Monitoring Water Uptake Research Articles

Automated estimation of cementitious sorptivity via computer vision.

Monitoring water uptake in cementitious systems is crucial to assess their durability against corrosion, salt attack, and freeze-thaw damage. However, gauging absorption currently relies on labor-intensive and infrequent weight measurements, as outlined in ASTM C1585. To address this issue, we introduce a custom computer vision model trained on 6234 images, consisting of 4000 real and 2234 synthetic, that automatically detects the water level in prismatic samples absorbing water. This model provides accurate and frequent estimations of water penetration values every minute. After training the model on 1440 unique data points, including 15 paste mixtures with varying water-to-cement ratios from 0.4 to 0.8 and curing periods of 1 to 7 days, we can now predict initial and secondary sorptivities in real time with high confidence, achieving R² > 0.9. Finally, we demonstrate its application on mortar and concrete systems, opening a pathway toward low-cost and automated durability assessment of construction materials.

Root water uptake and water transport to above-ground organs compensate for winter water losses and prevent shoot dehydration in apple trees

Plants need to maintain a minimum moisture content in their tissues to preserve their living functions not only during the growing season but also during periods of dormancy. Whereas water uptake of trees during the growing season has been widely investigated, very little attention has been paid to tree water uptake and losses during winter dormancy. A study was therefore conducted aiming at quantifying root water uptake of apple trees in winter, comparing the water content of two groups of field-grown apple trees for two winter seasons. One group of trees was isolated from its roots by a transversal cut at the base of the trunk and the other was left intact. In an additional experiment, deuterium-enriched water was added to the soil of potted apple trees during winter dormancy, to monitor water uptake and translocation within the plant. The field experiment revealed incrementing moisture losses of annual shoots in late winter, driven by the rising evaporative demand of the atmosphere. Trees with unimpaired water transport systems compensated shoot water losses by root water uptake and internal translocation, whereas trees with severed trunks only partially mitigated losses by internal translocation from trunk and larger branches. Root water uptake during winter dormancy was also confirmed in the potted tree experiment with deuterium-enriched water. This work provides evidence that water flow along the soil-plant-atmosphere continuum in apple trees takes place also in winter, with possible impacts on tree survival during prolonged periods of soil or trunk freezing.

Characterization of hydrothermal aging induced voids in carbon fiber reinforced epoxy resin composites using micro-computed tomography

The main aim of this work is the voids characterization of carbon fiber reinforced epoxy resin (CFRP) composites after hydrothermal aging. The composites aged at varying time and temperature were investigated using micro-computed tomography, scanning electron microscope, fourier transform infrared spectroscopy, dynamic mechanical analysis as well as monitoring water uptake and inter-laminar shear strength. It is shown that the porosity increases rapidly in first 45 days while maintains stable in following 105 days. The equilibrium porosity at 35 °C, 55 °C, 75 °C and 95 °C are 0.52%, 0.54%, 0.67% and 0.72% respectively. The strip-like voids and fracture morphology indicate the destruction of interface and resin, but the former is more vulnerable. However, the resin matrix embrittlement is caused by network damage while chemical structure is almost unchanged. As a result, the water diffuses and inter-laminar shear strength deterioration. This study clarifies the influence of voids on structure and properties of CFRP composites and is expected to deepen the understanding of hydrothermal aging mechanism of CFRP composites.

Mechanical characterization and adhesive properties of a dental adhesive modified with a polymer antibiotic conjugate

This study is a follow up investigation on recent work by our group demonstrating synthesis, release and strong antibacterial character of resins modified with penicillin V (PV)-based polymer-antibiotic conjugates (PACs). Here, we aimed to evaluate the mechanical, bonding, and other relevant biomedical properties of a commercial adhesive resin modified with PV-PAC. Single Bond Plus (SB+) was modified with PAC containing 1.8 wt% conjugated PV. Adhesive resins were bonded to dentin from extracted human molars and restorative resin added. Beams of cross-sectional area of 0.9 ± 0.1 mm (Kutsch and Young, 2011) (n = 20) were obtained from the molars and tested for micro-tensile bond strength (μTBS) at 24 h and 4 months. For cohesive strength, hourglass beams (10 × 2 × 1 mm; n = 10) were assessed for ultimate tensile strength (UTS), beam-shaped specimens (25x2x2 mm; n = 10) evaluated for flexural strength and modulus (FS/FM) via three-point bending, and cylindrical specimens (3 × 2 mm; n = 10) assessed for ultimate compressive strength (UCS). For surface micro-hardness (MH), cylindrical specimens (3 × 2 mm; n = 6) were assessed before and after an EtOH challenge. The degree of conversion (DC) (5 × 1 mm; n = 6) was determined based on changes in absorbance ratio between peaks at ∼1637 cm-1 and ∼1608 cm-1 before and after curing of adhesive resins using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. To monitor water uptake and diffusion kinetics over a 28-day period, specimens (5 × 1mm) were desiccated, weighed and stored in deionized water. Control and PV-PAC modified adhesive resins demonstrated similar μTBS at 24 h and 4 months; both showing decrease in values after 4 months (p = 0.001 and 0.004). No significant differences between adhesive resins were shown in UTS, FS/FM or UCS (p<0.05). MH of PV-PAC adhesive resin was significantly reduced relative to the control (p<0.001). The DC values of the adhesive resins were not significantly different. While sorption and solubility were no different between materials, the diffusion coefficient of PV-PAC modified adhesive resin was higher than the control (p<0.001). We conclude that incorporation of PV-PAC with 1.8 wt% PV into an adhesive resin does not adversely affect its mechanical, bonding, and physical properties, thus providing a promising option for materials with long-term antibacterial character and on-demand release.

Rapid Characterization of Water Diffusion in Polymer Specimens Using a Droplet-Based Method.

Water diffusion testing is typically carried out by immersing specimens in a water bath and monitoring water uptake until saturation is reached. Determination of diffusivity may require several months and even years for thick specimens. In this paper, we present a water droplet-based method for rapid characterization of diffusivity. The method involves placement of a water droplet on a flat surface of the testing material. A tensiometer is used to monitor and record the evaluation of droplet dimensions. The small volume of the water droplet (below 10 μL) ensures that diffusivity can be determined in a couple of hours. The capability of this method is demonstrated by determining the water diffusion (D) of polymethylmethacrylate (PMMA) and epoxy plastics. The water diffusivity measured for PMMA matched well with published results. The droplet method was also applied to void-free epoxy and epoxy with a range of void contents. The diffusivity for the epoxy with voids increased with increasing void content. The diffusivity results for the epoxy without voids and with small void content agree with those determined from the long-term water immersion method. For the high-void-content epoxy, the diffusivity was much higher than that in the immersion method. This may be because of the rough surface caused by large exposed voids.

Monitoring water uptake in whole barley (Hordeum vulgare L.) grain during steeping using near infrared reflectance spectroscopy

The aim of this study was to evaluate the use of near infrared reflectance (NIR) spectroscopy to monitor water uptake and steeping time in whole barley samples as a rapid and easy to use technique. Whole barley grain samples were steeped in water, and subsamples were analyzed for water uptake (gravimetric method) and using NIR spectroscopy. The spectra and the analytical data were used to develop partial least squares (PLS) calibrations to predict water uptake and steeping time. Cross validation models for water uptake and steeping time gave a coefficient of determination in cross validation (R2) and the standard error of prediction (SEP) of 0.90 (SEP=5.36g/100g fw) and 0.92 (SEP=3.93h), respectively. This study showed that NIR spectroscopy combined with PLS regression showed promise as a rapid, non-destructive method to monitor and measure water uptake and steeping time in whole barley during soaking.

A fully coupled diffusion-reaction scheme for moisture sorption–desorption in an anhydride-cured epoxy resin

Thermoset materials frequently display non-classical moisture sorption behaviors. In this paper, we investigated this issue from an experimental point of view as well as in terms of modeling the water transport. We used the gravimetric technique to monitor water uptake by epoxy samples, with several thicknesses exposed to different levels of humidity during absorption and desorption tests. Our results revealed that the polymer displays a two-stage behavior with a residual amount of water that is desorbed progressively. We proposed a phenomenological reaction-diffusion scheme to describe this behavior. The model describes water transport as a competition between diffusion and the reaction, during which the local diffusivity and solubility depend on the local advancement of the reaction. We then implemented our model using COMSOL Multiphysics and identified it using a MATLAB-COMSOL optimization tool and the experimental data. We discussed the relation between the hydrophilicity of the product of the reaction and the diffusion behavior. We examined the reaction-induced modification of the water concentration field. It is worth noting that part of the phenomenology can be explained by the presence of hydrolyzable groups.

Study of Water Adsorption in Poly(N-isopropylacrylamide) Thin Films Using Fluorescence Emission of 3-Hydroxyflavone Probes

The noncontact measurement of water uptake in microscale (1−100 μm), thermoresponsive poly(N-isopropylacrylamide) thin films is challenging. We assessed the efficacy of three different 3-hydroxyflavone (3-HF)-based fluorophores to monitor water uptake in pNIPAM thin films close to the lower critical solution temperature (LCST) at 25 and 37 °C. These 3-HF fluorophores undergo excited-state intramolecular proton transfer, yielding emission from normal (N*) and tautomeric (T*) excited-state forms. The emission intensity ratio, log(IN*/IT*), and N* band position are environmentally sensitive. Water adsorption in pNIPAM thin films follows a nonlinear, two-phase process: at low relative humidity, the adsorbed water disrupts polymer−fluorophore hydrogen bonding, yielding small changes in log(IN*/IT*) ratios and overall intensity; at higher relative humidity, these intensity parameters (but not fluorescence lifetime) change dramatically, indicating a larger change in local polarity. These probes are thus sensitiv...

MODELING VARIETAL EFFECT ON THE WATER UPTAKE BEHAVIOR OF MILLED RICE (ORYZA SATIVA L.) DURING SOAKING

ABSTRACT Milled rice is soaked until saturation before cooking and other processing. The soaking behavior of the milled rice is affected by varietal factor as well as initial moisture content (M0) of the samples. In the present study, tests were performed for milled whole kernels of 10 rice varieties ranging from low to high amylose content (16–29% d.b.) with three initial moisture levels (approximately 8, 12 and 16% d.b.) for monitoring water uptake in rice kernels during soaking at room temperature (25 ± 1C), in relation to the varietal differences manifested by the physicochemical properties. The water uptake by milled rice kernels took place at a faster rate in the beginning and was followed by a diminishing rate finally leading to a saturated value during soaking. The water uptake of the kernels during soaking could be best expressed by a modified exponential relationship with R2 values ranging from 0.971 to 0.998 for all varieties. The slope of the fitted straight line between actual and estimated moisture contents of milled rice during soaking using a modified exponential relationship was about unity (0.998) with a high R2 value of 0.989 and a root mean square error of 1.2% d.b. The parameters of the fitted model were the function of the M0 and the physicochemical properties of the milled rice. Using developed relationship, the water uptake of the milled rice during soaking could be estimated from its M0 and the physicochemical properties within±10% of the actual values.PRACTICAL APPLICATIONSThis information would be useful for the scientific world working on the soaking characteristics of various varieties of rice, mainly for the modeling of the soaking process. It could also be used as a tool in selecting the rice varieties to meet their desired water uptake properties in relation to their psychochemical properties by rice breeder scientists.

Water uptake and solid loss during cooking of milled rice ( Oryza sativa L.) in relation to its physicochemical properties

Tests were performed for milled rice of 10 Thai varieties ranging from low to high amylose content (16–29%) with three initial moisture levels (approximately, 8%, 12% and 16% d.b.) for monitoring water uptake in rice kernels and solid loss during cooking in relation to the varietal differences manifested by their physicochemical properties. Water uptake of milled rice increased with an increasing rate in the beginning followed by a diminishing rate during cooking in excess water while the solid loss was a power function of cooking duration. The moisture content during cooking could be best expressed by a modified exponential relationship with R 2 values ranging from 0.995 to 0.999 for all varieties. The regression coefficients of the fitted relationship for describing moisture adsorption by cooked rice were found to be the function of physicochemical properties, namely, the AC and AS of milled rice. It was concluded that the water uptake during cooking of milled rice could be estimated by the physicochemical properties of the milled rice within ±10%.

Relationship between water absorption and dielectric behaviour of natural fibre composite materials

Gravimetric and dielectric measurements have been used to monitor water uptake in composites with glass, jute and washed jute fibres. The results showed that the dielectric constant of jute fibre composites is higher than that of the composites based on glass fibres. Also, when the frequency increases the permittivity decreases. A Fickian diffusion model was applied and the effective diffusion coefficient was calculated. The results obtained show that when the sizing is removed in fibres washed with hot water, the effective coefficient diffusion increases. Changes in the dielectric permittivity were measured at different frequencies and at different times during water absorption at room temperature. A non-linear behaviour has been found in the changes of the permittivity with water absorption in the frequency range of 200 Hz to 1 MHz.

Monitoring water uptake of polyurethanes by in situ fluorescence technique

The water uptake of three polyurethane adhesives was studied by an in situ fluorescence method applying extrinsic fluorescent probes. The measurements were made in water immersion at 50 and 80°C, and in water vapor at 50°C. An intensity ratio method was applied, in which ratios of the highest and lowest intensity changes in the fluorescence emission bands were used to determine the amount of water sorbed in the polymer films. The ratio method was used to compare the fluorescence data with those obtained by a conventional gravimetric method. Comparable results were obtained. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1593–1599, 2001

Mobility‐sensitive fluorescence probes for quantitative monitoring of water sorption and diffusion in polymer coatings

AbstractThe fluorescent molecular rotor probes 4‐tricyanovinyl‐[N‐(2‐hydroxyethyl)‐N‐ethyl]‐aniline, tricyano‐4‐(dimethylamino) benzylidene, and tricyanovinyljulolidene have been used as extrinsic fluorescence probes for quantitative monitoring of water uptake in polymeric coatings. The presence of water causes plasticization of the polymer, which results in increased local mobility within the film. The nonradiative decay pathways of the rotor probes are increased as local mobility increases, and the resulting decrease in fluorescence intensity of the probes is directly proportional to the amount of water sorbed. Beyond allowing for the characterization of sorbent content, this fluorescence technique can be used to determine the diffusion coefficient of water in a polymer film. The relative change in fluorescence fits well to a Fickian diffusion model, yielding a diffusion coefficient for water of 3 × 10‐8 cm2/s in poly(vinyl acetate), and a value of 6 × 10‐9 cm2/s in a room‐temperature cured epoxypolyamide, in excellent agreement with diffusion coefficient values determined from gravimetric analysis. Preliminary studies also demonstrate the utility of molecular rotor probes to monitor water uptake in individual layers of multilayered polymer systems. © 1995 John Wiley &amp; Sons, Inc.

Optical sensors for monitoring water uptake in plants

The monitoring of water uptake in plants is becoming increasingly important. Optical sensors offer considerable advantages over conventional methods and several sensors have been developed including an optical potometer that monitors water uptake from individual roots, the detection of xylem cavitation using audio acoustic emissions with an interferometric force feedback microphone, and an optical fiber displacement transducer that detects changes in leaf thickness in relation to leaf-water potential.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Fluorescence characterization of cure and water uptake in polymers and composites

This paper summarizes our recent research on using intrinsic fluorescence for cure characterization, and extrinsic and intrinsic fluorescence approaches for monitoring water uptake in epoxy cured with a widely used aromatic diamine curing agent (diaminodiphenyl sulfone, DDS). Intrinsic fluorescence from DDS is used by correlating the red spectral shifts in excitation spectra with the extent of cure. This spectral shift is due to the reaction of DDS amine with epoxide which converts primary amine groups to tertiary amine groups. The technique is applied to neat epoxy cured with DDS as well as composite prepregs reinforced with fibers, using a fiber-optic fluorimeter, and taking into account the effects of temperature on the spectral shift. Use of the fluorescence technique to monitor water uptake is explored, by adding a small amount of extrinsic fluorophore, or by investigating the intrinsic fluorescence near 460 nm in cured epoxy which is probably due to side reaction products. As the water is absorbed, the fluorescence intensity decreases, allowing small amount of water to be detected.