Decrease In Water Absorption Research Articles

Influence of Firing Temperature on Phase Composition and Color Properties of Ceramic Tile Bodies.

This study is focused on the behavior of the cream-firing clays from Opoczno region (Poland). The ceramic masses on which tests were carried out consisted of cream-firingBorkowice clay and dolomite in two different grain sizes as an additive that changes the color of ceramic materials. Test samples were prepared by plastic method and fired at range of 1100–1240 °C. Phase composition of theinvestigated materials was characterized by XRD method with quantitive analysis of the amorphous phase determined by the Retvield technique. Color properties of the surface of the obtained ceramic materials were determined in CIE-Lab color space. The phase composition of the obtained ceramics depends on the firing temperature. The color of the surface of the ceramic materials also depends on the firing temperature. There was a tendency to decrease the brightness, decrease the blue shade, and increase the yellow shade of the surface of materials with increasing the temperature. The conducted tests allowed to conclude that the color of ceramic materials depends on their phase composition. The most important role in the formation of color correspond to the amorphous phase, formed during the process. The lower content of the amorphous phase in the material allows to obtain brighter products with a lower proportion of yellow, and therefore closer to white. Moreover, following tests were carried out: total water absorption, total open porosity, linear shrinkage, and flexural strength. With increasing the temperature, total water absorption and total open porosity decrease, and total linear shrinkage increases due to the progressive sintering process. Flexural strength increases with the increase of the firing temperature for materials consisting of Borkowice clay. The addition of dolomite introduced new pores into the material, which resulted in an increase in flexural strength at lower firing temperatures and a decrease in flexural strength at higher firing temperatures.

Effect of Moisture Distribution Changes Induced by Different Cooking Temperature on Cooking Quality and Texture Properties of Noodles Made from Whole Tartary Buckwheat.

While precooking and processing have improved the quality of gluten-free noodles, the effects of different cooking temperatures on their quality—neither gluten-free noodles nor whole Tartary buckwheat noodles—have rarely been clarified. This study investigated the key role of moisture distribution induced by different cooking temperatures in improving the noodle quality of whole Tartary buckwheat. The results showed that cooking temperatures higher than 70 °C led to a sharp increase in cooking loss, flavonoid loss and the rate of broken noodles, as well as a sharp decrease in water absorption. Moreover, the noodles cooked at 70 °C showed the lowest rate of hardness and chewiness and the highest tensile strength of all cooking temperatures from 20 °C to 110 °C. The main positive attribute of noodles cooked at 70 °C might be their high uniform moisture distribution during cooking. Cooking at 70 °C for 12 min was determined as the best condition for the quality improvement of whole Tartary buckwheat noodles. This is the first study to illustrate the importance of cooking temperatures on the quality of Tartary buckwheat noodles. More consideration must also be given to the optimal cooking conditions for different gluten-free noodles made from minor coarse cereals.

Influence of the NaOH-treated hemp fibres on the properties of fly-ash based alkali-activated mortars prior and after wet/dry cycles

The conducted study investigates the influence of sodium hydroxide-treated hemp fibres on fibre reinforced fly ash-based alkali-activated mortars and their durability under wet/dry cycles, by examinating mortars’ physical and mechanical properties. This is the first study where the natural fibre reinforced alkali-activated materials under wet/dry cycles are examinated.The sodium hydroxide treatment of hemp fibres leads to separation of fibre bundles and increases the fibres’ surface roughness. This leads to the mortar’s porosity and water absorption decrease, the mortar’s compressive and flexural strength increase and importantly energy absorption capacity increase, all prior and after wet/dry cycles.

The counterbalance of the adverse side effects of releasing agent on the properties of cementitious materials with nano-particles

Organic releasing agent (RA) has been widely used on concrete formwork during casting and structuring for good surface quality. However, the harmful side effects introduced by the organic RA on cement hydration would finally lead to decreased property gain of hardened cementitious materials at the surface. In this work, 5 wt% RA was added into cement paste/mortar to simulate its effects on cementitious materials at the superficial layer when applied to formwork. Moreover, nano-particles (nano-SiO2 and nano-TiO2) have been introduced into the RA for counterbalancing the adverse effects on cement hydration by taking advantage of cement hydration acceleration effects of nano-modification. Results showed that the incorporation of nanoparticles into RA could result in a good dispersion with ultra-sonication. The addition of 4 wt% NS and 16 wt% NT into RA can improve the compressive strength of mortar by 28.2% and 38.1%. Meanwhile, they decrease water absorption rate up to 41.9% and 46.2% to that of the control sample (mortar with RA). Hydration heat calorimetry results demonstrated that the reaction of RA-added cement can be accelerated by nanoparticles, resulting in the microstructure's enhanced compactness (MIP). This work shed light on the nano-modification of concrete surface in a comfortable, efficient, and economical way.

Novel Nano-Precursor Inhibiting Material for Improving Chloride Penetration Resistance of Concrete: Evaluation and Mechanism.

Durability improvement is always important for steel–concrete structures exposed to chloride salt environment. The present research investigated the influence of a novel nano-precursor inhibiting material (NPI), organic carboxylic acid ammonium salt, on the mechanical and transport properties of concrete. The NPI caused a slight reduction in the strength of concrete at later ages. NPI significantly decreased water absorption and slowed down the speed of water absorption of concrete. In addition, the NPI decreased the charge passed and the chloride migration coefficient, and the results of the natural chloride diffusion showed that the NPI decreased the chloride concentration and the chloride diffusion coefficient. The NPI effectively improved the resistance of chloride penetration into testing concrete. The improvement in the impermeability of concrete was ascribed to the incorporation with the NPI, which resulted in increasing the contact angle of cement pastes. The contact angle went up from 17.8° to 85.8° for 0% and 1.2% NPI, respectively, and cement pastes became less hydrophilic. Some small pore throats were unconnected. Besides, the NPI also optimized the pore size distribution of hardened cement paste.

Hydrothermal treatments affect the development of the hard‐to‐cook defect in cowpeas

AbstractThe hard‐to‐cook defect is a well‐known problem in stored legumes, including cowpeas, which reduces the consumption and utilization of these nutritious foods. It is a generally held view that the enzyme, phytase is involved in the development of the defect. The effectiveness of steam treatments in preventing the characteristic hardening of cowpeas stored under unfavorable conditions was investigated. The factors considered were steaming temperature (100°C, 121°C), steaming time (2, 4, and 6 min) and initial seed moisture content (13%, 20%). The treated cowpeas were stored at either 4°C (no relative humidity [RH] control) or 42°C/80%RH. The texture of cooked treated cowpeas was comparable with the control; the peak forces were 504–639 N and 616 N, respectively, for treated and control cowpeas before storage. Although the treatments reduced the texture of cooked cowpeas prior to storage, only steaming at 121°C for 4 or 6 min prevented hardening during storage. Steaming reduced the phytase activity of cowpeas to 53%–64% of original activity; however, a significant increase occurred with storage. Steaming and storage significantly decreased water absorption from 91.28 g/100 g to 75.68–88.02 g/100 g after 24 h soaking. A decrease in phytate content and increases in electrolyte leakage and pectin loss were also recorded. A lack of significant correlation between cooked bean hardness and the physicochemical indices implies that the improved texture of cooked treated cowpeas occurred through a pathway not typically associated with the development of the hard‐to‐cook defect in cowpeas.

Perilaku water absorption pada komposit hybrid serat agel tenun dan serat gelas

This study aimed to investigate the effect of alkali treatment and stacking sequences on water absorption and flexural strength in woven agel and glass fibers reinforced hybrid composites. The research materials are woven agel fiber, E-200 glass fiber, unsaturated polyester resin Yukalac 157 BQTN, and catalyst of methyl ethyl ketone peroxide (MEKP). The alkali treatment is carried out on the woven agel fibers by soaking the fiber in 5% NaOH solution for 1 hour. Then the fiber is washed with fresh water and dried for 48 hours. Manufacturing techniques used vacuum bagging with suction pressure of 70 cmHg at room temperature. The amount of reinforcing fiber 7 fibers consists of 3 glass fibers and 4 agel woven fibers. The water absorption test uses a 3.5% NaCl solution for 1080 hours at room temperature. Water absorption test specimens based on ASTM D570 standard. The research results showed that alkali treatment with glass fiber arrangement on the specimen surface effectively decreased water absorption and increased the flexural strength of woven agel and glass fibers hybrid composites. This can be seen from the decrease in water content in equilibrium by 8.67%, the diffusion coefficient of 5.74 x 10-12 m2/s, and the flexural strength before and after immersion, which are 135 MPa and 125 MPa respectively.

ОПТИМІЗАЦІЯ СКЛАДОВИХ ЗАХИСНОГО ПОКРИТТЯ ТЕРМОМОДИФІКОВАНОЇ ДЕРЕВИНИ ДО ВПЛИВУ ВОДИ

Abstract. Paints and varnishes are used to a large extent to protect wood surfaces in outdoor conditions, as they are easy to maintain and reapply. Also, when developing a coating, manufacturers are guided by the need to obtain a number of properties that generally determine its ability to protect against moisture. To obtain a protective coating that meets the specified requirements, it is necessary that the components that make up the coating belong directly to the group of protective materials or form such compounds under operating conditions, be able to adhere to the surface of the product. It was found that thermal modification provides a decrease in water absorption of wood. Additional processing of the wood surface helps to reduce moisture absorption by 2 times, and for samples modified at a temperature of 220 °C – 3 times. Geometric dimensional stability is also improved by a factor of 2. The effect of heat treatment on the water absorption of wood is somewhat less – for samples modified at 190 and 220 °C for more than 10 hours. Protective substances for thermally modified wood provided similar protection of open thermally modified surfaces of wood from the effects of water. The positive effect of thermal modification on a decrease in the level of water absorption has been established. It has been proven that it is temperature that has a significant effect on such changes. Since the protective coating is also susceptible to photochemical degradation, it is very important to renew it in a timely manner in accordance with the manufacturer's instructions for the pleasant appearance of wood surfaces during external use. The optimal ratio of components in the surface layer of thermally modified wood has been determined, which ensures the fulfillment of the task, namely for a mixture of oil and wax: the density of a wood – 724 kg/m3; oils – 70.0%; wax – 17.5%. Therefore, such treatment is beneficial for the protection and aesthetic appeal of wood products.

Physical and Chemical Properties of Waste Foundry Exhaust Sand for Use in Self-Compacting Concrete.

The reuse of waste in civil construction brings environmental and economic benefits. However, for these to be used in concrete, it is necessary a previous evaluation of their physical and chemical characteristics. Thus, this study aimed to characterize and analyze the waste foundry exhaust sand (WFES) for use in self-compacting concrete (SCC). Foundry exhaust sand originates from the manufacturing process of sand molds and during demolding of metal parts. It is a fine sand rich in silica in the form of quartz collected by baghouse filter. Characterization of WFES was conducted through laser granulometry, scanning electron microscopy (SEM) in the energy dispersive spectroscopy (EDS) mode, X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and derivative thermogravimetry (DTG) techniques. The waste was classified as non-hazardous and non-inert, with physical and chemical properties suitable for use in SCC composition, as fine aggregate or mineral addition. Five mixtures of SCC were developed, in order to determine the waste influence in both fresh and hardened concrete. The properties in the fresh state were reached. There was an increase in compressive strength and sulfate resistance, a decrease in water absorption of self-compacting concrete by incorporating WFES as 30% replacement.

Characteristics of sugarcane bagasse fibers after xylan extraction and their high-solid hydrolysis cellulase-catalyzed

The enzymatic hydrolysis of sugarcane bagasse to obtain a high efficiency conversion of polysaccharides in monosaccharides is dependent on factors related to the morphology and chemical composition. Therefore, a pre-treatment step is necessary to obtain a less recalcitrant substrate. Here, alkaline sulfite with ethanol (ASE) was employed to pretreat sugarcane bagasse aiming to produce substrates enriched in carbohydrates with greater cellulose accessibility. A xylanase stage was evaluated as a strategy to remove arabinoxylan fraction from pretreated bagasse and to verify the influence of the addition of the enzyme xylanase (5, 50, and 500 IU/g material) on the characteristics of ASE pretreated bagasse from 5 to 15% dry matter. The highest xylan extraction yield of 59% was achieved when working at 15% solids and xylanase dosage of 500 IU/g substrate. The interaction of enzyme and solid loadings was positive to arabinoxylan extraction, however the excessive removal of arabinoxylans caused changes on biomass fiber surface and a decrease in water absorption. The cellulase-catalyzed hydrolysis of ASE bagasse ASE pre-extracted by xylanase was nearly paralleled to the control sample, at 15% solids. This study shows that the enzymatic removal of xylan from pretreated bagasse provides a promising condition for the generation of the value-added product in the biorefinery process.

Optimization of microbial induced carbonate precipitation treatment process to improve recycled fine aggregate

Microbial induced carbonate precipitation (MICP) is a novel and environmentally-friendly method to improve the properties of recycled aggregate. This study focused on the optimization of MICP treatment process, mainly including the modification duration, the addition method of calcium source and the number of modification cycles, to improve the quality of recycled fine aggregate (RFA). Weight increase and water absorption decrease of RFA after MICP modification were used to evaluate the effects on the improvement in properties of RFA. The properties of the mortar with modified RFA were examined to investigate the effectiveness of the proposed MICP treatment process. The results show that the optimal MICP treatment process consisted of disposable addition of calcium source and repeating 3 modification cycles with single modification duration of 1 d, verified by the SEM observation and XRD analysis; the mortar with RFA modified by the proposed MICP process showed higher flexural strength and carbonation resistance, which can be explained by the better pore structure at a microscopic level.

Investigation of the Effect of Using Activated Sludge Treated with Acetic Acid on Physical and Strength Properties of Recycled Pulp

This study aimed to scrutinize chemical treatment of Mazandaran Wood and Paper mill activated sludge with 3 % acetic acid for the manufacture of environmentally eco-friendly bio composite. In this study, the paper pulp required was obtained from the waste newsprint paper. The activated sludge was treated in a beaker for 3 min in 3 % acetic acid and then in a water bath at 75 and 100 °C for 45 and 90 min. After that, the treated activated sludge was mixed and refi ned with waste newsprint paper pulp at ratios of 0, 5, 10, 15 and 20 %. The test specimens were prepared according to TAPPI standard and the physical properties (water absorption and porosity) and mechanical (tensile strength, tear strength, ring crush test, burst strength and folding strength) were measured. The results showed that the activated sludge treatment caused the increase in tear strength, ring crush test, burst strength and porosity as well as the decrease in water absorption, tensile strength and folding strength. FT-IR spectrum of the treated samples showed that the treatment with acetic acid strengthened and activated the functional groups on the surface of activated sludge fi bers. The activated sludge added at a level of 5 % at 100 °C for 90 min as well as at a level of 20 % at 75 °C for 45 min was more suitable than other treatments.

EFFECTS OF POLYMER ADDITIVES ON SOME MECHANICAL AND PHYSICAL PROPERTIES OF CEMENT BONDED PARTICLEBOARDS

The effects of some polymer additives, also called super plasticizers, on selected physical and mechanical properties of cement bonded particle board were investigated. Two different kinds of poly carboxylic ether (PF300, DX40) and a melamine based polymer (300M) were added to the wood cement mixture. The ratios of polymer additives to the wood cement mixture were 1%, 1.2% and 1.4%. Cement bonded particleboards were manufactured with wood/cement (w/w) ratio of 1:3; target density of 1300 kg.m-3, and CaCl2 content of 5%. The cement bonded particleboards were tested for water absorption (2 and 24 hour), thickness swelling (2 and 24 hour), bending stiffness and strength and internal bond strength. Results of the study showed that most of the polymer addition decreased water absorption and thickness swelling of the boards. Replacement of cement with polymers increased internal bond strength and bending stiffness of the boards while bending strength was slightly reduced. Use of small amount of super plasticizers significantly improves most of the board properties.

New method for the protection and restoration of calcareous cultural heritage stones by polyelectrolytes and hydroxyapatite nanocrystals

We have investigated the feasibility of a new two-step protocol for the restoration of marbles. The process employs a polyelectrolyte multilayer film that enhances the chemical affinity between the treated stone and restorative material (hydroxyapatite nanocrystals), through functionalization, while at the same time it attributes an acid resistant property to the resulting system. Surface functionalization and material deposition is achieved through spraying; a simple and versatile application method suitable for objects of various sizes and geometries. Polyelectrolyte (polyethylenimine and polyacrylic acid) deposition was examined through Attenuated Total Reflection Fourier-Transform Infrared Spectroscopy (ATR-FTIR) and Atomic Force Microscopy (AFM), and tested through contact angle, water absorption and dissolution experiments. The hydroxyapatite nanocrystals were studied by ATR-FTIR, z-potential, AFM and Scanning Electron Microscopy (SEM), and characterized via contact angle and color alteration measurements. Our results show that the polyelectrolyte multilayer was stable in an aqueous environment with increased acid resistance (up to 46% decrease in mass weight loss when compared with untreated samples) and decreased water absorption (up to 39%). Color measurements of the outer hydroxyapatite layer showed a minimal color alteration for one type of the tested substrates showing low color difference values (ΔΕ* < 5). The results suggest that the proposed method holds great potential for marble restoration as it attributes multi-functionality and is easy to apply.

Influence of pregelatinized starch on rheology of composite flour, in vitro enzyme digestibility and textural properties of millet-based Chapatti

The current study is designed to diversify daily diets like Chapatti with millet (minor cereal) flour. Wheat-millet composite flours (WMCFs) were prepared by incorporating millet flour at 20 %, 40 % and 60 %, and then the rheology of WMCFs was assessed through Mixolab 2. Afterwards, pregelatinized starch (PGS) was added to WMCFs to prepare Chapatti. The product's quality was evaluated by determining water-soluble starches, in-vitro enzyme digestibility, textural hardness, color and sensory characteristics. The results showed that adding millet flour to Chapatti decreased water absorption, and dough development time from 56 % to 50 % and 2.7 min. to 1.5 min. respectively. The Chapatti's hardness was increased, while color (l* values) of Chapatti decreased with millet flour's addition at a constant level of PGS. In the product, Chapatti containing 40 % millet flour and 2 % PGS showed excellent textural hardness and sensory characteristics.

Esterification of Lignin Isolated by Deep Eutectic Solvent Using Fatty Acid Chloride, and Its Composite Film with Poly(lactic acid).

In this study, the effect of lignin esterification with fatty acid chloride on the properties of lignin and lignin/poly(lactic acid) (PLA) composites was investigated. Lignocellulose (Pinus densiflora S. et Z.) was treated using a deep eutectic solvent (DES) with choline chloride (ChCl)/lactic acid (LA). From the DES-soluble fraction, DES-lignin (DL) was isolated by a regeneration process. Lignin esterification was conducted with palmitoyl chloride (PC). As the PC loading increased for DL esterification, the Mw of esterified DL (EDL) was increased, and the glass transition temperature (Tg) was decreased. In DL or EDL/PLA composite films, it was observed that EDL/PLA had cleaner and smoother morphological characteristics than DL/PLA. The addition of DL or EDL in a PLA matrix resulted in a deterioration of tensile properties as compared with neat PLA. The EDL/PLA composite film had a higher tensile strength and elastic modulus than the DL/PLA composite film. DL esterification decreased water absorption with lower water diffusion coefficients. The effect of lignin esterification on improving the compatibility of lignin and PLA was demonstrated. These results are expected to contribute to the development of high-strength lignin composites.

The effect of silica nanocapsules on self-healing concrete

Concrete mixtures containing silica nanocapsules underwent a cracking procedure and were exposed to a natural atmospheric environment and a humidity chamber for 180 days to analyze self-healing. Mechanical recovery was observed in both exposures with increases of 26.94% and 25.82% for the 6% content. A decrease in water absorption was detected in humidity chamber environment. Formation of albite in the cracks interior and silica nanocapsules were detected using XRD, indicating the addition disponibility to continuous healing. The concretes healed completely, verified by OM and FEG/SEM-EDS, after 180 days in the humidity chamber, proving the nanocapsules applicability in high humidity regions.

Evaluation of the mechanical and durability properties of eco-efficient concretes produced with porcelain polishing and scheelite wastes

The construction industry uses large-scale natural resources to production of concrete among which cement and aggregates are fundamental components. This process causes environmental impacts that are not aligned with sustainable propositions and perspectives. Likewise ceramic and mining industries generate various wastes disposed of inappropriately which can be harmful to environmental systems. Given these facts the present study aims to understand better the physical mechanical and durability of eco-efficient concrete produced with partial and hybrid substitutions of cement and sand by porcelain polishing residue (PPW) and scheelite residue (SW) respectively. For this an experimental campaign was developed divided into two stages. The first phase consisted of performing tests (consistency water absorption and porosity by immersion and compressive strength) in concretes with fixed fine aggregate contents (mixture of 81% and 19% of SW and sand respectively) and with partial replacement of Portland cement by 0 5 10 15 20 25 and 30% of PPW aiming to select the mixture with better physical and mechanical performance. Finally the second experimental phase consisted of evaluating the evolution of compressive strength and durability (capillary water absorption and chloride penetration) properties of the selected eco-efficient concrete. A microstructural analysis using XRD was also conducted to identify the main phases present in the concretes with wastes. The results showed that 15% is the optimum content to replace cement with PPW. A decrease in the consistency compressive strength water absorption and porosity of the concretes with this waste compared to the reference mixture was also observed 28 days. However at 90 days the mechanical behavior of the concretes was improved due to the filling effect and the pozzolanic activity of PPW. The durability properties indicated less pore connectivity and resistance to chloride migration equivalent or slightly higher than the reference concrete.

Mechanical and durability properties of steel fiber‐reinforced concrete containing coarse recycled concrete aggregate

AbstractThe focus of this study is to investigate the effect of using coarse recycled concrete aggregates (RCAs) as an alternative material to natural coarse aggregate on the fresh, mechanical and durability behavior of concrete reinforced with steel fiber. Eighteen unique concrete mixes with RCA content of 0%, 50%, and 100% and steel fiber content of 0%, 1%, and 2% were prepared, and tests were performed to study slump, density, compressive and splitting tensile strengths, flexural behavior, surface hardness, surface abrasion resistance, water absorption, and sorptivity of each mix. It is shown that concrete containing RCA has a lower unit weight, compressive, splitting tensile and flexural strength, flexural toughness, surface hardness, and abrasion resistance, and a higher water absorption and sorptivity in comparison with conventional concrete. An increased compressive, splitting tensile and flexural strength, flexural toughness, surface hardness, and abrasion resistance, and a decreased water absorption and sorptivity of concrete with an increased steel fiber content from 1% to 2% is less significant compared to those from 0% to 1%. The results also show that, at RCA content of 50%, incorporating 1% steel fiber develops a concrete mix with similar or even better properties compared to unreinforced conventional concrete. At 100% RCA content, incorporating 2% steel fiber develops a concrete mix with similar properties to unreinforced conventional concrete having water to cement ratio of 0.3, but inferior properties to unreinforced conventional concrete having water to cement ratio of 0.5. These findings indicate that recycled aggregate concrete with similar or even better properties compared to concrete with natural aggregate can be developed through properly designing mixes, providing a great avenue toward the production of green construction material for structural applications.

Impact of Water-Repellent Products on the Moisture Transport Properties and Mould Susceptibility of External Thermal Insulation Composite Systems

External Thermal Insulation Composite Systems (ETICS) are constructive solutions widely used to increase the thermal insulation in new and retrofitted buildings. However, these systems can present several anomalies due to their constant exposure to weathering agents and anthropic factors. Water is generally the major cause of degradation. Thus, the application of water-repellent products can minimize the appearance of anomalies and increase the durability of the systems. In this paper, acrylic-based and siloxane-based hydrophobic products were applied to ETICS, with the aim of assessing the compatibility, effectiveness, and durability of these products. The moisture transport properties and mould susceptibility were assessed through laboratory tests on untreated and treated specimens. The durability of the hydrophobic treatments was also evaluated through artificial aging tests (heat-cold and freeze-thaw cycles). Results show that the protection products generally decreased water absorption, slightly decreased the drying rate, and presented adequate water vapor permeability. After aging, the products still had reasonable effectiveness and, with one exception, improved the water vapor diffusion of the systems. Additionally, ETICS underwent an alteration in the finishing coat (possible modification of the porosity) due to the aging cycles. No clear linear correlation was found between the contact angle values and water absorption results, evidencing the influence of other factors related to the composition of the water-repellent products.