Mechanical Properties of Rammed Earth Stabilized with Local Waste and Recycled Materials

Traditional techniques of construction using natural and locally available materials are nowadays raising the interest of architects and engineers. Clayey soil is widely present in all continents and regions, and where available it is obtained directly from the excavation of foundations, avoiding transportation costs and emissions due to the production of the binder. Moreover, raw earth is recyclable and reusable after the demolition, thanks to the absence of the firing process. The rammed earth technique is based on earth compressed into vertical formworks layer by layer to create a wall. This material owes its strength to the compaction effort and due to its manufacture procedure exhibits layers resembling the geological strata and possessing high architectural value. The hygroscopic properties of rammed earth allow natural control of the indoor humidity, keeping it in the optimal range for human health. Stabilization with lime or cement is the most common procedure to enhance the mechanical and weather resistance at once. This practice compromises the recyclability of the earth and reduces the hygroscopic properties of the material. The use of different natural stabilizers, fibers, and natural polymers by-products of the agriculture and food industry, can offer an alternative that fits the circular economy requirements. The present study analyses the mechanical strength of an Italian earth stabilized with different local waste and recycled materials that do not impair the final recyclability of the rammed earth.

Temporal Viability of Aedes aegypti and Aedes albopictus Eggs Using Two Hygroscopic Substances as Preservatives under a Sterile Insect Technique (SIT) Program in Southern Mexico

Dengue and other Aedes-borne diseases have dramatically increased over the last decades. The Sterile Insect Technique (SIT) has been successfully used as part of integrated pest strategies to control populations of insect-plant and livestock pests and is currently being tested as a potential method to reduce mosquito populations in an environmentally friendly approach. However, during the mass rearing steps needed to produce millions of mosquitoes, egg storage and preservation are essential for a certain amount of time. Eggs of Aedes aegypti have a chorionic pad that functions as a sticky substance to glue them onto the inner walls of larval breeding sites. The chorionic pad is chemically made of hyaluronic acid, a hygroscopic compound, responsible to protect them from desiccation over time. Two commercial products with hygroscopic properties, hydrolyzed collagen, and Hyalurosmooth®, both were tested to assess their ability to prolong egg life storage for A. aegypti and A. albopictus. Results showed that 85–95% of Ae. aegypti eggs were able to hatch up to week 8 after being treated with both hydrophilic compounds, compared with the control 66.3%. These two substances showed promising effects for keeping Ae. aegypti eggs viable during prolonged storage in mass rearing insect production focused on vector control SIT programs.

EFFECT OF CHITOSAN ADDITION DURING PAPER-MAKING ON AGEING STABILITY OF DOCUMENT PAPER

The aim of the present work has been to study the influence of chitosan addition into the composition of paper intended for documents on its ageing stability, with a view of enhancing the resistance of paper strength and optical properties over time. The chitosan solution was added during the formation of the paper sheets in various amounts: 0.2%, 1% and 2% o.d.f. Paper samples of different fibrous compositions were prepared from bleached sulphate softwood pulp (BSWP) and bleached sulphate hardwood pulp (BHWP) in the following ratios: 50% BSWP:50% BHWP, 80% BSWP:20% BHWP, 100% BSWP and 100% BHWP. Then, paper samples were subjected to accelerated thermal ageing for 24 hours at 105 °C. It was found that the use of chitosan as additive in the composition of bleached cellulose paper samples led to improved strength and hygroscopic properties. The study showed that chitosan could be used in the production of kraft document papers comprising aluminium sulphate, as the presence of aluminium sulphate had no negative effect on the action of the biopolymer. Regarding the complex evaluation of the properties of the obtained papers, it could be summarized that, for the studied fibrous compositions, the optimum amount of the additive was 1% chitosan for a fibrous composition of 50% bleached softwood pulp and 50% bleached hardwood cellulose. Therefore, preparing document paper with the addition of chitosan is a convenient procedure to enhance a number of paper properties, even after the ageing process.

Hygroscopic Properties of Sweet Cherry Powder: Thermodynamic Properties and Microstructural Changes

Understanding sorption isotherms is crucial in food science for optimizing the drying processes, enhancing the shelf-life of food, and maintaining food quality during storage. This study investigated the isotherms of sweet cherry powder (SCP) using the static gravimetric method. The experimental water sorption curves of lyophilized sweet cherry powder were determined at 30°C, 40°C, and 50°C. The curves were then fitted to six isotherm models: Modified GAB, Halsey, Smith, Oswin, Caurie, and Kühn models. To define the energy associated with the sorption process, the isosteric sorption heat, differential entropy, and spreading pressure were derived from the isotherms. Among the six models, the Smith model is the most reliable in predicting the sorption of the cherry powder with a determination coefficient (R2) of 0.9978 and a mean relative error (MRE) ≤1.61. The values of the net isosteric heat and differential entropy for the cherry increased exponentially as the moisture content decreased. The net isosteric heat values varied from 10.63 to 90.97 kJ mol−1, while the differential entropy values varied from 27.94 to 273.39 J. mol−1K−1. Overall, the enthalpy-entropy compensation theory showed that enthalpy-controlled mechanisms could be used to regulate water adsorption in cherry powders.

Heat Sterilization Effects on Polymeric, FDM-Optimized Orthopedic Cutting Guide for Surgical Procedures

Improvements in software for image analysis have enabled advances in both medical and engineering industries, including the use of medical analysis tools to recreate internal parts of the human body accurately. A research analysis found that FDM-sourced elements have shown viability for a customized and reliable approach in the orthopedics field. Three-dimensional printing has allowed enhanced accuracy of preoperative planning, leading to reduced surgery times, fewer unnecessary tissue perforations, and fewer healing complications. Furthermore, using custom tools chosen for each procedure has shown the best results. Bone correction-related surgeries require customized cutting guides for a greater outcome. This study aims to assess the biopolymer-based tools for surgical operations and their ability to sustain a regular heat-sterilization cycle without compromising the geometry and fit characteristics for a proper procedure. To achieve this, a DICOM and FDM methodology is proposed for fast prototyping of the cutting guide by means of 3D engineering. A sterilization test was performed on HTPLA, PLA, and nylon polymers. As a result, the unique characteristics within the regular autoclave sterilization process allowed regular supplied PLA to show there were no significant deformations, whilst annealed HTPLA proved this material’s capability of sustaining repeated heat cycles due to its crystallization properties. Both of these proved that the sterilization procedures do not compromise the reliability of the part, nor the safety of the procedure. Therefore, prototypes made with a similar process as this proposal could be safely used in actual surgery practices, while nylon performed poorly because of its hygroscopic properties.

Mechanical and Hygroscopic Properties of Molded Pulp Products Using Different Wood-Based Cellulose Fibers

With an increasing interest for molded pulp product (MPP) in the industry, it is important to fully understand how the manufacturing process is different from papermaking. One specific way to differentiate the processes is to compare their resulting products. As the paper industry uses several wood fibers with various pulping processes, it is interesting to compare some of these fibers, to further progress our understanding of the MPP process. In this study, six different wood fibers were used (as received) and analyzed to obtain the sample with the lowest moisture uptake and highest tensile properties. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and fiber analysis module (MorFi) observations were performed, as well as moisture uptake measurements after sorption and tensile tests. We observed significant differences between the fibers tested. Kraft fibers (bleached softwood kraft pulp (BSKP), bleached hardwood kraft pulp (BHKP), and unbleached softwood kraft pulp (USKP)) showed smoother surfaces and less non-cellulosic molecules, such as hemicellulose, lignin, and pectin, in the SEM images. Bleached chemi-thermomechanial pulp (BCTMP) and recycled pulps (R-NPM and R-CBB) both showed non-cellulosic molecules and rougher surfaces. These results were confirmed with the FTIR analysis. With kraft fibers, MPP mechanical properties were lower than non-kraft fibers. Resulting moisture uptake is in between the recycled fibers (lowest moisture uptake) and BCTMP (highest moisture uptake). The removal of non-cellulosic molecules reduces the mechanical properties of the resulting MPP. The incorporation of non-wood molecules, as found in recycled fibers, also reduces the mechanical properties, as well as moisture uptake, when compared with BCTMP.

Hygroscopicity of Fresh and Aged Salt Mixtures from Saline Lakes

The high hygroscopicity of salt aerosol particles makes the particles active in aerosol and cloud formations. Inland saline lakes are an important and dynamic source of salt aerosol. The salt particles can be mixed with mineral dust and transported over long distances. During transportation, these particles participate in atmospheric heterogeneous chemistry and further impact the climate and air quality on a global scale. Despite their importance and potential, relatively little research has been done on saline lake salt mixtures from atmospheric perspectives. In this study, we use experimental and model methods to evaluate the hygroscopic properties of saline lake brines, fresh salt aerosol particles, and aged salt aerosol particles. Both original samples and literature data are investigated. The original brine samples are collected from six salt lakes in Shanxi and Qinghai provinces in China. The ionic compositions of the brines are determined and the hygroscopicity measurements are performed on crystallized brines. The experimental results agree well with theoretical deliquescence relative humidity (DRH) values estimated by a thermodynamic model. The correlations between DRHs of different salt components and the correlations between DRHs and ionic concentrations are presented and discussed. Positive matrix factorization (PMF) analysis is performed on the ionic concentrations data and the hygroscopicity results, and the solutions are interpreted and discussed. The fresh and aged salt aerosol particles are analyzed in the same way as the brines, and the comparison shows that the aged salt aerosol particles completely alter their hygroscopic property, i.e., transferring from MgCl2− governed to NH4NO3− governed.

Modification of the Hygroscopic Properties of Textile Materials Containing Polyurethane Threads

The article discusses the influence of the presence of polyurethane (elastomeric) threads in the composition of a textile material on the effect of plasma modification of hygroscopic properties. The objects of the study were textile (knitted) fabrics based on cotton fibers with the addition of Dorlastan threads. The samples were processed in the plasma of a high-frequency capacitive discharge at a reduced pressure, as the plasma-forming gas was used air. Experiments have shown that the water absorption of the samples after plasma treatment is increased by an average of 1.5 times. The presence of Dorlastan thread does not significantly affect the result of the plasma modification, since the samples are completely immersed in water and the elastomeric threads do not limit the water absorption of its cotton component. The degree of capillary rise, on the contrary, depends on the presence of polyurethane threads. In samples made of 100% cotton, the increase occurs up to 190-. According to these samples, polyurethane threads prevent the capillarity of water by about 4 times. Kinetic curves of water absorption are given. The results suggest that other processing treatments are required to render the polyurethane threads hydrophilicity by plasma treatment. This should be considered in the development of plasma methods for treating textile materials, including in terms of matrix for composite materials.

INFLUENCE OF ELECTROMAGNETIC FIELD OF EXTREMELY LOW FREQUENCIES ON HYGROSCOPIC PROPERTIES OF WHEAT GRAIN MASS

The research results of the influence of electromagnetic field (EMF) of extremely low frequencies (ELF) on hygroscopic properties of Shestopalivka wheat variety of 2019 harvest have been given. Grain processing was performed on the experimental stand that consisted of the polymeric cylindrical container for grain, solenoid coil, generator of electromagnetic waves GZ-112/1 and a power amplifier of low frequency. The output signal of generator was set in the form of sine wave and controlled by oscillograph C1-78. The studies were performed at EMF frequencies of 10, 16, 24 and 30 Hz. Magnetic induction of grain treatment was constant and equaled 10 mTl. The duration of grain processing was 6 minutes.The equilibrium moisture content of wheat grain was determined by the tensometric method at temperatures t 9 °C and 23 °C and relative humidity φ 33…36 % and 82…82.5 %. The necessary conditions of air were created in desiccators with solutions of sulfuric acid placed in thermostats and refrigerators.It has been determined that the equilibrium moisture of wheat grain processed by EMFof ELF – is in the range of 12.17…20.56 %, and unprocessed grain – in the range of 12.62…21.03 %. Regardless of the frequency of EMF, equilibrium moisture content of the grain wheat processed by EMF varies according to the known laws – decreases with temperature increase and increases with increasing of air relative humidity. It has been shown that the impact of processing by EMF of ELF on the equilibrium moisture contentof wheat grain is manifested at different frequencies in different ways, which is likely due to the resonance phenomena. It has been established that the processing of grain by EMF with frequencies of 10...30 Hz practically has no effect on the equilibrium moisture content of grain at 23 °C and a relative humidity of 33...82.5 % which remains practically at the level of the unprocessed grain. It has been shown that the processing of grain by EMF with frequencies of 24 and 30 Hz under conditions of t = 9 °C and φ = 33 % leads to higher equilibrium moisture content compared to unprocessed wheat grain from 14.45 % to 16.85...16.95 %. Processing of grain with frequencies of 10 and 16 Hz under the same conditions, on the contrary – leads to a decrease in the level of equilibrium moisture content to 13.74…13.86 %. Empirical coefficients have been determined and the equation has been proposed that describes the dependence of equilibrium moisture content of not processed and processed wheat grain by EMF with frequency 10...30 Hz on temperature and relative humidity of the ambient air.