric analysis (TGA) and rheological properties. The results illustrated that the solution of PS-g-MPOE in water behaved as a Newtonian fluid, but the solution of PAM-g-MPOE as pseudoplastic at higher acrylamide ratios. The TGA analysis showed that the thermal stability of PAM-g-MPOE was highest. Some of these polymers were evaluated as cement admixtures. The water of consistency and setting time of the cement pastes premixed with the polymers decreased sharply than those of the blank, i.e., these polymer admixtures can act as superplastisizers and at the same time as accelerators. The combined water and free lime contents as well as compressive strength of the cement pastes premixed with PS-g-MPOE or PAM-g-MPOE were slightly lower than the blank at the early ages up to 7 d, and then became higher during the later hydration ages. Their total porosities are higher during the early ages and lower during the later ages of hydration. The SEM images confirmed that the addition of the organic polymer solutions to the cement powder does not affect the chemical composition of the normal hydration products, but only affects the physical state, shape or morphology and size of crystals of the formed hydrates.

INFLUENCE OF THERMALLY TREATED PHOSPHOGYPSUM ON THE PROPERTIES OF PORTLAND SLAG CEMENT

In this study, thermal treatment of phosphogypsum(PG) at different temperatures 200,400,600 and 800 oC were attempted to purify PG and improve its quality to make it fit for the manufacture of Portland slag cement (PSC). PG is a waste of phosphoric acid manufacturing by dehydrate process in Egypt. It is a fine powder with high calcium sulphate content. This waste causes various environmental problems when discharged directly to the environment. The thermally treated PG was found to have lesser amount of impurities of phosphates, fluorides and organic matter than the impure material. In this investigation, preparation of Portland slag cement (PSC) in laboratory was carried out by mixing Portland cement clinker (PCC) and Blast-furnace slag (BFS) with thermally treated PG at different temperatures instead of raw gypsum (RG). The characteristics of prepared mortars were investigated by determination of compressive strength, bulk density and total porosity. The hydration kinetics of cement mortars was evaluated by determination free lime and chemically combined water contents. IR spectroscopic analysis was used to investigate the change in structure of mortars after curing... The change in morphology and microstructure of some hardened pastes were investigated by scanning electron microscopy (SEM) tests. The results show that, Portland slag cement produced using 6% thermally treated PG at 800oC improves its hydraulic properties.

焼結ケーキ中の空隙構造制御のための層構造設計

Design of bed structure is a promising approach to maintain/increase the productivity of sinter under the condition of increasing use of iron ores having high combined water content. In this paper, a new process image, MEBIOS, is illustrated and further “in situ” observation of the change in the void structure of the sintering bed by using X-ray CTS and a numerical simulation have been conducted in order to preliminary evaluate the possibility of this proposal.X-ray CTS observation suggests that the existence of pellets of 15 mm in size does not significantly affect the formation of macroscopic void network in the sintering bed and not lead to inhomogeneous sintering. A series of the laboratory-scale of sinter pot experiment was also carried out to obtain parameters for the simulation. The gas flow near the pellet surface and the differences in the temperature profiles among the pellet center and surface were simulated by using the numerical model although further studies are necessary, e.g., on the considering ways of structural changes of void in the sintering bed, reduction and oxidation reactions and a mesh generation method properly representing the contraction of bed height.

Equifinality and sensitivity in freezing and thawing simulations of laboratory and in situ data

Numerical models of soil freezing and thawing are being increasingly used in, e.g., agriculture, forestry, ecology and civil engineering. This study was conducted to 1) elucidate the sensitivity in simulation output to the variability of model parameters for the hydrodynamic model Hydrus-1D and 2) investigate how two operational considerations in the model setup, groundwater level and subgrade material (soil texture), affect indicators of road accessibility in northern Sweden. The analysis was carried out by applying the generalized likelihood uncertainty estimation (GLUE) procedure when simulating laboratory measurements of freezing cylinders and by a more conventional sensitivity analysis, varying one parameter at a time, using road surface temperatures measured during nearly 1 year as upper boundary condition. For the simulation of the laboratory experiment, it was found that, although the thermal conductivity scaling factor, λ f, and the convective heat transfer coefficient, h c, most strongly affected the output, no parameter was redundant for the given problem. The frost depth was most sensitive to changes in λ f and h c, while the water content in the unfrozen zone was most sensitive to changes in the hydraulic conductivity impedence parameter Ω. For the 1-year road simulation, the frost depth was larger for sand than for the loam and silt subgrades; the thawing period was shortest for sand and longest for the silt subgrade; and the silt subgrade allowed for the largest frost-induced upward water flow. Thus, among the subgrades studied, roads built on silt show the potential of being most frost-susceptible as a consequence of having the largest elevated water content in combination with the longest time of thawing. The study performed indicates that the model can provide information of interest from an operational perspective, allowing for local predictions important in the road construction and maintenance process.

Synthesis, Characterization, and Cement Application of Vinyl Acetate Water-Soluble Graft Polymers

: Three different composition ratios of polyvinyl acetate-g-polyoxyethylene monomethylether (MPOE-g-PVAc) were prepared in the presence of benzoyl peroxide as an initiator using a macroradical initiator technique. The grafted copolymers were characterized through Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), and ultraviolet (UV) spectronomy; the rheological properties expressed as viscometry and creep analysis were also studied. The solutions of MPOE-g-PVAc are Newtonian in nature and by increasing the monomer content in the composition, the viscosity of the solution decreases. The creep analysis demonstrates that the resultant strain increases by increasing the monomer composition ratio.The effect of grafted copolymers on the physicomechanical properties of ordinary portland cement (OPC) pastes was investigated. The results showed that the addition of water mixed to the cement with graft copolymer improves most of the specific characteristics of OPC. As the concentration of the grafted copolymer increases, the water-to-cement (WC) ratio as well as setting time decreases. The combined water content increases with the addition of copolymer to the mixing water. The compressive strength was sharply increased at nearly all hydration ages.

Properties of Core Ore in Quasi-particle Required for Large Amounts Usage of Limonitic Ores in Iron Ore Sintering Process

The fluidity of melt formed in the sintering process of iron ores is an important factor for producing a high-strength sinter. When using a large amount usage of limonitic ores as core ore of the quasi-particle of sinter mix, it is predicted that the fluidity of formed melt decreases, because the solid ratio in the melt increases by an acceleration of the assimilation of the core ore with the melt.In order to control the assimilation of limonitic ore, basic researches were conducted using a modeled briquette, which consisted of a disk-shaped iron ore core and a shell layer of fine mixture composed of Fe2O3 and CaCO3 reagents. Assimilation rate of various iron ores was measured, and then solid phase ratio in the melt was calculated based on the phase diagram of CaO-Fe2O3 system. According to the calculated solid phase ratio in the melt, the fluidity of melt was discussed. The results obtained are summarized as follows:Fair linear relations were obtained between the porosity of core ore after dehydration and the combined water content of the ore. The assimilation rate of core ore at a specified temperature was represented as a function of the porosity of core ore after dehydration and the holding time at the temperature. The diameter and the apparent density of core ore influenced the calculated solid phase ratio in the melt. It was suggested that an optimal sinter structure was achieved by mixing a large and dense core ore at about 20 mass% in raw mix.

Marra Mamba Ore, Its Mineralogical Properties and Evaluation for Utilization

This paper provides an overview of chemical and physical properties of Marra Mamba ores as well as their influence on sintering performance. Evaluation tests focusing on basic characteristics, granulation ability and melting behavior have been conducted by using Ore W, a newly shipped bland of Marra Mamba ore. Although the amount of gangue minerals in Marra Mamba ores is smaller than that of other Australian ores, they have high combined water content and high fraction of fine particles. They have inferior granulation ability and required high moisture content in granulation due to their porous structure. Cohesive strength of fine ores is still low level even at high moisture content due to small kaolinite content. Penetration behavior of melt from fine particles is superior due to their low gangue mineral content, while assimilation behavior of coarse ores is inferior, resulting in poor agglomeration despite favorable behavior during heating-up in term of crack formation. Pot test results performed by BHP Billion showed decrease of strength and product yield with large amount of use. Improvement of strength was achieved by increasing moisture content during granulation. Intensification of granulation with pre-treatment or palletizing of Marra Mamba ores must be one of the key technologies for utilization of them.

Summarized Achievements of the Porous Meso-mosaic Texture Sinter Research Project

Research Group on Porous Meso-mosaic Texture Sinter in ISIJ was established from 2001 to 2004 fiscal years to overcome difficulties to use the great amount of goethite in sintering and at the same time to improve the sinter quality. Especially, since the beginning of the present research project the ratio of Marra Mamba goethitic ore was considered to increase rapidly, and the amount of sinter necessary for the Japanese integrated steel industries was thought hard to be produced satisfactorily, because Marra Mamba ore having high combined water content and high porosity was expected unsuitable for sintering. Therefore, the method of using goethite had been studied and the combination with low slag ratio important for melting behavior of goethite was investigated.Each university had been engaged in basic research such as granulation, agglomeration, evaluation of reaction in a blast furnace to propose a new process for “porous meso-mosaic texture sinter” which was anticipated simultaneously to realize high strength and high reducibility under the conditions of low slag and high goethite ratio in sintering.By combining these basic researches, the theory of agglomeration and the engineering foundation for raw material/sintering/blast furnace process were discussed and a new process for “porous meso-mosaic texture sinter” based on improving granulation process of raw material was searched. As a result, proposed was the MEBIOS (Mosaic Embedding Iron Ore Sintering) method which involved arranging dense pre-granulated pellets (firing cured bed) in a sinter induction bed with a raw material composition capable of forming a suitable void network under normal sintering conditions.

Design of Bed Structure Aiming the Control of Void Structure Formed in the Sinter Cake

Design of bed structure is a promising approach to maintain/increase the productivity of sinter under the condition of increasing use of iron ores having high combined water content. In this paper, a new process image, MEBIOS, is illustrated and further “in situ” observation of the change in the void structure of the sintering bed by using X-ray CTS and a numerical simulation have been conducted in order to preliminary evaluate the possibility of this proposal.X-ray CTS observation suggests that the existence of pellets of 15 mm in size does not significantly affect the formation of macroscopic void network in the sintering bed and not lead to inhomogeneous sintering. A series of the laboratory-scale of sinter pot experiment was also carried out to obtain parameters for the simulation. The gas flow near the pellet surface and the differences in the temperature profiles among the pellet center and surface were simulated by using the numerical model although further studies are necessary, e.g., on the considering ways of structural changes of void in the sintering bed, reduction and oxidation reactions and a mesh generation method properly representing the contraction of bed height.

Effect of silica fume or granulated slag on sulphate attack of ordinary portland and alumina cement blend

The effect of silica fume or granulated slag as high alumina cement (HAC) substitutes, on sulphate attack of ordinary Portland and alumina cement blend up to complete substitution and up to 12 months, was studied. The results indicate that the cement pastes with silica fume give higher combined water and lower free lime contents than those containing granulated slag. The increase of HAC substitution by silica fume or granulated slag in the OPC–HAC blend decreases the aggressive attack of sulphate ions on the hardened cement pastes, yet the granulated slag is more effective than the silica fume.

Limestone as an accelerator and filler in limestone-substituted alumina cement

The effect of substitution of alumina cement by limestone up to 25% as well as its fineness on the physico-mechanical properties of the hardened cement pastes is studied. The results revealed that the replacement of alumina cement by limestone slightly decreases the water of consistency and the setting times (initial and final). The combined water content increases with the curing time and the fineness of limestone. The total porosity decreases, and accordingly the compressive strength improves with the content and fineness of limestone. Hence, the limestone has a little accelerating action on the hydration process of the alumina cement but acts only as a filler reducing the porosity due to its compact structure. Therefore, the compressive strength of the hardened cement pastes is enhanced. The addition of finely ground limestone filler only up to 15% gives better results on strength. The XRD and DTA analyses of samples cured up to 28 days show that the addition of higher amounts of limestone filler to the aluminous cement tends to decrease the conversion reaction due to the partial carbonation of C 3AH 6.

Effect of calcium formate as an accelerator on the physicochemical and mechanical properties of pozzolanic cement pastes

The aim of the present work is to study the effect of calcium formate (CF) as an accelerator on the properties of pozzolanic cement pastes. Three types of cements were used in this investigation. These cements were OPC and pozzolanic cements containing 80 mass% OPC and 20 mass% silica fume (SF) or 20 mass% ground clay bricks (GCB). The dosages of CF were 0.00, 0.25, 0.50, and 0.75 mass% of cement. The compressive strength, total porosity, and hydration kinetics such as free lime and combined water contents were investigated. The results obtained in this study showed that the addition of CF shortens the initial and final setting times and increases the compressive strength and combined water content as well as gel/space ratio at all ages of hydration. On the other hand, it decreases the total porosity. CF activates the liberation of Ca(OH) 2 of OPC pastes. The free lime content of pozzolanic cement in the presence of CF increases up to 7 days, then decreases at the later ages of hydration.

Strength impairment of concrete mixed in hot weather: relation to porosity of bulk fresh concrete paste and maturity

Normal-strength concrete mixed in summer can be less strong than the annual average. One cause of these variations is the effect on concrete strength of the temperature of the constituents. Concretes were cast at different temperatures because of different temperatures of the constituents. The slump value, which is the criterion for acceptance on the building site, was kept constant whatever the initial temperature may be, either by the addition of water or by the use of a plasticiser at the end of mixing. Concretes were cured for 24 h under either the conditions specified in the French standard for manufacturing control or simulated hot weather conditions, and then stored in water at 20°C up to the time of test. Compressive strength was determined at 1, 7 and 28 day ages on 11 × 22 cm cylinders. The results show that the decrease in strength is dependent on the combined effective water and air content of the bulk paste of fresh concrete, and on the maturity of the concrete, which is influenced by its temperature history. By combining two classical relations: strength and design factors (Feret's relation) and strength and maturity (Arrhenius Law), decreases in strength could be analysed for any mixing and curing conditions.

Strength impairment of concrete mixed in hot weather: relation to porosity of bulk fresh concrete paste and maturity

Normal-strength concrete mixed in summer can be less strong than the annual average. One cause of these variations is the effect on concrete strength of the temperature of the constituents. Concretes were cast at different temperatures because of different temperatures of the constituents. The slump value, which is the criterion for acceptance on the building site, was kept constant whatever the initial temperature may be, either by the addition of water or by the use of a plasticiser at the end of mixing. Concretes were cured for 24 h under either the conditions specified in the French standard for manufacturing control or simulated hot weather conditions, and then stored in water at 20°C up to the time of test. Compressive strength was determined at 1, 7 and 28 day ages on 11 × 22 cm cylinders. The results show that the decrease in strength is dependent on the combined effective water and air content of the bulk paste of fresh concrete, and on the maturity of the concrete, which is influenced by its temperature history. By combining two classical relations: strength and design factors (Feret's relation) and strength and maturity (Arrhenius Law), decreases in strength could be analysed for any mixing and curing conditions.