Variation Of Water Absorption Research Articles

Utilization of high-sulfur iron ore tailings in cement mortar by considering the influence of curing temperature and tailing content

This work investigates the usage of graded iron ore tailing sand (GIOT) as aggregates in cemented mortar to reduce the pollution of iron ore tailings (IOT) and shortage of river sands. Fresh and hardened properties of graded tailings cemented mortar (GTCM) with partial replacement of standard sand (SS) by GIOT were investigated, by considering the effect of substitution ratios (0 %–50 %) and curing temperatures (20 °C, 40 °C and 60 °C). It is illustrated that an increase in the GIOT content leads to the reduction in fluidity and increment in apparent density of fresh GTCM. With increasing GIOT content, the dry density and UCS of hardened GTCM show a decreasing trend first (0 %–20 %) and then increase against the substitution ratios of GIOT (30 %–50 %). The variation of water absorption with increasing GIOT is opposite to that of dry density. In addition, the curing temperature is also proved to be a remarkable influencing factor, which can promote the hydration reaction and improve the properties of GTCM, even at 60 °C. The physico-mechanical properties of 28 d samples are better than that of 7 d samples because the increasing hydration products are produced with increasing the curing age. The XRD results show that the sulfur facilitates the formation of AFt. The SEM images and MIP results further confirmed that a low tailing content of 10 % may induce micro-cracks due to the unmatched particle size and shape, however, mortars with 50 % IOT content possess a denser microstructure, but more capillary and gel pores. For the curing age of 28 d, the optimum substitution ratio may exceed 50 %, and the best curing temperature is 60 °C. The influence of GIOT content and curing temperature on the long-term properties of high-sulfur GTCM beyond 28 d need further research.

Influence of the Extraction Location on the Physical and Mechanical Properties of the Pseudo-Trunk Banana Fibers

ABSTRACT The specific properties and availability of banana pseudo-trunk fibers make them a promising alternative for the development of green composites. However, the wide dispersion of their properties can hinder their use. In this study, the influence of the sampling area of the banana pseudo-trunk on the physical and mechanical properties of the fibers was evaluated. Prior to retting, the trunk was sampled longitudinally (bottom, middle and top) and transversely (periphery, intermediate and heart). Gravimetric tests were carried out and revealed variations in water absorption (347.1–517.4%), density (0.92–1.45 g.cm−3) and linear mass (25 -34tex). Tensile tests were also performed and showed a significant effect of fiber location on Young’s modulus (6.60–34.6GPa), tensile strength (91-350MPa) and elongation at the break (0.9–2.6%). Due to diameter scatter, variations of 42% were found for fibers in the same area. In a region, the physical properties increase from the periphery to the core, and the mechanical properties decrease in the same direction, except for elongation. The results of this study showed good agreement with those of other natural fiber types. However, we recommend the peripheral areas of the pseudo-trunk to extract reinforcing fibers from composites because of their low density (0.9 g.cm−3) and their high stiffness (34GPa).

Kitchen cloths: Consumer practices, drying properties and bacterial growth and survival

Kitchen cloths have an important role in maintaining kitchen surfaces hygienically clean but may also act as vehicles for cross contamination of pathogens from food spills to hands and other foods. The aim of the present study was to map consumer practices across Europe and identify main factors that may contribute to unsafe use of kitchen cloths, such as type of cloth and storage practices. Consumer practices related to cloths were investigated in a web-based survey (N = 2394), while drying properties and growth and survival of Salmonella , Campylobacter and non-pathogenic food associated bacteria in inoculated cloths were studied in laboratory tests mimicking consumer practices. Among consumers in six European countries, cotton and microfiber cloths were reported to be the most used cloth types for cleaning food preparation areas and wiping up spills. . Fifty-seven percent of the consumers reportedly hang the cloth to dry after use. A large majority (72%) changed their cloths at regular times, with an average reported frequency of every 6 days. Large variations in water absorption (63–201 g) and drying rate (31.8–99.8% water loss after 4.5 hours ) among 17 types of commercially available cloths were found. Hanged up cloths dried faster than cloths stored crumpled as balls. Salmonella multiplied in all types of new cloths that were not hung to dry (crumpled), but about 3 log reduction or more were found after hanging cloths to dry for 24 hours. For cloths collected from consumers, growth of inoculated Salmonella was not observed, but hanging the cloths resulted in more than 3 log reduction in numbers. A large variation in survival of Campylobacter was found depending on the type of cloth, but more than 5 log reduction was found after 24 hours in all hanging cloths. A polypropylene and a viscose cloth with low water uptake and fast drying appeared to be the safest choice with a rapid reduction of both pathogens when hung (respectively 2 log and >6 log reduction for Salmonella and Campylobacter after 4.5 hours) and reduction of Campylobacter when stored crumpled. The least safe cloth regarding pathogen growth and survival was a knitted cotton cloth with high water uptake and slow drying. There was no systematic difference in growth and survival of bacteria between microfiber cloths and cloths of other materials, nor between cloths with and without antimicrobial compounds. The present study shows that 16% of consumers have practices that would allow pathogens to contaminate, grow and survive in cloths until the next use. Touching and using these cloths can lead to contamination of hands and food contact surfaces, and potentially to ingestion of pathogens. Consumers should be advised to change cloths after using them for meat spills, but also to choose cloths that dry fast and keep them hanging to dry between use. • Cloths commonly used for cleaning food preparation areas. • Large variation in drying rate between cloths. • Salmonella grows in humid cloths. • Less survival of pathogens in hanging cloths.

Quantifying leaf-scale variations in water absorption in lettuce from hyperspectral imagery: a laboratory study with implications for measuring leaf water content in the context of precision agriculture

Variations in water absorption across lettuce leaves (Latuca sativa L. var. longifolia) were quantified from hyperspectral imagery acquired in the laboratory using selected spectral indices, specifically, the Moisture Stress Index (MSI), the Normalised Difference Water Index (NDWI) and the intensity of specific water absorptions at 970 nm (IA970), 1170 nm (IA1170) and 1775 nm (IA1775). Absorption was separately quantified for the midrib, the green parts of the leaves and for whole leaves. Indices were non-linearly related to water content expressed per weight of wet plant material (g g−1) but linearly to water content per unit area of leaf (g cm−2). Indices were weakly correlated with water content in the stem but strongly correlated with water in the green parts of leaves and in whole leaves. Water content in whole leaves was significantly underestimated (P < 0.01) when it was predicted from a model developed for the green parts of leaves, indicating that water content must be derived from the same leaf component used to derive the predictive model. Some indices (NDWI, MSI, IA1170) highlighted intricate reticulated patterns of water absorption across the leaves but these were poorly defined by other indices (IA970, IA1775). Indices extracted from the leaf along transverse and longitudinal transects were qualitatively similar but quantitative analysis indicated that they were significantly different (P < 0.05). The principal contribution of this study is that it highlights the implications of quantifying leaf water content from hyperspectral imagery acquired at spatial resolutions great enough to resolve individual leaf components.

Filler technology for improving robustness and reducing cementitious paste volume of SCC

The flowability, cohesiveness and passing ability of self-consolidating concrete (SCC) are very sensitive to changes in free water content, aggregate grading and superplasticizer dosage, among which the free water content is the most difficult to control because of intrinsic variations in water absorption and moisture content of the aggregate. Hence, there is the robustness problem of maintaining the required performance during large scale production. Moreover, there is also the problem of large cementitious paste volume, which leads to low dimensional stability and high carbon footprint. In this study, the possible use of filler technology to overcome these two problems has been explored by adding limestone fines and ground sand as cementitious paste replacement and evaluating their effects on the performance and robustness of SCC. It was found that such filler technology can significantly improve the robustness of SCC and the key factors are to have sufficient mortar volume and cohesiveness. However, this technology is not suitable for application to concrete mixes for long distance pumping.

Distribution of Water Infiltration Rate in Ciliwung Watershed

Floods in Jakarta showed that the Ciliwung watershed and surrounding areas in critical condition. More than 50 % of land cover Ciliwung watershed is residential. Planting trees in residential areas have been insufficient to infiltrate as much water into the ground. Infiltration well is one possibility for absorbing water in residential areas. The purpose of this study was to determine the variation in the level of water absorption Ciliwung watershed and surrounding areas. The method used is overlaying analysis of the factors that determine the rate of water infiltration with geographic information system. Each of these factors gave weights and scores to obtained variations Ciliwung water infiltration rate. The results showed that the regions with the highest levels found in the upper catchment area and the city of Bogor, middle absorbtion water area was in Bogor Regency, low water absorption areas in Depok , South Jakarta , and East Jakarta . While in North Jakarta, Central Jakarta and West Jakarta the water absortion is very low level due to the shallow ground water level and very low soil permeability. Map variations in water absorption can be used as a material consideration for determining the locations of recharge wells effectively.

Internal curing of mortar with low water to cementitious materials ratio using a normal weight porous aggregate

A normal weight porous aggregate (NWPA), with the saturated surface dry density of 2.3g/cm3, was prepared. Impact of NWPA on performance of mortar with water to cementitious materials ratio of 0.3 was presented in this paper. The results show that NWPA has smaller pores and higher water absorption speed than expanded clay, but lower desorption speed. Strength of mortar accompanying NWPA is higher than or close to that of a plain one. Mortar containing NWPA expand less than that with expanded clay under sealed condition, which suggests the lower internal curing efficiency of NWPA. However, still it could diminish the shrinkage of low w/c mortar and be used as internal curing agent. Variation of water absorption and dynamic modulus from top to bottom of mortar with NWPA is similar to that of plain one, and lower than that of expanded clay mortar, which certifies that NWPA could promote the uniformity of internally cured mortar.

Effect of Plasma Treatment on Water Absorbability of PP Nonwovens

The surface of polypropylene (PP) nonwovens was modified by low-temperature plasma technology. Three factors influencing the plasma treatment, i.e. current, time and distance between nozzle and fabric surface, were studied by single factor experiments. The effect of hydrophilic modification of PP nonwovens was evaluated with water absorption. The variation of water absorption of PP nonwovens after plasma treatment was tested. The experimental results show that the plasma treatment can improve the water absorbability of PP nonwovens. The water absorbability increases with the increasing current, but decreases with the increasing distance from nozzle to fabric surface. With the increase of time, the water absorbability increases firstly then decreases.

Inorganic polymeric foam as a sound absorbing and insulating material

A mixture of 70% metakaolin and 30% blast furnace slag powders is used as the raw material in the production of inorganic polymeric foams (IPF) with various densities ranging from 0.4 to 1.0g/cm3 and different thicknesses of 6, 10 and 14cm using a mechanical foaming method. The water absorptions, sound absorption coefficients and sound transmission losses of the IPF specimens were measured and then compared with each other to evaluate the effects of their density and thickness. It was found that the variation of water absorption with respect to density was similar to that of the noise reduction coefficient. In addition, the sound transmission losses of sandwich panels with different-thickness and various-density IPF cores were measured to determine if two faces of calcium silicate boards can enhance their noise reducing effects. As a result, the feasibility of using inorganic polymeric foam as a sound absorption and insulation material can be evaluated.

Effect of Milling and Particle Size on Functionality and Physicochemical Properties of Cowpea Flour

ABSTRACTCowpeas (Vigna unguiculata) were milled through 0.5‐, 1.0‐, and 2.0‐ mm screens, and the flour was subsequently separated into different particle‐size ranges. Such procedures caused only minimal changes in moisture, fat, protein, ash, and total carbohydrate. The amount of extractable starch, however, varied from 34.5 to 52%. The effects of both mill screen and sieve mesh size were significant (P &lt; 0.05). Differences in milling and separation procedures resulted in significant variations in water absorption (0.41–2.81 g of water/g of flour), solids lost (0.34–1.17 g/g of flour), and protein solubility (21.2–37.4%) (P &lt; 0.05). Finely milled flours (91% moisture) had lower initial gelatinization temperatures (70–73°C), as measured by differential scanning calorimetry (DSC) (P &lt; 0.01). Gelatinization peaks in high‐moisture flour were similar to that of pure starch. At lower moisture, a second peak was observed indicative of protein. Light‐scattering analysis showed that different conditions produced a bimodal particle‐size distribution when samples were suspended in water. The small size had relatively constant diameters (19–21 μm) and was associated with starch granules. The latter had a large size distribution and varying peak size and was associated with aggregated flour particles. These results indicate that changes in processing produces cowpea flours with differing chemical and physical properties.

Prediction of water absorption of nonglazed tiles made by semidry molding using a regression model

The possibility of predicting water absorption in semi-dry molding of ceramic tiles using data on linear dimensions of molded tiles and their firing regime is considered. An empirical formula is given, which makes it possible to estimate the quantitative effect of tile sizes, molding pressure, and firing parameters on the variations in water absorption. The possibility is demonstrated for predicting water absorption in tiles 40–50 min before they leave the firing furnace.

Short-chain fatty acids and water in the hindgut contents and feces of rats after hindgut bypass surgery.

Omnivorous experimental animals with different levels of short-chain fatty acids in hindgut contents or in feces were established by surgical bypass of the colon and/or the cecum. Levels of short-chain fatty acids, amounts of luminal contents, and the water contents in these animals were compared. Regional variations in water absorption and retention of luminal contents are likely to be major factors in the regulation of hindgut functions.

Ionic conduction in polymer films. III Influence of temperature on water absorption

AbstractThe variation of water absorption with temperature of three varnish films, a pentaerythritol alkyd, an epoxy‐polyamide and a phenol‐formaldehyde tung oil, has been measured. In the case of the first two, minima were observed the temperatures of which corresponded to glass transition temperatures of the polymers. In contrast, films of the phenol‐formaldehyde tung oil varnish showed neither a minimum in the water absorption‐temperature curve nor a glass transition temperature over the range 5–34°C. Further work is necessary to establish whether this relationship has general application.