Degree Of Moisture Saturation Research Articles

Inversion Based Retrieval of the Profile of the Degree of Moisture Saturation in Concrete Using Electrical Impedance Measurements

Inversion Based Retrieval of the Profile of the Degree of Moisture Saturation in Concrete Using Electrical Impedance Measurements

Modeling Anomalous Moisture Transport in Cement-Based Materials with Kinetic Permeability.

The durability of reinforced concrete structures is closely related to moisture state in cement-based materials. Therefore, it is crucial to develop moisture models that can accurately predict moisture state in the materials. However, many studies reported anomalous moisture transport in cement-based materials that cannot be well simulated by the conventional models. Several reasons have been investigated in the literature, such as the complex pore structure, chemical reactions with water, dimensional changes of the tested specimen, etc. Nevertheless, only a few models are able to capture the anomaly of moisture transport. This study viewed the main moisture transport coefficient—permeability—as a kinetic variable that depends on both the degree of moisture saturation and the contact time. The time-dependence was formulated by the decay (for drying) or growth (for wetting) functions. The saturation-dependence was calculated by the van Genuchten–Mualem (VGM) model. These functions were then implemented into a moisture transport model that was developed in previous studies. The proposed model was validated by experimental data and showed a good agreement for cement pastes that were dried or wetted in the hygroscopic range. Numerical simulation results were also compared with the simplified solutions to a fractional derivative model (FDM) of anomalous diffusion and the empirical Weibull function. We found that the solutions to the FDM cannot provide appropriate results. Weibull function performs as well as the proposed model, but the empirical function lacks physical meanings.

Time-scale through-thickness interphase in polymer matrix composites including hygrothermal treatment

For the first time, the physical effects of long-term environmental conditions on through-thickness interphase in polymer matrix composites (PMCs) were studied. Atomic force microscopy (AFM) -based Peak Force Quantitative Nanomechanical Mapping (PF QNM) technique was utilized to study the effects of heat and humidity on the mechanical properties of interphase at nanometer resolution. Samples were aged with a heat of 60 °C and relative humidity of 90% for up to 2 years. The width of the interphase is uneven and ‘river-like’ through the thickness in unaged and aged composites. The width of interphase depends on its location and the degree of moisture saturation. The difference in thickness of the interphase, through the thickness, reduces with exposure time. While the mechanism of expansion and shrinkage of interphase is different through-thickness, the range of material modulus is almost the same through-thickness in unaged and aged conditions. Rate of debonding increases from unaged to one-year aged and reduces in the second year of exposure.

Electrical Conductivity, Dielectric Permittivity, and Degree of Saturation of Cement Mortar at Low Radio Frequencies

Abstract The relationship between the electrical properties and the degree of moisture saturation (DoS) in cement-based materials is a topic of interest with regard to material durability. In this article, an impedance-based approach is presented to characterize the electrical properties as a function of DoS using simplified instrumentation and a new measurement technique. The variation of the real and imaginary parts of the impedance is investigated for saturated and partially saturated conditions at electromagnetic radio frequencies (RF) between 100–500 kHz. Mortar prism samples with water to cement ratios (w/c) of 0.60 and 0.70 are used. A circuit model is proposed to explain the behavior and to calculate the bulk conductivity and permittivity for various saturation degrees. The bulk conductivity of the material is found to follow a systematic pattern for various DoS and at different excitation frequencies, which facilitates the establishment of an empirical quantitative relationship between conductivity and the DoS. Moreover, the enhancement of bulk permittivity at low RF is noticed, and its variation for various DoS is investigated.

Spatial and fractal characterization of soil properties across soil depth in an agricultural field, Northeast Iran

The present study was conducted to explore the fractal behavior and establish fractal dimensions of soil physical and chemical properties (i.e., sand, silt, and clay contents, bulk density, degree of moisture saturation, pH, organic carbon content, total nitrogen, available phosphorus, and available potassium) to characterize their spatial patterns. Soil samples were collected from 0-30 (surface) and 30-60 cm (subsurface) depths from an agricultural field, Mashhad Plain, Northeast Iran. Descriptive statistics and fractal analysis were used to describe the extent and form of variability. Spatial patterns of the soil properties were estimated using GS+ 10.0 software. Soil properties showed low to high variations in both surface and subsurface layers across the field, where bulk density and pH being the most reliable soil physical and chemical properties in the study area. The variability was high (CV > 35%) for total N, available P, available K and organic carbon in both surface and subsurface soils and it could be attributed to management practices and micro-topographical variations as these are the dynamic properties of soil. The fractal dimension (D) values of soil physical properties ranged from 1.398 to 1.913 at the surface, and from 1.874 to 1.934 at the subsurface indicating both short and long range variations. The D values for the chemical properties ranged from 1.331 to 1.975, and 1.148 to 1.990 in the surface and subsurface layers, respectively. The results showed that fractal analysis could be employed to effectively describe the structure of soil heterogeneity in spatial scale for effective agricultural and environmental management of soil.

Determining the quality of diterpene glycosides, obtained from stevia leaves

Aim. To determine the quality of diterpene glycoside powders, produced in Ukraine using the stevia leaves of plants of domestic and foreign origin. Methods. Differential scanning calorimetry and thermographic analy- sis. Results. It was demonstrated that the increase in the production of powders of diterpene glycosides in the world results in stepping up the requirements to the selection material of stevia and the quality of powders, obtained from its leaves as a fi nal product. The quality of diterpene glycoside powders, produced in Ukraine us- ing the stevia leaves of plants of domestic and foreign origin, was investigated. Conclusions. It was determined that special attention in the analysis of the powder samples of diterpene glycosides should be paid to the sample preparation: increased humidity of the sample promotes a weakening of carbohydrate bonds and rapid decline in their quality. Differential scanning calorimetry allows determining the content of additives, the degree of moisture saturation, and may further be used in the screening of selection samples and forecasting the shelf life of powders of diterpene glycosides.

Thermal Properties and Transient Temperature Response of Full-Depth Asphalt Pavements

An improved laboratory test procedure for measuring thermal conductivity of asphalt concrete (AC) pavement is proposed. In this preliminary work, a simple device for thermal diffusivity of AC is developed and the corresponding thermophysical properties are measured. The measurement results indicate that the thermal conductivity and thermal diffusivity of AC are functions of compaction degree, degree of moisture saturation, and temperature. From the estimated thermal conductivity and the measured thermal diffusivity, the transient temperature response to changes in environmental conditions of an AC pavement is analyzed numerically with an incremental recursive method by applying the energy balance principle and the Fourier heat transfer equation. The analysis results show that an AC pavement undergoes diurnal temperature cycles whose amplitude decreases with depth and changes sharply at the pavement surface. In addition, with the changing frequency of the temperature, thawing and refreezing effects of the AC pavement increase progressively from January to March in New Brunswick, Canada.

Laboratory Study of Microtexture-Related Skid Resistance Characteristics of Concrete Pavement Materials

Abstract This paper reports the results of a laboratory test program conducted to study the variations of microtexture-related skid resistance of concrete materials with moisture condition, measurement temperature, and surface polishing. The materials used for concrete pavement construction in Singapore were studied. Surface wetting was found to produce a surface-wet frictional resistance considerably lower than the initial surface-dry value. However, neither the surface-wet nor surface-dry measurement was affected by the degree of moisture saturation of the materials tested. Surface temperature had a strong influence on the results of surface-wet tests, but not the surface-dry tests. The temperature-dependent variations was highly correlated to either measurement temperature or viscosity of water, always showing a coefficient of correlation exceeding 0.94 in absolute value. Polishing had the effect of reducing both surface-wet and surface-dry resistance. However, cement mortar specimens were found to respond differently from granite and steel slag aggregates due to differences of their surface wear behaviors in the process of polishing.

The gravimetric method of soil moisture determination Part III An examination of factors influencing soil moisture variability

The influence of various environmental factors on soil moisture variability in the 0–8 cm horizon is examined. The investigation of the influence of vegetation types revealed at least three tentative variability groups (in order of increasing variability) corresponding to areas of recent cultivation, areas of permanent or ley grass, and predominantly uncultivated moor or heathland areas. The dynamic nature of seasonal variability changes are illustrated and correlations established with the amounts of rainfall and insolation in the week preceding sample collection, and the degree of moisture saturation at the time of sampling. Required sample size was directly related to mean moisture content, or the degree of moisture saturation, and the amount of insolation. It is suggested therefore that a decrease in soil moisture content is associated with a decrease in the variance of sample means, and an increase in moisture content is associated with an increase in variance.