Limited Water Content Research Articles

Energy Efficiency Evaluation of Green Roofs as an Intervention Strategy in Residential Buildings in the Field of Spanish Climate

The use of green roofs entails environmental, economic and social benefits as sustainable tools of architecture. They present proven benefits in the path towards carbon neutrality and the reduction of the consumption of energy resources, especially in the field of renovation and improvement of the thermal envelope. In Spain, the current climate crisis also implies a problem of water stress, so it is necessary to analyse in more detail the behaviour of self-sustaining green roofs in the different climatic and rainfall zones into which the territory is divided. Evapotranspiration is the main mechanism of heat dissipation in green roofs, but in this study, it is observed that in the case of self-sustaining roofs with limited water content, the greatest losses through evapotranspiration occur in climates with high temperatures and solar radiation, above cities with higher rainfall and colder climates. On the contrary, the greatest energy savings are obtained in this type of cold climate. Evapotranspiration in self-sustaining roofs is not the most determining factor for achieving energy savings. The design of the roof, the geometry and orientation of the building, as well as the cooling energy consumption, play a more determining role.

Physicochemical and pasting properties of corn starch as affected by hydrothermal modification by various methods

ABSTRACT Native corn starch has a lack of characteristics such as low thermal stability, low resistance to shear force, and a high tendency to retrograde. To address this problem, it needs to be modified to improve its application in the food sector. Hydrothermal modification is one of the physical modifications by heating the starch above the gelatinization temperature with a limited water content. In this study, native corn starch was modified using various methods of hydrothermal modification which did not cause full gelatinization of starch and maintained starch granule integrity i.e., heat-moisture treatment (HMT), autoclave-heat treatment (AHT), microwave-heat treatment (MHT), and osmotic-pressure treatment (OPT). HMT, AHT, and MHT were modified by limited moisture content (30%) and then was heated using an oven, autoclave, and microwave, respectively, while OPT was heated in Na2SO4 2- solution using an autoclave. The results showed that the thermal modification did not alter the A-type crystallinity pattern of its native starch, but an amylose-lipid complex occurred resulting A + V-type crystallinity pattern. AHT starch has the highest V-type peak which indicated the highest amylose-lipid complex. The relative crystallinity increased after modification treatment except for OPT. The thermal modification increased thermal stability and increase the retrogradation ability of native corn starch. Parameters of thermal characteristics such as To, Tp, and Tc increased and Range of Tc – To decreased (except for HMT) after thermal modification. Solubility, water absorption capacity, gel strength, and syneresis of native corn starch tend to increase after modification. The best thermal modification of corn starch was OPT because it can produce the modified starch that not only had the highest thermal stability but also a lower retrogradation ability, the lowest swelling volume, higher water absorption capacity, and gel strength. Therefore, the hydrothermally modified corn starch could be applied to canned food, noodle, and bakery.

Prediction of Undisturbed Clay Rebound Index Based on Soil Microstructure Parameters and PSO-SVM Model

The rebound index Cr is an important design parameter in engineering construction, and its determination is cumbersome and susceptible to errors. Explaining the macroscopic rebound characteristic parameter Cr from the perspective of microscopic mechanism is an important research area that is addressed in this study. In this paper, the different soil parameters, including the Cr parameter and the physical parameters (void ratio er liquid limit water content WL, and plasticity index Ip), have been determined through experiments for the undisturbed clay of Chongming East Shoal (CES), Shanghai. Further, scanning electron microscopy (SEM) imaging was used to analyze the microstructural features. Through SEM, the grey correlation degree, the average abundance of structural units ACp and the average equivalent diameter of pores ADv were determined as the soil microstructure parameters with the most significant correlation with Cr. The predictive analysis model of Cr was then carried out combined with the PSO-SVM algorithm. In order to evaluate the influence of microscopic parameters of soil on the prediction accuracy, four sets of input parameter combinations were used. The results indicate the high prediction accuracy of the developed model. Sensitivity analysis was also carried out, which showed that the sensitivity of Cr to ACp and ADv was significantly lower than e; however, the difference from wL and Ip was small, indicating that it is imperative to consider microscopic parameters while predicting Cr. This study, thus, provides a basis and method for predicting the rebound index of soil from the microstructure perspective.

Analysis of Geotechnical Characteristics of Coastal Clay Soil Found in Incheon and Gwangyang

Recently, there has been an increase in the number of projects involving the planning and construction of business complex facilities and land development in coastal regions. However, coastal regions are characterized by very soft clay soil. Consequently, such clay soil needs to be augmented for facilitating land procurement. Furthermore, to realize land improvement, the associated geotechnical characteristics need to be analyzed through laboratory tests by acquiring pristine samples of cohesive soil. According to the results obtained from previous studies, the characteristics of the cohesive soil found in Korea can vary depending on the region and depositional environment. The objective of this study is to examine the representative physical and mechanical characteristics of marine clay found in Namhae coast (Gwangyang) and Seohae coast (Incheon) by comparing and analyzing these characteristics. To this end, land examinations were conducted during planning and construction, and data were gathered from 445 sites in Incheon and 844 sites in Gwangyang for comparing the associated physical and mechanical characteristics. Subsequently, by conducting regression analysis, equations of correlation between liquid limit and natural water content, effective surface load and pre-consolidation load, compression index and liquid limit, and compression index and natural water content were deduced. The obtained results indicate that compared to the soil found in Incheon, the clay fraction, natural water content, liquid limit, plasticity index, liquidity index, initial void ratio, and compression index of the soil found in Gwangyang are higher.

A Comprehensive Study on the Competition Between Starch and Sucrose on Access of Water During Heating

AbstractStarch gelatinization and water penetration into starch granules are studied in the presence of sucrose by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). The water content of the samples ranged from 70% to 20% (w/w wsb) and two modes of preparation are used: All‐In‐One (AIO) and Sucrose‐Syrup mixed with Flour (SS + F). A shift of the gelatinization to higher temperatures is observed and an increase in its enthalpy, thus implying stabilization of the granular structure during heating. In addition, the AIO method shows that sucrose has priority over wheat starch in terms of access to water. With either an excess of water or a limited water content, the AIO method shows that the solubilization of sucrose is favored water penetration into the starch granules. XRD analysis is performed in a heating cell using the same time‐temperature profile, showing that there is a link between the endotherm of gelatinization and the moment when the amorphous regions of the granules are sufficiently mobile to impose stresses on the lamellar crystals and thereby trigger their destruction. This work provides new information showing the importance of sucrose dissolution and water content on starch gelatinization in the cake and biscuits application.

Lateral Strength of Traditional Adobe Walls Affected by Moisture: A Numerical Parametric Study

ABSTRACT This paper studies the lateral strength of traditional (unstabilized) adobe walls subjected to lateral loading, either in-plane or out-of-plane, using the finite element method. The focus of the numerical parametric study is on adobe walls that have a moist region in their lower part immediately above the footing. The variables of the parametric study are the length, height, and water content of the moist region. The lateral strength of adobe walls can be affected by the moist region depending on its size and water content. Generally, the threshold of gravimetric water content of the moist region associated with a considerable decrease in lateral strength is 12% for I-shaped walls under in-plane lateral loading and 10% for cantilever walls under out-of-plane lateral loading. A short moist region that is at most one-third or one-fourth of the wall length for out-of-plane or in-plane loading, respectively, does not compromise significantly the wall lateral strength even at relatively high water content. Even though the results depend on the model geometry and characteristics, this information can be useful to those working in adobe repair and preservation because approaching or exceeding these limiting water contents might indicate an immediate need for shoring the walls.

Strength and Deformation Characteristics of Fiber Reinforced Longdong Loess and Experimental Study of Modified Duncan -Chang Model

Fiber yarn reinforced loess is prepared through mixing plain loess with a certain proportion of polyester fiber yarn, which is formed by loosening, carding and cutting waste synthetic textile polyester fabric and has rough surface properties and good acid-alkali corrosion resistance. The strength and deformation characteristics of Longdong Loess reinforced by fiber yarn were studied. The test results show that the uniaxial compressive strength of fiber yarn reinforced loess increases with the increase of fiber yarn proportion and fiber yarn length, and decreases with the increase of fiber yarn fineness. Combined with the uniaxial compressive strength data of fiber yarn reinforced loess under the optimal water content and liquid limit water content, an index which can comprehensively reflect the reinforcement performance of fiber yarn reinforced loess is proposed-- Fiber reinforced index. The shear stress-strain relationship of triaxial consolidation drainage of fiber-reinforced loess with different proportion of fiber yarn is strain hardening type. The hypothesis of hyperbolic form is in accordance with Duncan Chang model. By discussing the relationship between the parameters of fiber yarn reinforced loess and plain loess model, the empirical expression of model parameters considering the influence of fiber yarn reinforced loess is obtained. A modified Duncan-Chang E-B model reflecting the influence of different fiber yarn blending ratio was constructed. The rationality of the model is verified by comparing the test curve with the model prediction curve.

Sahilkent (Bafra, Samsun) yöresindeki alüvyal zeminlerin sıvılaşma potansiyelinin CPT verileri kullanılarak araştırılması

In this study, liquefaction potential of the alluvial soils consisting of clay, silt, and sand sized materials in Sahilkent (Bafra, Samsun) area was investigated using CPT data. Within the scope of the study, 20 boreholes each having a depth of 15 meters were drilled throughout Bafra district, and one undisturbed soil sample were obtained per meter from 5 of these boreholes located in Sahilkent area. Wet sieve, hydrometer, plastic limit, liquid limit, and natural water content determinations were conducted on 20 samples with high silt and sand content. In the preliminary evaluation, it was determined that there is a liquefaction potential in some regions at different depths, and in order to perform detailed liquefaction analyses, 15-meter-deep CPTu were carried out in 1 meter distance from those 5 borehole locations. In CPTu tests, data including cone tip resistance, sleeve friction, effective stress, relative stiffness, etc. were recorded every 5 cm, and average values of these data for each meter depth were used in the liquefaction analysis. Liquefaction analyses was conducted for an earthquake scenario of Mw = 7.2 and the liquefaction potential of the 15-meter soil layer in the study area was determined. As a result of the analyses, it was determined that no liquefaction will occur for an earthquake scenario of Mw = 7.2 in Sahilkent region. It is thought that high fine-grained content of the alluvium, and the fact that existing clean sand levels are located between fine-grained soil layers increase the resistance of the soil against liquefaction.

Effect of Relative Humidity on Secondary Brown Carbon Formation in Aqueous Droplets.

Atmospheric brown carbon (BrC) is a significant contributor to particulate light absorption. Reactions between small aldehydes and reduced nitrogen species have been shown to produce secondary BrC in atmospheric droplets. These reactions can be substantially accelerated upon droplet evaporation. Despite aqueous droplets undergoing continuous water evaporation and uptake in response to the surrounding relative humidity (RH), secondary BrC formation in these droplets under various RH conditions remains poorly understood. In this work, we investigate BrC formation from reactions of two aqueous-phase precursors, glyoxal and methylglyoxal, with ammonium sulfate or glycine in aqueous droplets after drying at a range of RH (30-90%). Our results illustrate, for the first time, that BrC production varies as a function of RH. For all four chemical reaction systems being investigated, mass absorption efficiencies (MAE, m2/g C) of aqueous aerosol products (from 270 to 512 nm wavelength range) generally increase with reducing RH to reach a maximum at ∼55-65% RH and subsequently decrease, caused by further drying. Chemical characterization using high-resolution aerosol mass spectrometry shows that the formation of nitrogen-containing organic species also follows a similar variation with RH. Our observations reveal that the acceleration of BrC production from evaporation of water may be diminished by other factors, such as limited particle-phase water content, phase transition, and volatility of reactants and products. Overall, our results highlight that intermediate RH conditions in the atmosphere may be more efficient in secondary BrC formation, indicating that the effect of RH needs to be included in atmospheric models for a more accurate representation of light-absorbing aerosol formation in aqueous droplets.

Rapid detection of mercury (II) ions and water content by a new rhodamine B-based fluorescent chemosensor.

A rhodamine B-based sensor (RS) was designed and synthesized by a combination of the spirolacton rhodamine B (fluorophore) and multidentate chelates (ionophore) with high affinity towards Hg2+. In the presence of Hg2+, the resulting red-orange fluorescence (under UV light) and naked eye red color of RS are supposed to be used for quantitative and qualitative measurement of Hg2+. Further fluorescent titration and analysis demonstrate that RS can selectively detect Hg2+ within 1s with a low limit of detection (LOD) of 16nM in acetonitrile media, meanwhile, the association constant (Ka) was calculated to be 0.32×105M-1. More importantly, the resultant complex (RSHg) of RS and Hg2+ has also been successfully applied to detect limited water content in acetonitrile solution.

Prediction of undrained shear strength using extreme gradient boosting and random forest based on Bayesian optimization

Accurate assessment of undrained shear strength (USS) for soft sensitive clays is a great concern in geotechnical engineering practice. This study applies novel data-driven extreme gradient boosting (XGBoost) and random forest (RF) ensemble learning methods for capturing the relationships between the USS and various basic soil parameters. Based on the soil data sets from TC304 database, a general approach is developed to predict the USS of soft clays using the two machine learning methods above, where five feature variables including the preconsolidation stress (PS), vertical effective stress (VES), liquid limit (LL), plastic limit (PL) and natural water content (W) are adopted. To reduce the dependence on the rule of thumb and inefficient brute-force search, the Bayesian optimization method is applied to determine the appropriate model hyper-parameters of both XGBoost and RF. The developed models are comprehensively compared with three comparison machine learning methods and two transformation models with respect to predictive accuracy and robustness under 5-fold cross-validation (CV). It is shown that XGBoost-based and RF-based methods outperform these approaches. Besides, the XGBoost-based model provides feature importance ranks, which makes it a promising tool in the prediction of geotechnical parameters and enhances the interpretability of model.

Intelligent modelling of clay compressibility using hybrid meta-heuristic and machine learning algorithms

Compression index Cc is an essential parameter in geotechnical design for which the effectiveness of correlation is still a challenge. This paper suggests a novel modelling approach using machine learning (ML) technique. The performance of five commonly used machine learning (ML) algorithms, i.e. back-propagation neural network (BPNN), extreme learning machine (ELM), support vector machine (SVM), random forest (RF) and evolutionary polynomial regression (EPR) in predicting Cc is comprehensively investigated. A database with a total number of 311 datasets including three input variables, i.e. initial void ratio e0, liquid limit water content wL, plasticity index Ip, and one output variable Cc is first established. Genetic algorithm (GA) is used to optimize the hyper-parameters in five ML algorithms, and the average prediction error for the 10-fold cross-validation (CV) sets is set as the fitness function in the GA for enhancing the robustness of ML models. The results indicate that ML models outperform empirical prediction formulations with lower prediction error. RF yields the lowest error followed by BPNN, ELM, EPR and SVM. If the ranges of input variables in the database are large enough, BPNN and RF models are recommended to predict Cc. Furthermore, if the distribution of input variables is continuous, RF model is the best one. Otherwise, EPR model is recommended if the ranges of input variables are small. The predicted correlations between input and output variables using five ML models show great agreement with the physical explanation.

Study on fluidity and strength of dredged sludge under water curing condition

Dredged sludge can be used in engineering by treating with flowing solidification method underwater, but the flow solidification characteristics of dredged sludge in underwater curing condition are not clear. The influence of initial water content, cement content and curing age on the fluidity and strength of solidified sludge was discussed through laboratory tests. The results show that the strength of solidified sludge under water curing situation increase linearly with cement content, decreases linearly with the initial water content, and increases logarithmically with the curing age. The relationship of unconfined compressive strength with liquid limit and initial water content for dredged sludge at 28 days curing age was proposed and verified, which provides an important basis for field application and strength prediction of flow solidification treatment.

Effect of Aging Time on Consistency Limits of Bentonites

The water contents of clay soils at liquid limit, plastic limit, and shrinkage limit are the three consistency limits and are used as fundamental index parameters for assessing the geotechnical behavior. The extensive application of highly plastic clays, such as bentonites, in the waste containment facilities and improvements in understanding of the double-porosity structure of plastic clays prompted the present work to relook into the determination of these consistency limits. The liquid limit water contents of three Indian bentonites were estimated using percussion and cone penetration tests; undrained shear strength at different clay-water interaction periods. The liquid limit water content obtained by the percussion method increased with the aging time. The variation in the liquid limit water contents with time was obtained for three different bentonites and mixtures of different percentages of sand and kaolinite. The results were analyzed based on the double-porosity hypothesis. The influence of aging time on the plastic limit and shrinkage limit was also observed. Simple linear equations were proposed to predict the equilibrium water contents at different consistency limits based on the routine testing that are valid for different plastic clays. Further, the significance of equilibrium consistency limits in understanding the soil–water characteristic relationships of the studied bentonites was presented.

Engineering behaviour of MICP treated marine clays

In the present scenario, with much focus on sustainable development worldwide, Microbially Induced Calcite Precipitation (MICP) is a promising biological soil improvement technology. However, only very limited research is reported on the effectiveness of this technique in marine clays. This paper presents the salient features of an experimental study conducted on two typical marine clays stabilised by MICP. Effectiveness of the technique was evaluated through a series of one-dimensional consolidation tests, unconfined compression tests, and index property determinations. It is found that biostimulation approach is not effective in marine clay; bio-augmentation is needed for soil improvement. Bio-augmentation results in the reduction of liquid limit and plasticity index to about 29% and 47%, respectively for the marine clays. A comparable improvement in volume change behaviour is also observed. There is a marked increase in undrained shear strength, upto about 148%, of MICP treated marine clays at toughness limit water content. Curing is also found to have a significant role in soil improvement. The observed transition in the nature of the tested marine clays from that of fat clay to elastic silt suggests the potential of the proposed approach. An empirical equation is also proposed to predict compression index of MICP treated marine clays.

Physiological Response of Advanced Lines of Rice under Water Deficit in Campeche, Mexico

Yields of rice (Oryza sativa L.) respond to complex interactions between the genotype and the environment; rice has the particularity of being a semi-aquatic crop, and as a result of this, it presents lower adaptation to the limiting water content of soil and is extremely sensitive to stress from drought; therefore, it is the most important limiting factor in rice production. The objective of this study was to research the physiological response of rice genotypes to water stress. The grain yield and its components, leaf area and transpiration efficiency under irrigation (I) and drought (D) were evaluated in eight advanced lines from the nursery of the Latin American Fund for Irrigated Rice (Fondo Latinoamericano para Arroz de Riego, FLAR) and a control variety of rice. The experiment was established in Campeche, in the 2015 autumn-winter cycle. The grain yield and its components, as well as the leaf area were greater under irrigation conditions than under drought. The transpiration from the water stress was reduced and the plants under drought increased their transpiration efficiency. The genotypes P-V 2006 and P-V 2009 were identified, with genealogies FL05392-3P-12-2P-2P-M and FL08224-3P-2-1P-3P-M, respectively, as the most outstanding compared to the rest of the genotypes in the grain yield and its components, leaf area, total root biomass, and transpiration efficiency.

Improvement of loess characteristics using sodium alginate

Loess often has poor engineering properties due to its loose accumulation and strong collapsibility. Therefore, improvement of the soil is necessary to meet the needs of engineering. In the current work, the improvement effect of sodium alginate added in different proportions to loess was studied. Limited water content test and particle size grading test were conducted to study the effect of sodium alginate on the basic physical parameters of soil. In addition, unconfined compressive strength test (UCS) and consolidated undrained test (CU) were used to analyze the changes in the mechanical properties of the soil after improvement. Additionally, permeation and disintegration tests were used to study the change in the soil’s water stability. What’s more, the microscopic mechanism of sodium alginate improved loess was also proposed based on the results of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that sodium alginate not only can change the liquid-plastic limit and particle size gradation of loess but also improve the strength, shear parameters, and water stability of loess. SEM and XRD studies revealed that sodium alginate changed the microstructure of the loess, formed a colloidal material to encapsulate the soil particles, filled the pores between soil particles, and caused aggregation of the clay material in the soil to form larger particle size via flocculation. These results show that sodium alginate can be used as a more environmental friendly and sustainable additive to replace the traditional soil stabilization additives, such as cement or lime to stabilize loess.

Geopolymer Brick by using Flyash, GGBS, Silica Fume and Kadapa Slab Dust

Brick is the former construction material, a standard-sized non load bearing building component. The ancient bricks manufactured by clay, earth or mud. By 2007 the new ‘fly-ash’ brick made up of cement and flyash which is reliable, weather & acid resistant. The cement is a hugely used building material and liberates CO2 leading to pollution. To minimize pollution and a step to advancement in sustainable development. The current research results to geo polymer brick, where the cement is replaced with GGBS, silica fume and Kadapa slab dust. For bonding, polymers were used with limited water content. Hence produced brick is a hybrid geo polymer brick with multi material combination. Fly ash 75%- GGBS 25% as a base material. GGBS is partially replaced with silica fume and Kadapa slab dust by 2 to 5%. Evaluated through compressive strength results in which we found three optimum proportions such as FA 75%-GGBS22%-SF3% & 75% FA-22% GGBS -3% KSP.

Liquid and plastic limits of clays by cone method

Undrained shear strength of a soil at the liquid limit water content can be considered to be around 1.7 kPa according to several researchers. Plasticity index of soils has been defined by one school of thought as a range of water content producing a 100-fold variation in their undrained shear strength. This has led to the redefinition of the plastic limit as the water content at which undrained shear strength is 170 kPa. The undrained shear strength-water content relationship has been found to be linear in the log–log plot for a wide range of water contents beginning from around the plastic limit to near the liquid limit. Normalization of undrained shear strength—water content relationship in a log–log plot has led to the conclusion that the water content at the liquid limit and at the plastic limit, obtained by cone penetration, could also be uniquely related. This contradicts the original understanding of Atterberg limits, namely liquid and plastic limits which are two independent parameter not related at all. It is more suitable to call this value of plastic limit from cone method as PL100 to differentiate it from Casagrande’s plastic limit.

Effects of Piecewise Electric Field Operation on Sludge Dewatering: Phenomena and Mathematical Model

Electro-dewatering (EDW) is an energy-efficient method for sludge dewatering. In this study, effects of piecewise electric field operation on EDW were investigated by experiments and simulation. Operational parameters were studied mainly in terms of sludge resistance variation during electro-dewatering process, which were evaluated by linear sweep voltammetry (LSV) analysis. Simulation of the sludge cake electro-dewatering processes was developed and validated, based upon time-dependent experimental data of electric currents and filtrate weights. The modeling results were in good agreement with experiments. It was proved by experimental and modeling results that the piecewise operation has positive effects on key performances of EDW devices, that is, limited water content, space-time yield, and mass specific energy consumption.